Experimental Chemistry - 1900 - PDF Free Download

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COLLEGE OF LIBERAL ARTS.

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Boston University*

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From

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T{eceived

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EXPERIMENTAL CHEMISTRY BY

NEWELL,

Ph.D. (Johns Hopkins)

ll.

C.

4a

LYMAN

'"^

D. C.

HEATH &

Library

College of Liberal Arts

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he

m

PROFESSOR OF CHEMISTRY, BOSTON UNIVERSITY, BOSTON, MASS.

Boston University

CO., 1909

PUBLISHERS

Poo PREFACE. book is to promote the more efficient The choice and modern methods. arrangement of subject-matter is based on the author's extended experience with students of varied abihty. The book as a whole purpose of

this

vn

The

outcome of a desire

the

shall

which

to provide a course in chemistry

be a judicious combination of the mductive and deductive

em

is

4a

ll.

teaching of chemistry by

methods.

.c h

concise directions and specific questions in the experiments

The

aim to obviate the

and perplexities which hinder the

difficulties

progress of beginners in chemistry.

w w

No

sentative.

The experiments

are repre-

important ones have been omitted, and no senseless

or dangerous ones have been included.

w

not be done by each pupil.

Indeed,

Every experiment need

many experiments may be

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advantageously performed by the teacher either on the lecture table or in

the laboratory

;

others

may be done by

more

the

students and the results utilized in the class-room.

skilful

Abun-

ht

dant material has been purposely provided to meet varied condi-

The Teacher's Supplement

tions.

suggests different uses of

many

experiments, and the author invites correspondence regarding the adaptation of the book to special demands.

Two

supplementary

experiments.'

One

sets of questions arise

class

may and

from most completed

often must be answered in the

The Laboratory demand. The second class of quesamount of descriptive and historical

laboratory where necessary data are available.

Exercises aim to meet tions

this

concerns the vast

matter indirectly connected with the experiments is

needed

for a

;

broad knowledge of the subject, but

this material its

presence

Preface.

iv

would often destroy the

real

value of the experiments by pre-

cluding original thought on the part of the student.

Hence,

are not to be considered in the laboratory, but

at

They

appropriate points, Class-room Exercises are inserted.

may be used

as

the basis of lectures, recitations, examinations, quizzes, or reviews.

Both kinds of exercises may be omitted in whole or in part, if the The Bibliography contains titles of books teacher so desires. mation may be found

Teacher's Supplement.

in the

infor-

and amount of matter presented in these will meet the student's needs

Despite the

exercises, the

ll.

variety

and additional

vn

helpful for a discussion of these exercises,

in

4a

ordinary text-books

most cases

except those involving the recent discoveries and appUcations.

library.

and

selection

will

the

obviate

distribution

It

points

actually

immediate necessity of an extensive

Facts not accessible to students

by the teacher.

of the

em

judicious

needed

may be

easily supplied

should not be forgotten, however, that refer-

.c h

A

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ence books are indispensable adjuncts to laboratory work. Opinions differ widely regarding the kind of experiments which

w

There is a growing should constitute a course in chemistry. involving accurate experiments selected that however, belief,

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measurements possess fundamental disciplinary value. This book quantitative experiments, most of which have been repeatedly performed in the author's classes under a variety

contains several

ht

of conditions.

The

details

have

been worked out with the

be noticed that each quantitative experiment illustrates one or more of the fundamental principles of chemistry, hence the results permit conclusions which furnish a greatest care.

It

will

sound and attractive basis for the treatment of chemical theory. Teachers are earnesdy urged to give these experiments a trial and to utilize the results in class work.

An

unusually large

number of problems has been intentionally among several classes

incorporated to allow a generous distribution or sections.

It is

the problems.

not intended that each student shall solve

The author

will

be grateful

for

errors or ambiguity detected in these problems.

all

information of

Only those who

v

Preface. have prepared similar work less

to

sources of error.

all

can realize the count-

for publication

The Teacher's Supplement

contains answers

problems.

The Appendixes

contain directions for manipulation which could

complete

treat-

and miscellaneous data not

easily

not be conveniently incorporated in the

ment of the

subject of gases,

text, a

found elsewhere. Material intended exclusively for teachers has been put in a

Teacher's Supplement.

believed that the contents and the

It is

presentation will not only lessen their labors, but

vn

its

in the choice of experiments, apparatus, etc.

Copies

ll.

manner of guide them

can be obtained only by ordering directly of the publishers. The entire manuscript has been read by

4a

—

Mr. Fred L. Bardwell, Assistant Professor of Chemistry,

Insti-

em

tute of Technology, Boston, Mass.

Dr. William B. Shober, Instructor in Organic Chemistry, Lehigh

.c h

University, Bethlehem, Pa.

Mr. Irving O. Palmer, Instructor

Chemistry and Physics, High

—

w w

School, Newton, Mass.

in

The proof has been read by Dr. Edward C. Franklin, Professor

of Chemistry, University

w

of Kansas, Lawrence, Kansas.

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Mr. F. F. Coburn, Principal of the State Normal School, Lowell, Mass.

Dr. Charles A. Pitkin, Professor of Chemistry, Thayer

Academy,

ht

South Braintree, Mass., and Professor of General Chemistry, Tufts College Medical School, Boston, Mass.

Mr. William H. Snyder, Master of Science, Worcester Academy, Worcester, Mass. Dr. A.

M. Muckenfuss, Professor of Chemistry,

Millsaps College,

Jackson, Miss. Dr. H. G. Shaw, Instructor in Chemistry,

High School, Melrose,

Mass. Dr. A.

J-

Hopkins, Assistant Professor of Chemistry, Amherst

College, Amherst, Mass.

Preface.

vi Dr.

E. Bucher, Professor of Chemistry, College of Agriculture

J.

and Mechanic

Arts, Kingston, R.

I.

Dr. C. E. Boynton, Instructor in Chemistry, North Division

High School, Chicago, 111. Dr. M. D. Sohon, Instructor

Mixed High School,

York.

Dr. Milo

S.

Walker, Instructor

in

High School, Chicago, 111. Mr. Ernest A. Congdon, Professor

Chemistry, West Division of Chemistry, Drexel Insti-

vn

New

in Physics,

tute, Philadelphia, Pa. in

Chemistry, High School,

ll.

Mr. George W. Benton, Instructor Dr.

J.

Elliott Gilpin, Associate in

4a

Indianapolis, Ind.

Chemistry, Johns Hopkins

Md. The chapter on "Some Common Organic Compounds" was

em

University, Baltimore,

The author and

is

and he gladly takes

Organic

in

profoundly grateful to these teachers

intelligent criticism,

w w

helpful

.c h

read in manuscript by Dr. James F. Norris, Instructor Chemistry, Institute of Technology, Boston, Mass.

for

this

their

oppor-

tunity to express his appreciation of their kindness.

courtesies have been received from the L. E. Knott Apparatus Co., and for these the author hereby tenders his thanks.

tp ://

former pupils and colleagues in the English High School Somerville, Mass., the author is under obligation for generous

To at

w

Numerous his

ht

assistance.

may be found on page 398. and careful examination of intelligent the that believed It is both manuscript and proof by the above teachers has produced a Suggestions for a short course

book

relatively free

may be found

from errors

;

nevertheless, for such errors as

the author willingly assumes responsibility. L. C. N,

Lowell, Mass., June, 1900.

vn

CONTENTS. Introduction Cutting

—

i-8.

—

— Form

em

Experiments

and Tasting.

Balance.

Experiments.

Class-room Exercise

II.

*

Glass.—

of

—

I.

Cleanli-

Record of

— Problems

.c h

I,

Glass.

— Filtration. — Smelling

ness.— Metric System.

— Bending

ll.

—

4a

Bunsen Heating.

Burner.

I.

w w

CHAPTER Physical and Chemical Changes

15

— Chemistry. — Preliminary Definitions. — when Heated. — Products from the heated Metals in Changes Red Powder. — Identification of the Gas. — Definitions. —Class-room Experiments 9-13- — Laboratory Exercise

tp ://

w

Introduction.

I.

ht

Exercise V.

CHAPTER

II.

.24 — Chemical — Properties. and Preparation Introduction. Compounds. — Combination of Oxygen with Magnesium. — — Relation of Oxygen to PoDiscussion of Experiment — Weight tassium Chlorate. — Discussion of Experiment of a Liter of Oxygen. — Definitions. — Oxidation. — Law of Definite Proportions by Weight. — Compounds and Mixtures. — ClassExperiments 14-17. — Laboratory Exercise room Exercise VI. — Problems VII.

Oxygen

15.

16.

11.

vii

Contents.

viii

CHAPTER

III.

PAGE

Hydrogen

38

Introduction.

Reaction.

Zinc

—

— Preparation —

Tests.

S'j'phate.

Examination

—

and Properties.

Crystallization.

Test

for

Zinc

—

— Chemical

Crystallization

Sulphate.

—

of

Quantitative

Reaction between Zinc and Sulphuric

of the

— Discussion of Experiment 22. — Burning Hydrogen. — Discussion of Experiment 23. — Weight of a Liter of — Laboratory

— Problems

Exercise

VIII.

—Class-

IV.

em

CHAPTER

III

4a

room Exercise VII.

ll.

Hydrogen. Experiments 18-23.

vn

Acid.

— Chemi-53 Symbols. — Formulas. — Conservation of Matter. — Chemical Equations — Quantitative Interpretation of Equations. —

Symbols — Formulas— Conservation of Matter cal Equations

...

Equations Studied.

w w

Other Chemical

.c h

.

Foregoing Equations.

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w

Class-room Exercise VIII.

— Problems

based on

— Problems IX.

CHAPTER

V.

General Properties of Water

64

— Water of Crystallization. — DetecCrystallization. — Determination of Water

ht

General Distribution. tion of

Water

of

— Definitions. — — Deliquescence. — Impure Water. — Simple Tests for Impurities in Water. — Purification of Water. — Distillation. — Relation of Water to Temperature. — Freezing and Boiling Points of Water. — Solution. — Solutions of Gases. — Solutions of Liquids. — Solubility of Liquids — Solutions of Solids. — Solubility of Solids. — Saturation and SuperPheSolutions. — Thermal saturation. — Supersaturated

of Crystallization in Barium Chloride.

Efitlo-

rescence.

nomena

of Solution.

— Solution

Experiments 24-37. Problems X.

—

and Chemical Action. Exercises IX-XII.

Class-room

ix

Contents.

CHAPTER

VI. PAGK

Composition of

Water

83

.

Introduction. —Electrolysis

Water. Water. tion of

— Decomposition — Decomposition

of

of

Sodium and Water.

— Hydrogen Iron. — Oxygen

and and

of Water.

Water by Water by Chlorine.

— Quantitative

— Interac-

Composition of

— —

—

Gravimetric Volumetric Composition of Water. Water. Summary. Density of Steam. Composition of Water. Reduction. Volumetric Composition of Steam.

—

vn

—

—

Experiments 38-44.

—

Class-room Exercises XIII, XIV.

CHAPTER

ll.

— Problems XI.

4a

VII.

The Atmosphere

i°5

.c h

em

Introduction. — Composition of Air. — Quantitative Exami— nation of Air. — Other Constituents of the Atmosphere. Nitrogen. — of Liter a of Weight Weight of a Liter of Air.

—

Laboratory Exercises V, VI. Problems XII. Class-room Exercises XV-XVII. 45-47-

CHAPTER

VIII.

116

and Salts

w

Acids, Bases,

—

—

w w

Experiments

— General

tp ://

Introduction.

clature of Acids.

— General

of

Properties

Acids. — Nomen-

Properties of Bases.

— Nomen-

— A General Property of Salts. — Nomenclature of Salts. — Testing the Nature of Substances. — Nature of Common Substances. — Nature of Salts. — Neuof tralization. — Quantitative Examination of the Interaction — and Experiments of 52 53. —Discussion Acids and Bases. of Bases.

ht

clature

Definitions.

Experiments 48-53.

room Exercise

— Laboratory

Exercise VII.

— Class-

XV 111.

CHAPTER

IX.

Atoms, Molecules, and Related Subjects Equivalent of Magnesium and of AluEquivalents. .

.

—

minium.— The Atomic Theory. —Atomic Weights.

.

.

— Law

132

Contents.

of Specific Heats.

—

PAGE

Atomic Weiglits. Calculation of Law.

—Various Figures

for

—

—

Avogadro's Weights. Atomic and Molecular Weights from Experimental Data. Elevation Formula. Percentage Composition. Valence. Ions Point. of Boiling Point and Depression of Freezing Molecular

—

—

—

—

and

Ionization.

— Applications of

the

Theory of

Electrolytic

Dissociation.

Experiments 54-55. —Class-room Exercise XIX.

Chlorine and Hydrochloric Acid

ll.

X.

i57

4a

CHAPTER

— Prob-

vn

lems XIII.

em

Chlorine. — Prepai'ation and Properties. — Bleaching by Chlorine. — Weight of a Liter of Chlorine. — Hydrochloric Acid. — Characteristic Properties. — Synthesis of Hydro-

— Preparation and Properties of Hydro— Interaction of Sodium Chloride and Sulphuric

chloric Acid.

Acid.

— Composition

.c h

chloric Acid Gas.

of Hydrochloric Acid

w w

CHAPTER XL

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w

Experiments Problems XIV.

Gas.— Discus-

— Formula of Hydrochloric Acid Gas. Class-room Exercises XX, XXI. — 56-63.

sion of Experiment 63.

172

Compounds of Nitrogen Ammonia.

— Preparation

and Properties of Ammonia Gas

—

Composition of Ammonia Hydroxide. QuantiComposition of Ammonia Gas. Ammonia Gas. tative Examination of the Composition of Equations for the Discussion of Experiments 66 and 67. Volumetric Chemical Action in Experiments 66 and 67.

and

Ammonium

—

ht

Gas. — Qualitative

—

—

Composition of 68.

_ Weight

Ammonia

Gas.

Ammonia

Gas.

of a Liter of

-

Law

— Discussion

Ammonia

of Gay-Lussac.

Gas.

—

of

Experiment

— Formula

— Ammonium

of

Com-

— Interaction of Ammonium Hydroxide and HydroAcid. — Preparation of Nitric Acid. — A Special Property of Nitric Acid. — Test for Nitric Acid. — Interaction

pounds. chloric

of

Sodium Nitrate and Sulphuric Acid. —Composition of Synthesis of Nitric Acid. —Analysis of Nitric

Nitric Acid.

—

xi

Contents.

PAGE

— Interaction of Nitric Acid and Metals. — General Character of this Interaction. — Interaction of Nitric Acid — Nitrates. — and Copper. — Discussion of Experiment Acid.

']'].

Action of Nitrates with Heat. —Action of Special Test for Nitrates. with Heat.

—

Ammonium

— Law

Nitrate

of Multiple

— Characteristic Property. — Laboratory Exercise VIII. — Classroom Exercises XXII-XXV. — Problems XV-XVII.

Proportions.

—Aqua

Regia.

Its

CHAPTER

Simplest Compounds

Introduction.

— Distribution

of

ll.

its

XII.

204

— Decolorizing

Carbon.

4a

Carbon and

vn

Experiments 64-81.

—

—

—

em

Reduction by Action and Deodorizing Action of Charcoal. Preparation and Properties of Carbon Dioxide.— Carbon.

Weight of a Liter of Carbon Carbonic Carbon Dioxide and Combustion. Acid Formation and Properties of Carbonates. Acid. Determination of Carbon Dioxide in a Calcium Carbonate. Carbonate. —Carbon Monoxide. — Action of Hot Charcoal Weight of a Liter of Carbon Monoxide. on Carbon Dioxide. Preparation and Properties of Carbon Monoxide. Laboratory Exercises IX-XII. Experiments 82-94. Problems XVIII, Class-room Exercises XXVI-XXVHI. Synthesis of Carbon Dioxide. Dioxide.

—

—

.c h

—

—

w w

—

—

—

—

w

—

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XIX.

—

XIII.

ht

CHAPTER

Compounds of Carbon and Hydrogen — Illuminating Gas — Flames — Oxidation and Reduction .221 .

.

—

.

Preparation and Properties of Methane. Hydrocarbons. Preparation Preparation and Properties of Ethylene. PreparaIlluminating Gas. and Properties of Acetylene.

—

—

—

—

—

Combustion of and Properties of Illuminating Gas. Construction of a Bunsen Burner. Illuminating Gas. Candle Flame. Bunsen Burner Flame. Bunsen Burner. Borax Bead.— Tests Oxidizing and Reducing Flames. Reduction and Blowpipe and its Use. with Borax Beads. tion

—

—

,

—

—

—

—

—

Oxidation with the Blowpipe.

—

Contents.

xii

— Laboratory

Experiments 95-106.

— Class-room

Exercises XIII,

—

XXIX-XXXIl.

Exercises

XIV.

Problems XX,

XXI.

CHAPTER

XIV.

Some Common Organic Compounds Introduction. — Composition

236

Compounds.—

of Organic

— Alcohols. — Preparation of Alcohol. — Properties of Alcohol. — Fermentation. — Formula of Alcohol. — Ether. — Properties of Ether. — Aldehyde. — Prepaand

of

Properties

Properties of Acetic Acid.

for

4a

— Hardness

— Prop-

— Preparation of Acetates. — Formula of — Soap. — Preparation and Properties of Soap.

Vinegar.

Acetic Acid.

Acid.—

Acetic

Acetic Acid.

of

Water

— Carbohydrates — Fehling's

em

erties of

—

Aldehydes.

— Test

ll.

ration

vn

Hydrocarbons.

Experiments 107-118 Class-room Exercises

XXXIll-XXXIX.

w w

XXIII.

CHAPTER

— Problems

w

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— Preparation and

XXII,

XV.

Bromine, Iodine, and Hydrofluoric Acid Introduction.

Test

— Laboratory Exercises XV-XX. —

.c h

for Sugar.

.

.

•

Properties of Bromine.

.250

—

—

ProperPreparation and Properties of Hydrobromic Acid. Preparation and Properties of ties of Potassium Bromide.

—

— Carbon Bisulphide Test for Iodine. — Starch Test Iodine. — Detection of Starch. — Preparation and Prop-

ht

Iodine. for

erties of

Hydriodic Acid.

— Preparation and

— Properties of

Experiments 119-128. — Class-room — Problems XXIV, XXV.

CHAPTER Sulphur and

its

Potassium Iodide.

Properties of Hydrofluoric Acid.

Exercises

XL, XLI.

XVI. 260

Compounds

Physical Properties of

Sulphur. — Amorphous

Sulphur.—

— Combining Power of Sulphur. — Hydrogen Sulphide. — Preparation and Properties of Hydro-

Crystallized

Sulphur.

Contents.

gen Sulphide.

Some

xlii

— Sulphides. — Preparation

Sulphides.

and Properties

— Separation

and Properties of

Sulphides.

of

of Sulphur Dioxide.

— Preparation

— Sulphurous

Acid.

— Action of Sulphuric Acid with Sulphuric Acid. and with Organic Matter. — Test Experiments 129-139. — Laboratory Exercises Sulphur Trioxide.

Water

for

XXIII.

—

Class-room

Exercises

XXI-

— Problems

XLII-XLV.

XVII.

Silicon and Phosphorus and their

— Preparation

Compounds — Review

273

Dioxide to Other Compounds

4a

of Silicon.

— Relation of Silicon

and Properties of Silicic Acid. Phosphorus. Review.

Discussion of Experiment 140.

—

—

em

Silicon.

ll.

CHAPTER

vn

XXVI, XXVII.

—

—

Laboratory Exercise XXIV. Experiments 140-141. Problems XXVIII, Class-room Exercises XLVI-XLVIII.

.c h

—

XXIX.

w w

CHAPTER

XVIII.

— Silver — Magnesium — — — Metals. — Properties of Sodium. — Compounds of Sodium and their Properties. — Preparation of Pure Sodium Chloride. — Preparation of Sodium Hydroxide. — Properties of Potassium. — Compounds of Potassium and their Properties.

—

ht

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w

Copper Potassium Sodium Zinc — Mercury Calcium

Preparation

of

Potassium

— Preparation and — General Properties of

Hydroxide.

Properties of Potassium Carbonate.

— Tests for Copper. — Interaction of Copper and — Important Compounds of Copper. — Oxides of Copper. — Preparation and Properties of Cuprous Oxide. — Alloys. — Preparation and Properties of Silver. — Tests for Silver. — General Properties of Magnesium. — Tests for Magnesium. — Tests for Calcium. — Compounds of Calcium. — General Properties of Zinc. — Tests for Zinc. — Interaction of Zinc and Metals. — General Properties of Mercury. — Preparation of Mercury. — Definitions. — Tests for Mercury. — Properties of Mercurous and Mercuric Compounds. Copper. Metals.

279

Contents.

XIV

PAGE

—

Laboratory Exercises XXVExperiments 142-166. XLIX-LVI. Problems -Exercises Class-room XXXIV.

—

XXX-XXXVI.

CHAPTER

Manganese — Iron

— .... —

—

—

XIX.

Lead Chromium Tin Aluminium Separation of Metals

—

-303

Action of Aluminmm General Properties of Aluminium. and Properties of Preparation Alkalies. and with Acids

vn

—

Aluminium Hydroxide. —Discussion of Experiment 169.— Preparation and Properties of ComTests for Aluminium. Action of Tin General Properties of Tin. mon Alum.

.c h

em

4a

ll.

— — — with Acids. — Tests for Tin. — Discussion of Experiment 174. — Deposition of Metallic Tin. — General Properties of — Lead. — Tests for Lead. — Soluble Lead Compounds. — Oxides of of the Properties Water. Action of Lead on Compounds. Chromium. —Chromium Lead. — Tests — Properties of Chromates. — Definition. — Chromic Comfor

in its

w w

pounds.— Reduction of Chromates to Chromic Compounds. Preparation and Properties Properties of Chrome Alum. Tests for Manganese. —Oxidation of Chromic Hydroxide.

—

—

w

with Potassium Permanganate.

— Ferrous

—

— General Properties of Iron. — — —

Behavior of Ferrous and Ferric Compounds. Reduction Behavior of Ferric Compounds. Compounds. Oxidation of Ferrous Compounds. of Ferric Compounds. Separation of Lead and Silver. Separation of Metals.

— —

—

—

ht

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—

Analysis Separation of Lead, Silver, and Mercury (-ous). Analysis of Solder. Analysis of Brass. of a Silver Coin.

— — — Separation of Copper, Iron, and Sodium. — Separation of Zinc and Iron. — Separation of Iron and Aluminium. — Sepaand Aluminium. Laboratory Exercises XXXVExperiments 167-201. Problems Class-room Exercises LVII-LXIll. XLI. ration of Zinc

—

—

—

XXXVII-XLII.

APPENDIX Manipulation

— Weighing

Hard Glass Tubing.

A.

and Measuring

— Making

.

Ignition Tubes.

.

•

.

•

— Heating

3^9

xv

Contents.

— Evaporation. — Filtration. — Stoppers, Corks, Joints, and Safety Tubes. — To cut off the Bottom of a Bottle. — To insert a Glass Tube into Rubber Tubing. — To a Glass Tube to a Stopper. — To dry the

'AGE

Glass and Porcelain.

tit

— To clean the Inside of a Bottle. into a Tube. — Pouring Liquids and transferring Solids. — To make a Platinum Tip. — To seal a Platinum Wire into a Glass Rod. — Collecting Gases. — Gas Holder. — Aspirators. — Metric System. — To counterpoise a Balance. — Weights. — Weighing. — Measuring Liquids and Gases. — Thermometer. — Barometer. or Bottle.

Powder

Experiment

vn

introduce a

ll.

— To

Tube

6.

APPENDIX

4a

Inside of a

B.

em

— Manipulation of Gases of Charles. — Correction Temperature. — Absolute Temperature. — Law of Boyle. — Correction Pressure. — Aqueous Tension. — Formula for the Reduction of Gas Volumes to Standard Conditions. — Manipulation of Gases.

Gas Laws Law

354

w w

.c h

for

w

Class-room Exercises II-IV.

— Problems III-VI.

APPENDIX

tp ://

for

C.

Miscellaneous Data

370

Glossary of Chemical Terms.

— — — —

— Bibliography. — Apparatus

—

ht

and Chei;nicals. Reagents. Important Elements and their Atomic Weights. Colors of Coatings on Charcoal. Colors of Borax Beads. Colors of Residues moistened with Cobaltous Nitrate. Conversion of TherColors of Flames. mometric Readings. Specific Gravity and Melting Point (Approximate) of Metals. Solubility of Salts in Water. Weight (in Grams) of a Liter of Dry Gases at 0° C. and Formula for preparing an Alcoholic Solution of 760 mm. Desired Strength. PeriComposition of Typical Coals. odic Arrangement of the Elements. Emergency Set.

—

—

—

—

—

—

—

—

Index

399

vn

ll.

4a

em

.c h

w w

w

tp ://

ht

CHEMISTRY.

of the apparatus used in this

and the student

is

advised not only to acquire at the outset reasonable in

glass

working and other operations performed

make

directions concerning general manipulation.

may

in the

More detailed

be found in Appendix A.

w w

directions

skill

constant use of the hints and

.c h

laboratory, but also to

con-

earnestly

em

exphcit,

book can be

directions for such

4a

work here given are

The

ll.

Much

structed in part by the student.

vn

INTRODUCTION.

w

BUNSEN BURNER.

tp ://

The Bunsen Burner

used as a source of heat

is

chemical laboratories.

A

common form

shown

is

attached to the

Fig.

i.

It

most is

ht

in

in

of this burner

gas cock by a piece of rubber tubing. When the gas is turned on, the current of gas draws air through the holes at the bottom of the tube, and this mixture,

when

lighted,

less, i.e.

burns with an almost

non-luminous, flame.

It is

flame and deposits no soot.

should be current

match

of

The burner

by turning on a full and holding a lighted

lighted

gas

in the

color-

a hot

gas about

5

Fig. t.— Bunsen burner.

centimeters (two inches) above I

Experimental Chemistry.

2

the height of the flame should

the top of the burner;

then be

The

regulated to

supply

air

meet the special demand.

may be reduced

or entirely cut off

by

turning the ring at the bottom of the burner so that the As holes in the tube are partly or completely closed. the air supply is lessened, the flame gradually becomes

and

flame deposits soot and

most laboratory work.

should be used otherwise

Bunsen flame," or simply "the flame,"

ll.

often called ''the

experiments, unless the directions

in all

4a

for is

Uke an ordinary gas flame. is not hot enough The non-luminous flame, which

finally is luminous,

The luminous

vn

yellow,

state.

.c h

considered in Chapter XIII.

em

The parts of a Bunsen burner are shown in Fig. The theory of the burner and structure of the flame

w w

A wing-top burner movable attachment tube (see Figs.

4, 5, 7)

which

flame,

is

shown

in Fig. 2.

This

over the top of the

and thereby produces a heat through a

used to

w

flat

is

slips

tp ://

longer space than the Bunsen flame permits, in

6S.

are

heating glass tubing which

is

to

c.o^.

be bent.

ht

GLASS WORKING.

—

Soft glass tubing is used for all purGlass Tubing. It poses except those in which intense heat is employed.

melts easily, and can be bent and blown into numerous shapes.

—

Cutting. Glass tubes and rods are cut as follows Determine the length needed, lay the glass on the table, and with a forward stroke of a triangular file make a short Grasp the but deep scratch where the glass is to be cut. and hold mark, tube in both hands, one on each side of the

Introduction.

thumbs together behind the scratch. Now push gently with the thumbs, pull at the same time with the hands,

the

and the tube

Hard in

will

desired

the

at

point.

glass tubing

the

break is

cut

same manner

as

soft tubing, though the

See Fig.

Fig.

3.

3.

vn

scratch must be deeper.

— Cutting a glass tube.

4a

ll.

The sharp ends should be rounded by rotating the end of the glass slowly in the See Fig. 4. flame until a yellow color is distinctly seen.

em

Certain precautions must

observed

be

in

cutting

.c h

glass.

Fig.

tp ://

w

w w

(i) If the glass does not break with slight pressure, do not push hard, but make a deeper scratch and try

4.

— Rounding the sharp

—

" fire-polishing."

erately glass,

cloth before attempting to break

large tubes

by

this

If

(2) ends of a

ht

glass tube

again.

method.

Ask

it.

the tube or

large

wrap it Never

—

tubes,

Use

a slightly yellow

and the

colorless

flat

modhard

in a piece of

try to

break

the teacher for directions.

General Directions. —( O Use Bending produces a flat flame. which burner, (2)

is

of

Bunsen flame

a

wing-top

for thin-walled

flame for thick-walled, or

hard

tubes.

Never put a glass tube into the flame suddenly, nor a hot tube on a cold surface, lest it crack. (3)

Experimental Chemistry.

Heat evenly, and

(4)

when

All bends

cool gradually.

made should be held at the top of the large yellow flame This deposit protects the outside until covered with soot. from the cooler

air,

and thus prevents sudden or unequal This operation

cooling.

called

is

annealing."

**

two or more

If

(5)

bends are made

the

vn

in

tube, they should

same

the same plane,

parts of the tube

4a

i.e. all

ll.

all lie in

touch

should

a

level

5.

— Bending

a tube into a

angle

—

the tube in the flame as

Hold

shown

between the thumbs and forefingers feels

soft

yield, take

it

and ready

as

it

a

into

shown

in

Compare the angle

tp ://

Fig. 6.

angled

Fig.

6.

-Bending

a tube into a right

ange —

object,

right

and

not correct, repeat the operation with another tube. 2. To bend a tube into an oblique angle.

ht

other

— Hold

Operation

tube in the flame, as

Rotate

HI Fig. 7.

the to

^.

^'"'"'^S^e

-

'"'° """ '''''^'' 1!

it,

the

shown and at

same time move it slowly the right and left so that

from

five to eight centimeters

are

evenly

heated.

soft,

remove

into

the

shown Fig.

it

When

to

with the corner of a square block of wood, or with any

if

rotate

evenly.

it

w

angle,

and slowly

out of the flame

and slowly bend right

in Fig. 5,

in order to heat

w w

it

Operation i. To bend a tube into a right angle.—

right

I.

.c h

Pig.

em

surface.

it

desired

in Fig. 8.

^^^ t^ ^^^^^ ^^^^^

When

and

bend

angle, It is

as

help-

^^Sle sketched

Introduction.

5

roughly on a piece of paper near by, so that the tube it

may be

held over

while being bent.

—

(i) Tubes to be bent at an oblique angle should Precautions. be heated through about twice the space required for a right angle. A very slight bend, however, is often made by heating a short space.

ll.

8.

— Bending a tube into an oblique angle —

Fig.

9.

— A worthless bend.

4a

Fig.

vn

v^^

II.

and therefore worthless.

w w

brittle,

.c h

em

never (2) The heat should be applied continuously, and the tube bent at a low temperature, otherwise the curves may be flattened or Such bends are creased, or may even collapse, as shown in Fig. 9.

CUTTING AND BENDING GLASS.

—

w

Cut into halves a glass tube about 30 centimeters Experiment i. Bend one piece into a right angle and the other into an oblique Submit each to the teacher angle.

tp ://

long.

^

for criticism.

ht

Experiment

2.

— Bend

—

.

a glass

tube, about 35 centimeters long

and

5 millimeters in external diameter, into a double right angle, so that

each arm long.

is

about 10 centimeters

See Fig.

tube, as

it

is

10.

Preserve this

used in many experi-

Fig. 10.

— A double right angle bend.

ments.

—

Bend a glass tube, 40 to 45 centimeters long, into Experiment 3. shown in Fig. 11. The numbers indicate the approximate length of the different portions. The shorter arm is made by holding

the shape

Experimental Chemistry. the tube at that point (7 centimeters from the end) at almost right angles to the flame, and then bending slowly,

regulating

by

pressure

the

Pre-

the cooling of the tube. serve this delivery tube

for

future use.

MAKING STIRRING RODS. Experiment

4.

—A

piece

ters in

—A

needed. convenient

is

Heat the

rod in the middle in

delivery tube.

the

— Bunsen

millime-

4a

Fig. II.

5

diameter

ll.

meters long and

vn

of glass rod about 25 centi-

and when

ordinary

— not

soft

.c h

flame,

em

draw it out slightly Cut it .into two rods by into the shape shown in Fig. 12. making a slight scratch at the desired point of the narrow flat

w w

5

I

I

portion.

is

— Stirring rod partially made.

convenient to have one rod rather blunt and the other somewhat pointed for

tp ://

It

12.

w

Fig.

for stirring hot metals

off in the

All rough points should be melted completed rod is shown in Fig. 13.

general use.

A

ht

flame.

CLOSING TUBES.

— Small

tubes are closed, or sealed, by Experiment 5. heating one end of the tube in the Bunsen flame the tube should be constantly rotated to insure even heating. Large ;

tubes are closed as described

in

Exp.

Close a small tube

6.

about 10 centimeters long, and submit

it

to the teacher for

13.—

Fig.

criticism.

A

Directions for working with hard glass tubing

may be found

in

Appendix A.

stirring

rod

— ex-

act size.

Introduction.

MAKING IGNITION TUBES. Experiment

— See Appendix A,

6.

OPTIONAL.

CLASS-ROOM EXERCISE. 1.

2. 3.

,

§ i.

I.

Why does thick glass crack when suddenly heated? Why is glass brittle, if has been suddenly cooled? Why does a hot tube crack, if laid on a cold surface it

or

if

wet

with w^ater?

HEATING.

4a

ll.

vn

Effective use of the Bunsen burner flame is learned only by experience, but a few preliminary hints may prove The burner should always be lighted before serviceable. any piece of apparatus is held over it, or before it is placed under the piece of wire gauze which supports a dish (see sudden heat may crack the apparatus. App. A, § 2)

small flame

is

more

easily con-

5

to

Usually

.c h

trolled than a large one.

a flame from

em

—

A

10 centimeters

4 inches) high gives sufficient and is not easily blown about by sudden drafts. Chemical glassware is made of uniformly thin glass, and if

w w

(2 to

tp ://

w

heat,

heated

with

certain

not crack.

ht

will

A

precautions

wet

tube

test

should never be put in or over the bare flame.

The temperature

of

dry test tubes, or of those containing only solids, should be raised

Fig.

14.

gradually by moving them in and

— Test

tube and

holder.

out of the flame or by holding them in the flame and ing them slightly between the

thumb and

forefinger.

roll-

If

the test tube contains a solid, special care must be taken to distribute the heat evenly

;

if

the test tube contains a

Experimental Chemistry.

8 liquid,

heat

should be slightly incHned so that the greatest not on the bottom, which is often thinner than

it

is

the sides

the flame should never

;

face of the liquid, or liquid

sur-

heat the tube and then the

will

it

come above the

touching this spot will cause the tube to crack.

In most experiments test tubes can be held between the thumb and forefinger without discomfort If they are too hot to handle, a test tube holder should be used. 14.

vn

See Fig.

divided solid suspended in a liquid

finely

filtration

or

may be

filtering.

A

.c h

em

separated from the liquid by

4a

A

ll.

FILTRATION.

w w

Fio. 16.— Folded paper

—

—

stage.

Fio. 17.— Folded

paper

— second

stage.

Fig.

18.

—A

fil-

paper folded ready for the ter

funnel.

w

Piece of Fig. 15. filter paper.

first

paper (Fig. 15) is folded so that a funnel, and when the mixture is poured

it

tp ://

circular piece of porous

exactly

upon

fits

this paper, the solid

the

ht

retained, while the liquid

paper.

folding

it

The paper

— the residue or precipitate — — passes through — the

is

is

filtrate

prepared for the funnel by

successively into the shapes

shown

in Figs. 16

17, and then opening as shown in Fig. 18, so that three thicknesses are on one side and one on the other. (See App. A, § 4.)

and

MISCELLANEOUS SUGGESTIONS.

—A

safe rule to follow is never Smelling and Tasting. unless so directed, substances, unfamiliar to smell or taste

Introduction.

9

and even then with the utmost caution. Never inhale a gas Taste by vigorously, but waft it gently toward the nose. touching a minute portion of the substance to the tip of the tongue, and as soon as the sensation is detected, reject never swallow it. the solution at once

—

— Successful laboratory work

Cleanliness.

is

largely meas-

All apparatus should be clean

vn

ured by general cleanliness. before use, and should be washed as soon as it has been In quantitative work it is absolutely necessary to used.

ll.

have balance, weights, crucibles, forceps, and every other

4a

piece of apparatus perfectly clean.

WEIGHING AND MEASURING.

by weight or volume are found by weighSuch operations require a ing or measuring, or by both. of weights and measures system working knowledge of the used in science and a familiarity with the chemical balance and other instruments of precision.

em

w w

.c h

Exact

relations

is

used

in

tables, see

The

tp ://

w

The Metric System of weights and measures For a brief outline of the system, with science. Appendix A, § i8. relation of the metric

common

in

ht

measures

*

I

meter

I

liter

use

is

system to the weights and

shown by the following:

Table of Equivalents.

=

39-37 inches

—

Experimental Chemistry.

lo

The

marked with a

*

should be learned. Other equivalents can be easily deduced from the above. (See App. A, § i8, Table of Transformation.)

A to

equivalents

convenient relation (true only in the case of water)

remember

is

i

1.

=

=

kg.

i

i

dm. = looo

cu.

cc.

= looo gm.

= 2.2 lb. The customary

abbreviations of the most

nominations are as follows

:

—

Liter,

Decimeter, dm.

Kilogram, kg. or Kg.

Milligram, mg.

Centimeter, cm.

Decigram, dg.

Cubic centimeter,

Centigram, eg.

cc.

I

(J))

I

Add

PROBLEMS.

—

km.

4.

w

Subtract

i

mm. from 4

How many

ht 6.

for loss

?

1.

I

How many

{b) 27 cu.

:

result in

in centi-

made from 249 m.

of

—

dm.

(c)

\'j'2\ 1.

(rt?)

24.8

1.

a tank 75 m. long, 27 cm. deep, and 3 dm.

liters in

?

7.

8

m.

Express in cubic centimeters {a)

and express the answer

cm.,

tubes 1.5 cm. long can be

tubing, allowing 1.5 5.

I.

{c) 127.5 ^^^' i^ inches.

in millimeters.

tp ://

3.

gm., 4 gm., .04 gm.

cm. in decimeters. I km., 2 m., 4 dm., 6 cm., 9 mm., and express the

centimeters.

meters.

i

.c h

(«)

e.g.

w w

2.

Express:

4a

used for

is

em

cm.

cc.

gram is gm. OccasionThe same abbreviation may be

used for the plural and singular,

1.

ll.

1.

preferable abbreviation for

ally cu.

de~

vn

Meter, m.

The

wide

common

What

is

dm. wide, and 8. 9.

10.

the capacity in cubic centimeters of a box 2 m. long, 7 cm. deep

How many How many Add

grams

?

in 1.647 kg.

?

cubic centimeters in 721

2 gm., 9 eg., 14 dg.,

1.

?

and 237 mg., and express the sum

grams. 11. 12.

How many How many

pounds

in 25 kg.?

milligrams in

5 cc.

of water at

4°C.?

in

II

Introduction. pressure at which a gas

The standard

13.

Express the same

How many How many

14. 15.

measured

is

meters in 100.056 dm.

In 0.005 m.?

In 0.5 m.?

m.?

millimeters in 1.575

In

?

1.5

dm.

In 50 dm.

?

box is 0.5 m. deep, 25 dm. long, and 1.2 m. wide. the volume in cubic centimeters ? height 17. If a cylinder holds 141. 3 gm. of water, and its diameter

is its

20.

In 0.5 cu. m.?

?

How many

22.

millimeters, centimeters,

contained in 0.437 dm.

How many How many A piece of

25.

0.723 gm.

A

26.

area

foil

circular piece of filter

cistern

A

2

is

it

m. long,

contain

How many liters 29. A wire 255 mm.

ht is

30.

necessary to

31

.

Alcohol

of alcohol 32.

34.

35.

36.

1.5

is

a

is

is

m. wide, and

is

hold

it

cm. weighs

may

it

What

is

i

m. deep.

How many

i

m. in diameter and

hold

What

length of this

How many

?

0.8 as heavy as watqr.

{b)

m. high.

eg.?

i

times heavier than water.

1.8

liter flask

1.5

?

a rider weighing

Express in meters and in.

1.5

10 cm. in diameter.

What is

?

{a) 6 33.

will

paper

long weighs 0.172 gm.

make

Sulphuric acid

grams of acid

measuring 10.5 cm. by

?

cyHndrical gas holder of gas will

wire

cm.

and meters are respectively

pieces each weighing one decigram

?

of water will

28.

platinum

?

A

27. liters

5

kg.?

in 1.725

tp ://

its

dm. high and

centigrams in 2.567 kg.?

how many

Into

be divided

grams

w w

24.

?

w

23.

in a cylinder 9

?

In 15 cu.

ll.

in diameter

grams of water

In 1565 dg. 1.?

4a

How many

21.

em

dm.?

20 cm.,

is

vn

How many grams in 2000 dg.? In 1800 eg.? How many centigrams in 21 gm.? In 1900 mg.? How many cubic centimeters in 100 1.? In 0.5

18. 19.

?

is

?

.c h

what

What

A

16.

mm.

760

is

in inches.

in millimeters

1.25

ft.

How many pints in 2.5 liters ? How many liters in 2 gal. ? How many grams in 150 grains? How many pounds in 7 kg.?

:

the weight of 1200 cc

— {c)

3.6 yd.

Experimental Chemistry,

12

A

balance sufficiently accurate for the exact experiments It is often called a book is shown in Fig. 19.

of this

"horn pan balance," because

»

the pans are

made Some of

of that

material.

the

periments

give

results,

the ordinary trip

if

ex-

satisfactory

— Horn pan balance.

Fig. 20.

— Trip or platform scales.

.c h

Fig. 19.

em

4a

ll.

vn

or platform scales are used.

w

w w

See Fig. 20. All rough or approximate weighing should be done on the trip scales. Both of the balances above mentioned must be counDirections for counterpoising and terpoised before use.

may be found

tp ://

for weighing

ht

Experiment

7.

— {a)

Appendix A,

in

§§ 19, 21.

WEIGHING.

Weigh

a small object such as a bottle, stone, Weigh to a decigram, and express

or piece of lead on the trip scales.

the result in grams and a decimal fraction of a gram.

Record the weight

in the proper place below. {b) Verify the result if one on the same scales.

balance,

(c^

is

Results

:

by weighing the same object on an accurate

available

;

if

one

is

not available, repeat the weighing in the proper place below.

Record the weight

—

^ ^

GrAMo.

Weight Weight

of object on trip scales of object on balance ^

Error in weighing

Introduction.

Form is

of

Record

of

Experiments.

— No one form

adapted to every experiment, but

at least

(^?)

13

all

of record

forms should include

a short description of the operation, {b)

all

weights and measurements, and {c) answers to all questions. The following will serve as a preliminary model :

—

WEIGHING. 7.

— A small bottle was weighed on the The

trip scales

—

and

vn

Experiment

then on a balance.

following results were obtained

:

Grams.

bottle

on trip scales on balance

ll.

bottle

4a

Weight of Weight of

Every record must,

of

course, include

of the experiment.

It is

the

title

and

often helpful, also, to

.c h

number

em

Error

know the date when a particular experiment was performed. The notes, or record, should be written, as far as possible,

w w

during the performance of the experiment.

8.

— {a)

tp ://

Experiment

w

WEIGHING AND MEASURING. Weigh

a small, dry, clean, empty bottle on

Record the weight

the trip scales.

once

at

in the

note-book.

neck with water and weigh again. Be sure that the outside of the bottle, including the bottom, is dry, before standRecord the result as shown below. ing it on the scale pan. Fill the bottle to the

ht

{b)

{c)

Transfer

all

the water to an empty graduated cylinder.

water into the cylinder without spilling a drop.

Pour the

This can be done by

down a glass rod (see App. A, § 12), or by a movement quick enough to prevent the water from running down the outside of the bottle. Read the exact volume of water in the graduate. Record the result as shown below. What is the rela-

pouring the water preli4ninary

tion between the weight

Form

of

Record

of

and volume of water?

Experiments.

should be somewhat as follows

:

—

— The record

of Exp. 8

Experimental Chemistry.

14

WEIGHING AND MEASURING. Experiment

— A small bottle was weighed empty and then nearly

8.

of water, and the volume of water measured.

full

Results

:

— Grams.

and water bottle, empty bottle

.

.

115.2

.

....

Weight of water Volume of water Weight of volume of water

50 .

.

.

.

.

.

50.0 0.2

4a

Error

cc.

vn

49.8

...

are nearly equal.

(date)

em

The weight and volume

65.4

ll.

Weight of Weight of

of tJiermometric readings

Foi'mnlas for the co7iversion

found

in

Appendix A,

§

23.

w w

will be

II.

.c h

PROBLEMS.

Convert into Fahrenheit readings the following readings on the :

(fi)

40

(c)

70

(e)

-36.6

(/) 643

C^) 720 (//)

860

(0 973

(/) 1000 (k) o

(O

100

Convert into centigrade readings the following readings on the

ht

2.

-5

(d)

tp ://

(a) 60.5

—

w

1.

centigrade scale

Fahrenheit scale (a) 207

:

—

CHAPTER

I.

PHYSICAL AND CHEMICAL CHANGES.

The

matter of the universe

constantly

changing.

vn

is

is

permanent and another substance or kind

When

the result.

is

tion of matter are so ter

is

of

4a

matter

the properties of a given por-

changed that a

different kind of mat-

em

change

ll.

Sometimes the change temporarily modifies the special properties of the matter under examination, but often the

formed, then the change

is

called a chemical change.

changed, then the subMost chemical

.c h

If the properties are temporarily

stance has undergone a pJiysical cJiange.

w

w w

changes are accompanied by physical changes, sometimes So closely related are as causes, sometimes as effects. they that it is often impossible to distinguish them, even for study.

largely

tp ://

Chemistry

is

a

study of these chemical and

physical changes, and, especially, their causes, products,

ht

and attendant phenomena. Preliminary Definitions. in experimental chemistry ties,

so simple that

it is

— Many

of the substances used have exceedingly simple proper-

believed that these substances can-

not be subdivided into simpler ones, and they are therefore

placed in a class by themselves, called elements. familiar

and others

will

become

Some

are

familiar as the experiments

The common metals are elements. Thus copper and zinc have properties which are so simple that chemists Platinum and magnesium regard these metals as elements. proceed.

'5

Experimental Chemistry.

1

may

not be familiar, but they resemble other metals in their

luster, hardness,

power

to

conduct heat and

electricity, as

well as in their chemical behavior toward other elements.

All metals do not have the

same

properties, but the best

known have an undeniable resemblance

to

the familiar

shining substances called metals.

Elements contain no other substances. Zinc is only zinc, if zinc changes into a substance having different properties, the change is due to something else than the zinc. This fact must be remembered in interpreting the experiments in this chapter. A broad knowledge of elements, whether metals or not, is obtained only by extensive study hence the ideas gained in this preliminary investigation will be enlarged by additional experiments.

4a

ll.

vn

hence,

Changes ical

Metals when

in

of the conditions

changes

is

—A

knowledge of accompanying chemical and physHeated.

w w

some

.c h

em

;

necessary as a foundation for the study

especially of experimental chemistry.

w

of chemistry,

An

tp ://

introductory study should be simple and limited, and the

present chapter will be

confined

the changes which metals undergo

to

an examination of are heated

when they

ht

in the air.

Experiment

9.

GENERAL CHANGES.

— Supplies:

Platinum wire, copper wire, magnesium

ribbon, sheet zinc, forceps.

Examine

successively a piece of platinum, copper, zinc, and

magne-

sium carefully enough so that they could be detected with certainty, Then take each successively if seen again under similar conditions. in the forceps and hold it in the upper part of the Bunsen burner flame long enough to produce a definite change. If the change occurs sud-

remove the metal and observe the character of the change. Try Look for simple things, is a definite result. such as change of color, new substances, etc. In examining the zinc denly,

each metal until there

Physical and Chemical Changes.

17

hold the burner at an angle, so that the melted zinc will not drop inside. When definite results have been obtained, answer the following :

—

Are all the metals changed? Are all changed permanently? Give reasons for the conclusion. (3) Examine each product and state briefly how they differ, if they

(i) (2)

do, from the original metal. (4) Since nothing in the metal assisted the heat in causing the

change, what did ? is

necessary to verify any theory of the in

Exp.

9.

ll.

changes

vn

Further study

auxiliary cause of the

Experiment

Supplies:

10.

em

4a

EFFECT OF HEATING A METAL WHEN UNCOVERED AND WHEN COVERED. Porcelain crucible, pronged tripod or

similar support, pointed glass rod (blunt form), lead,

magnesium oxide.

.c h

{a) Put a small piece of lead in a porcelain crucible and stand the If such a support is not crucible on a tripod as shown in Fig. 21.

and ring of an iron stand. few minutes with a low flame,

Heat the crucible

w w

available, use a triangle for a

—

—

tp ://

w

then gradually increase the about 5 cm. high, heat until the bottom of the crucible is hot. Occasionally scrape aside the greenish product with the blunt glass stirring rod.

The heat must

not be

suffi-

cient to melt this product.

Continue to heat

enough of the new While the lead is still molten,

until there is

ht

substance to examine.

^^^^^^'""^^'''^'^^^

firmly grasp the crucible near the edge with the for-

^

^

j^^po^!^^

ceps, and pour out the contents of the crucible upon an iron pan, or a piece of asbestos board, or a block of wood. Compare the product with the unchanged lead, stating briefly the differences. How does the change in the lead resemble the changes in Exp. 9 ? Is (If the crucible is not clean, heat it a similar chemical change? where the lead sticks, and scrape off the softened lead with a file.) com{F) In the same crucible put another piece of lead and cover it it

pletely with

magnesium

stance with the finger. the contents.

The

oxide, pressing

down

Heat the crucible as

the white, infusible sub-

in {a), but

do not disturb

lead should be completely covered during the whole

Experimental Chemistry.

1

operation.

minutes

can form.

formed?

Heat

until

— long enough

it is

produce the greenish powder,

Pour out the contents as before. What, then, assists heat in the chemical changes

Why.-'

Exp. 9 and Exp. lo (a) drawn from Exp. 9? If

The

been melted several if any Has any greenish powder

certain that the lead has

at least to

Does

?

not,

this conclusion verify

in

your theory

modify your notes accordingly.

Exp. 10 gives a clew to the nature of the

result of

considered in the next experiment.

4a

is

ll.

vn

permanent changes which metals undergo when heated in the air, but it does not prove conclusively whether by the change the metals undergo a loss or a gain. This question

11.

— Supplies:

.c h

Experiment

em

RESULT OF HEATING A KNOWN WEIGHT OF A METAL THE AIR. Powdered

iron, zinc dust, crucible

IN

and

support, glass rod used in Exp. 10, crucible block.

w w

{a) Clean and dry a porcelain crucible and weigh Slide

the trip scales.

powdered iron

it

to a

decigram on

into the crucible from a

narrow

smooth paper creased in the middle, until about 3 gm. have been added. (See App. A, § 12.) Do not spill the iron on the scale

w

strip of

The iron should not coat the inside of the crucible, but be heap on the bottom. Wipe off any iron which is on the outside oi" the crucible or on the inside above the heap, before weighing the The iron need not weigh exactly 3 gm., but crucible and contents. Record the weights the exact weight, whatever it is, must be known.

ht

in a

tp ://

pans.

n the note-book, as soon as made, thus:

—

Grams.

Weight of crucible Weight of iron and Weight of

12.2 crucible

iron

.

.

c

15.4 3.2

and from the scales, it should not be carried hand nor by the forceps, but placed in the crucible block which Support the crucible as before and heat it for is shown in Fig. 22. about ten minutes. Heat with a low flame at first and gradually inIn carrying a crucible to

in the

crease the heat.

Finally stand the burner under the crucible, taking

Physical and Chemical Changes. however, that the flame

care,

19 Touch

below the top of the crucible.

is

the metal occasionally with the pointed glass rod

and

if

the

hard, pierce

is

it

crust

cautiously

several places to expose a fresh surface.

in

If iron

pointed end over the and tap the rod gently against the crucible Avoid losing the particles will fall back.

clings to the rod, hold the

so that

anything from the crucible.

After the crucible

is

—

enough to bear the hand without discomfort, weigh again. If the weight has changed, record cool

thus

Crucible Fig. 22. block.

:

vn

crucible

Grams.

15.4

If there is

loss in weight

no change

in weight, heat again,

What

no change, consult the teacher.

The

general result obtained in {a)

Weigh

dust, observing the

same precautions

may be

as in {a)

.

verified

by heating

:

—

13-0 15 -9

2.9

zinc

The zinc must be heated low flame, not more than 5 not stand the burner under off" a white smoke, remove

ht

in

Grams.

crucible

tp ://

Weight of

if still

about 3 gm. of zinc Record thus

it

w

Weight of crucible Weight of zinc and

;

proved by the change

the crucible and weigh in

w w

{b)

is

.c h

weight? zinc dust.

and then weigh

em

Gain or

4a

ll.

Weight of crucible and contents before heating Weight of crucible and contents after heating

with the utmost care to avoid loss.

Use a

cm. high, during the entire heating. Do the crucible, and if the zinc glows or gives This smoke weighs the burner at once.

which cannot be estiAvoid losing any zinc or any of the white product. Heat the crucible for about 10 If there is a change in weight, record minutes, then cool and weigh.

something, and

mated.

thus

If

its

loss

means a

loss in weight

a crust forms on the zinc, break

it

as in (a).

:

Grams.

Weight of crucible and contents before heating Weight of crucible and contents after heating Gain or

loss in

weight

15.9

Experimental Chemistry.

20 If there is

no change, heat again and then weigh What is proved by the change

magnesium,

If

any metal,

lead, copper, or

heated

is

as in

in

The nature

are produced.

weight

mercury, in

Exps. lO and

no change,

if still

;

consult the teacher.

?

fact,

almost

ii, similar results

of the interacting substance,

as far as the above experiments show,

is

unknown, but

4a

ll.

vn

whatever it is, it has combined with them in such a way It forms chemical comas to change their properties. pounds of which the metal is one part and this " unknown substance" is another part. If the process could be reversed by decomposing one of these compounds and getting this ''unknown substance," it could be studied, and nature would throw some light on the real cause of the changes which metals undergo when heated in the air.

II

—

of the is

compounds

— the

products of Exps. lo and

.c h

None

em

its

Fortunately

such an experiment.

suited to

we

w w

have available the very compound used by the chemist who discovered this ''unknown substance." It is a red

formed by heating the metal mercury in the powder was formed from zinc, the black film from copper, and the greenish powder from When heated, this red powder decomposes, into a lead. well-known metal and a gas which is the "unknown is

just as the white

ht

tp ://

air,

w

powder and

substance."

PRODUCTS OBTAINED BY HEATING THE RED POWDER.

—

Experiment 12. Supplies: Apparatus shown in Fig. 23, pneumatic trough, small bottle, iron stand and clamp, the red powder, splinter of soft

The

wood, ignition tube.

ignition tube tions in

was made in Exp. may be made according to

delivery tube for this experiment is

not available,

Appendix A,

§

i.

If

it

the ignition tube

attached to the delivery tube as

shown

is

in Fig. 23

not large, ;

if it is

3.

If the

the direcit

may be

rather large,

Physical and Chemical Changes. then

it

must be attached

to the delivery tube

21

by putting the rubber con-

nector inside the ignition tube, the upper end of the delivery tube

4=,

itsell

Fig. 23.

Apparatus

for heating the

em

4a

ll.

vn

r-^

red powder and collecting the gaseous

.c h

product.

lemaining, as before, within the connector

connection

shown

cross section of such a

powder from a paper into the and connect with the deHvery tube. (See

a Httle of the red

ignition tube

A

in Fig. 24.

w w

Shp

is

The

tp ://

w

App. A, § II.) Clamp the tube near the top so that the apparatus shall have about the position shown in Fig. 23. Tap the tube gently to spread out the powder in the tube. outer end of the delivery tube reaches just below the

shelf of a pneumatic trough arranged to collect the gas Fill

ht

over water.

the bottle full of water, invert

it,

and

on the shelf near the hole. (See App. A, § 15.) Heat the whole ignition tube with a low flame at first, gradually increasing the heat where the red powder is located. As the heat increases, bubbles pass up through stand

it

the water.

Reject the

first

few,

which are

air,

then

i

v^

fU

slip

If the powder the bottle over the hole in the shelf. " crawls up the ignition tube, tap the tube gently until ''"'

the contents slips back. heat more strongly.

Do

If the evolution of

gas ceases,

not wave the burner back and

forth, but apply the heat steadily by a low flame which envelopes that part of the tube containing the powder.

Fig. 24.— Section of inside an

connector.

Experimental Chemistry.

22

Avoid heating the end of the tube, as

it

often

is

so thin that

jt

melts.

Collect the bottle at least half

the bottle from the shelf,

full

of gas and remove

it

thus

:

Slip

keeping the mouth under water, and

still

cover the mouth with a piece of moistened filter paper. Keep hold of the paper with one hand and with the other invert the bottle and stand covered, on the desk.

it, still

Remove

the delivery tube at once from

the trough to prevent the water from being

drawn up

into the hot

apparatus.

4a

ll.

vn

The gas from the red powder is the " unknown substance " which was taken from the air by a certain metal when heated in the air. Examine the deposit on the inside of the ignition tube. If its nature is What is it? Test the gas doubtful, pour it out on a block of wood. thus Light a splinter of wood, let it burn a few seconds, then blow it out and plunge the glowing end into the gas in the bottle. What happens ? Remove the splinter, if there is any decided change, and once more it,

while glowing, into the gas.

(i) Is the gas air?

A

substance

erties

Why not?

the gas have

come from

the following

usually identified by comparing

is

with those of some

:

—

originally?

w w

Where must

(2)

Answer

.c h

plunge

em

:

its

prop-

known substance with which

it is

tp ://

w

suspected to be identical.

ht

IDENTIFICATION

Experiment

13.

OF THE GAS OBTAINED FROM THE RED POWDER.

— Obtain

istic

a bottle of oxygen from a gas holder

Has oxygen the same characterit. property as the " gas obtained from the red powder " ? What one

and plunge a glowing

splinter into

conclusion can be drawn from this experiment?

Definitions.

— An Oxide

one other element, such

is

a

compound

of

oxygen and

as iron, zinc, or lead.

Chemical

action is a term applied to all classes of chemical changes, such as the addition of oxygen to iron, or the decomposition of

the red powder into oxygen and

mercury.

The

Physical and Chemical Changes. cause, accompaniments,

'

23

and products of chemical action

be constantly studied.

LABORATORY EXERCISE. 1.

2.

3.

Summarize the

results of

I.

Exps. 9 to 13 into a concise argument.

Name all the oxides studied or used in this chapter. What is the chemical name of the red powder? CLASS-ROOM EXERCISE.

V.

Discuss the states and properties of matter. Physical and chemical changes.

ll.

1.

2.

vn

will

(d)

What

is

4a

(a) Give three illustrations of both occurring in every-day

life.

supposed to cause many chemical changes?

4.

Manipulation.

.c h

em

3.

change constant or intermittent? (c) What aids and what retards chemical change ? Review the Metric System.

and porcelain. Bunsen flame.

(a) Precautions in heating hard glass effective use of

(c) Give the successive steps in collecting gases. Give evidences of chemical action observed in Exps. 9

ht

tp ://

w

5.

Most

w w

(d)

to 13.

Is

CHAPTER

II.

OXYGEN experiments in Chapter I. teach that one important Subsequently, air will be is oxygen.

vn

The

constituent of the air

em

4a

ll.

examined with special reference to its composition. We shall now study oxygen, which is the most important of the few simple substances to which the matter of the universe may be reduced.

Experiment

14.

.c h

PREPARATION AND PROPERTIES OF OXYGEN. Retort, ring and

Supplies:

w w

trough, six bottles (about 250 cc. capacity),

wood, deflagrating spoon,

filter

roll sulphur, piece

wire, short piece of wire picture cord

stand, pneumatic

paper, splinter of soft

of charcoal fastened to a

unwound

at

one end, magne-

chlorate,

and

15

gm.

ht

tp ://

w

sium ribbon, 15 gm. of crystallized potassium of coarsely powdered manganese dioxide.

Fig. 25.

Procure

all

— Apparatus

for the preparation of

oxygen.

the supplies before attempting to prepare the oxygen.

Arrange the apparatus as shown

in Fig. 25,

24

and

collect the gas ovei

Oxygen. (See App. A,

water.

be

dioxide should

25

The potassium chlorate and manganese from pieces of cork, paper, straw, or wood

§ 15.)

free

the retort must be dry and clean and provided with

a tightly

Mix

fitting glass stopper.

and manganese dioxide on a piece of smooth paper, and pour the mixture into the potassium chlorate

the retort as

shown

in Fig. loi.

Invert the bottles

of water in the trough, and have the it

can be conveniently reached.

filter

full

paper where

Adjust the apparatus,

not collect the gas before

the stopper for a leak.

covering each

when

full

if

not at

Collect

all,

six

it

bubbles

evolved too

then examine bottles of gas,

with a piece of wet

em

rapidly, lessen the heat;

If the gas is

ll.

Do

through the water.

4a

the mixture. freely

vn

and heat the bare retort carefully with a low flame. Direct the heat upon the part of the retort containing

filter

paper, as soon as taken from the trough.

When

the gas has been collected, remove the neck

.c h

of the retort immediately from the water, lest the cold retort, as

w w

water be drawn up into the hot bulb of the the gas contracts.

Proceed at once to study the properties of oxygen by the following experiments :

—

wood into one Remove the splinter, if there is any change, and repeat as many times as possible. Describe the result. What property of oxygen does this experiment show? What is the essential difference observed be-

tp ://

ht

bottle.

w

{a) Thrust a glowing splinter of

tween burning

in air and in oxygen? Put a small piece of sulphur in the deflagrating spoon (Figs. 26 and 27), hold the spoon in the flame

{b)

until the faint blue flame of the

bufning sulphur can be seen, then lower the spoon into a bottle of oxygen. Describe and explain any change in the flame. Smell

Fig. 26. — Deflalittle toward the grating spoons. what the odor reminds you. To what class of compounds, in all probability, does this vapor belong? (If the odor of the burning sulphur is disagreeable, plunge the spoon into water, or remove it to the hood.)

the vapor cautiously by wafting a

nose,

and

state of

Experimental Chemistry.

i6

Hold the charcoal

{c)

then lower

it

in the

flame long enough to produce a glow,

Describe and explain any change

into a bottle of oxygen. in

the appearance

of

the

How

charcoal.

chemical change resemble that in {b)

does

the

?

{d) Dip the unwound end of the picture cord into containing the melted sulphur

the deflagrating spoon

used above. light

The

If the

sulphur on the end

and quickly lower

it

picture cord should take

picture cord

is

is

not burning,

into a bottle of oxygen. fire

and burn

brilliantly.

chemically the same as iron.

Can

the

vn

A

it,

em

4a

ll.

change be explained similarly to that in {b) and (^) ? Is there any visible, material proof of change besides the vapor from the burned sulphur ? Does the product of the chemical change belong to the same class as the products in (/;) and {c) ? {e) Hold one end of a piece of straightened magnesium ribbon about 10 cm. long in the forceps, light oxygen.

it

into a bottle of

.c h

the other end, and instantly lower

In what general ways does the result resemble

those obtained in the other experiments with oxygen?

w w

What conclusive evidence is there that the magnesium was chemically changed ? How does the product resemAre ble that formed by burning magnesium in the air?

w

the products identical

?

tp ://

Write a short account of

this

experiment in your

notebook, including a sketch of the apparatus used for

(or deflagrating spoon)

what

in the order of the

letters,

and answering

made from a piece of copper wire and a piece of crayon having a cavity at the

end.

upper

Arrange the notes someabove directions, using the same

the preparation of oxygen.

ht

FlG. 27.— Combustion cup

all questions.

LABORATORY EXERCISE. 1.

2. 3.

4.

II.

Summarize the properties of oxygen.

What is its most characteristic property? What oxides were formed in Exp. 14? From what class of substances might oxygen be

prepared ? 5.

6.

From what substances have you previously prepared What chemical change probably takes place when

burns ?

it?

a substance

Oxygen. 7.

27

contains something besides

If air

oxygen, what must be the

general properties of this other constituent?

It

was shown

in the air

the gain

it

is

composed oxygen,

in

Exp.

that

1 1

when

a metal

is

heated

gains in weight, and in Exps. 12 and 13 that

new substance, The experiments with

actually due to the formation of a of the metal

also,

show that

and oxygen.

gas unites easily and vigorously

this

vn

with metals, like iron and magnesium, and with other sub-

and charcoal (chemically known as These oxides belong to a large carbon), forming oxides. The expericlass of substances called Chemical Compounds. ments thus far performed show that chemical compounds are produced under special conditions, and that they possess specific properties.

em

4a

ll.

stances, like sulphur

may be

Additional facts

learned about

oxygen

to

two of

its

compounds.

w w

of

.c h

chemical compounds by studying the mathematical relation

THE COMBINATION OF OXYGEN WITH MAGNESIUM.

— Method:

w

Experiment

15.

Heat a weighed quantity of magnesium

covered crucible at a low temperature, weigh the product, and the gain will be the weight of oxygen which has combined with the known

tp ://

in a

weight of magnesium. :

Porcelain crucible and cover, powdered magnesium, for-

ht

Supplies

pronged tripod or similar support, crucible block. Process: Clean and dry the crucible and cover, and weigh both Record the weight as shown below. Weigh in the crucible together. from 0.4 to 0.5 gm. of magnesium, taking care to weigh to a centigram Record the weights thus the exact amount.

ceps,

:

—

Grams.

Weight of crucible, cover, and magnesium Weight of crucible and cover

.

.

Weight of magnesium 1

These and

similar results

which

will

13.32

^

12.81

0.51

be given are solely

for illustration.

Experimental Chemistry.

28

Stand the crucible on the tripod, as shown in Fig. 28, and heat for minutes with a flame which just touches the bottom of the crucible.

five

Grasp the cover firmly by the ring with the clean and if the magnesium glows, cover the crucible

lift it,

forceps, cautiously

Repeat

instantly.

glow mass

this operation at frequent intervals, until the

dull red

is

and ceases

to spread through the

then adjust the cover so that a small opening

between the cover and the

left

strongly for ten or fifteen minutes.

is

and heat

crucible,

If the contents

Take

for five minutes.

by a

ll.

crucible

tripod.

The

operation

is

high

roughly speaking, the flame should reach ^ tlie magnesium does inside.

outside as

,

.

complete when the product

When

the crucible gradually. to weigh.

; '

,

,

as

4a

—

crucible supported

em

28.

care not to upset the cover

by accident or insecure handling with the forceps. Covered At no time should the flame touch the cover of the

cool

Weigh, and record thus

Weight of crucible, Weight of crucible,

enough

:

is

—

it is

cool

1

Cool

enough Grams.

and contents, after heating cover, and contents, before heating cover,

•

•

1

gray or white.

to handle,

.c h

Fig,

vn

has ceased to glow, heat the crucible, uncovered,

.

13.66

.

.

13.32

Weight of oxygen which has combined with the magnesium

0.34

w

w w

.

crucible again strongly for five minutes, cool,

tp ://

Heat the uncovered

weigh again as before. If the weight is not the same, continue the last two weights are approximately the same.

ht

Calculation:

magnesium, the proportion

—

and until

Since 0.34 gm. of oxygen combined with 0.51 gm. of which they combined may be expressed by the

ratio in

.w.x x= 1.5

0.34 :o.5i .'.

Class average

=

—

This result means that gram of oxygen one and one-half grams (approximately) of magnesium are necessary to form a chemical compound. The truth of this statement is more vivid when the class average is known for if the work has Discussion of Experiment 15.

for every

;

Oxygen.

29

been done accurately, the class average

will

be drawn later from this experiment, but

will

agree closely

More important conclusions

with the theoretical result.

it is

sufficient

grasp the idea of definite relations by iveigJit exist between which the components of a chemical comat present to

pound.

THE RELATION OF OXYGEN TO POTASSIUM CHLORATE. Experiment

— Method:

vn

Heat a weighed quantity of potassium all the oxygen is evolved, and the be the oxygen which was in chemical combination in the 16.

loss will

ll.

chlorate in a covered crucible until

potassium chlorate. :

Crucible and cover, forceps, support (as in Exp. 15), dry, chlorate, crucible block.

4a

Supplies

powdered potassium

Weigh

Weigh

to a centigram the exact

—

Weight of Weight of

amount

crucible, cover,

crucible

which

little

ht

spatter a

.

.

chlorate

w

tp ://

as the oxygen,

may

Grams.

and potassium chlorate

Arrange the apparatus as shown heating somewhat as in Exp.

it

and record the weights

and cover

Weight of potassium

and

taken,

.c h

:

w w

thus

the crucible and cover as in Exp. 15, and weigh 1.5 gm. of dry, powdered potassium chlorate.

about

em

Process:

in the crucible

Regulate the heat,

if

is

15.

1.34

in Fig. 28,

it

and proceed with the

The potassium

liberated, bubbles

chlorate

first

melts,

through the molten mass,

potassium chlorate up on the inside of the cover. possible, to avoid this difficulty. Remove the

cover with the clean forceps occasionally, and

sium chlorate, lay

15-34 14.00

(ring side

if it is

coated with potas-

down) on a block of wood,

deftly loosen

the thin layer with a pin or sharp rod, then hold the cover over the crucible

rod. finger,

If

and gently scrape the pieces off into the crucible with a sharp any fall upon the desk and are touched with the moistened

they will cling to the finger and

may be

returned thereby to the

will be slow. As and the action apparently Increased heat, however, drives off more oxygen. As soon as stops. the second evolution of oxygen is passed, remove the cover, lay it (ring

crucible.

Regulate the flame so that the bubbling

the temperature increases, the

mass

solidifies,

Experimental Chemistry.

30 side

down) on a block

wood where

of

be

will

it

complete when the product

is

safe,

and then heat

The decomposition

the crucible strongly for five or ten minutes.

and

perfectly white

non-crystalline,

is

and

not changed in appearance by a flame nearly as high as the top of the crucible.

Cool gradually, and when cool, weigh the crucible, cover, and

contents, as before.

Record the weights thus

:

—

Grams.

and contents before heating cover, and contents after heating

crucible, cover,

.

15.34

crucible,

.

14.82

Weight of oxygen

vn

Weight of Weight of

0.52

lost

ll.

Heat again strongly for ten minutes, then cool and weigh as before. weight is the same as after the first heating, proceed with the calculation if not the same, heat and weigh until two successive weights

4a

If the

;

:

From

gm.

1.34

oxygen was obtained, or

—

1.34

:

em

heat to constant weight.

i.e.

Calcidatwn

of potassium

chlorate 0.52

gm.

of

x

.c h

are the same,

0.52

:

100

:

:

X=

39.3 per cent.

=

per cent.

w w

Class average

—

This result means that a oxygen by weight can always be ob-

w

Discussion of Experiment 16.

tp ://

definite proportion of

tained from potassium chlorate.

may produce

Individual experiments

slightly varying results, but

an average of

As

ht

several results will be substantially identical with the theory. in

Exp.

15,

the full significance of the result

is

not yet

apparent, and later the experiment will be discussed in

its

This experiment is intended to teach, widest application. at this stage of the experimental work, that definite zveigJit relations are essential to chemical

compounds.

a Liter of Oxygen will be serviceable, later, fundamental facts. Before it can be determined, however, the contents of Appendix B should be

The Weight

in explaining

mastered.

of

Oxygen. PROBLEMS.

III.,

31

IV., v., VI.

See Appendix B, §§

2,

CLASS-ROOM EXERCISE. See Appendix B, §§

5,

II.,

7.

III.,

IV.

5, 6, II.

WEIGHT OF A LITER OF OXYGEN. Experiment

17.

— Method:

Weigh

the volume of water displaced

Apparatus : The apparatus

is

shown

in Fig. 29.

vn

by generating a known weight of the gas.

A

is

a test tube

containing a mixture of potassium chlorate and manganese dioxide

a

bottle

water;

it

to

is

two-hole

be

filled

provided

rubber

through which pass

B

with

with

a

stopper,

F

and

C,

it

em

is

;

ll.

by a small rubber stopper.

F

4a

attached to the bent tube

.c h

is

the latter being the glass portion of the whole delivery tube,

while

C

is is

rubber.

A

w w

CC,

Hofmann screw

attached at

point E. A large bottle, D^ serves to catch the w^ater forced over from B through by the oxygen generated Fig. 29. — Apparatus for determining the in ^. The bent tube /^ retains weight of a liter of oxygen. any moisture driven over from A^ and is weighed with A. All joints must be air tight. Process: (i) Fill A two-thirds full of a mixture of manganese dioxide (2 parts) and potassium chlorate (3 parts). Each substance must be powdered and free from organic matter {e.g. paper, cork, straw). The mixture should be dried by heating it in an oven to about 110° C, Push a little on a radiator or on some convenient heated object. glass wool, or shredded asbestos (previously ignited to a red heat), into the tube to hold the contents in place. The tube must be free, inside and out, from loose particles of manganese dioxide, or other matter clean, in other words. which might be rubbed off after the weighing Weigh Weigh the empty, dry, clean bottle, D, to a centigram. to a decigram on the trip scales.

ht

CC

tp ://

w

the

—

AF

Experimental Chemistry.

32 (2) Fill

tighten the

B

with water nearly to the neck.

Hofmann screw

first,

then hard

if

;

with water and

from running out. into the bottle,

water rises in F^ loosen the screw at

remove A, and blow gently

slightly,

CC

Push the stopper

Insert AJ*^ into the stopper of B.

slowly at

Fill

to prevent the water

into

E

F io force the water back into

properly adjusted, the water should be in B and CC, but not Replace A, taking care not to crush the thin glass by pushing it If the apparatus is too hard upon its stopper open the screw at E. It should be adjusted until air tight. tight, the water will not flow out.

When

B. in

B\

vn

;

is

just hot

enough

about three-fourths

to cause a gentle flow of water into

decrease the heat gradually.

full,

em

A

Heat

D

4a

ll.

Leave the screw open. (3) Heat A gently with a low flame, beginning at the closed end and keeping the flame back of any moisture which might be driven out of the mixture. The liberated oxygen will force the water from B into D.

appears near the top of the mixture, heat behind

While

tube. in

D

F or cool A

;

A

is

it,

and

When moisture

either drive

it

so gradually that the moisture will not shatter the

.c h

over into

D. If

cooling sufficiently to weigh, stand a thermometer

When A

also read the barometer.

is

cold, raise

B

until the

C

at the

ht

tp ://

w

is

w w

tight and remove it same level in B and D, pinch from D. Read and remove the thermometer. Dry D on the outside, if necessary, and then weigh it, using the same large weights as before the gain in weight (in grams) of D gives the volume (since i gm. of water =1 cc.) of oxygen liberated. Weigh AF\ its loss in weight is the weight of the oxygen which passed into B. Calculation : The observed volume must be reduced to the volume it would occupy, if it were at 0° C, 760 mm., and in the dry state, i.e. (See App. B, § 7.) This is done by reduced to standard conditions.

water

the formula

—

^,^

V-(P--^) (i + .00366/)

760

Substitute the proper values in this formula, and solve for

rected volume of oxygen liberated.

F= Since

i

1.

cc.

contains 1000 cc, then

= 1000

1.

liberated. of oxygen ^°

F— the

cor-

Oxygen. The

weight of oxygen liberated

3;^

found thus

is

—

:

Grams.

Weight of A/"' before liberation of oxygen Weight of A/^ after liberation of oxygen

Weight of oxygen Therefore the weight of

i

1.

Wt. of oxygen

liberated

.

.

of oxygen equals liberated

_

gm.

Substitute in this formula the proper values. :

—

Tabulate the

total result

1

OF OXYGEN.

L.

— Combination

may mean

a process or

its

tp ://

Definitions.

w

w w

.c h

em

WEIGHT OF

4a

ll.

of the experiment thus

vn

Vol. of oxygen liberated

Thus the process employed in Exp. 1 5 is called magnesium oxide, is also a combination of magnesium and oxygen. The

product.

combination, and the product,

ht

called

context, however,

synonym of the literally means "

a putting together."

the separation of

These

usually eliminates any ambiguity.

process, combination,

a

is

A

Synthesis, which

Decomposition means

chemical compound into

its

parts.

parts are called decomposition products, or, better,

Components.

And

as decomposition

complete, these components

pounds. literally

A

may be

may

be partial or

elements or com-

synonym of decomposition is Analysis, which means "a breaking up." Thus in Exp. 16, the

Experimental Chemistry.

34

potassium chlorate was actually broken up into the ment, oxygen, and the compound, potassium chloride.

ele-

an accurate chemical examination.

It

Determination

may

be

is

analytical,

synthetical,

weights, or volumetric

gravimetric

— involving volume.

A

— involving

Experiment i6

was a gravimetric determination of the per cent of oxygen Residue is usually the product in potassium chlorate.

A

vn

remaining after something has been removed from a compound or a mixture. Thus in Exp. i6 the residue is

4a

of

Chlo-

compounds, each member of the element chlorine and one other ele-

ride belongs to a class of

which consists

A

ll.

the potassium chloride remaining in the crucible.

em

Chlorides bear the same relation to chlorine as

ment.

oxides bear to oxygen.

— Oxides

were

mentioned

in

.c h

Oxidation.

Chapter

I.

process of forming an oxide, or in general of adding oxygen to an element or compound, is called Oxidation.

w w

The

The 15 was an oxidation of magnesium. heated in the experiments performed in Chap-

metals I.

easily

were

also oxidized.

Compounds which

tp ://

ter

w

Thus Exp.

are

called

oxidizing

agents

;

thus

yield

nitric

oxygen acid,

a

ht

compound to be studied later, decomposes easily, and one of the decomposition products is oxygen, which often immediately combines with some other element or Oxidation is an important chemical some compound. operation.

Law of

—

Experiment 1 by Weight. showed that when magnesium is heated so that it has access to oxygen the two elements combine in the ratio of I This also means that the product, magnesium to 1.5. oxide, always contains 1.5 times as much magnesium as oxygen by weight. Experiment 16 shows that potassiucn Definite Proportions

Oxygen.

35

A vast

chlorate always yields about 39 per cent of oxygen. number of experiments has verified these, and

similar

The

fact of

results,

the

in

proportions

definite

experiments (15 and others,

is

other compounds.

case of

by weight revealed 16), and extended a law

the result of

known

Definite Proportions by Weight."

It

by

these

cover

to

two

many

Law

of

was estabHshed

as

the "

as

the outcome of a controversy between two chemists, Proust Berthollet,

which lasted from 1799 to 1806, though had previously appeared.

vn

and

isolated suggestions of the law

A

:

chemical compound ahvays contains the same elements same proportions by weight.

em

in the

Or,

chemical compoimd has a definite composition by weight. is one of the foundation stones of chemistry.

.c h

A

—

ll.

stated thus

4a

The law may be

w w

This law

Compounds and Mixtures. with Berthollet, showed

— Proust,

his

in

w

conclusively the

discussion

distinction be-

tp ://

tween mixtures and compounds. The "gradual changes " found in the substances analyzed by Berthollet were shown by Proust to be due to the fact that Berthollet analyzed mixtures masses contai7iing ingredients in varying pro-

ht

—

portions.

they

Mixtures

may have any

are

the

opposite

composition

their

of

compounds

ingredients

are not held together by that fornr of energy called chemical ;

A

or attraction. mixture of sulphur and iron can be easily separated by mechanical means, but in a

affinity,

compound

of iron and sulphur the components are held together by a force which does not yield to the influence of a solvent or a magnet, nor to any other purely physical agent.

Experimental Chemistry,

^6

CLASS-ROOM EXERCISE. 1.

VI.

Additional study of oxygen. (a) Occurrence {d) (c)

and

distribution.

Chemical relation Liquid oxygen.

to plants

and animals.

(^) Uses. (e)

Historical.

vn

2.

Preparation on a large scale.

(a) Discovery of oxygen.

Scheele's and

life.

Lavoisier's actual

CO very.

whom

so called,

and why.

em

(d) Names of oxygen, by 3.

contribution to the dis

4a

{c)

ll.

(d) Essential facts of Priestley's

Combustion.

(a) Theories of Becher and Stahl.

(c)

Manipulation.

w w

4

Present views.

.c h

(d) Lavoisier's work.

(a) Rules for weighing.

tp ://

(<^)

Heating and cooling porcelain. General precautions in accurate experiments. Sources of error in Exps. 15 and 16, how detected,

w

(d) (c)

avoided, and remedied.

5.

Elements and compounds.

ht

(a) Definition of each. (d)

Enumerate

all

the elements and

compounds thus

far

used

or studied.

(c)

What compounds have been made in the previous experiments? What compounds have been decomposed?

(d) Define and tion,

illustrate

:

a mixture, combination, decomposi-

determination, residue, oxide, oxidation, chloride,

component. 6.

Law

of Definite Proportions by Weight.

(a) Historical development. (d)

Statement

(c)

Illustrations.

in several different forms.

Oxygen. PROBLEMS.

37 VII.

How many

grams of magnesium will exactly combine with 16 With 32 gm. of oxygen? With 79 gm. of oxygen? 2. How many grams of oxygen will exactly combine with 24 gm. of magnesium? With 48 gm. of magnesium? With 90 gm. of magnesium ? 1.

gm. of oxygen?

What

3.

weight of oxygen gas could be obtained by decomposing What weight of oxygen, if the potas-

200 gm. of potassium chlorate?

weight of potassium chloride, what would be the difference in the

its

4a

of

ll.

vn

sium chlorate had contained 10 per cent of an impurity? 4. What weight of oxygen gas could be obtained from 100 gm. of pure potassium chlorate? If the chlorate used contained 12 per cent

.c h

em

amount of oxygen obtained ? 5. If a liter of oxygen weighs 1.43 gm., what will be the weight of oxygen in a room 25 m. long, 17 m. wide, and 15 m. high? 6. How many liters of oxygen can be obtained from 122.5 S^- ^^ potassium chlorate? From 255 gm. of potassium chlorate, allowing 2 per cent for impurities in the potassium chlorate

A

7.

no gas remains.

{c)

ht

(d)

is

burned

What weight of oxygen is produced ? What volume of oxygen is produced? What weight of magnesium is required? What weight of magnesium oxide is produced?

w

(d)

tp ://

(a)

magnesium

w w

posed, the oxygen collected, and until

?

quantity of potassium chlorate weighing 721

gm.

is

in the

decomoxygen

CHAPTER

III.

HYDROGEN.

The

element hydrogen

vn

is a gas under ordinary condiwas recognized as a ''peculiar and distinct substance " in 1766 by the English chemist Cavendish. It is a component of many compounds, and is the standard of

tions.

4a

ll.

It

Hydrogen was

em

several scientific measurements.

prepared by the interaction of an

first

.c h

acid and a metal.

PREPARATION OF HYDROGEN BY METALS AND AN ACID.

— Supplies:

w w

Experiment filings, dilute

18.

Test

tubes,

granulated

zinc,

iron

sulphuric acid, dilute hydrochloric acid.

w

{a) Put a few pieces of granulated zinc in a test tube and cover dilute sulphuric acid.

tp ://

them with

A

gas

will

bubble through the

liquid.

After a minute or two test the gas by holding a lighted match at the

mouth of the

test tube.

Describe the

result.

Repeat («), using dilute hydrochloric acid. Is the final result the same ? If not, repeat both {a) and (Jb). (^) Put a little iron filings in a test tube and cover them with

ht

{b^

dilute sulphuric acid.

Test the gas evolved, as

in {a).

Is

it

the

same

gas? (^d)

Repeat

before.

What istic

using dilute hydrochloric acid, and test the gas, as

same gas ?

it

is

the source of the hydrogen?

properties

The

(^),

the

Is

What

are

its

most character-

?

heard in some, perhaps all, of the above experidue to impure hydrogen. What, in all probability, is the impurity? Does the observation suggest any danger in working with hydrogen? What is the simplest way to avoid the danger?

ments

slight explosion

is

38

Hydrogen. hydrogen than scale on larger a preparation

The

of

its

specific nature of

39

may in

be learned from its Exp. i8 and a study

properties.

PROPERTIES OF HYDROGEN. Experiment

19.

— Supplies:

Hydrogen generator,

25

gm. of granu-

lated zinc, dilute sulphuric acid, pneumatic trough, five bottles (each

250 cc), taper.

shown

in Fig.

30

B

is

is

a rubber connector

Q

E

about 4 cm. long. is a delivery tube of

500 cc flask

C is

B

its

w

w w

end is level with the bottom of the flask. The flask stands on the desk, and E dips into the pneumatic

.c h

such length that

a.

4a

made

is

a safety tube.

em

bend which was D in Exp. 2.

gle

A

vn

is

ll.

Apparatus: The generator

provided with a two-hole rubber stopper. the double right an-

tp ://

trough.

Precaidions

All

:

II

must be tight. The stopper must fit perfectly, and both B and C must turn with

ht

joints

pushed flask. left

the

in

the

after

difficulty

stopper

has

been

well into the

Acid must be the bend of

safety

tube

Fig. 30.

— Hydrogen generator.

to

(See App. A, §5.) All about the point indicated by the dotted line. flames, large and stnall, should be extinguished in the vicinity during mixtures of air and hydrogen, when Save the contents of the generator for Exp.

this experiment, because

ignited,

explode violcjitly.

20.

Experimental Chemistry.

40

Incline the flask

Process:

Do

not drop

stopper with

in

it

— the

and

bottom

slide the zinc into is

and may

thin

it

from a paper. Insert the

crack.

tubes by holding the flask by the neck in one hand

its

and with the other working the stopper slowly" into the flask. Adjust is on the bottom of the the flask and delivery tube so that the end of pneumatic trough and under the hole in the shelf. Have the bottles filled with water and inverted in the trough, and filter paper ready to

E

cover the bottles of gas.

Pour enough

dilute sulphuric acid

through the safety tube into the

vn

cover the zinc, taking care to leave some acid in the lower bend of the safety tube. This latter precaution prevents the gas from flowing if at any time the gas should flow backout the back of the apparatus

ll.

flask to

;

more acid

little

into the bend.

If

down Remember, how-

the acid will not run

4a

ward, pour a

the safety tube, loosen the stopper for an instant.

few minutes interact,

will

may admit air, and the gas evolved for the next As soon as the acid and zinc begin to

em

ever, that this operation

be impure.

hydrogen

will

Allow the action to proceed

be rapidly evolved.

several minutes to free the apparatus from

then collect

.c h

air,

As

of gas over water, as in the case of oxygen.

remove and cover them with wet filter paper. collected, remove the generator to the hood. study the properties of hydrogen as follows been

Uncover a

:

tp :// Remove

—

When

the gas has

Proceed at once to

an instant and then drop a lighted match

Describe and explain the

into the bottle. {b)

bottle for

w

{a)

w w

full,

five bottles

fast as the bottles are

result.

the paper from a bottle of hydrogen and allow

remain uncovered

for three

minutes

— by

the clock.

it

Then show

to

the

ht

presence' or absence of hydrogen by dropping a lighted match into the Explain the result. bottle. {c)

thus

:

Verify the result in

Hold a

bottle

over a bottle of

(J?)

of air

hydrogen,

remove the paper from the hydrogen bottle, then bring the bottles into the relative

shown ia Fig. 31. Hold them there for a minute

positions Fig. 31.

hydrogen.

or two, then stand the lower

on the desk, cover the upper one with wet filter paper and stand on the desk. Drop a lighted match into each bottle. What has

bottle it

— Pouring

Hydrogen. become of the hydrogen? {b) and (0 ?

What

41

property of hydrogen

is

shown by

{d) Read the directions carefully and watch all parts of the apparatus for definite residts. I nvert a bottle of hydrogen, remove the paper, and thrust a hghted taper up into it. Withdraw the taper slowly and

then insert

it

Does the hydrogen burn

again.

the taper burn

when

When

in the bottle?

If so,

?

where

out of the bottle?

Does

?

Feel of

Repeat with the the neck of the bottle, and describe and explain. remaining bottle of hydrogen. What three properties of hydrogen are in

{d)

?

Exp.

in

your note-book the generator used to prepare hydrogen

4a

Sketch

1.

19.

3.

What

4.

Why

How may 5.

is

em

Summarize the properties of hydrogen. is its most characteristic property?

2.

there danger of an explosion in generating hydrogen?

the danger be averted?

From what

.c h

in

III.

ll.

LABORATORY EXERCISE.

vn

shown

class of substances

—

may hydrogen be prepared?

each other,

is

called a Reaction.

come together there

tp ://

sulphuric acid

w

to

w w

The mutual chemical action which Chemical Reaction. results when two or more elements or compounds are added Thus when is

zinc

and

chemical action, ap-

ht

Inasparent so far only by the formation of hydrogen. much as every experiment involves one or more reactions, an examination of the reaction which takes place in the

preparation of hydrogen will serve as a preliminary study Not every fact about a reaction can be proved of reactions. at the outset.

Certain fundamental facts are always

util-

by chemists. For our present purpose, we must regard zinc as an element and sulphuric acid as a compound Now in this reaction of hydrogen, sulphur, and oxygen. the zinc and hydrogen exchange places, and the result is and zinc already shown the formation of hydrogen

ized

—

sulphate.

Furthermore,

we can prove

—

that a definite rela-

Experimental Chemistry.

42 tion

by weight

between the zinc used and hydrogen

exists

The

produced.

present problem, then, has two steps: (i)

the identification of zinc sulphate as the second product of the reaction, and (2) the actual determination of the relations by weight between the interchanging zinc and

hydrogen.

— The

identity of an element or a

by subjecting and comparing the chemicals various

it

compound

is

to the action

results with the

ll.

of

i.e.

vn

Tests.

established by a Test,

Sometimes the

4a

recorded properties of the substance under examination. test is a single operation,

em

different examinations are necessary.

sometimes several

The

test for

zinc

sulphate involves two distinct steps: (i) the identification

group

to

which

it

determination

belongs

— the sulphate group, and

.c h

of the

(2) the

of

the

kind of sulphate,

i.e.

the

sulphate from If the

w w

establishment of those properties which distinguish zinc

in

it is

tp ://

ht

Crystallization. purified.

lization.

A

Most

is

a

solid substances are

air,

be tested must is

much

more soluble

in

hot

a hot liquid on cooHng will

solid in solution. is

first

crystal-

of the dissolved solid, especially

is

If the

if

the

hot liquid

deposited in masses having

called Crystallization,

said to Crystallize.

the

to

or less definite geometrical form, called crystals.

This operation is

Hence

cooled slowly, the solid

more

nature.

— Most substances

some

liquid contains

its

convenient method of purification

than in cold water. often deposit

of the sulphate group.

not zinc sulphate, and other tests must

be applied to determine

be

members

question does not show these properties,

w

then, of course,

other

all

substance

crystals will

If a solution

and the substance

evaporates slowly in

form when the solution reaches the

Hydrogen. same condition

43

a cooled solution,

as

the liquid cannot hold

must be found by

all

a

i.e.

point where

the solid in solution.

This point

hence no rules can be given

trial,

to

obtain well-shaped crystals, except perhaps (i) slow evaporation in the

air,

time permits, or (2) frequent cooling,

if

caused by heating. When a substance crystallizes, most of the impurities remain behind in soluthe evaporation

tion,

is

hence the crystallized

crystallization

—

whenever

is

it

usually pure.

—

is

a

Usually every

applicable.

is

Repeated

common method

ll.

of purification,

solid

recrystallization

vn

if

identification, but the

of

chemical tests are more

em

means

4a

chemical substance has one or more distinct geometrical forms in which it crystallizes. This crystal form is also a decisive.

Experiment water to hold

20.

— Fold

8, fit it

it

a

filter

paper according to the directions

into a glass funnel,

and moisten the paper with

Support the funnel by a ring or

w w

given on page

.c h

CRYSTALLIZATION OF ZINC SULPHATE.

in place.

filter

stand,

is

tp ://

w

and pour the contents of the hydrogen generator gradually upon the filter, taking care that no liquid comes above the edge of the paper. (See App. A, § 4.) If the contents of the generator consists partly of a white solid, add a little hot water and shake the mass until the solid dissolved.

The

filtrate

should be caught in a casserole, or evaporating

remaining zinc with water to remove the acid, and preserve for future use. When the filtrate measures about 100 cc. place

Wash any

ht

dish.

the casserole on a gauze-covered tripod, or similar support, and heat the liquid for ten or fifteen minutes, but

do not allow

it

to boil violently.

(See App. A, §§ 2, 3.) Then cool it slowly, and crystals of zinc sulIf no crystals separate after a few hours, phate will be deposited. evaporate again until a thin film appears on the surface when the solution Then if none are deposited from the cold solution, conhas cooled.

any reason the filtrate cannot be immediately remain undisturbed, and crystals will be deposited This liquid, of course, should not be boiled. as the water evaporates. In any case remove the crystals and dry them between filter paper. sult the teacher.

evaporated,

let

If for

it

Describe them, giving color,

luster,

approximate shape and

size,

and

Experimental Chemistry.

44

Put any remaining crystals into the stock

any other striking property. bottle

marked Zinc Sulphate.

TEST FOR ZINC SULPHATE. Experiment

21.

— Dissolve

some of the

obtained in Exp. 20, in a test tube half into halves, and proceed as follows :

—

full

crystals of zinc

sulphate

of water, divide the solution

To

one part add a little sodium hydroxide soluA white jellylike solid will be formed, but it will disappear if tion. considerable sodium hydroxide solution is added and the mixture well shaken. The insoluble jellylike compound is zinc hydroxide, which is

ll.

vn

(a) Test for zinc:

Shake the

test

tube containing the zinc sulphide to sus-

em

hydroxide.

4a

changed by the excess of sodium hydroxide into soluble sodium zincate. Now add a little hydrogen sulphide solution, and a white solid is formed. Compare its color and texture with those of zinc It is zinc sulphide.

and divide into halves. To one add dilute Shake each tube hydrochloric acid, and to the other add acetic acid. and observe the results. Zinc sulphide is decomposed by hydrochloric These facts are characteristic of compounds acid, but not by acetic acid. solid in the Hquid,

.c h

pend the

w w

Hence containing zinc, but not true of compounds of other metals. zinc must be one of the components of the solid product of the reaction

tp ://

w

between zinc and sulphuric acid. {b) Test for a sulphate: To the other half of the original solution add a little barium chloride solution. A white solid is formed, called barium sulphate, which will be found to be insoluble, in both hydrochloric and acetic acids. Try it. Barium sulphate is always formed when

ht

barium chloride is added to the solution of a sulphate, or to sulphuric Hence the zinc comacid, which is closely related to all sulphates. pound formed in the hydrogen generator must be a sulphate. {c) Draw a final conclusion from the results obtained in («) and {b). Definitions.

— The

that zinc sulphate

is

made in Exp. 21, which showed compound formed by the reaction

test

the

which liberates hydrogen, is called a Qualitative test, since not the it determined only the quality of the compound, The quantity by weight or volume of each component. latter operation is called a Quantitative test.

The

replace-

ment of one element or group of elements by another

ele-

Hydrogen. ment

group

or

of elements

is

45

called Substitution.

the formation of zinc sulphate

is

Thus,

the substitution of zinc

hydrogen in sulphuric acid. So also the formation of barium sulphate consists in the substitution of barium for zinc in the zinc sulphate the zinc, as could be easily proved, takes the place left by barium in the barium chloSubstitution is a broad, complex subject, which has ride. It will be a deeper meaning than mere replacement. A Sulphate is a comclearer as the experiments proceed. pound derived from sulphuric acid by substituting a metal for the hydrogen in the acid. A Sulphide is a compound of sulphur and ojie other element or group acting like an Sulphides correspond to oxides and chlorides element. all being binary compounds, i.e. compounds of two elements or groups acting like elements. for

—

.c h

em

4a

ll.

vn

;

—

w w

QUANTITATIVE EXAMINATION OF THE REACTION BETWEEN ZINC AND SULPHURIC ACID.

tp ://

w

MetJwd: Experiment 22. Measure the hydrogen liberated from sulphuric acid by a known weight of zinc.

Apparatus : The construcand arrangement of the apparatus is shown in Fig. 32.

^

is

ht

tion

a large test tube provided

with a two-hole rubber stopper.

The

tube

B

passes through one

hole to the bottom of the test

tube and

is

connected by a

short piece of pressure tubing

with

the

cup D.

A

Mohr's

pinchcock, C, controls the flow of acid from

D into A.

pinchcock

not strong enough

is

If the

Fig. 32.

— Apparatus for determining the

quantitative relation between zinc

hydrogen.

and

Experimental Chemistry.

46

to close the pressure tubing, then ordinary rubber tubing will answer, is made by cutting a thistle tube into the The part if fresh.

DB

The ends

requisite lengths.

B

of

and

D

are as

close together as the pinchcock will permit.

n

a shallow dish, and

The

6^ is

a 100

cc.

F

is

graduated tube.

shown in Fig. 33 is more convennot easily broken and requires no

modification

ient, since it is

support.

Process

:

Select a single piece of zinc weighing

it

into

A.

Fill

A

full

Fill the

insert the stopper with its tubes.

repeatedly until all air

used

full, fill

in this

Fill the

=>

'

is

j^^

Fill /J

^^^ ^^^^^^ j^

^

^^j^

^^_

F

low the point indicated by the dotted line. Fill G full and invert it in over the end of F. All water

F

.c h

nearly

^^^^^ ^^

em

FIG. 33.-Alternate apparatus.

:

w/iok

and admit water forced out of A, B, and

4a

apparatus with water thus

of water and

ll.

and drop

it

vn

not less than .22 nor more than .24 gm., weigh it exactly, wind a short piece of platinum wire around

experiment must have stood in the laboratory at least a day. with hot dilute sulphuric acid, and let the acid run

cup

D

w w

Introduce in this way slowly into A, but never below the dotted line. and at this time about 50 cc. of acid. Do not add acid after the action

tp ://

w

begins unless absolutely necessary, as the zinc may be forced over up into G. Hydrogen will be liberated and will pass through into F. at the top, and there will be little danger Let the gas accumulate in

F

A

Let the action continue until the zinc disappears, then force over into G any gas in the apparatus by admitting water, observing the precautions previously given. Unclamp G, close the end with the second finger, remove it to a tall jar of water which has been standing long enough to assume the tem-

ht

of losing the zinc.

perature of the room, and clamp

it

so that the water

is

about the same

Stand a thermometer in the water height within and without the tube. and allow the whole to remain undisturbed for at least fifteen minutes, Then, without touching the tube where it conif possible. tains gas, adjust the height so that the meniscus just touches the sur-

and longer

(See App. A, § 22, (i), (2).) the gas volume, the thermometer, and the barometer, observing

face of the water in the jar.

Read all

Record II., (3) and (4). Perform the calculation as directed

the precautions mentioned in App. B,

numerical results as

shown below.

Hydrogen.

47 ft

below, and,

precaution

if

G

possible, before the tube

may

is

Calculations : (The figures recorded here are only Those actually obtained will probably be different.) Data Weight of zinc, 0.24 gm. :

The

used again.

latter

obviate a repetition of the experiment. for illustration.

—

Volume

of hydrogen, 88.5 cc.

Temperature, 14° C.

mm.

Barometer, 758

Aqueous

vn

tension, 11.9.

Reduce the observed volume of hydrogen to the volume at 0°, 760 mm., and in the dry state by the formula

would

it

ll.

—

„_

V{P-a^

4a

occupy

If the

proper values are substituted in this formula, the corrected volA liter (1000 cc.) of dry is found to be 82.64 cc.

of hydrogen

.c h

ume

em

760 {I +.00366^)

w w

hydrogen under standard conditions weighs .0896 gm. weight of 82.64 cc. is found by solving the proportion 1000

:

82.64

'•

'

w

X=

=

tp ://

Weight of corrected gas volume Since .0074 gm. of hydrogen

ht

weight of zinc which

will

is

replace

—

-0896

:

Hence the

X

.0074 gm. .0074

gm.

.24 gm. of zinc, the gm. of hydrogen is found by the

replaced by i

proportion

.0074

:

.24 II

:r=

I

:

X

32.43.

Therefore 32.43 gm. of zinc are chemically equivalent to hydrogen. Class average =

Final Directions

:

Wash

gm.

the whole apparatus free from acid.

serve the platinum wire for future use. first

i

of

Pre-

If the final result is incorrect,

examine the arithmetical work, then repeat the readings (gas volume, and temperature), and recalculate, if blunders were made.

pressure,

Experimental Chemistry.

48

Discussion of Experiment 22.

— The

experiment should be approximately

32.5.

is

found in this The number,

The Equivalent

32.5, is called the equivalent of zinc.

an element

result

of

the weight of that element which will replace

one part by weight of hydrogen. The equivalent of zinc The fact that an is the same whatever the acid used. average of independent results, such as would be obtained

4a

ll.

vn

by a class, agrees within the limits of experimental error shows that definite relations by weight exist between hydrogen and zinc, when zinc and sulphuric acid interact. This definite and fixed relation has a deeper meaning than

Just now,

mulated.

it

em

can be considered at this stage of the subject. Its significance will be explained after more facts have been accuserves as an

introduction

to

the

.c h

quantitative study of chemical equations.

—

tp ://

w

w w

It was shown in Exp. 19 that Burning Hydrogen. It hydrogen burns, but the product was not examined. was shown in Chapter I. that when metals are burned in air, they combine with oxygen.

PRODUCT OF BURNING HYDROGEN.

ht

Perform

this

cxperimciit

since a mixture of air ignited.

Proceed exactly according

Experiment

23.

— Method:

product, from a burning

Supplies

and

with the

:

to the directions.

Generate hydrogen, and examine the

jet.

Hydrogen generator used

hole stoppers, platinum

utmost precaution,

Jiydrogen explodes violeiitly, if

tip,

in

Exp.

19,

U-tube with two one-

small bottle, calcium chloride.

Apparatus: The construction and arrangement is shown in Fig. 34. portion of the delivery tube is removed and the generator is then connected directly with the U-tube, which is filled about two-thirds full of lumps of calcium chloride separated from the stoppers by plugs

The lower

Hydrogen. of cotton.

shown

The

delivery tube

bent and attached to the U-tube as

is

The platinum

in the figure.

49

tip,

which

made by

is

the

method

given in App. A, § 13, is attached to the delivery tube by a short, All joints and connections must be gas gas-tight^ rubber connector. tight.

Process: Pour slowly but continuously through

the

tube

safety

enough (about 50 cc.) dilute sulphuric acid upon at least 25 gm. zinc

produce a

to

vn

of granulated

steady current of hydrogen gas for It

is

advis-

ll.

about eight minutes.

able to use considerable zinc and

is

begun anew.

Let

K:^

Apparatus for burning hydrogen.

Fig. 34.-

em

tion of gas begins, unless, of course,

the experiment

4a

a moderate amount of acid. Acid must not be added after the evolu-

.c h

the gas bubble through the acid for at least two inimiies by actual observation, then attach the platinum tip to the rubber connector at

the end of the delivery tube, leaving a short space between the ends

may be compressed

This

if

w w

of the two glass tubes so that the rubber tube

suddenly,

necessary.

is

to

the

drive

gas

run for another full viinute.

all air

out of the

tip.

Light the

w

latter precaution

Let

hydrogen, and observe at once the nature of the flame,

its

color,

and any other striking property Then hold a small dry bottle over the flame in such a position that the flame is just inside the bottle. When conclusive evidence of the product of burning hydrogen is seen inside the bottle, remove the bottle, and extinguish the flame at once by heat (by holding a match, or copper, or platinum wire over

ht

tp ://

it),

pinching the rubber connector.

and

if

the evolution of hydrogen

Remove is

ing water through the safety tube.

What

still

the generator to the hood,

brisk, dilute the acid

Examine the

in ail probability is the deposit

?

Explain

previous experiments does this one resemble

?

by pour-

inside of the bottle.

its

formation.

What

What

experiment would

have enabled you* to predict the result in this experiment ? Sketch in your note-book the apparatus used in this experiment. Final Directions : When the apparatus is taken apart, replace the stoppers of the U-tube with corks to preserve the contents for further use.

Insert the glass

end of the platinum

tip into the hole at the

smaller

Experimental Chemistry.

50

end of a rubber stopper or cork and insert it into a test tube. This Pour off the acid device will protect the platinum end of the tip. from the zinc, wash the zinc with water to remove all acid, and preserve for further use.

Discussion of Experiment 23. is

— The product

water

until the composition of

is

made

studied.

LABORATORY EXERCISE.

IV.

?

Weight

known

of

em

luminosity

4a

ll.

Explain the use of the U-tube 1. Calcium chloride absorbs water. Exp. 23. Why ? 2. Is water an oxide ? 3. How does the heat of the hydrogen flame compare with its

a Liter of Hydrogen.

A

substance.

liter at

only .0896 gm., while a

liter of

is

the lightest

mm. weighs

oxygen under the same

1.43 gm., as was found by Exp.

w w

conditions weighs

The number

— Hydrogen

0° C. and 760

.c h

in

of burning

water, though the final proof cannot be

vn

hydrogen

.0896 must be remembered.

Hydrogen

17. is

w

usually taken as the standard of density in the case of

tp ://

gaseous elements and compounds, though

Thus

times so regarded. air

standard

is

ht

approximately

The

—

.0896: 1.43

::

I

:

someis

16.

significance of this relation will subsequently appear.

CLASS-ROOM EXERCISE. I.

is

and on the hydrogen standard

1.105,

16,

air

the density of oxygen on the

VII.

Additional study of hydrogen. (a)

Distribution.

(d)

Compounds

(^)

Uses.

of hydrogen thus far studied or used.

(d) Liquid hydrogen. (e)

Solid hydrogen.

Hydrogen. History of hydrogen. {a)

Discovery.

(d)

Essential facts of Cavendish's

(c)

Names

Som-ces of error in Exp. 22

how detected,

Weighing the zinc. Reading the graduated instruments.

(c)

Blunders in the calculation.

Compound

Structure (with outline sketch).

Action.

(c)

Properties of

its

flame. it.

em

Uses.

Lavoisier's experiment.

steam through a red-hot tube containing iron combustible gas and a black solid were obtained.

(d)

What What

is

the

name

of the gas

?

in all probability are the

solid

components of the black

w w

(a)

.c h

Lavoisier passed

A

vn

(a)

(d) Precautions in using

filings.

?

blow-pipe.

{d)

(e)

why

avoided, and remedied.

(d)

(a)

4.

;

life.

so called, and

ll.

3.

whom

of the gas, by

4a

2.

5.

^i

?

w

(c) Devise an apparatus for this experiment. (d) Read the historical value of this experiment in a history

tp ://

of chemistry.

Impurities are often removed from hydrogen gas by passing it through a solution of potassium permanganate. This compound con6.

ht

tains a relatively large proportion of oxygen,

ditions

is

change

in the

7.

easily liberated.

What must be

which under certain con-

the general character of the

removal of the impurities ?

and

Crystallization

precipitation.

(a) Favorable conditions for crystallization.

(c)

Why are perfect crystals rare How does precipitation differ

(d)

The

(
Define

(d)

?

from crystallization

distinguishing characteristics

of

the

six

?

crystal

systems. "crystallized,"

"amorphous,"

"dimorphous,"

"pseudomorph.'"

(/) Define "precipitate

"

and "precipitation."

Experimental Chemistry.

r2

Miscellaneous.

8.

(a)

What ing

effervescence,

is

What

?

effervescence (d)

What

and how does

it

differ

from

experiments in this chapter

boil-

illustrate

?

meant by the "diffusion of part of Exp. 19 illustrates diffusion is

gases''

?

What

?

(c)

Describe a generator, a safety tube, a delivery tube, a

(d)

What

tripod.

synthesis was

made

in

one or more of the ex-

?

em

prepared or used

4a

ll.

vn

periments with hydrogen ? What oxidation ? What What chemical compounds addidetermination ? tional to those in previous experiments were made or used ? What new elements (free or combined) were

1

.

VIII.

.c h

PROBLEMS.

Calculate the equivalent of zinc from the following data actually

obtained by a student

—

:

zinc .12

w w

Weight of

gm.

Corrected volume of hydrogen 40.89 Calculate the equivalent of zinc from

—

w

2.

cc.

tp ://

Weight of zinc .50 gm. Observed volume of hydrogen 183 Pressure 748

Temperature 9° C.

ht

cc.

mm. (a

=

8.57.)

the weight of 500 cc. of dry hydrogen at o" C. and

What is mm.? Of 1800 cc? OfQl.? hydrogen from 4. How many grams of zinc will liberate 100 gm. of How many grams of zinc will liberate 100 ? sulphuric acid ? hydrogen measured over water 5. What is the weight of a liter of — c)\ 50" {a ? mm. .98.) C. and 790 at 6. How much zinc (in grams) is necessary to liberate from sulphuric acid 100 1. of dry hydrogen at 9i°C. and 800 mm.? hydrogen is a liter of 7. How many times heavier than a liter of 3.

760

1.

oxygen, both being dry and under standard conditions

?

CHAPTER

IV.

H

has the same

is

ll.

O

for nitrogen

;

as

more than one element some cases is

Ba of barium, The symbol of several

derived from their Latin name.

Fe

is

the

the symbol of boron, but

w w

is

bol of iron

letter of

letter in

Bi of bismuth, Br of bromine, etc.

metals

first

the symbol for oxygen,

is

another

initial letter,

Thus B

added.

N

usually the

Thus

of the element.

for hydrogen,

an abbreviation of the name of

It is

.c h

name

is

4a

— A symbol

em

Symbols.

a chemical element.

vn

SYMBOLS — FORMULAS — CONSERVATION 01 MATTER — CHEMICAL EQUATIONS— QUANTITATIVE INTERPRETATION OF EQUATIONS — PROBLEMS BASED ON EQUATIONS—PROBLEMS.

{fei'nnn), of lead

is

Thus, the sym-

Pb {plinnbum),

of

tp ://

w

sodium is Na {natrinui), of potassium is K {kaliuni), etc. These symbols denote one atom of the element, i.e. H means the smallest particle of hydrogen which can take

They

also represent a certain

ht

part in a chemical change.

number, called the atomic weight, which belongs to that atom. They are sometimes loosely used to mean any A list of symbols convenient amount of the element. If more than one is given in Appendix C, Table I. atom is to be designated, the proper numeral is placed before the symbol.

O

Thus

:

—

means 2 atoms 3 H means 3 atoms 4 P means 4 atoms 2

of oxygen.

^^ ^ YA\5\ of phosphorus, r \ \V)6^ of hydrogen.

rk<%c\(\ft

\

kt*^

Experimental Chemistry.

j4

But if the atoms are in chemical combination, either with themselves or other atoms, then a small numeral is

H2 means

little

atoms of hydrogen

2

Ng means 3 P4 means 4 atoms

—A

of

is

in combination.

a group of

expresses the composition of a compound.

formula

the

potassium

of

chlorate,

symbols which Thus, KCIO3 and MnOg of

ll.

is

—

in combination.

phosphorus

formula

:

in combination.

atoms of nitrogen

Formulas.

Thus

below the symbol.

vn

placed after and a

em

4a

manganese dioxide. Formulas represent single molecules. Thus KCIO3 means one molecule of potassium chlorate containing one atom each of potassium and chlorine and

They also represent the molecular compound. More than one molecule is

weight of the

.c h

three atoms of oxygen.

designated by the proper numeral placed before the formula,

w w

:

2

KCIO3 means

2 molecules of

3

HgO means

molecules of water.

3

potassium chlorate.

w

thus

tp ://

4 H2SO4 means 4 molecules of sulphuric

Groups

of

atoms acting

like a single

atom

in reactions

by a

period.

ht

are enclosed in a parenthesis, or separated

acid.

Thus (NH4)N03 represents a molecule of ammonium nitrate, in which the group of atoms (NH4) bears such relations to the

NO3

that the group

is

represented as a

and CgH^ OH A group of atoms to be multipHed is also enclosed in a parenthesis. Thus, Pb(N03)2 is the formula of lead nitrate, and means that the (NO3) group bears to the atom of lead (Pb) such relations that the group Many facts similar to the must be multipHed by two.

unit;

•

similarly represents a molecule of

alcohol.

last will

be clearer as the experiments proceed.

Conservation of Matter

— Chemical

Symbols and formulas have a deeper

Equations. 55

significance,

which

will be considered as the necessary facts accumulate.

CLASS-ROOM EXERCISE.

VIII.

Give the symbol of each of the following elements, 1 have been used or studied in the preceding experiments :

Oxygen, Hydrogen, Sulphur, Carbon,

Iron,

all

—

Magnesium,

of which

Zinc,

Mer-

Name

the elements which correspond to the following symbols

4a

Fe, Pb, Pt, Zn, Hg, Na, K, Cu. 3.

:

—

ll.

2.

vn

cury, Platinum, Lead.

Give the formula of each of the following compounds

em

Magnesium Oxide, Mercuric Oxide, Potassium

:

—

Chlorate, Potassium

Chloride, Sulphuric Acid, Hydrochloric Acid, Zinc Sulphate, Sulphur

.c h

Dioxide, Carbon Dioxide.

— Most

experiments transform matter, but they never destroy or create it no weight is gained or lost. The total weight of matter involved in a reaction is the same before and after. This vast conception ;

w

w w

Conservation of Matter.

demonstrated by Lavoisier, and, largely as a result it has become a fundamental law of It is called the Law of the Conservation of chemistry. first

tp ://

was

of his initial work,

is

ht

Matter, and

No

weight

often stated thus: is lost

Chemical Equations.

—

or gained in a cJiemical reaction.

— The mathematical

significance of

symbols and formulas, together with the conception of the conservation of matter, allows reactions to be represented

Chemical equations differ from algebraic equations in one vital respect: they are the result of experiment. Thus in Exp. 15 it was shown that magnesium unites with oxygen to form magnesium quantitatively

by equations.

Experimental Chemistry.

^6 oxide.

thus

:

—

These

facts are represented in the simplest

Mg

MgO

=

O

+

(i)

Magnesium

Oxygen

Magnesium

way,

Oxide

simplest

This reaction

way by the equation

KCIO3 Potassium

=

:

—

3O

is

represented in the

ll.

potassium chloride).

oxygen and a residue (called

yields

4a

when heated

Oxygen

(2)

Potassium Chloride

.c h

Chlorate

KCl

4-

em

chlorate

vn

This equation means that one atom of magnesium unites with one atom of oxygen, and forms one molecule of In Exp. i6 it was shown that potassium magnesium oxide

This equation means that one molecule of potassium chloby decomposition three atoms of oxygen and one molecule of potassium chloride. It has been shown as

w w

rate yields

tp ://

w

the result of several experiments that the interaction of zinc and sulphuric acid produces hydrogen and zinc sulphate.

This fact

is

represented by the equation

ht

Zn

:

—

(3)

Quantitative Interpretation of Equations.

—

should be noted

It

57

(i) That these equations are expressions between atoms and molecules, not between the quantities actually seen in action.

(2)

it

That some substances are not included

Thus

tion.

in equation (3)

water

takes no chemical part in the reaction

equa-

;

simply serves

it

from the surface

of the zinc,

vn

to dissolve the zinc sulphate

in the

not represented because

is

Likewise

magnesium only when the

That only the beginning and end Thus,

represented.

Exp.

in

em

(3)

latter is at a red heat in the

— obviously impossible

4a

absence of oxygen

ll.

in and thereby allow the reaction to proceed. equation (i) no nitrogen appears. Nitrogen combines with

certain

9,

in

Exp,

15.

of reactions are

compounds are

.c h

formed and decomposed again as the temperature increases but these facts do not appear in the equation, ;

w

w w

because here we are concerned not with phases, but only with the actual ultimate decomposition of potassium chlorate into oxygen and potassium chloride. (4) That chemical equations /;'
tp ://

help us interpret an experiment.

They

are not a sufficient

record of an experiment, and they should never be used

ht

unless they have been proved in whole or in part.

The atoms

or molecules entering into the initial stage

of a reaction are called factors, those present in the final

stage are called prodjicts.

and molecules

Thus

in

equation (3) those atoms

at the left of the equality sign are factors,

Chemical equations are and are very rarely reversible.

those at the right are products.

read from

left to right,

Quantitative Interpretation of Equations.

cannot be destroyed,

accounted

for.

all

Much

— Since matter

weight entering a reaction can be more information, however, lurks

Experimental Chemistry.

58

an equation. It was found by Exp. 15 that when magnesium is heated in air, the ratio of the weights in which magnesium and oxygen combine is 1.5:1. Equa-

in

tion (i) might, therefore,

be written

—

Mg + O = MgO =2.5 1.5 + I

is

i

:

—

provided,

of

the above

4a

equation might be written

i,

Hence

not destroyed.

ll.

course, the ratio 1.5

be substituted for

vn

Any number might

is

the simplest kind of an equation, but the facts

.c h

This

em

Mg + O = MgO 24 + 16 = 40 similar to those revealed here

may be

discovered about

Equation (3) might be written

w w

every equation.

—

Zn + H2SO4 = H2 + ZnS04

=2 +

161

tp ://

w

65+98

Experiment

proved that 32.5 (approximately) gm. of zinc correspond to i gm. of hydrogen. If the work had been extended, it would have been found that 65 gm.

ht

22

of zinc correspond to

161

gm. of zinc sulphate.

The

equation would then become, as the result of experiment,

Zn + H2SO4 = 65

+

98

=

H.3 2

+ ZnS04 + 161

163 Finally, in Exp. 16

it

163

was shown that potassium chlorate

yields about 39 per cent of oxygen.

If

we

select for 3

O

Other Chemical Equations Studied. the

number 48 (equal

to 3

x

then

16),

^9

we can form

the

proportion

48 39 :

:

:

.r

:

1

00

X=

123

If the experiment should be conducted with the utmost care and precaution, the proportion would be slightly modified, so that instead of equalling 123, x would have equalled

true relation existing between

potassium chlorate and the oxygen

may now be written —

3

the above discussions

accurately evolved

it

is

evident that equations,

and correctly interpreted, reveal the

.c h

From

O + KCl 48 + 74.5

4a

122.5

= =

Equation (2)

em

KCIO3

yields.

it

vn

number nearer the

ll.

122.5, a

exact proportions by weight in which

compounds

react in

w w

the particular chemical change expressed by the equation. Other facts of fundamental importance are contained in

w

chemical equations, and these will be considered in the

tp ://

proper place.

—

ht

Experiment 12 was Other Chemical Equations Studied. a qualitative experiment, but if the factors and products

had been weighed, the pressed thus

final result

might have been ex-

:

HgO = Hg + O 216 = 200 + 16

(4)

This means not only that mercuric oxide decomposes into mercury and oxygen, but that 216 parts by weight of mercuric oxide produce 200 parts of mercury and 16 parts of oxygen, since careful experiments show that these numbers represent the correct proportions.

vn

ll.

4a

em

.c h

w w

w

tp ://

ht

Problems Based on Foregoing Equations. numbers given

are represented by the

Thus

in equation

(

in

6

the equation.

i ),

Mg + O = MgO, 24 + i6 = 40 gm. of magnesium are taken, then 8 gm. of oxygen be necessary to convert all the magnesium into magthe sum of the nesium oxide, which will weigh 20 gm. weight of one the from Hence factors. two weights of the

if

12

will

vn

—

we know

4a

ll.

substance participating in a reaction, we can calculate by proportions the actual weights of all other participants, if the equation corresponding to the reaction. of magnesium are to be converted into

em

Suppose 17 gm.

oxide, and it is desired to know (a) how much oxygen is necessary and (l?) how much magnesium oxide The questions are answered by solving will be formed.

.c h

magnesium

the following proportions

:

40

:

ly

:

:

:

17

X.

X=

:

1

1.3

gm. of oxygen.

x.

X—

when 45 gm.

ht

Similarly,

-

w w

:

tp ://

24

16

:

w

24

:

28.3

gm. of magnesium oxide.

of zinc interact with sulphuric

acid, the weights of {a) acid required, {b)

hydrogen formed,

and {c) zinc sulphate produced are found by the proportions

:

65

:

98

:

:

45

:

^•

X= 65

:

2

:

:

45

:

:

161

::

45

'.

gm. of sulphuric

1.38

gm. of hydrogen.

acid.

.r.

X= 65

6'].'^

x.

X=

1 1

1.4

gm.

of zinc sulphate.

Experimental Chemistry.

62

PROBLEMS.

How many grams

1.

How much

2.

hydrogen can be prepared from 65 gm. of zinc?

From 297 gm. ? How much zinc is needed to

130 gm.

3.

?

prepare 2 gm. of hydrogen

?

4 gm.

?

gm.?

How much

4.

zinc sulphate can be prepared from 98

From 196 gm.? From 427 gm. ? How much mercury and how much oxygen

phuric acid? 5.

How much

was heated and 298 gm. weight of potassium chlorate

certain weight of potassium chlorate

of potassium chloride remained.

em

A

obtained by heat-

oxygen can be prepared from 50 gm. of potassium

chlorate? 7.

is

4a

6.

sul-

ll.

ing 10 gm. of mercuric oxide?

gm. of

vn

17

of oxygen can be prepared from 122.5 S^- ^^ 245 gm.? From 421 gm.?

From

potassium chlorate?

From

IX.

What

A

?

.c h

was heated and what weight of oxygen was formed

was heated until comWhat pletely decomposed, and the residue weighed 20.246 gm. weight of potassium chlorate was heated, and how much oxygen was certain weight of potassium chlorate

w w

8.

evolved?

w

9. If 60 gm. of mercuric oxide are completely decomposed, what volume of oxygen is obtained at 91" C. and 380 mm. ?

11.

tp ://

10. If 400 gm. of potassium chlorate are completely decomposed, what volume of oxygen is obtained at 27° C. and 760 mm.?

If

100 gm. of zinc interact with sulphuric acid, what volume of

is

evolved

ht

hydrogen 12.

A

?

balloon holds 132.74 kg. of hydrogen.

sulphuric acid are needed to produce the gas 13.

How much

potassium chlorate

is

How much

zinc

and

?

needed to prepare 36.48

1.

of

and 750 mm.? 14. How many liters of oxygen can be obtained from a kilogram of potassium chlorate, if the gas is measured at 10° C. and 755 mm. ? oxygen

15.

enough 16.

at 15° C.

How much to

fill

If 12

is

and sulphuric acid

gm. of carbon

composing 122.5 dioxide

zinc

(in kg.) will yield

a 350 cc. flask at 15° C. and 735 g"^- of

are burned in the

hydrogen

mm.? oxygen obtained by de^

potassium chlorate, what weight of carbon

formed, and what weight of oxygen,

if

any, remains?

Problems. 17.

A

lump of carbon weighing 24 gm.

(d)

What What

{c)

If a liter of

(a)

is

18.

What

burned in formed ? needed?

weight of carbon dioxide

weight of oxygen

6;^

is

oxygen weighs needed?

is

1.43 gm.,

weight of carbon dioxide

air.

is

what volume of oxygen

may be

obtained by burning

112 lbs. of coal containing 15 per cent of impurities? 19. A sulphuric acid maker accidentally set fire to a storehouse containing 8794 kg. of sulphur.

20.

What

A

rough estimate showed that 67 per

weight of sulphur dioxide was formed?

vn

cent had burned.

Calculate the weight of oxygen necessary to burn 731

of

oxygen required.

of sulphur dioxide formed.

ht

tp ://

w

w w

.c h

em

(/^)

The weight The weight

air.

4a

(a)

ll.

sulphur containing 15 per cent of impurities. 21. A lump of sulphur weighing 32 gm. is burned in

gm. of

Calculate

—

CHAPTER

V.

GENERAL PROPERTIES OF WATER. all chemical compounds, remarkable and varied properties it

the most abundant of

account of

study.

4a

demands extensive

its

vn

and on

is

ll.

Water

GENERAL DISTRIBUTION.

.c h

em

Supplies: Test tubes, wood, meat, potato. Experiment 24. Heat successively in dry test tubes a small piece of wood, of meat, and of potato (or any fresh vegetable). Hold the test tube at such an angle that any moisture which

may be

liberated will not flow

w w

upon the hot glass. Is there conclusive evidence of water? amount unexpectedly large in any case? These substances are types of animal and vegetable matter.

down Is

the

Draw

ht

tp ://

w

a general conclusion.

Fig. 35.

— Potato showing

(by shaded

part) the proportion of water.

Re-

mainly starch and

fiber.

mainder

is

Fig. 36.

— Carrot showing

(by shaded

part) the proportion of water. Remainder is mainly starch, sugar,

and

fiber.

The water driven off by heating many organic substances may be simply mixed with other ingredients, or it may be 64

General Properties of Water.

65

due to the presence in them of hydrogen and oxygen in such proportions that these two gases combine to form

decomposed. Many known and will be sub-

water at the instant the compound

examples

kind are

of this latter

is

sequently examined.

The wide

distribution of water in vegetables

Figs. 35

Water

cent water.

Water

and

essential to

is

— Dry

of Crystallization.

many

the water solution of

which seems

strikingly

is

The human body

36.

is

70 per

life.

vn

in

crystals deposited

from

ll.

shown

contain water,

often

solids

4a

be an essential part of the chemical comThis water is called water of crystallization. In some crystals the water passes off at the ordinary temperature, and in all crystals when they are heated. to

.c h

em

pound.

DETECTION OF WATER OF CRYSTALLIZATION. 25.

alum

liberated

may run

in a

out.

What

w

?

Heat a few small

If there is

in the

appearance of

it.

Repeat, using a crystal of gypsum.

{]))

sodium carbon-

the evidence that they contained water

is

any marked change

the crystals, describe and explain

Answer

the question asked

time permits, examine successively crystals of the following

ht

in {a).

crystals of

dry test tube, inclining the test tube so that any water

tp ://

of crystallization

— {d)

w w

Experiment ate or of

{c)

If

compounds case

:

for

water of crystallization, and describe the result in each

Potassium

nitrate,

potassium dichromate, and magnesium

sul-

phate.

{d^ Heat two or three small crystals of copper sulphate in an evaporating dish which stands on a gauze-covered tripod.

proceeds, hold a dry funnel or glass plate over the dish. clusive evidence of escaping water of crystallization?

As

the action

Is there

Do

con-

the crystals

change

in color? In shape? Can the form of the crystals be changed by gently touching the mass with a glass rod? Continue to heat until the resulting mass is a bluish gray. Let the dish cool. Meanwhile

heat a test tube two-thirds

full

of water.

When

the dish has cooled

Experimental Chemistry.

66 somewhat, pour

tlie

hot water slowly into the dish upon the copper

Explain the change in color,

sulphate.

If there are

any.

if

any lumps,

crush them with a glass rod and heat the solution over the gauze until Let the solution evaporate for several hours. Are crystals it is clear.

Have

few minutes, and cool again;

If not, heat a

deposited?

they water of crystallization, and,

The amount

so,

if

when

if

so,

did they get

why?

it ?

of water of crystallization in crystals

is

not

Its necessity

limits in different substances.

ll.

between wide

vn

arbitrary. It is constant in the same compound when crystallized under uniform conditions, but the amount varies

and not in others, as well as quantity, has never been explained.

some

crystals

its

varying

em

4a

in

DETERMINATION OF WATER OF CRYSTALLIZATION

IN

BARIUM

Experiment

26.

.c h

CHLORIDE.

— MetJwd:

Heat

to

constant weight a weighed

w w

quantity of crystallized barium chloride in an uncovered crucible, and the loss will be the water of crystallization.

Supplies: Porcelain crucible and support, crystallized barium chlo-

w

ride, forceps, crucible block.

Weigh accurately a clean, dry crucible. Weigh in it from gm. of barium chloride, weighing exactly the amount taken.

tp ://

Process: 1.5

to 2

Record the

results thus

:

—

Grams.

ht

Weight of crucible and barium Weight of crucible Weight of barium

chloride

.

.

chloride

Stand the crucible on a pronged tripod or similar support, and heat with a low flame for about fifteen minutes, then gradually increase the heat, as in previous experiments, until the flame

of the crucible.

is

just

below the edge

Continue the intense heat for ten minutes, then gradu-

it just touches the bottom of the crucible. and fro under the crucible, until all danger of crackStand the crucible in the crucible block, and weigh ing disappears. when cool enough to bear the hand. Record the results thus

ally

lower the flame until

Move

the flame to

:

—

General Properties of Water.

67 Grams.

Weight of crucible and crystallized barium chloride Weight of crucible and barium chloride

Weight of water of

To five

be sure that

all

.

.

crystallization

water has been driven

off,

minutes, then cool and weigh, as before.

heat again strongly for

an appreciable two weights are constant. If there is no upon the second heating, calculate the per cent of If there is

loss, repeat until the last

appreciable loss

Per cent of water

lost

gm. of which

on heating, 0.22 gm. lost, on heating, per cent of the sample was water of crystallization ?

1.5

lost,

student found that 2 gm. of barium chloride

g'""-

What

.c h

A

— Crystals which have

w w

0.295

4a

Calculate the per cent of water of crystallization in a sample of

barium chloride, 2.

X.

em

PROBLEMS. 1.

=

=

Class average

vn

lost.

ll.

water

lost water of crystalbe Dehydrated or Anhydrous. Thus the bluish white product obtained by heating the blue crystal-

Definitions.

w

lization are said to

ht

tp ://

copper sulphate is usually called " dehydrated copper sulphate." The words dehydrated and anhydrous have been extended to mean any substance from which water has been removed, as anhydrous alcohol or ether. The lized

is sometimes applied to a compound emphasize the fact that it contains water of crystallization. The term Dissociation is applied to that special kind of decomposition in which the components may reunite under favorable conditions. If crystallized copper sulphate is heated, water, which is driven off by heat, readily reunites with the copper sulphate to form the blue crystal-

opposite term Hydrated

to

lized

compound, which,

strictly

united with water, though

it

speaking, is

is

copper sulphate

loosely called copper sul-

Experimental Chemistry.

68

Crystallized copper sulphate, therefore,

phate.

dissociate of this

when

There are many

heated.

is

said to

different varieties

kind of chemical action.

Efaorescence.

— ^Nlany

crystals contain

water of

crys-

tallization so loosely combined that the water passes off This is readily when the crystal is exposed to the air.

and the

crystals are said to effloresce,

vn

called efflorescence,

4a

EFFLORESCENCE.

ll.

or to be efflorescent.

—

It

is

believed

that

.c h

em

Put a fresh crystal of sodium carbonate and of Experiment 27. sodium sulphate on a piece of filter paper and leave them exposed to the Describe any marked change. What does air for an hour or more. this change show about the air ?

the water in the

crystals

w w

efflorescent tends to pass off into the atmosphere.

called

This

tp ://

w

tendency resembles the tendency of water to evaporate. And like water, this water of crystallization passes off only when the vapor tension of the crystal exceeds the tension of the water vapor in the atmosphere. Thus sodium sulphate at ordinary temperatures has a greater vapor ten-

ht

sion than the atmospheric water vapor, but

gypsum

(crys-

calcium sulphate) has a lower vapor tension than Hence sodium sulphate the atmospheric water vapor. This is an easy effloresces, but calcium sulphate does not.

tallized

way

to distinguish the

Deliquescence.

two compounds.

— Many

substances, crystallized and un-

absorb water when exposed to moist air, or often even to ordinary air, which always contains a little water This is called deliquescence, and such substances vapor. crystallized,

are said to deliquesce, or to be deliquescent

General Properties of Water.

69

DELIQUESCENCE. Experiment

— Place

on a piece of glass or

an evaporating sodium hydroxide, and potassium carbonate, and leave them exposed to the air for an hour or more. Describe any marked change which takes place. How does the action differ from tliat in Exp. 27 ? Where and why was 28.

in

dish a small piece of calcium chloride, potassium hydroxide,

this property of calcium chloride utilized

Deliquescence

?

a property of substances very soluble such substances, potassium carbonate or calcium chloride for example, are exposed to the air, the

vn

is

When

ll.

in water.

em

4a

water vapor forms with the substance a small quantity of a saturated solution. This saturated solution has a lower

the substance

is

.c h

vapor pressure than that of the atmosphere, that is, the water is held by the substance, it does not tend to escape, hence more water vapor is added from the air, and finally entirely dissolved in this

w w

Common salt or sodium chloride

condensed vapor.

often appears to deliquesce,

is due to the very soluble magnesium and calcium chlorides which are usually mixed with commercial sodium chloride. Sodium nitrate is very soluble

in is

tp ://

w

but the deliquescence

water at the ordinary temperature, but potassium nitrate only slightly soluble. Hence potassium nitrate, and not nitrate, is

ht

sodium

Impure Water.

used in the manufacture of gunpowder.

— Water,

if

impure,

nated with two kinds of impurities,

The former table matter

is, ;

in general,

is

usually contami-

—-organic and inorganic.

decomposing animal and vege-

the latter consists of various mineral sub-

stances dissolved from the earthy matter through which

the water percolates.

preted broadly, since

some.

"

The

The term impure must be intermany mineral zvatei's are whole-

rule generally adopted

by chemists

in dealing

Experimental Chemistry.

70

with water is to pronounce any water dangerous which contaminated by sewage." (Remsen.)

is

SIMPLE TESTS FOR IMPURITIES IN WATER.

—

(a) Organic Matter : Fill a clean test tube two29. of distilled water and another with water containing a little

Experiment thirds

full

dirt or a bit of paper.

trated sulphuric acid

Add and

to each test tube a

sufficient

drop or two of concen-

potassium permanganate solution

water) to color each liquid a light purple, as nearly Label one tube, and then heat gently nearly to the As soon as a boiling point the tube containing the impure water. definite change is seen, heat the other cautiously, as too sudden heat

(made from

vn

distilled

may

cause the liquid to ''bump potassium permanganate solution. Chlorides

:

To

nitric acid,

a test tube half

the same with faucet water or water

What

or solid,

is

is

silver nitrate is

added

in solution.

Silver chloride

is

is

silver nitrate solution.

Do

to contain a chloride in solu-

The

cloudiness,

which

silver chloride,

is

always

to hydrochloric acid or a chloride

soluble in

ammonium

hydroxide.

w

This

of distilled water add a few

the difference between the results?

due to the precipitation of

formed when it.

full

known

w w

tion.

tube shows the more organic

and then a few drops of

.c h

(J))

Organic matter decolorizes

Which

em

matter?

drops of

out.'''

4a

ll.

alike as possible.

the usual test for chlorides (and conversely for soluble

Try sil-

tp ://

ver compounds), and will hereafter be used without further description.

ht

(c) Sulphates: Apply the usual test for sulphates to distilled water and to impure water known to contain sulphates (see Exp. 21 (<^)){d) Calcium Coiupounds : Add a few drops of a fresh solution of ammonium oxalate to a test tube half full of clear lime water. Lime water is a solution of calcium hydroxide, and the white precipitate formed is calcium oxalate, which is soluble in hydrochloric acid but not Try it. This is the test for calcium compounds, often in acetic acid. called " lime " compounds, because lime, which is calcium oxide, is so well known. Apply this test to distilled water and to water known to contain calcium compounds, and compare the two results.

Purification of Water. to the air,

tion

is

by

— Water

filtration, or

by

is

purified

distillation.

by exposure

The

last opera-

convenient only with relatively small quantities, and

General Properties of Water.

71

performed by means of a condenser, which is shown in The condenser consists of an Fig. 37 arranged for use. an inlet and outlet for a with provided AA', tube, outer

— Condenser arranged for the purification of water by distillation.

w w

Pig. 37,

.c h

em

4a

ll.

vn

is

current of cold water, which surrounds an inner tube,

boihng

Fig. 38.

in the flask, C,

BB\

The vapor from

the

condenses .in the inner tube,

ht

tp ://

liquid

w

These tubes are shown

in

J Pig. 38.

owing

to the decrease in temperature,

lower end

The

— Inner and outer tubes of a condenser. and drops

off the

of this tube, as the distillate, into the receiver,

D.

condenser and receiver should, obviously, be scrupu-

lously clean.

Experimental Chemistry,

72

DISTILLATION, Experiment 30.

—

Fill the

cc. flask, C, half full of watei

500

known

to contain the impurities mentioned in Exp. 29, add a few crystals (3 or 4) of potassium permanganate, and connect with the condenser shown in Fig. 37. Attach the inlet tube to the faucet, fill the con-

as

denser slowly, and regulate the current so that a small stream flows continuously from the outlet tube into the sink or waste pipe. Heat

C

gradually,

the ebullition

is

not too violent.

and when

D.

this distillate for organic matter, chlorides,

and calcium compounds.

Is

organic matter found

Is

?

ll.

Test separate portions of sulphates,

boils, regulate the heat so that

it

Collect about 25 cc. in the receiver,

vn

the liquid in

C

had contained some volatile substance like alcohol, ammonia, or hydrochloric acid, where would this Can water be volatile matter have been at the end of the operation ? If the liquid in

?

Sketch the apparatus used

em

separated from any solid by distillation

4a

mineral matter found

?

.c h

this experiment.

CLASS-ROOM EXERCISE.

w w

{a)

Color, odor, and taste of pure water.

{b)

Distribution of water in animal and vegetable matter.

{c)

Rain water.

kinds, general character, medicinal value.

:

tp ://

{d) Mineral waters

Water

of crystallization.

{a)

Relation to color and form of crystals.

{b)

Additional examples.

ht

2.

IX„

Additional study of water.

w

1.

in

(<:)

Theories.

3.

Efflorescence and Deliquescence.

4..

Drinking water.

{a)

Additional examples.

(a) Organic matter

:

source, danger of

other than chemically,

its

presence,

how

{b)

Significance of presence of sulphates and chlorides.

{c)

Hard water

:

meaning of term, meaning of

" permanent,"

how

softened,

other than chemically, boiler scale

?

What

detected

how removed.

why

how

''

temporary " and

estimated,

objectionable.

causes the

''

how detected What causes

furring " of a kettle

?

General Properties of Water. {d)

How

{e]

Why should drinking water be exposed to the air ? Why are lead compounds often found in water ? How detected ? Why dangerous ?

(/)

What

city

is

ters

5-

73

water filtered

Of what

?

value are large

fil-

?

is

a " water analysis "

?

Distillation.

meaning.

{u)

Literal

{b)

Is

{c)

Is there

it

a recent process of purification

?

any dilTerence between water vapor and steam

?

Experimental.

cally

substances have a moist surface and some have water mechaniHow would you distinguish this moisture

ll.

Some

enclosed within them.

from water of crystallization

?

4a

6.

vn

(^) industrial applications.

— The freezing point

of water (or the melting point of ice)

and the boiUng point

em

Relation of Water to Temperature.

They

thermometer.

They

are

easily

vary, however, under

w w

found.

on a

.c h

of water are the fixed points

w

certain conditions.

tp ://

THE FREEZING AND BOILING POINTS OF WATER,

— Supplies:

ht

Experiment 31. mometer fitted loosely and clamp, funnel, 250

Ther-

to a cork, iron stand

cc.

Erlenmeyer

flask

or similar vessel, tripod or iron ring, ice (or sLLw), salt.

Crush the ice, if snow is not availand put it in a funnel which stands Clamp the thermometer in the flask. around the cork, as shown in Fig. 39, and (a)

able,

adjust the height so that the bulb in the ice.

thermometer. intervals

is

buried

After a short time, read the

until

—

Apparatus for determining the melting point

Fig. 39.

Repeat the reading at brief the mercury is constant.

of ice.

Experimental Chemistry.

74 Record the

final

reading.

When

the whole experiment

is

finished,

sketch this apparatus in the note-book.

Remove

{b)

and

fill

the thermometer, carefully transfer the ice to the flask,

the flask half

tripod or

ring,

full

of water.

and clamp

it

Stand the

flask

on a gauze-covered Adjust the

loosely around the neck.

thermometer so that the bulb dips into the liquid. The mouth of the Heat gently and watch should be open. Read the thermometer. What happens ? Repeat the readings until the the thermometer. mercury is constant. Record the final reading. Remove the thermometer and add from lo to 20 gm. of sodium (<;) common salt. Adjust the thermometer as before, and find chloride If not appreciably different, add the boiling point of this solution.

vn

flask

ice,

Record the boiling point.

a mixture of equal parts by weight of salt and

Make

and

4a

salt.

{d)

find, as in {a), the

melting point of this mixture.

em

more

melting point. (e)

ll.

—

Summarize the

results as follows

:

—

ht

w w

tp ://

w

Substance.

.c h

Table of Freezing and Boiling Points.

cmshed

Record the

General Properties of Water. Effect of a dissolved substance on the boiling point.

(c)

of

Cause

this effect.

Other conditions affecting the boiling point.

((/) 2.

75

Freezing. (a) Exact definition. {&) Effect of dissolved substance

on the freezing point.

Cause

of this effect. 3.

Miscellaneous. (a) Explain the term

{c)

maxivuun

density of water.

What is the scientific reason for using water to extinguish fires ? What scientific measurements are based on water as a

vn

ip)

ll.

standard ?

— Many

liquids,

solids,

into water.

or putting into solution.

The

The

w w

is

is

called a

which the

and the substance

If the solute is not volatile,

recovered by evaporation or distillation of the The degree of solubility is usually expressed by

tp ://

may be

called dissolving

liquid in

called the Solvent,

called the Solute. ^

w

dissolved it

is

is

resulting liquid

solution of the substance used.

substance dissolves

and gases disappear

This operation

.c h

Solution.

when put

em

4a

{d) State the changes in volume which occur when (i) ice melts, (2) water freezes, (3) water is heated from o^ C. to 15° C, (4) water is cooled from 15° C. to o" C.

solution.

ht

It is the terms slightly soluble, soluble, and very soluble. desirable, however, to state in all possible cases the exact

proportions of solvent and solute.

not dissolve are called insoluble.

Substances which do solution which con-

A

tains a relatively small proportion of the solute

is

called a

Dilute solution; one containing a relatively large proportion is

called a Concentrated solution.

acid contains usually one

or

more

Thus, dilute sulphuric

volume of sulphuric acid

to three

volumes of water, while concentrated sulphuric *

See Glossary, Appendix C.

Experimental Chemistry.

.76

acid

is

The terms

nearly 98 per cent acid.

dilute

and

con-

centrated are loosely used in several senses, which will be

Other descriptive terms

clear as the experiments proceed.

are applied to solutions, and these will be discussed in the

proper place.

Usually a solution means a solution in water,

and the term

is

so used in this book, unless otherwise

stated.

—

4a

ll.

vn

There is no general relation beSolutions of Gases. tween the solubility of gases and their chemical composiTheir solubility varies between wide limits. tion. SOLUBILITY OF GASES.

Warm

a

faucet water in a test tube.

em

Experiment 32. — (a)

little

there immediate evidence of a previously dissolved gas?

Warm

Do

in a test tube.

soon as the

and

effect

has increased heat?

ammonium hydroxide ? As remaining liquid down the sink

slightly a few cubic centimeters of

result

is

the results resemble the observations in {a)

obtained, pour the

w w

(^)

.c h

What

dence of much gas?

flush well with water.

{c)

Repeat

{b),

using a

little

concentrated hydrochloric acid.

w

the results resemble those of {a) and {b)

is

the temperature

which

is

following: —

constant.

This relation

is

dis-

illustrated

Table of Solubility of Carbon Dioxide Gas. Vol. of Water.

is

directly proportional to the pressure,

ht

by the

Do

?

of a moderately soluble gas

tp ://

The volume

solved by water if

Is

Is there evi-

General Properties of Water.

CLASS-ROOM EXERCISE. 1.

in

What

"soda

is

Is

2.

''

Why should

water?

Why

a strong vessel?

oxygen soluble

it

77

XI.

Why

be kept cold?

kept

so called?

water?

in

Is

hydrogen?

(Consult a

Is air?

text-book regarding the solubility of hydrogen and of oxygen in water.; Sulphur water? 3. What is carbonated water? 4.

Why

5.

Henry's

are subterranean gases often easily dissolved by water?

of the solubility of gases.

— The

Solutions of Liquids.

vn

Law

water

solubility of liquids in

between wide limits. Some liquids, especially oils and organic liquids, are practically insoluble in water, and their insolubility is seen by the formation, after agitation, of two distinct layers of liquid.

em

4a

ll.

varies

.c h

SOLUBILITY OF LIQUIDS. Alcohol, ether, carbon dis nip hide,

be 7iear.

— {a)

and

test

If a pipette is used,

which are should

No flames

tube 10

cc. of

water from

proceed as follows

:

Rinse

tp ://

a graduate or a pipette.

kerosene,

easily.

Measure into a

w

Experiment 33.

w w

used in tins experiment, take fire

out the pipette with water, dip the

ht

pointed end into water and suck up the liquid nearly to the top, then

remove the pipette from the mouth and quickly close the top with the

shown

forefinger, as

in Fig.

40

now

;

cautiously lessen the pressure of the finger

enough

to allow the liquid to

sink slowly to the

stem, then press the test If

it

mark around the

down

tightly,

lower

end of the pipette into a dry tube, and remove the finger. is

a ID cc. pipette,

let

all

the

Fig.

40.

— Using

illustration

water run out

run into the

;

if

test

not, then let

10 cc.

tube and reject the

position

of the

pipette has

This a pipette. the correct

shows been

hand filled

after

the

with liquid.

Experimental Chemistry.

78

Add to the water about half as much alcohol, and shake. Is Add a little more, and shake. Then there evidence of solution? Draw a Is there still evidence of solution? add a third portion. rest.

general conclusion regarding the solubility of alcohol in water. Observe the result {b) To 10 cc. of water add a few drops of ether.

and draw a conclusion. Add to the water about half its volume of Observe the result. ether, and shake. From these two results make a general statement about the solubility of ether in water.

vn

Repeat {b), using successively kerosene, carbon disulphide, and Observe the results and conclude accordingly. glycerine. {c)

:

—

ll.

results as follows

4a

Summarize the

em

Table of Solubility of Some

ht

tp ://

w

w w

.c h

Liquid.

Liquids.

General Properties of Water, powdered potassium chlorate, to III. add Shake each test tube, and then allow them few minutes.

Is there

i

gm. of calcium

sulphate.

to stand undisturbed for a

evidence of solubility in each case?

evidence of a varying degree of solubility?

79

Is there

If III. is doubtful, carefully

an evaporating dish by means and evaporate to dryness. Is there now

transfer a portion of the clear liquid to

of a pipette, or glass tube,

conclusive evidence of solution?

experiment.

Save solutions

I.

Draw

and

a general conclusion from this

II. for {b).

:

—

Solids.

4a

ll.

Table of Solubility of Typical

vn

Tabulate the results of {a) as follows, using the customary terms to express the degree of solubility

ht

tp ://

w

w w

.c h

em

Solute.

Experimental Chemistry.

8o

Since the maximum amount of solute upon the temperature, it is customary to say that a solution is saturated at such and such a temperaFurthermore, the weight of the solvent must be ture. of solid dissolved.

usually depends

Usually, solubility

given.

grams soluble

in

is

the

as

stated

number

Thus the number of grams of potassium which lOO gm. of water dissolves at ture.

13.3

is

31.2

50°C.

is

85.0

ioo°C.

is

246.0

ll.

is

em

4a

0°C.

20°C.

nitrate

vn

—

In Exp. 34 an excess of undissolved solid was present in If, however, cases when the solution was saturated.

.c h

all

of

lOO gm. of water at a certain tempera-

solutions can be brought to the point of saturation, either

tp ://

w

w w

by cooling or by evaporation, frequently no solid will That is, solutions can exist separate from the Hquid. which contain a larger amount of dissolved solid than is These required for saturation at a given temperature.

ht

solutions are called Supersaturated.

Experiment

SUPERSATURATED SOLUTIONS.

35.

— {a)

Fill a

test

tube nearly

sodium sulphate, and add not more than

As

5 cc.

solution occurs, heat gradually to boiling.

until

no more and

will dissolve.

test tube

let it

full

of water.

of crystallized

Warm

Add sodium

Pour the solution into a warm,

stand until cool.

Then drop

clean, dry

in a small crystal of

sodium sulphate and watch for any simple but definite change. happens? Is the excess of solid large? {b) Repeat with sodium thiosulphate, if time permits.

A

slowly.

sulphate

What

supersaturated solution seems to be a case of unstable

equilibrium.

General Properties of Water.

8i

THERMAL PHENOMENA OF SOLUTION. Experiment

^Jb.

— Supplies

:

Test tubes, thermometer,

of fused calcium chloride, potassium nitrate,

drated copper sulphate,

i

ammonium

5

gm. each

nitrate,

dehy-

gm. each of sodium hydroxide and potassium

hydroxide, and a few cubic centimeters of concentrated sulphuric acid. Measure 10 cc. of water into a test tube, take the temperature, add at

sodium hydroxide, and concentrated

sulphuric acid (add the acid to the water). :

—

Tabulate the results as

4a

follows

ll.

sulphate, potassium hydroxide,

vn

one time 5 gm. of fused calcium chloride. As it dissolves, stir with the thermometer and observe the highest reading. Record in the proper place in the table below. Repeat successively with separate portions of water and the ammonium nitrate, potassium nitrate, -dehydrated copper

em

Summary of Thermal Phenomena of Solution.

ht

tp ://

w

w w

.c h

Substances.

Experimental Chemistry.

82 its

water of crystallization.

of temperature due to the

due

doubt there was a slight

heat alone

been proved that

compounds

sulphuric acid

is

so

much

in excess that

observed as the result of solution.

is

when

of

fall

act of solution, but the heat

chemical combination

to the

water,

No mere

sulphuric

acid

is

has

It

dissolved

water and sulphuric acid — hydrates

— are actually formed.

So great

is

in

of

the heat

ll.

vn

produced with large quantities that the solution often boils, and sometimes so suddenly that the hot acid is spattered. Hence, the acid should always be poured slowly into water

4a

with constant stirring.

em

SOLUTION AND CHEMICAL ACTION.

—

Supplies: A gram each of powdered Experiment -^. sodium bicarbonate, lead nitrate, potassium dichromate

tartaric

mortar

;

.c h

acid,

or evaporating dish, large vessel of water.

in a dry mortar or evaporating dish i gm. of powdered tarand an equal weight of sodium bicarbonate. Is tliere any decided evidence of chemical action ? Pour the mixture into a large

Mix

{a)

Is there

conclusive evidence of chemical action

?

w

vessel of water.

w w

taric acid

Repeat, using powdered lead nitrate and powdered potassium

{b^

tp ://

dichromate.

Describe the results in {a) and {b^ and interpret the whole experi-

ht

ment from the standpoint of

1.

CLASS-ROOM EXERCISE.

{d) Solvent of chemicals.

Composition of sea water.

{b)

Erosive agent.

{c)

Solvent of drugs and medicines.

{e)

Relation of taste and solution.

2.

4.

XIL

Solvent powder of water. {a) Cleansing agent.

3.

solution.

Why are so many solutions used in the laboratory ? A liter of sea water was evaporated to dryness, and

weighed 36.4 gm. 5.

rise of

How

is

What

the residue

per cent of the sea water was " salt "

?

a cold saturated solution of sodium chloride influenced by

temperature

?

CHAPTER

VI.

Water was

vn

COMPOSITION OF WATER. thought to be an elenient until about the end At that time its composition

ll.

of the eighteenth century.

mingled

it

em

4a

was shown by the efforts of Cavendish, Priestley, and Lavoi^ sier, and, later, by Humboldt, Gay-Lussac, Nicholson and Carlisle, Dumas, and Davy. Their labors were so interbe impossible to follow their experiments

will

We shall, therefore, consider only the main

facts

.c h

chronologically.

which contributed

to the discovery of the

some

w w

of water, together with

composition

later work.

w

DECOMPOSITION OF WATER BY ELECTRICITY.

decomposed by

tp ://

Water was

first

electricity in

Nicholson and Carlisle, and confirmed by

1800 by

Davy by

a series

through a period of six The decomposition of water by electricity is called

ht

of brilliant experiments extending

years.

Electrolysis.

ELECTROLYSIS OF WATER. Experiment containing

38.

—

Fill

the

Hofmann

10 per cent of sulphuric

apparatus, Fig. 41, with water

acid

so

that

the

water in the

reservoir tube stands a short distance above the gas tubes after the

Connect the platinum terminal wires and collect at the top of each tube. Allow the current to operate until the height of the gas in the smaller tube is from 8 to 10 cm. Measure the

stop-cock in each has been closed. with a battery.

As

the action proceeds, small bubbles of gas rise

63

Experimental Chemistry,

84

Assuming that the tubes have the same height of each gas column. diameter, the vokunes are in approximately the same ratio as their How do the volumes compare ? heights. Test the gases as follows

:

(a)

Hold a glowir>g

taper over the tube containing the smaller quantity of gas, cautiously open the stop-cock to allow

JL

JL

^

'^

the water (or air) to run out of the glass tip, and then let out a little gas upon the glowing taper. II

What

Repeat until the gas is ex? Care must be taken not to lose the gas by clumsy manipulation. It is advisable to have at hand several partially burned tapers or thin

™

the gas

is

ll.

vn

hausted.

escaping water extinguishes the other stop-cock long

the

first

enough

to force out the water in the glass tip;

i

^^^^^fcg^

and

stop-cock again,

out the gas slowly, and hold

at the

^«*i^^^^^

the

—

a platinum tip (see

close the stop-cock,

em

if V

Open

(^)

let

slip

.c h

I

one.

4a

splints, in case the

same time a lighted match

tip,

at the

What small and almost colorless flame. gas ? Repeat until the gas is exhausted.

w w

Hofmann Fig. 41. apparatus.

end of

then immediately thrust a taper into the the

Describe the

tp ://

w

Draw a general conclusion from this experiment. whole experiment and sketch the apparatus.

is

— Optional Method.

ELECTROLYSIS OF WATER.

ht

Experiment one shown

39.

— The Hofmann apparatus

in Fig. 42.

method described

in

A

App. A,

§ 6.

may be

replaced by the two parts by the The upper part is used in this

large bottle. A,

is

cut into

experiment and it is about 15 cm. deep. A bottle with a small mouth is preferable, though the one shown in the figure gives satisfactory results. Through these Provide A with a stopper or cork having two holes. holes pass two glass tubes into the upper ends of which are sealed platinum wires. 'The upper end of each wire is attached to a narrow strip of

platinum

foil

by passing the wire

in

and out through several holes

The lower ends pricked by a pin along the longer diameter of the strip. When of these wires are attached to the battery by double connectors. the stopper

is fitted

with

its

tubes, press

it

into the neck of the bottle so

Composition of Water. firmly that there

8s

no crack between the neck and stopper. This is if the neck is small and the stopper is rubber.

is

easily accomplished,

Corks are

difficult to

and neck are

warm water

ill

to heat the glass.

Meanwhile melt some bottle

the

Place the

an iron stand and

bottle in the ring of

pour

unless both cork

fit,

perfectly circular.

paraffine

warm enough

is

and when

not to be

about

fills

the neck of the bottle.

press

cools,

it

around the tubes

and where the glass and

When

cold,

to detect

paraffine meet.

pour water into the bottle If the apparatus is

any leak.

ll.

it

it

not tight, add more paraffine.

It.

may be

4a

As

em

until

vn

cracked by the hot paraffine, pour out the water and pour in the paraffine slowly

necessary to adjust the position of the

C

platinum strips when the test tubes,

in

Exp.

38.

is

into the bottle.

accomplished the same as IS nearly filled with water

A

w w

electrolysis

The

.c h

and D, are lowered

containing 10 per cent of sulphuric acid,

and Z^ are filled with the same soluand clamped over the platinum strips as shown in Fig. 42. When one tube is

C

tp ://

full

w

tion

of gas, the current

volume measured as is

is

Exp.

stopped, the 38,

and each

tested with a lighted taper or blaz-

ht

gas

in

ing stick of wood.

What What are It

is

Fig. 42.

the ratio of the volumes

the gases

Method.

?

has been shown by

ment 38

(i)

that

— Apparatus for the elec— Optiotial

trolysis of water.

?

many

only two

hydrogen and oxygen,

accurate trials of Experi-

gases

(2) that

the

are

produced,

ratio

of

their

viz.,

vol-

umes is 2 to I, (3) that the sum of the weights of the It products equals the weight of the water decomposed. therefore follows that water is composed of hydrogen and

Experimental Chemistry.

86

oxygen combined

in the proportion of 2 to

i

by volume.

Additional experiments are necessary to prove the exact composition of water.

Hydrogen and Water.— The fact that hydrogen is a component of water, as shown in Exp. 38, may be verified by an experiment first performed by Lavoisier. He passed steam through a red hot gun barrel containing bits of iron. solid

product was, he

said,

''

in the state of the black

vn

The

oxide precisely Uke that which had been [formed from iron

This experiment

oxygen." it

the

to

em

hydrogen, that

us more suitable than that of

I

produce."

'

— from

is

to

say,

hudor water, and

.c h

generative principle of water

gehiomai^

is

name " hydrogen." "No name has appeared to

led

Lavoisier says in his notes,

*

historically

ll.

in

because

interesting

4a

when] burnt

w w

DECOMPOSITION OF WATER BY IRON.

—

w

Method: Pass steam over heated iron filings Experiment 40. and collect the gaseous product over water. Apparatus: An iron tube about 30 cm. long and 2 cm. in diameter,

tp ://

iron filings, steam generator, glass trap, pneumatic trough, three bottles

for

ht

(250 CO.), and stoppers and connectors. Process: Fill the iron tube about half full of clean iron filings, hold provide a free channel it horizontal, and tap it gently on the table to the gases.

Support the tube in a furnace, or lay it on the Provide each end with a one-hole rubber

rings of two iron stands.

To one end pneumatic trough. To

stopper.

attach

a

delivery

tube which passes into a

This the other end attach the steam generator. a two-hole rubber is a 500 cc. flask half full of water and provided with stopper; through one hole passes a straight glass tube about 40 cm.

—

to open at both ends, and reaching to the bottom of the flask any excessive back pressure through the other hole passes a short glass tube bent at right angles and connected by rubber tubing with a glass trap,i which in turn is connected by rubber tubing with a

long,

relieve

;

1

See Teachers' Suppleinent.

Composition of Water.

87 The

short glass tube projecting from the stopper of the iron tube.

The

trap collects any water driven over from the flask.

tween the

flask

distance be-

and iron tube must be as short as possible

condensation of the steam before

it

reaches the iron tube.

to prevent

advis-

It is

able to put in the flask several pieces of granulated zinc, pipe stem, or glass tubing, to insure steady boiling.

the bottles with w^ater and invert in the trough, but not over the

Fill

first bubbles will be air. Heat the whole by means of one or more wing-top burners. Meanwhile heat the water in the steam generator, and by the time the steam has

hole in the shelf, since the iron tube

vn

been formed, the iron tube will be sufficiently hot. If drafts cool the it at the ends with asbestos boards. It is advisable, also, to keep the ends of the tube cool by hanging a piece of asbestos board from each end just inside the stoppers. Excessive heat may melt the If

they should melt and stop up the tube, the pressure gauge

steam generator

tions of the gas.

few minutes for

will indicate the difficulty.

As soon for

the iron tube

is

cool,

many

first

por-

Test the gas

full.

different tests as the

examine the contents.

w w

When

two bottles nearly

oxygen, applying as

circumstances permit.

Reject the

as the hydrogen begins to be delivered, a

will suffice to collect

hydrogen and

em

in the

.c h

stoppers.

4a

ll.

tube, protect

Compare

it

with

the original iron and with magnetic oxide of iron.

Describe this experiment, stating exactly what

it

proves.

ht

tp ://

w

Other metals, zinc and magnesium, for example, will also decompose water, and hence furnish additional evidence of the fact that hydrogen is one component of water.

1.

CLASS-ROOM EXERCISE.

State exactly what Exp. 40 proves

XIII.

and suggests

alDOut the

com-

position of water. 2.

water

What

does Exp. 23 prove and suggest about the composition of

?

3. If coal instead of iron had been used in Exp. 40, what industry would be illustrated ? (Hint look up "water gas.'') 4. Summarize the evidence thus far presented about the composition :

of water. 5.

Actual facts contributed by

position of water.

Davy

to our

knowledge of the com-

Experimental Chemistry.

88

—

The fact that oxygen is a constituOxygen and Water. shown in Exp. 38 and suggested in Exp. 23, may be verified by allowing chlorine and water to interact Chlorine is a gas and an element, and in the sunlight. ent of water,

be fully studied.

later will

DECOMPOSITION OF WATER BY CHLORINE.

— Construct

a

chlorine

generator and

prepare

vn

Experiment 41.

chlorine as directed in Exp. 57.

Pass the gas into a deep vessel of

The Com-

4a

ll.

water until a sample of the liquid smells strongly of chlorine. delivery tube should reach to the bottom of the vessel of water.

a flask with a slender neck with this saturated solution of cork tightly, and stand in the sunlight. After several hours a small quantity of gas will collect at the top. Test the gas with a glowRepeat the experiment, if the result is not satisfactory. ing match.

pletely

fill

em

chlorine.,

.c h

As the amount of gas is usually small, the apparatus shown in Fig. 43 gives more satisfactory results than the flask. It is a glass tube about 2 cm. in diameter and i m. long,

w w

closed at one end, either by sealing or

]

— Tube for the decompowater by ^ chlorine.

tp ://

sition of

w

Fig. 43.

i\

by inserting a cork or solid stopper, and drawn out at the other end so that the smaller portion is about 4 cm. long and ,. ^ r^, a filled The tube is nu I cm. m diameter. with chlorine water, and the smaller end .

.

-,

:

ht

immersed in a vessel containing the same solution. When sufficient gas has been collected, cover the smaller end of the tube with the thumb, invert the tube, and

test the gas,

which

will

nearly

fill

the

smaller portion of the tube.

Describe this experiment, stating what tion of water.

it

shows about the composi-

Sketch the apparatus used.

Interaction of

Sodium and Water.

cerning the composition of water

— Additional tacts conmay be

obtained by a

study of the interaction of sodium and water.

Sodium so soft

it

is

an element.

It is also

can be cut with a knife,

a metal, though

and

is

much

it is

lighter in

Composition of Water.

89

weight than those metals which are familiar. Nevertheless it has the luster characteristic of the metals, and chemically Its

behavior

is

markedly

like the other metals.

Sodium

oil

to protect

atmosphere.

//

should be tised cautiously and

iccording to left

it

Small fragments

directions.

is

from the moisture of the

kept beneath

strictly

sJiould not be

about or thrown into the refuse jar, but into a large

of zvater

especially

provided for the purpose,

vn

vessel

tJie

precautions

Experiment 42.

to

be observed in iising .^odiuin.

4a

Remember

ll.

INTERACTION OF SODIUM AND WATER.

Sodium, pneumatic trough

-Supplies:

filled

with

em

water as usual, tea lead, test tube, forceps, litmus paper, iron stand and clamp.

w w

.c h

{a) Scrape the brown coating from a piece of sodium, press it between filter paper to remove the excess of oil, cut off a piece not larger than a small pea, and drop it upon the water in the trough. Stand far enough away so that you can just see the action. Wait until you are sure the action has stopped, and then describe all you have seen.

The

action in {a)

it

further studied as follows

and clamp

tp ://

is

may be

w

{b)

tube with water, invert

it

over the hole in the shelf of the trough.

sodium loosely

in a piece of tea lead

about

5

Wrap

Fill a test

mouth

a small piece of

cm. square, make two or

three small holes in the tea lead, and then thrust

ht

:

in the trough so that the

it

under the shelf of

A gas will rise into the test tube.

Proceed sodium and dry tea lead until the test tube is nearly full of gas then unclamp and remove, still keepHold a ligKted match, for an instant, at the ing the tube inverted. mouth cf the tube. Observe the result, watching especially the mouth of the tube. What is the gas ? Why ? Remembering that sodium is an element, where must the gas have come from ? If there is any doubt about the nature of the gas, collect more, and subject it to those tests

the trough with the forceps.

similarly with additional small pieces of ;

which (c) it

will

prove

its

nature.

Put a piece of

filter

paper on the water in the trough, and before

sinks drop a small piece of sodium upon

it.

Stand back and observe

Experimental Chemistry.

^o

which usually occurs soon you have seen. What burned ? What caused it to burn ? To what is the vivid color probably due ? (In answering these questions, utilize your knowledge (i) of the properties of the gases previously studied, and (2) of the usual accompanithe result.

for the slight explosion

Wait

ifter the action stops.

Describe

all

action, suggested here by the melting of the sodium.) {d) Test the water in the trough with red litmus paper. Push the paper to the bottom or to the place where it is certain that chemical Test, until the red action between water and sodium has taken place. Describe this litmus paper has undergone a decided change in color. With another piece of red litmus paper test a solution final result.

vn

ment of chemical

of water.

full

(see

App. A,

Describe the

same

and hold

Is the color of this flame

result.

?

in the Bunsen flame. and that noticed in {c)

it

em

the

§ 14) into this solution

4a

half

ll.

dissolving a small piece of sodium hydroxide in a test tube Dip the platinum test wire Is the result similar ?

made by

verifies the previous observation regard-

Experiment 42

.c h

It shows also ing the presence of hydrogen in water. that when water and sodium interact another substance is

This is sodium hydroxide. Its name suggests its components, for it is a compound of sodium, hydrogen, and oxygen. It belongs to a class of substances called alkaUes, which will be considered later. These alkalies turn red Htmus paper blue; and sodium hydroxide, like all sodium compounds, colors a Bunsen flame an intense yellow. The color is due to the volatiUzed sodium, and is the test not for hydroxides, but for sodium compounds. The sodium

ht

tp ://

w

w w

formed.

hydroxide

is

in solution in the trough,

and by evaporating

the water could be obtained, as a white solid, having properties of the sodium hydroxide actually used to

the solution in(<^). water,

and forms

all

the

make

Since sodium liberates hydrogen from

at the

same time a compound

also contain-

ing hydrogen, then the hydrogen in water must be divisible If in Exp. 42 \b) the sodium had been into two parts.

weighed and

its

weight compared with the volume of

Composition of Water.

91

hydrogen liberated, it would have been found that .1 gm. And if the sodium liberates 48.22 cc. of hydrogen. sodium hydroxide thus formed had been dried and then heated with sodium, 48.22 cc. more of hydrogen would This shows that the hydrogen in have been obtained.

of

water

is

The

divisible into

facts

two equal

parts.

revealed by the interaction of sodium and

water, together with others which have been proved, permit

Na + Sodium

H.,0 Water

23

18

H

=

simplest form by the

its

—

vn

:

NaOH

+

Hydrogen

4a

following equation

ll.

us to express the reaction in

Sodium Hydroxide

(7)

40

em

I

.c h

This equation means that 23 gm. of sodium are needed to liberate i gm. of hydrogen from 18 gm. of water, and to form, at the same time, 40 gm. of sodium hydroxide.

—

tp ://

w

w w

The preceding The Quantitative Composition of Water. experiments on the composition of water have been mainly They have shown by analysis and synthesis qualitative. composed of hydrogen and oxygen, and that water is that approximately 2 to i. The most decisive evidence of the quantitative composition of water is obtained by the determination of (i) its exact volumetric composition, (2) its exact gravimetric composiis

ht

the ratio of their volumes

tion,

and

(3) the density

"by volume," and

of

gravimetric

steam.

Volumetric means

^eans "by

weight."

VOLUMETRIC COMPOSITION OF WATER.

—

Method: Explode measured volumes of hydrogen Experiment 43. and oxygen and measure the residual gas, using an excess of either gas. Apparatus : The apparatus is shown in Fig. 44. ^ is a level tube about 90 cm. long, provided with a base, or fitted at one end with a one-hole stopper, to which

is

connected a piece of pressure tubing, I^

Experimental Chemistry.

92

about 50 cm. long. When not in use, A is clamped in any convenient IS 2. eudiometer so arranged that the open end can be

position.

F

moved about in the and is made from a is

E.

This reservoir

is

about 15 cm. deep according to the

five-pint acid (or similar) bottle

App. A,

directions given in

and

reservoir,

§ 6.

It is

supported by a ring or clamp,

provided with a one-hole stopper, through which passes a short

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

^\.

Fig. 44.

— Apparatus for determining the volumetric composition of water.

glass tube, G, the ends of which have a flange,

end

in the

Bunsen flame and pressing

it

made by

melting, each

quickly upon a hard surface.

made, a rubber stopper, C, just large enough to pushed down firmly upon the other stopper. After the flange is made, the upper end of G is pulled down hard upon C, the tubing, B, is pulled over the lower end of G until it touches

Before the flange fit

is

the eudiometer,

is

Composition of Water.

93

the large stopper, and tied securely near the stopper and near the

A Hofmann

lower flange by shoemaker's waxed thread.

screw

is

attached near the point D. Process: Loosen the Hofmann screw, pour into A water that has been standing in the laboratory for at least twenty-four hours, until the then tighten the screw and add more reservoir, E, is two-thirds full water until the level tube, A, is three-fourths full clamp A at any con;

;

venient height to the iron stand which supports the apparatus.

B

Pinch

remove any imprisoned air. Fill the eudiometer, F, with some of the same water, invert in the reservoir, and clamp it so that the open end is just below the surface and near the wall of E. Introduce into /^ about 10 cc. of oxygen free from air. The oxygen

may be taken from

a gas holder, or

it

ll.

vn

to

may be prepared from

and press

Hofmann tus to

it

down upon

the stopper, C\ clamp

screw, stand a thermometer in E^

remain undisturbed

loosen the

Meanwhile, read

for at least ten minutes. all

necessary notes.

Hold the top of the

.c h

the barometer, and write

Unclamp

F again,

and allow the whole appara-

em

/^

the usual

needed.

is

4a

mixture in a test tube, since only a small volume

eudiometer and raise or lower the level tube, until same height in both A and F, then read the volume of oxygen in the eudiometer and the temperature of the water in E. Clamp A again in any convenient position. Record all readings as level tube near the is

at the

w w

the water

illustrated below.

tp ://

w

Unclamp the eudiometer and lift it from C, and introduce into it from 25 to 30 cc. of hydrogen free from air. The hydrogen may be prepared from zinc and sulphuric acid in a test tube. Proceed as in the reading of the oxygen, observing the same precautions, especially the interval before reading the gas volume.

ht

This time, however, the eudiometer must be pressed down hard upon the stopper, C, taking care, of course, not to force the larger stopper out of place.

volume and other readings as

Make

sure that

all

stoppers and jaints are tight, lower

the gases in the eudiometer, clamp the sible just

Record the

total

illustrated below.

Hofmann screw

below the glass tube, G, and clamp

A

A

to

expand

as tight as pos-

as before.

Explode the

mixture of hydrogen and oxygen by passing an electric spark through the eudiometer. plate

machine.

The The

spark

may be

explosion

is

obtained from a RuhmkorfF

coil

or

indicated by a slight click, often

accompanied by an instantaneous flash passing down the tube from the platinum wires to which the coil is connected. The ends of the plati-

Experimental Chemistry.

94 num

wires must be about

mm.

5

apart in order to insure an explosion.

After the explosion, loosen the screw and allow the water to seek

own

level in the

its

Let the whole apparatus remain undis-

two tubes.

turbed for ten minutes or more, then read as before the gas volume, thermometer, and barometer. A minute quantity of water is formed when the two gases unite, but so minute that

its

volume

proved by the usual

not measurable.

is

be hydrogen.

tests to

The residual gas can be The data obtained enable

us to compute at once the volumetric composition of water.

The

:

may be

recording of the data and calculation of the

final

vn

Calculation

by an experiment actually performed by a Other determinations will vary somewhat student with this apparatus. from these figures, though the final result may be the same. :

I.

ll.

—

Oxygen.

V=

II.

Hydrogen and oxygen.

y - 51.5

10.7 cc.

=i7"C. P' = 767 mm. a = 14.42 mm.

cc.

=i7°C. P' = 767 mm. a = 14.42 mm. /

w w

.c h

/

III.

4a

Data

illustrated

em

result

Residue

after the explosion.

tp ://

w

y = 20.4 cc. =i7°C.

/

P' = 767 mm.

=

a

14.42

mm.

ht

These volumes, corrected (see App. B, formula pressure, and aqueous tension, become I.

II.

III.

—

Oxygen added

5)

9.97 cc.

Hydrogen and oxygen added 48.01

Hydrogen

for temperature,

cc.

19.02 cc.

left

hydrogen remain, then the volume of hydrogen and oxvsren which combined must be Since 19.02

cc. of

48.01

-

19.02

=

28.99 cc.

and volume of hydrogen which united with th^xygen must be 28.99

~

9-97

=

^9-°2 cc.

^

Composition of Water. If 19.02

of hydrogen

cc.

with

united

water, then the ratio in which they

19.02

Accurate repetitions of

:

9.97

cc.

95 of oxygen to form

combined was

9.97 or 1.9

this

:

i.

experiment have shown that

the ratio in which the pure gases, hydrogen and oxygen,

combine

is

2 to

i,

that

is,

the vohuiietric composition of

two parts hydrogen and one part oxygen. The was obtained in Exp. 38, to be sure, but the result of Exp. 43, ^^btained by a more accurate method, establishes the fact beyond dispute. water

is

result

4a

ll.

vn

same

GRAVIMETRIC COMPOSITION OF WATER.

—

19,

but

.c h

generated as in Exp.

em

Method: Pass dry hydrogen over a weighed Experiment 44. amount of copper oxide and collect the water formed in a weighed tube. Apparatiis : The construction and arrangement of the apparatus, except the generator, is shown in Fig. 45. The hydrogen may be it

is

difficult

with this apparatus to obtain

w w

a slow evolution of gas as well as to be sure the generator will not be

w

exhausted before the experiment

ht

tp ://

in, r-

is

completed.

If

a gas holder or a

Experimental Chemistry,

96 ing

it

from the bent tube

the screw and

A

fill

Tighten

bottom by a plug of cotton.

at the

with dilute sulphuric acid.

When

the screw

loosened, acid will flow into B, and hydrogen will be evolved. />r

1

1.

—

is

It is

B into a permanent position, open the passage a little, and regulate the evolution of hydrogen by raising or lowering A by another clamp. A height will be found by trial

advisable to clamp '

II.

which In

produce the desired rate of evolution.

will

^

Fig. 45

a Drechsel drying bottle

is

vn

which should be half full of concentrated sulphuric acid, and B is aK^-tube to be filled with both serving to dry the hycalcium chloride drogen. CC is a hard glass tube from 15 cm.

4a

to 20

ll.

—

cm. long, and from

diameter.

B

em

pers to

1.5

and

Z),

the latter being a small (10 cm.)

iMarchand tube to be

E

is

filled

with fused calcium

a U-tube to be

filled

with calcium

.c h

chloride.

cm. to 2 cm. in

attached directly by rubber stop-

It is

chloride to prevent the moisture in the air from

V

are Only the tubes CC and weighed before and after the experiment. At a copper wire (No. 20) is the points C and wound once or twice loosely around the com-

w w

entering D.

w

C

bustion tube, and allowed to project at several

46.

-A

tube from cracking and the stopper from melting This wire is fto^ weighed with at these points.

generator

ht

FIG.

tp ://

points, like the spokes of a wheel, to prevent the

^j^^

ratus

subsequently studied)

^yjn

.

^jj

^^^^^

producing a steady current of hydrogen (and other gases to be

for

•'

-^^ ^^^t ^^

1,1

,

^j

sary points, interfere

CC.

but not, of with

the

The appa-

l^t^

may be supported by clamps course,

^

^1

at the neces-

where

they

application of heat to

Clean and dry the tubes

B

and E, and

provide them with one-hole rubber stoppers, the holes of which are temporarily plugged with a short glass rod fill each three-fourths full ;

with lumps (not powder) of fused calcium chloride, push a plug of cotton down loosely upon the calcium chloride, wipe oflf any small particles of calcium chloride,

stoppers

— removing

Clean and dry

D

and

close the tubes with the

the plugs, of course,

and prepare

it

when

as follows

:

plugged

the tubes are in use.

Push enough absorbent

Composition of Water. down

cotton

the straight limb and up the other limb to

lower bulb, and then

fill

put in the upper bulb

is

97 fill

loosely the

the tube with fused calcium chloride

;

the straight limb

nothing

;

provided with a one-hole

is

rubber stopper, which has previously been cleaned by boiling

it

succes-

sodium hydroxide, hydrochloric acid, and water. This stopper should have a short glass connector, bent at a right angle, and each end of the tube -Z^^^^--- -ll should be protected from { the air by a short rubber sively in dilute

^

'

1

,

,

.

,

Fig. 47.

,

plug.

vn

tube plugged with a glass

— Glass

ll.

rod (see Fig. 47). The water which collects in the empty bulb during the experiment may be removed by a bit of rolled filter paper, and the tube thereby used several times without

CC

The

refilling.

4a

to

stoppers fitted

should be cleaned, before use, by boiling as above described.

Process:

Clean and dry the combustion tube

CC

and put

in

it

iron or porcelain dish to

em

about 20 gm. of granulated copper oxide which has been heated in an

remove moisture and organic matter.

Intro-

.c h

duce the copper oxide by the method illustrated in App. A, § ii, and hold it in place by two loose plugs of shredded asbestos which has been heated red-hot by the blast lamp. if

the dish

is

It

may be heated in a porcelain Weigh the combustion

heated and cooled gradually.

w w

dish,

tube and contents.

Weigh

Marchand

D, without the proConnect the apparatus as shown in Fig. 45, joining CC directly to B and Z>, after the copper wires have been slipped over the ends of the combustion tube. Attach the generator, and pass a slow current of gas through the whole apparatus to drive out the air and incidentally to detect any leak. If there is no leak, then the gas will not bubble through A, when the open end of E is covered for an instant with the finger. If there is a leak, stop it Regulate the flow of hydrogen so that about three before proceeding. bubbles a second pass through A. An ordinary Bunsen burner and a the

tube,

Record the weights as shown below.

ht

tp ://

w

tectors.

wing-top burner are needed, the latT;er for constant use, the former for an emergency. Heat the whole combustion tube slowly at first with the wing-top burner, gradually increasing the heat where the copper

oxide

is

located.

As

the heat increases, moisture will collect in

Heat the combustion tube from

C

toward

C

CC

so that the moisture will

not collect at C, but be driven along beyond the copper oxide toward

C

and over

into the bulb oi

D.

The

point

as hot as possible without melting the stopper

C ;

must be kept if

hot. just

the moisture collects

Experimental Chemistry.

^8 here,

The moisture often collects in the to remove. must be kept hot enough from the outset to volatilize drops gather at C, heat this point cautiously with a low

difficult

is

it

oxide, hence this

the water.

If

The wing-top burner may be held at various angles allowing heat to be easily directed upon short spaces. When the copper oxide ceases to glow, lessen the heat somewhat and any moisture seen, or thought to be, in the combustion drive over into Bunsen

to

flame.

CC, thereby

D

Allow the hydrogen to run while the apparatus is cooling. When CC is cool enough to handle, disconnect the generator and draw of E. air through the apparatus by applying the lips at the open end Disconnect CC, wipe out any organic matter from the inside at theand weigh as before. Record Disconnect ends, and then weigh.

vn

tube.

ll.

D

shown below.

4a

the weights as

The form of recording the data and calculating the may be illustrated by figures taken directly from a studenfs

em

Calculation: final result

Other determinations of the gravimetric composition of water may, of course, give entirely different figures, though the final note book.

may :

—

w w

Data

agree.

.c h

results

Combustion tube.

I.

Grams.

tp ://

w

Weight of combustion tul)e and copper oxide before heating Weight of combustion tube and copper oxide after heating

Weight of oxygen II.

Marchand

lost

-

.

ht

1.021 are in the

same :

I

is,

:

ratio as 8

1.021

x—\

That

64.783

.

0.905

75-720

1021

0.905

But

.

76-741

....

Weight of water formed

Thus

65.688

tube.

Marchand tube after experiment Weight Weight of Marchand tube before experiment of

But 0.905 and

.

1.128

:

and 9 (approximately).

;: I ;;r

J28 :8 ;9.024

oxygen makes up | of water, and the remaining \

is

hydrogen.

Composition of Water.

99

Final dh-ections : Protect from the air the whole drying apparatus by connecting it "tandem"' and plugging the ends with the rod or rubber plug, as the case demands. Protect with its rubber plugs. Pour the acid from the generator, wash the zinc and rubber tube free from acid, and recharge, or preserve empty, for future use.

B

Numerous

whose work

chemists,

is

have found

reliable,

proportion (|) to be approximately correct.

— The density

Density of Steam.

of

steam

is

the ratio of

vn

this

ll.

the weight of a given volume of steam to an equal volume

hydrogen under the same conditions. It could easily be if we knew the weight of a liter of steam under given conditions of pressure and temperature, because the weight could then be compared directly with the weight of a liter of hydrogen. It has been found that .8063 gm. is the weight which a liter of steam would have, if it could exist as steam at the normal temperature and pressure. of

.c h

em

4a

calculated

which

are

w

conditions,

w w

The determination is carried on, of course, at a temperaC, and the volume reduced to standard

ture above 100°

the weight of a

liter of

ht

hydrogen, we have

The

simply arbitrary points, selected

the physical states of matter.

tp ://

irrespective of

—

Dividing steam by the weight of a Hter of

:8o63^ .0896

when the now all that

significance of this fact will appear later,

subject of molecular weights

can be said its

^

is

studied.

Just that the molecular weight of a gas is

is

twice

Hence 18 is the molecular weight of steam. Summary. The following facts have been revealed, density.

—

partly by our experiments, and partly by suggestion, in the study of the composition of water :

—

Experimental Chemistry.

lOO 1.

Water

is

compound

a chemical

of

hydrogen and

oxygen. 2.

It is

formed by burning hydrogen

in the air, or

by

exploding a mixture of hydrogen and oxygen.

ll.

vn

It can be decomposed by electricity into hydrogen 3. and oxygen in the proportion of two volumes of the former to one volume of the latter. Sodium liberates hydrogen from water, and forms at 4. the same time a solid containing hydrogen equivalent to the hydrogen liberated. Iron also liberates hydrogen from

5.

4a

water.

Chlorine liberates oxygen from water.

6.

Two

8.

The molecular weight

of water

is

18.

foregoing facts permit us to write the equation

w

The

w w

.c h

em

volumes of hydrogen and one volume of oxygen combine to form water, and the weight of the water formed equals the weight of the gases. Water is formed by the union of two parts by weight 7. of hydrogen with sixteen parts by weight of oxygen.

tp ://

H^

ht

(8)

as the simplest expression of the reaction for the formation of water

is

from hydrogen and oxygen. density of oxygen (see page 50)

The significance of the now apparent, at least

in part, since 16 is

the smallest

number which can be used in the above equation. meaning of the result of the determination of the metric clearer.

The gravi-

page 98) is likewise All facts point to the truth of equation (8).

composition of water (see

Composition of Water. CLASS-ROOM EXERCISE.

Actual facts contributed to our knowledge of the composition of

—

Cavendisho

{i^^

(^)

Dumas.

(^)

Gay-Lussac.

The formula (/^)

{c)

3.

of water.

Why HP? Why riot HO, as Why not U.,OJ

Which

formerly?

ll.

(a)

vn

water by

2

of the following are oxidation and which reduction

{a) Burning of hydrogen.

{c)

w w

ice,

Hydrogen, Oxygen, Chlorine,

sodium hydroxide, copper oxide,

iron.

w

Define gravimetric, volumetric, eudiometer, Sources of error in Exps 43 and 44, and Litmus.

ratio, density.

how

avoided.

tp ://

8.

Iron, Copper,

Formula of water, steam,

magnetic oxide of

7.

.c h

Symbol of Sodium,

Platinum.

6.

—

Formation of iron oxide from steam and iron. Formation of magnesium oxide by heating magnesium in air.

5.

:

em

(<^)

4.

XIV.

4a

I,

loi

(a) Source.

Preparation of commercial form.

ht

(d) (c)

Uses.

Volumetric Composition of Steam.

—

If

water

is

decom-

""are exploded when the surabove 100° C, then the product is gaseous water, that is, steam. If the experiment is performed quantitatively, it is found that three volumes of the

posed, and the mixed gases

rounding temperature

mixed gases

form,

is

two volumes of steam.

tance of this fact will appear

later,

when

The imporsimilar facts

regarding the two gases, hydrochloric acid and ammonia,

vn

ll.

4a

em

.c h

w w

w

tp ://

ht 2H2

+

Composition of Water.

A

7.

piece of sodium weighing 150

Calculate

water.

gm.

allowed to interact with

is

The weight and volume of hydrogen liberated. The weight of sodium hydroxide formed.

(a) (d)

A gram of

8.

—

103

sodium amalgam (a mixture of sodium and mercury) hydrogen at 13° C. "What per cent of

liberated from water 200 cc. of

sodium did the amalgam contain? 9. How many centigrams of hydrogen

will

How many

be liberated when 23 eg.

if the sodium had contained 8 per cent of impurities? 10. How many grams of hydrogen can be obtained by using 3 gm. How many cubic centimeters ? of sodium ? 11. Hydrogen is passed over 2.48 gm. of copper oxide, which at the end of the experiment weighed only 2.24 gm. the water formed weighed In what ratio did the hydrogen and oxygen combine? 0.27 gm. 12. Calculate the ratio in which hydrogen and oxygen combine to

centigrams,

4a

ll.

vn

of sodium interact with water?

em

;

form water from the following data

Grams.

.c h

oxide tube before the experiment

.

105.6

.

10 1.6

....

84.8

oxide tube after the experiment tube after the experiment

tube before the experiment

.

.

.

80.3

.

Calculate the ratio in which hydrogen and oxygen combine to

w

13.

—

w w

Weight of copper Weight of copper Weight of drying Weight of drying

:

tp ://

form water from the following data, which were obtained by

14.

What

of copper oxide tube after the experiment

of drying apparatus after the experiment

If

—

.

334-598 314.236

.

449.263

of drying apparatus before the experiment

.

426.358

weight of copper remains after 159 gm. of copper oxide ?

20 gm. of hydrogen are passed without loss through a tube

containing hot copper oxide, what weight of w^ater 16.

.

.

have been reduced by hydrogen 15.

:

Grams.

of copper oxide tube before the experiment

ht

Weight Weight Weight Weight

Dumas

Berzelius

and Dulong,

in 1820,

is

formed

?

obtained the following data in

three determinations of the gravimetric composition of water

:

—

Loss of copper oxide tube in grams, respectively, 8.051, 10.832,

and

8.246.

Experimental Chemistry.

I04

Weight of water formed

in

grams, respectively, 9.032, 12.197, 9.27. What is the average

Calculate in each case the ratio of combination. result 17.

?

Dumas and

Stas, in 1843, repeated the

work of Berzelius and

Dulong, and as an average of nineteen determinations found that 840.161 gm. of oxygen formed 945-439 g^'^- of water. Calculate the

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

ratio of combination.

CHAPTER

VII.

THE ATMOSPHERE.

The atmosphere

is

the gaseous envelope surrounding

ll.

vn

the earth and extending into space. It is often called the The word air was used by the earUer chemists in the air. The words sense in which the word gas is now employed.

em

4a

atmosphere and air are often used interchangeably. The study of the atmosphere has occupied the time of many skilful chemists, and the progress of science has been has-

the influence of its

weight, and the proportion and inter-

Boyle

constituents.

(i

626-1 691) began these

w w

action of

its

.c h

tened by their labors, especially by their investigations of the action of air on living things, its relation to combustion,

A new and they are still in progress. impetus has recently been given to the work by the discovery of argon in the atmosphere by Rayleigh and Ramsay. This gaseous element, which had hitherto es-

tp ://

w

investigations,

caped detection, forms about ^Jq part

ht

Composition of Air.

—

It

of the atmosphere.

has already been shown that

contains oxygen and at least one other gas.

It is

air

now

a

favorable time to study this other constituent and the proThese portions in which these two^ases exist in the air.

two objects may be simultaneously accomplished by a

QUANTITATIVE EXAMINATION OF Phosphorus

is

used in

this experiment,

AIR.

before touching

the phosphorus, read carefully the precautions stated belozv,

and

observe them. 105

Experimental Chemistry,

io6

air

Apparatus

^

is

a

—

Method: Remove the oxygen from a measured by phosphorus, and measure the residual gas.

Experiment 45. volume of

The arrangement

:

B

tall jar,

is

shaped phosphorus attached Z^ is a clamp to support B. Process

:

Fill

A

of the apparatus

is

shown

C

is

a piece of

a 100 cc. graduated tube, to a

two-thirds

full

in Fig. 48.

worm-

long piece (40-60 cm.) of copper wire,

of water which has been exposed to

B,

Fill the tube,

the air in the laboratory for at least twenty-four hours.

with the same water, cover

thumb

finger,

vn

the end with the

hold

over the

it

or

jar,

and allow enough water

ll.

to

run out so that when the

lowered into the jar

4a tube

is

the 100

mark

cc.

is

a short

em

distance below the surface, the water

if

at the

is

same

.c h

height within and without

in

w w

in

exam-

prepare

ht

To

it

oxidation

piece of phosphorus about

a large

of water. Fig. 48.

porcelain

Wind

is

made 5

is

it

enclosed,

phosphorus.

the

Phosphorus

handle, since the burns

a

and allow the

over which

for the quantitative

in the air that

to

jar,

stand

the water

in

the temperature of the water

which oxidizes so quickly its

the

the tube

whole to remain undisturbed for about fifteen minutes. While the air is coming to

ination of air.

prevent

position,

this

thermometer

w tp :// Apparatus

Fig.

Clamp

the tube.

is

an element

often burns unexpectedly.

it

kept under water. // /s dangerous to Transfer a it are deep and painful.

by

cm. long with the forceps from the bottle

mortar, battery

jar,

the copper wire around

or metal it

in the

dish

nearly

full

manner shown

in

Quickly, but deliberately, transfer the phosphorus to the jar

of water, A.

Without touching the tube with the hand (see App. B, II., (3) and same level within and without (4) ), adjust it so that the water is at the

The Atmosphere. the tube.

barometer.

Read the volume of air in Record as shown below.

107

the tube, the thermometer,

and

Push the phosphorus up into the tube just above the surface of the White fumes indicate immediate action. In about ten minutes push the phosphorus half-way up the tube, attach the wire to the jar as shown in the figure, and allow the whole to remain undisturbed for an hour or more. Then pull the phosphorus down into the jar, still keeping it under water, and gently rub off with the fingers any Insert the cleaned phosdeposit on the surface of the phosphoms. phorus into the tube as before, and if the white fumes appear, let the phosphorus remain a half-hour longer. If no fumes appear, then lower the phosphorus into the jar and let it remain there, taking care to keep

ll.

vn

water.

for fifteen minutes.

Then

em

4a

the copper wire below the surface (to avoid accidental removal of the phosphorus from the jar). Lower the tube, without touching it with the hand, until the water is about the same level within and without, stand the thermometer in the water, and let the whole remain undisturbed readjust the tube,

if

necessary, so that the

inner and outer levels are the same, read the volume of gas, the ther-

w w

.c h

mometer, and barometer. Record as shown below. Unclamp the tube, grasp it near the end with the hand, close the open end with the thumb or finger, lift it from the water, invert, and test the residual gas several times with a glowing stick. Observe carefully its action with a flame,

Calculations

tp ://

Data

:

of this gas

is

nitrogen.

Before the removal of oxygen.

ht

I.

—

The name

w

and record the observations.

Volume

of air taken

Temperature Pressure

Aqueous tension Reduce

this

volume

to the

volume

it

= V =/ = P' =a

= = = =

would occupy under standard

conditions by the formula

^

760(1

-f-

.00366 X t)

Corrected volume

—

V-^=

Experimental Chemistry,

io8 II.

After the removal of oxygen.

From

= =

P'

=.

Pressure

Aqueous tension

—a =

of gas remaining

to standard conditions as in

I.

Corrected volume

=

Kj

F'

=

vn

Reduce

/

= = —

Volume

Temperature

V^ and K, find the percentage of oxygen and nitrogen in

4a

ll.

Insert the answer in the proper place in the

em

Table of the Composition of Air.

ht

tp ://

w

w w

.c h

Constituent.

air.

The Atmosphere.

3.

Atmospheric oxygen. (a) Physical and chemical functions (a) Give several

Suppose

(d)

methods

tively,

for

showing that

air contains

oxygen.

experiment were conducted quantita-

If the

what would

it

prove

?

Historical. first

sphere

?

proved the gravimetric composition of the atmoDescribe the apparatus and state the method.

vn

Who

(a)

(d)

Bunsen's work on the volumetric composition of the

(^)

Lavoisier's

work on the composition of the conception of the word ai'r.

air.

air.

ll.

(d) Aristotle's 5.

atmosphere.

passed over red-hot copper, what are the

air is

products?

4.

in the

Experimental.

Miscellaneous.

4a

2.

109

(a) Sources of error in Exp. 45.

not entirely composed of oxygen and

is

.c h

The atmosphere

em

(d) Precautions in handling phosphorus.

Experiment

46. is

— (a)

Prove by an experiment

present in the atmosphere.

w

that water vapor

w w

OTHER CONSTITUENTS OF THE ATMOSPHERE.

an apparatus

tp ://

(d) Construct

Fig. 49.

Fill

and draw

air

that

like

the test tube half

full

shown

in

of lime water

through the apparatus by means of an

aspirator bottle or

filter

pump.

(See App. A,

§ 17.)

ht

no pump or aspirator is available, expose lime water Allow the operation in a bottle or beaker to the air. to continue, in either case, until a definite change is produced in the appearance of the lime water. In the aspirated lime water the change will appear throughIf

out the liquid

;

in the

exposed lime water look upon

the surface for the change. satisfactory,

hydroxide

If neither operation

is

use a concentrated solution of barium

in place of lime water.

Fig. 49.

— Appara-

tus for detecting

the presence of

The change

is

calcium carbonate.

due

to the

formation of

Lime water

is

the pop-

parbon dioxide in the air.

vn

ll.

4a

em

.c h

w w

w

tp ://

ht Ca(OH),

The Atmosphere. (c)

"The

Give

a mixture/''

air is

in

Ill

your

own language

tliree

reasons for this statement, nitrogen were entirely removed from a vessel of air. would the physical properties of the oxygen be changed ? (e) If air is a mixture, why do we speak of its '* composition"? (/) Chemical effect of lightning on the atmosphere. If the

WEIGHT OF A LITER OF

AIR.

Method: Find the weight and volume of

Experiment 47.

pump from a bottle. Apparatus : The apparatus is shown

hausted by a

A

is

air ex-

a large bottle

ll.

in Fig. 50.

vn

(rt')

more) provided with a one-hole rubber stopper, through which passes a glass tube, B^ bent as shown in the figure. C is a piece of pressure tubing (40-50 cm. A Hofmann screw is atlong). tached at the point D.

make

It is

advis-

a flange on the outer

.c h

able to

em

4a

(2 liters or

end of the glass tube by melting it Bunsen flame and pressing quickly upon a hard surface. it The stopper must fit air tight, and a little vaseline should be rubbed on that part of the stopper which

tp ://

w

w w

in the

enters the neck of the bottle.

a

filter

is

tube,

If

used to exhaust the

a straight calcium chloride as

ht

bottle,

pump

filled

should

be

pump and

the

usual,

placed between the bottle.

Process

:

C

Slip

B^ and unless

it

over the end of fits

exceedingly

Fig. 50.

— Apparatus

for

determining

the weight of a hter of air. above the flange Attach the with waxed thread. screw loosely at Z>, push in the stopper as far as possible, wipe the bottle with a piece of cheese cloth or soft paper, and weigh the whole

tight,

tie

it

just

Stand the bottle in the center of the pan and arrange the weights symmetrically around the Weigh to a decigram, and leave the weights on center of the other.

apparatus on the trip scales. left-hand scale

Experimental Chemistry.

112

the scales ready for the second weighing, so that the

may be used each

This precaution

time.

Call this weight «,

errors due to weighing.

same

large weights

will eliminate

and record

as

many

of the

shown below.

Slip the end of the rubber tube over the exhaust nozzle of an air pump, and exhaust the air by rapid, short strokes of the handle. Tighten the Hofmann screw so that it will be air tight. The screw should not be more than five centimeters from the end. Detach from on the same scales. If less than i gm. of the pump, and weigh again Call this weight b, and record air has been removed, exhaust again.

—

shown below. Lower the rubber tube into a jar of water, open the clamp cautiously under water and allow the water to run in slowly. The sudden rush

vn

as

ll.

^

is easily controlled by pinching C near the end between the thumb and forefinger. The jar can be kept full by allowing water to flow continuously through a tube reaching to the bottom Care must be taken to keep the jar free from air bubbles by of the jar.

em

4a

of water into the bottle

When

adapting the inflow to the outflow.

no. more water runs into is

.c h

the bottle, raise or lower the bottle until the water

at the

same

both jar and bottle, pinch the tube and remove it from the jar. Tighten the screw, loosen the stopper, wipe the whole apparatus dry,

level in

w w

and weigh again, observing the previous precautions. weight as c, as shown below.

—

tp ://

Data

w

Calculation :

Record

Grams.

a Weight of bottle before exhaustion

Weight of

c

Weight

ht d

bottle after exhaustion

of bottle and water

Therefore

a

—

b

= Weight

of air removed

=

gm.

c

—

b

= Volume

of air removed

=

cc.

c

—

b: a

Therefore

—

b\\ looo

:

x

x=

gm.

this

The Atmosphere. Summary

of results

:

113

-^

Weight of a Liter of

Air.

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

Found.

Experimental Chemistry.

114

PROBLEMS.

A

1.

of dry air

liter

What

gm.

contained in this sample of air

A

2.

mixture of 25

cc.

3.

sample of

Dumas,

in

air

per cent of oxygen by weight

inis

?

of air

the residue measures 60.3 cc. in this

The copper

passed over heated copper.

is

creases in weight 0.297

XII.

and 50

What

of hydrogen

cc.

exploded, and

is

per cent of oxygen was contained

?

determining the composition of

by passing

air

air

over

heated copper and measuring the residual nitrogen, obtained the follow:

—

vn

ing data

Grams.

120.00

.

ll.

Weight of tube and copper before experiment Weight of tube and copper after experiment Weight of globe exhausted Weight of globe and nitrogen

121. 15

.

4a

.

852.00

em

855.85

Calculate the per cent of each constituent by weight and volume.

.c h

4. Bunsen analyzed the air at Marburg in 1846 by exploding a measured volume with a measured volume of hydrogen. Calculate the per cent of each constituent from the following analyses :

—

.... ....

Air used

cc.

74977

cc.

Residue

480.09 cc.

II.

Air used

5.

tp ://

w

w w

428 93

Air and hydrogen used

.

.

448.00

.

Air and hydrogen

Residue

A

.

461.72 cc.

.

student placed a piece of phosphorus in a volume of air which,

ht

when

.

cc.

743.01 cc.

corrected,

was 87.9

cc.

The

residue

Calculate the per cent of each constituent.

when

corrected was 70.58 cc.

Is the result

high or low?

How much? 6.

If the

composition of normal

air

by weight

of nitrogen and 23.005 per cent of oxygen, what

is

is 76.995 per cent the per cent of each

constituent by volume? 7.

Dumas and

Boussingault in

1841

found

12-373 gm. of nitrogen and 3.68 gm. of ox3'gen.

in

a

sample of

What

air

per cent of

each constituent did they find? 8.

in 100

What

weight of hydrogen

gm. of

air to

form water?

is

necessary to unite with the oxygen

The Atmosphere. Assuming

9.

iic

that air contains exactly 23 per cent of

weight,

how many grams

oxygen

in

loogm. of

oxygen by

of carbpn are necessary to unite with the

air to

form carbon dioxide?

(Hint: see equa-

tion (6).)

How many

10.

kilograms of

air are

necessary to yield 100 kg. of

oxygen ?

mixed with 30 cc. of hydrogen and the of what gases remain? The simplest equation for the reaction between phosphorus and is

cc.

of

air

are

What volumes

exploded.

—

2

How much

phosphorus

O =

P,05

nev^essary to

remove the oxygen from a

of air?

Calculate in the following cases the weight of a liter of air

(a)

Weight of Volume of

air

exhausted

air

exhausted

14.

tp :// ht

•

3.4 am.

2571.6 cc. 1.3

990.6

gm. cc.

how much.

Calculate the weight of the following volumes of air: 10 1.

w

1.,

high or low, state

w w

If the results are

.c h

Weight of air exhausted Volume of air exhausted

em

13.

(d)

8.5

is

5

4a

liter

P +

vn

12.

oxygen

is

ll.

20

11.

mixture

5

1.,

CHAPTER

VIII.

AND SALTS.

ACIDS, BASES,

The

distinguishing terms have not been modified to meet

its

the

new compounds. is

The nomenclature Even to-day each

"

antiquated.

and

base,

salt)

comwords of

almost impossible to set it present chapter is, therefore, a preliminary

ancient usage from which

is

it

w

The

of these of these

encumbered with a residue

is

w w

pounds

.c h

and

free."

old limits of the classification

em

occasionally overlap.

(acid,

4a

ll.

vn

Extensive study of the properties of chemical com pounds has led to a general, though incomplete, classification of many of them into three grand divisions, long known Each division has its distinctive as Acids, Bases, and Salts. are closely related and divisions the though properties,

tp ://

study, not from choice, but from necessity.

GENERAL PROPERTIES OF

ACIDS.

ht

Experiment 48. Supplies: Test tubes, dilute sulphuric, nitric, and hydrochloric acids, acetic acid, glass rod, litmus paper (both colors), zinc, calcium Fill a test

carbonate (marble), lime water. tube one-third

sulphuric, hydrochloric,

and

of concentrated acetic acid.

full

of one of the. following dilute acids

nitric

:

fill

another test tube one-third

Label the tubes

in

:

full

some distinguishing

manner. ' (^) Dip a clean glass rod into each acid and cautiously taste it. Describe the taste by a single word. {b) Dip a clean glass rod into each acid and put a drop on both kinds The striking change is characteristic of acids draw of litmus paper. ;

a general conclusion from

it.

116

Acids, Bases, and Salts.

117

Slip a small piece of zinc into each test tube successively.

(c)

chemical action results,

warm

by holding a lighted match

at

action results, provide the test tube with a stopper

and simple

and collect any product in a test tube over water. method will probably be unnecessary except with the

no

general conclusion from the result in the case of

delivery

This

tube,

Draw a

If

Test the most obvious product If no decisive the mouth of each tube.

gently.

latter

acetic acid.

all

except the

nitric acid.

Wash

((^)

the test tubes, add fresh acid, and slip a piece of calcium

vn

carbonate (marble) into each tube successively. Proceed as in (c), only in this case the gas must be tested not only with a burning match, Dip a clean glass rod into lime water, and hold it in but as follows :

Draw

is

the gas?

(Hint: recall a similar experi-

a general conclusion from these results.

4a

ment under

air).

ll.

What

the escaping gas.

Exp. 48 are characteristic of all acids, and substances acting thus are said to be acid, or to have acid The action in {b) properties, or to have an acid reaction. is true only for litmus, but it is a striking, simple test, and In {c) nitric acid seems excepshould be remembered.

The

.c h

em

results in

however, and its action with metals will Any Nitric Acid (see. page 197). under be explained is in {d) result The zinc. of place in metal could be used the case as in action, the true of all carbonates, though

w w

It is not,

tp ://

w

tional.

of metals, varies in vigor.

An

acid

may be

solution of each.

a solid, Hquid, or gas, or an aqueous

ht

It

may be

the general properties vary of the acid.

Each

dilute or concentrated,

and

somewhat with the strength

acid has special properties, which will

be considered under the

acids^

themselves.

—

Oxygen is a constituent of these acids correspond to of names most acids, and the The best the proportion of oxygen which they contain. Nomenclature

known

of

Acids.

acid of an element usually has the suffix

sulphuric, nitric, phosphoric, etc.

If the

-ic, e.g.

element forms

Experimental Chemistryo

ii8

another acid containing less oxygen, this acid has the suffix Some elements -oils, e.g. sulphurous, nitrous, chlorous, etc.

foim an acid containing

oxygen than the -ous acid; -oiis, and have, also, the prefix

less

these acids retain the suffix

hyposulphurous, hyponitrous, hypochlorous, etc. an element forms an acid containing more oxygen than the -ic acid, such acids retain the suffix -ic, and have, also, /lypo-, e.g.

If

the prefix /^r-,

e.g.

persuli^huric, perchloric, periodic, etc.

:

—

em

series of chlorine acids

4a

ll.

vn

Acids which do not contain oxygen have the prefix hydro and the suffix -ie, e.g. hydrochloric, hydrobromic, This last class is small. etc. The nomenclature of acids is well illustrated by the

ACIDS OF THE ELEMENT CHLORINE.

Hydrochloric

.

Chlorous Chloric

,

.

.

,

.

Formula.

HCl .

.

,

series is incomplete in the case of

tp ://

The

,

w

Perchloric

,

w w

Hypochlorous

.c h

Name.

HCIO HCIO2 HCIO3 HCIO^ many

elements,

but the names are formed according to the above principles.

ht

GENERAL PROPERTIES OF BASES.

Experiment /^^.— Supplies: Test

tubes, litmus paper (both kinds),

sodium hydroxide and potassium hydroxide; ammonium hydroxide and calcium hydroxide. Make dilute solutions of sodium hydroxide and potassiun, hydroxide

glass rod, short glass tube, solid

by adding a very small piece to a test tube half full of water, provide, also, an equal quantity of dilute ammonium hydroxide and of calcium hydroxide. little of e^ch liquid between the fingers, and describe Cautiously taste each liquid by touching to the tip of the tongue a rod moistened in '-ach, and describe the result.

{a)

Rub

the feeling.

a

Acids, Bases, and Salts,

119

Describe the {b) Test each liquid with both kinds of litmus paper. most striking result. Compare with the action of acids on litmus paper. {c) Blow through a glass tube into each liquid, except ^the ammo-

nium hydroxide, for several minutes. Describe the change, if any. Then add to each test tube in succession a few drops of dilute hydrochloric acid and test the gas evolved for carbon dioxide by holding in each tube a glass rod with a drop of lime water on the end. The amount of gas may be small, hence the rod must be held near the surface of the Explain the liquid as soon as possible after the acid has been added.

vn

chemical change.

49 are characteristic of bases, and substances acting thus are said to be basic, to have basic The word alkaline properties, or to have a basic react io?i. results in Exp.

4a

ll.

The

The result in {a) is typical, often used instead of basic. though it varies in intensity between wide limits from mere unpleasantness to violent caustic action. The results in {b) are generally true, though there are important excepThis is the customary test for a base. The result tions. in {c) is not usually significant, though it serves to emphawhich acids and bases bear

w

size the relation

w w

.c h

em

is

Bases.

of

tp ://

Nomenclature ingly broad in

— The

meaning and

term

to carbonates.

base

is

loose in appUcation.

exceed-

Most

bases are Jiydroxides, since they consist of hydrogen and

ht

oxygen combined with a metal.

Hydrate

is

sometimes used

as a synonym of hydroxide, both words suggesting the lation of these

compounds

called alkalies,

and

to water.

re-

Hydroxides are usually

their chemical action

is

called alkaline.

no general rule covering the nomenclature of Hydroxides are distinguished from each other by placing the name of the metal before the word hydroxide, e.g. sodium hydroxide, potassiunv hydroxide, calcium hyThe common hydroxides have droxide, barium hydroxide. names. Thus sodium different long been known by several

There bases.

is

Experimental Chemistrv,

I20 hydroxide

sodium hydrate, or caustic soda; amcalled ammonia, or ammonia water.

called

is

monium hydroxide

is

A GENERAL PROPERTY OF SALTS.

— Supplies:

Experiment 50. glass rod,

Test tubes, litmus paper (both colors)^

sodium chloride, potassium

potassium sulphate, and

nitrate,

barium chloride. solutions of sodium

JVlake, as in the preceding experiment, dilute

(common

classification

em

salty or saline taste this

is

characteristic

property doubtless led to their

with sodium chloride as a type, since this

compound has been known salts

for ages.

Some compounds

as far as their chemical relations are con-

w

which are

Sub-

which act toward litmus be neutral, or to have a

.c h

and

salts,

are said to

A

such as water.

salts,

not,

w w

most

or

salts

salt,

neutral reaction.

which are called normal bodies which

It is also characteristic of

whether

Hke common of

vn

true only of salts

is

below).

chemically speaking, not

stances,

potassium sulphate, and

ll.

This result salts (see

nitrate,

the action of acids and of bases on litmus paper.

Compare with

result.

potassium

Test each solution with litmus paper and describe the

barium chloride.

are,

salt),

4a

chloride

tp ://

Thus sodium cerned do not have a neutral reaction. carbonate, which is the sodium salt of carbonic acid, is one most marked alkahes, being, merce simply as "alkali."

ht

of the

known

in fact,

in

com-

—

Salts containing only two Nomenclature of Salts. elements follow the rule for binary compounds, aiid hence end in -ide. This suffix is added to an abbreviated form of the

name

ide, etc.

the

name

of the non-metal, e.g. chloride, bromide, fluoris omitted, and that sodium chloride, potas-

Notice that the prefix hydroof the metal precedes, e.g.

sium bromide, calcium

fluoride, etc.

experimentally that salts

It will

may be regarded

soon be shown

as derived from

Acids, Bases, and Salts.

121

by replacing the hydrogen of the acid by a metal. Only the ending of the acid is changed to indicate this Thus relation. acids

—

Hence

—

-ic

becomes

-ate.

-oiis

becomes

-ite.

Sulphuric acid forms sulphates. sulphites.

vn

Sulphurous acid forms

nitrites. cJilorates.

JiypocJilorites.

em

Hypochlorous acid forms

4a

Nitrous acid forms Chloric acid forms

ll.

Nitric acid forms nitrates.

Permanganic acid forms permanganates.

tp ://

w

w w

.c h

The name of the replacing metal is retained, e.g. potassium sulphate, sodium nitrite, calcium hypochlorite, potassium permanganate. Notice that the prefixes, hypo- and per-, are not changed. Salts in which all the hydrogen is replaced by a metal Sometimes only a part of the are called normal salts. hydrogen is replaced, and the salt still has acid properties; such salts are called acid salts, e.g. acid sodium sulphate is

ht

the salt derived from sulphuric acid by replacing half of the hydrogen by sodium;

its

formula

formula of normal sodium sulphate other hand,

if

of the base,

bismuth

a salt it

is

is

so

made ^that

is

HNaS04; On

is

Na2S04.

it still

the the

retains a portion

called a basic salt, e.g. basic nitrate of

may be regarded

as the salt derived

from

bis-

muth hydroxide, in which only a portion of the base is replaced by the essential part of nitric acid its formula is Bi(OH)2N03. Basic lead nitrate, Pb(0H)N03, is formed by boiling solutions of lead nitrate and lead oxide. Basic ;

Experimental Chemistry.

122 salts

bear the same relation to hydroxides as the acid They are prepared in numerous ways, and

salts to acids.

are often complex compounds. ate (white lead) has the formula

Thus basic lead carbon2PbC03 PKOH)^, and .

formula

copper carbonate (malachite) has the

a basic

CuCOg Cu(0H)2. .

—

but such a test reveals only the properties of the

substance examined.

Other

tests

ll.

test,

vn

The presence or Testing the Nature of Substances, absence of an acid or base may be found by the litmus must be made

salt.

is

an

acid, base,

em

or

4a

mine whether or not a particular substance

to deter-

THE NATURE OF COMMON SUBSTANCES.

— Determine by the litmus

.c h

Experiment 51.

juice, vinegar, soap,

test the nature of

sweet and sour milk, washing soda, borax,

lemon

wood

Make

and any green

fruit.

a solution of each of the solids before testing. :

—

Tabulate the

tp ://

results as follows

w

ripe fruit

w w

ashes, faucet water, baking soda, sugar, cream of tartar, the juice of any

ht

Nature of Common Substances.

Acid.

Neutral.

Acids, Bases, and Salts.

LABORATORY 1.

EXPZRCISE.

123

VII.

the reaction of ''acid phosphate," "^soda water," sour

Predict

bread, basic lead acetate, sour wine, tart preserves, pickles. 2.

Determine experimentally and then explain the reaction of (a) cop(/?) ammonium chioride, (c) alum, (d) potassium carbon-

per sulphate,

a text-book for the explanation.)

—

salts to acids

of

—

and

ll.

The relation of The Nature of Salts. bases is found experimentally by a study

vn

(If necessary, consult

ate.

4a

THE INTERACTION OF ACIDS AND BASES.

—

evaporate to dryness by heating over a piece

Since the residue mechanically holds traces of the excess

of wire gauze.

of hydrochloric acid added, test.

it

is

Heat the dish

necessary to remove this acid before

w w

applying any

.c h

Then

blue litmus paper.

em

Dissolve a small piece of sodium hydroxide in Experiment 52. an evaporating dish half full of water. Slowly add dilute hydrochloric acid, until a drop taken from the dish by means of a glass rod reddens

until all the yellow color disappears,

then moisten the residue carefully with a few drops of

w

heat again to remove the last traces of acid. to the success of the experiment.

tial

ties.

and

tp ://

with litmus paper to find whether

T?ste a

it

warm water and

This precaution

is

essen-

Test a portion of the residue

has acid, basic, or neutral proper-

Test (a) a solution of the residue for a chloride,

little.

{d) a portion of the solid residue for

sodium.

Draw

a definite con-

ht

clusion from the total evidence.

— The

operation in Exp. 52 is called Other acids and bases produce similar results. It shows qualitatively the relation existing between acids and bases, and the relation of salts to each of the Further information on the subject of other two classes. neutralization may be obtained by determining the quantitative relation between acids and bases when representatives Neutralization.

neutralizatioit.

cf the

two classes

interact.

Experimental Chemistry.

124

A QUANTITATIVE EXAMINATION OF THE INTERACTION OF ACIDS AND BASES. Experiment

53.

— Method:

Neutralize a measured quantity of an

acid with a base.

Two burettes and a support, two beakers of the same : two glass rods (blunt form).

Apparatus size,

Solutions: (a)

Add

to 3 vols, of water) to

8 cc. of dilute hydrochloric acid (i vol. of acid

200

Keep

cc. of filtered water.

the solution in a

is

labelled Hydrochloric Acid.

Make

a solution of dilute

ll.

(d)

vol.

of acid

4a

sulphuric acid (i

water) as in (a).

5 vols, of

to

Label

Sulphuric Acid.

Dissolve about 2 gm. of so-

em

it

which

vn

clean, stoppered flask or bottle

(6)

dium hydroxide

in

200

cc. of filtered

Preserve as described above,

ht

tp ://

w

w w

.c h

water.

and label it Sodium Hydroxide. (d) Make a solution of potasLabel sium hydroxide as in (c). it

Potassium Hydroxide. (e)

Dissolve

i

gm. of

solid phe-

nolphthalein in 100 cc. of alcohol (50 see Table X., App. C). per cent

—

Keep

a glass stoppered bottle.

in

This solution of litmus. tions

It

is

to be used instead

colors alkaline solu-

magenta, and undergoes no

appreciable change in acid solutions.

This

solution

similarly

because

is it

or

any other used an md/cator,

called

indicates the nature of a

whether acid or alkaline. Process : Wash two burettes with

solution, Fig. 51.

— Burettes arranged for use.

distilled or

filtered water,

and dry

the inside with a stick having a piece of soft paper attached to one end. Arrange them as shown in Fig. 51. Label one clamp "acid'' and the

other ''alkali."

Fill the burette

marked "acid" with the hydrochlui:^

Acids, Bases, and Salts. acid already prepared, taking care that the liquid at the lower end,

correct position. it

is

free

from

air

bubbles

finally that the surface of the acid is level

with

Remember that the lowest point of the meniscus is The burette holds 50 cc. from the o mark to

the zero mark.

50 mark, but

and

125

should be

the glass

filled to

tip,

and drawn

off

the the

from o to

—

but no lower. Any number of cubic centimeters may be obtained 50 by opening the pinchcock and allowing the liquid to flow out of the glass tip until the level has fallen to the desired point.

When

" alkali

'^

the operation

be washed and

Fill the burette

with the sodium hydroxide solution in the same way.

left

is

over, temporarily or finally, the burettes should

standing

full

See that each burette reads

o,

of clean water.

vn

marked

then place a beaker on a sheet of white

4a

ll.

paper under the "acid" burette, open the pinchcock, and allow 15 cc. of acid to run into the beaker. Add two or three drops of phenol-

Then allow the sodium hydroxide solution to run by drop, into the acid. Stir constantly with the glass rod. As the action proceeds, the magenta color will be more permanent add the alkali very slowly, as this point is approached. The aim is to add just enough alkali to neutralize the acid. It is customary to pass slightly beyond this point, just far enough to be sure the color is permanent. It requires skill and judgment to stop the action at the right time. Record as shown below the exact number of cubic centimeters of sodium

phthalein solution.

em

slowly, drop

w w

.c h

;

hydroxide necessary to neutralize the 15

cc. of

hydrochloric acid.

Draw

and find the exact amount of alkali necessary to neutralize it. Do the same with 10 cc. of acid, refilling the " alkali " burette, if necessary. The tint should be the same in each

tp ://

w

into another beaker 15 cc. of acid

Tabulate the results thus

case.

:

—

Hydrochloric acid and sodium hydroxide.

ht

I.

cc.

15 cc. of acid neutralize

cc. of alkali.

10 cc. of acid neutralize

cc. of alkali.

Ratio If the

in

I.

will

of alkali.

15 cc. of acid neutralize

:

1

Acid, 3-3-2.

— Alkali,

- -

.

work has been performed with reasonable accuracy, the show :

—

results

(i)

Definite quantities of acid neutralize definite quantities of alkali.

(2)

Neutralizing power

is

independent of the amount of solution

used.

iSame

as 15-15-10.

Experimental Chemistry.

126 Wash

the burette used for the alkali, and, after drying

potassium hydroxide solution.

and proceed with these solutions as before.

chloric acid, results thus

—

:

with the

with hydro-

Tabulate the

Hydrochloric acid and potassium hydroxide. cc. of alkali.

15 cc. of acid neutralize 15 cc. of acid neutralize

cc. of alkali.

ID cc. of acid neutralize

cc. of alkali.

— to —

.

((3)

is

found by comparing the quantity of each alkali of 15 cc. for example

necessary to neutralize a definite quantity

dry the "acid" burette, and

Refill the " alkali " burette with the

fill

15,

.c h

15,

—

with the sulphuric acid.

potassium hydroxide solution.

ceed as before, using successively necessary amount of alkali.

—

em

acid.)

Wash and

.

They I. (i) and (2;. power of the two alkalies,

results likewise reveal the facts stated in

also give (3) the ratio of the neutralizing

and 10

Pro-

of acid and the

cc.

Tabulate the results thus

:

—

w w

Sulphuric acid and potassium hydroxide. 15 cc. of acid neutralize

cc. of alkali.

15 cc. of acid neutralize

cc. of alkali.

w

III.

-

-

ll.

These

— Alkali,

vn

Ratio: Acid, 3-3-2.

4a

II.

viz.,

it, fil\

Refill the " acid " burette

10 cc. of acid neutralize

tp ://

Ratio: Acid, 3-3-2.

cc. of alkali.

— Alkali,

-

-

.

Refill the "acid" burette, but replace the potassium hydroxide bj sodium hydroxide. Proceed as above, and tabulate the results thus

—

ht

:

IV.

Sulphuric acid and sodium hydroxide. 15 cc. of acid neutralize

cc.

15 cc. of acid neutralize

cc. of alkali.

ID cc. of acid neutralize

cc. of alkali.

Ratio: Acid, 3-3-2.

— Alkali,

of alkali.

-

-

.

whole experiment has been performed with reasonable accu^be found that (4) the ratio of the neutralizing power oi An actual example will the two alkalies is the same for both acids. make this point clear. A student found that the ratio of the alkalies in If the

racy,

it

will also

the case of one acid was 11. 7: 19.5, and in the case of the other acid

Acids, Bases, and Salts. was 12.9:

21.6.

Now, by

calculation the second ratio

slight difference being readily explained

mental errors are combined in

Tabulate the results so that alkalies

is

the

same

for

12'

this it

is

12.9: 21.5, the

fact that the

experi-

one quantity, 21.6.

will

both acids.

by the

be seen that the

ratio of the

two

Sketch the apparatus.

—

These experiDiscussion of Experiments 52 and 53. ments show that when a base and an acid interact a salt formed. Accurate repetitions of these and similar experiments permit the chemical changes involved in the above experiments on neutralization to be written thus is

vn

—

ll.

:

ht

tp ://

w

w w

.c h

em

4a

HCl

(II)

Experimental Chemistry.

128 Definitions.

— The experiments

in this

chapter show that,

in addition to certain general properties, acids, bases,

and

chemically related to a marked

No

salts

are

degree.

adequate definition can be given of each. The following, An Acid is a substance however, are generally accepted. containing hydrogen which

The

replacing metal

the metal,

r.^'-.

is

may be

easily .replaced

the oxide, carbonate, or hydroxide.

HNO3. two,

atoms,

e.g.

Dibasic, Tribasic, etc.,

ll.

nitric acid,

of replaceable

three,

etc.,

4a

e.g.

acids contain, respectively,

Acids

A monobasic

vn

are, as a rule, sour, and turn blue litmus red. acid contains in a molecule only one atom

hydrogen,

by a metal.^

obtained from a compound of

replaceable

sulphuric acid, H2SO4, and phosphoric acid,

.c h

em

H3PO4. The basicity of acids explains the existence of normal and acid salts. A base is a substance containing a metal combined with oxygen and hydrogen, the metal of which easily replaces the hydrogen of acids when the base

A

Bases, as a rule, turn red litmus

w w

interacts with an acid.

monacid base is one in which the metal can be replaced by one atom of hydrogen, e.g. sodium Diacid and Triacid bases contain a hydroxide, NaOH. metal replaceable by respectively two and three atoms of hydrogen, e.g. Ca(OH).^and A1(0H)3. A Salt is the main

tp ://

w

paper blue.

ht

product of the interaction of an acid and a base. Salts may be formed in several ways, but they may always be theoretically viewed as

if

they were formed directly from

a fundamental acid or base. A Metal can now be regarded not merely as a hard, A lustrous substance, but as a base-forming element. acid-forming an as defined be Non-metal likewise may All non-metallic elements, except hydrogen. element. 1

Water

is

an exception.

Acids, Bases, and Salts.

129

and a few others, form oxides which unite with water and thereby produce an acid

SO3

;

thus

—

:

+ H.p = H2SO4 Water

Sulphur

Sulphuric

Acid

Trioxide

These oxides are often called Anhydrides. Similarly, many metallic elements form oxides which unite with water and thereby form hydroxides; thus

vn

H2O =

ht

tp ://

w

w w

.c h

em

4a

CaO +

—

ll.

:

Experimental Chemistry.

ijo 3.

illustrate the

Explain and

—

expressions:

(a) Acidity of bases. {d) Basicity of acids. (c) "Every oxygen acid has a corresponding anhydride." (^) " Most normal salts are neutral/'

{e)

" Sulphuric acid

the starting-point of sulphates."

is

(/) "Metals form basic compounds." (g) " Hydroxyl is a radical." 4.

Historical. ac/(/, alkali^ and salt. development of the subject of

ll.

(J?)

Lavoisier's contribution to the acids.

5.

Davy's work on the theory of Lavoisier.

4a

{c)

vn

(a) Historical development of the terms

Miscellaneous.

What

alkali.

em

(i) Explain the terms volatile alkali, caustic alkali, are the alkali metals

(2)

Why

(3)

Are there any exceptions

are there no acid nitrates

and Jixed

?

?

.c h

to the statement, " all substances

from which a metal liberates hydrogen are acids"'?

(5)

What

(6)

The

is

w w

meaning of acid

(4) Literal

(adj.), per-, hypo-, alkali.

the etymological relation of hydrogen to the terms

hydrate, hydroxide, hydro- (in hydrochloric), anhydride?

w

operation in

Nomenclature. (a)

Name

the

Sodium

ht

6.

is

called

titration.

What

is

color"?

—

salt of

Potassium

Lead

Exp. 53

''titration to

tp ://

meant by

hydrochloric acid.

salt of

salt of

hydrochloric acid.

hydrochloric acid.

Calcium salt of hydrochloric acid. Barium salt of hydrochloric acid. Zinc

salt of

hydrochloric acid.

Silver salt of hydrochloric acid. {b) {c)

Name Name

the same salts of nitric acid and of sulphuric acid-

the same salts of hypochlorous and of nitrous acid

{d) Name the base corresponding nium, calcium, barium,

acid, of chloric acid,

to sodium, potassium,

zinc, lead, copper.

ammo-

Acids, Bases, and Salts.

Name

the

—

Sodium

salt of

Potassium

Lead

sulphurous acid.

salt of

manganic

acid.

salt of nitric acid.

Potassium

salt of perchloric acid.

Calcium

salt of hydrofluoric acid.

Sodium

salt of nitrous acid.

Calcium

salt of

Sodium

salt

Potassium

Lead

hypophosphorous

acid.

of carbonic acid.

salt of tartaric acid.

salt of

chromic

vn

(e)

131

acid.

(2)

KOH

(3)

Ca(OH),

(5)

A1(0H)3

(4)

Ba(0H)2

(6)

C^H^COH)

em

NaOH

ht

tp ://

w

w w

.c h

(1)

—

4a

hydroxyl. {g) Select the hydroxyl groups from

ll.

(/) Significance of the terms hydroxide, hydrate, anhydride, and

CHAPTER

IX.

ATOMS, MOLECULES, AND RELATED SUBJECTS.

22,

— The

and the

which may be

equivalent

result,

of

was found

zinc

together with

similar results,

fundamental data

ll.

easily obtained, furnish

in

vn

Equivalents.

Exp.

4a

for the subjects discussed in this chapter.

54.

— Determine Use

22.

the

the equivalent of

same apparatus.

.c h

Experiment method of Exp.

em

EQUIVALENT OF MAGNESIUM.

so easily that only about 25 cubic centimeters 0.08 gm. of clean

no platinum wire) are needed. Use from 0.06 to magnesium ribbon, which should be slipped into a

w w

chloric acid (and

short glass tube so that

:

—

tp ://

calculate as follows

Data:

—

ht

.

it

will sink.

Collect the gas in a 100 cc. tube.

in other respects exactly as directed in

w

Proceed

magnesium by the

The reaction proceeds of warm dilute hydro-

Exp.

22.

Record and

Atoms, Molecules, and Related

Subjects.

Corrected volume of hydrogen

=

cc.

Weight

=

gm.

of hydrogen

Since

gm. of magnesium

is

then

gm. of magnesium

are equivalent to

133

gm. of hydrogen,

equivalent to i

gm. of hydrogen.

=

Equivalent of magnesium

vn

EQUIVALENT OF ALUMINIUM.

—

acid instead of sulphuric acid

forced over into the dish.

no platinum wire

is

needed.

The

action

Otherwise, proceed as in the other deter-

Record and calculate as

in

Exp.

54.

.c h

minations.

equivalent or equivalent weight of an element was

w w

The

;

vigorous and must be watched to prevent the metal from being

em

may be

4a

ll.

Determine the equivalent of aluminium by the Experiment 55. method used for zinc and magnesium. Use from 0.06 to 0.07 gm. of aluminium for a 100 cc. tube. Use warm concentrated hydrochloric

defined in Chapter III. as that weight of an element chemically equivalent to

the

one part by weight of hydrogen. More number of grams of an element which

w

specifically

it is

ht

tp ://

combines with or replaces one gram of hydrogen. Thus in Exp. 22, 32.5 gm. (approximately) of zinc were found to In Exps. 54 and 55, be equivalent to i gm. of hydrogen. I gm. of hydrogen was found to be equivalent respectively to 12 gm. of magnesium and 9 gm. of aluminium (approx-

and these numbers, 12 and 9, are the equivalents Some metals do not liberate two elements. hydrogen easily from acids, and their equivalents are Sodium, for example, liberates hydrogen indirectly found. from water, and careful experiments show that 23 gm. of sodium are equivalent to i gm. of hydrogen. Oxygen is withdrawn from water by passing steam over powdered iron (see Exp. 40), water itself is formed by passing

imately),

of

these

Experimental Chemistry.

134

hydrogen over heated copper oxide (see Exp. 44), and both of these experiments, if performed accurately, show that 8 gm. (approximately) of oxygen are equivalent to i gm. of hydrogen. Exp. 1 5 also shows that 8 gm. of oxygen always combine with 12 gm. of magnesium, a number which has been found by an independent experiment (Exp. 54) to

easily found, thus

is

:

—

ll.

the equivalent of one

vn

be the equivalent of magnesium. Many metals precipitate another when one is suspended in the solution of the other, and if the metals are weighed

gm.

I

gm. of magnesium

I

gm.

of

I

gm.

of copper precipitates

we

magnesium

.97 of copper.

333

of silver.

em

of zinc precipitates

precipitates 2.64 of copper. precipitates 9.00 of silver.

.c h

if

I

precipitates

recalculate these values

3.43 of silver.

and express the

results

w w

Now

gm. of zinc

4a

Grams. I

terms of the equivalents already known, the table reveals other equivalents, thus in

—

w

:

tp ://

G-RAMS.

Grams.

317

32.5 of zinc are equivalent to

of copper.

108.2 of silver.

32.5 of zinc are equivalent to

31.7 of copper.

of

magnesium

are equivalent to

12.

of

magnesium

are equivalent to 108.

of silver.

108.

of silver.

ht

12.

31.7 of copper are equivalent to

Actual analysis of chlorides reveals the following facts gm. of hydrogsn combines with 35.5 gm. of chlorine. 35.5 gm. of chlorine. 23 gm. of sodium combine with 35.5 gm. of chlorine. 16 gm. of sulphur combine with I

gm. of chlorine. 39 gm. of potassium combine with 35.5 108 gm. of silver combine with

35.5

gm. of

chlorine.

:

—

Atoms, Molecules, and Related

Subjects.

Analysis of bromides gives the following results I

:

135

—

gm. of hydrogen combines with 80 gm. of bromine.

23 gm. of sodium combine with

80 gm. of bromine.

39 gm. of potassium combine with 80 gm. of bromine. 108 gm. of silver combine with

80 gm. of bromine.

Analysis of some oxides shows the following results

—

23 gm. of sodium combine with

gm. of oxygen, gm. of oxygen.

8 oti. of oxygen. -J &"

sulphides show similar results I

:

—

em

Some

8 8

4a

39 gm. of potassium combine with 108 gm. of sih-er combine with

in

vn

:

ll.

addition to those given above

gm.

of hydrogen combines with 16

.c h

23 gm. of sodium combine with

16

gm. of sulphur.

gm. of sulphur.

39 gm. of potassium combine with 16 gm. of sulphur.

summary

of the

16

gm. of sulphur.

above data may be tabulated thus

w

A

w w

108 gm. of silver combine with

Element.

tp ://

i

Oxygen

8

Magnesium

ht

12

Aluminium

Copper Silver

Sodium

—

Equivalent.

Hydrogen

Zinc

:

9 ,

.

.

.

32.

31.7

108

23

Potassium

39

Chlorine

35.5

Bromine

80

Sulphur

16

(by definition)

Experimental Chemistry.

136

A

comparison of some equivalent weights and the approx-

imate atomic weights of the same elements accepted by chemists reveals a remarkable coincidence.

Comparative Table of Equivalents and Atomic Weights.

Hydrogen Oxygen

.

ll.

.

Bromine

4a

Chlorine

vn

.

Sulphur .

.

em

Zinc

Copper

.c h

Magnesium Sodium Potassium Silver

.

.

w

many

cases they are the same, but in

tp ://

In

w w

Aluminium

some cases the

atomic weights are a simple multiple of the equivalent.

The

first

many inhas taken much

weights called atomic weights were, in

and

it

ht

stances, identical with equivalents,

labor and thought to select the multiple which

atomic weight of the element

is

the proper

in question.

Atomic weights cannot be interpreted without a preliminary consideration of the atomic theory.

—

The Atomic Theory. Up to the time of Dalton (17661844) there were two views regarding the constitution of matter.

The

first

view advocated

of these

is

known

infinite subdivision

;

as the dynamic. it

This

claimed that there

Atoms, Molecules, and Related

Subjects.

137

no limit to the division of matter. A piece of iron, for example, according to this theory, could be divided forever. The other view is known as the atomic. This view advoIt said that if subdivision goes on, cated finite divisibility. particles will finally be reached which cannot be further These particles were called atoms by the subdivided Greeks, and this latter theory is substantially the atomic is

theory of the Greeks. ;

They

they date from the time of

vn

Both these views are old Lucretius (95-52 b.c).

are opposed to each other,

and

finally

have no relation

chemistry as

to

4a

scientific,

know

ll.

they are entirely speculative, they are metaphysical, un-

it.

we

em

Dalton shared the general views of his contemporaries regarding the constitution of matter.

He

Newton,

i.e.

in the

.c h

solid particles of

He

believed in the

corpuscular theory.

also believed in the existence of individual gases, par-

units.

tp ://

w

w w

which were discovered by Priestley, CavenHe believed in the law of definite others. and dish, Black, proportions by weight, and in the law of multiple proportions (see page 201), discovered by Dalton himself, both of which emphasized the general idea of combination by ticularly those

ht

Dalton's meteorological observations led him to believe

that aqueous vapor exists separately from the other constituents of the air, also that gases themselves are

made up

His work on the solubility of gases in water led him to undertake to determine "the relative weights of ultimate particles of bodies." Now the above work was largely physical. His views on all matter seem to be the result of shrewd generalizations from his general and vaguely supported ideas of of distinct particles.

matter, mainly in

its

physical relations.

These ideas were

Experimental Chemistry.

138

expressed at several times and more particularly in a course of lectures delivered in 1809- 18 10 at the Royal Institution

London. Regarding atoms, he said in substance in this " Matter is composed of particles of definite size lecture and weight. These particles are called atoms. All atoms

in

:

of the

same kind

kinds of

of matter

matter are

Atoms

are alike.

different.

All

of different

atoms combine by

wholes to form compounds their relative weight only can be determined." This is the atomic theory of Dalton. One of the essential properties of matter is weight, and Dalton's first efforts were to determine some of the weights

ll.

vn

;

To do this he formulated rules and actually found several weights, which he called atomic weights. This work, mingled with crude speculation on the shapes of atoms, seems to have been done at different times and probably preceded to some extent Dalton's final views and work on atoms, though the public expression of his views undoubtedly gave an impetus toward the gravimetric conDalton's contemporaries did not receive ception of atoms. It is true, no facts, then known, conhis theory favorably. flicted with the theory, but it is equally true that no set The work of determining of facts actually supported it.

tp ://

w

w w

.c h

em

4a

of atoms.

ht

atomic weights spread, however, and was given a strong impetus by the Swedish chemist, Berzelius. It has never ceased to attract

skilful, persistent

workers.

Analysis of chemical compounds reveals the proportions Thus, one part by weight of the components by weight.

hydrogen combines with 35.5 parts by weight of chlorine, and with 80 of bromine. These parts by weight of chlorine and bromine combine in each instance with 39 parts by weight of potassium. The early experimenters soon found

of

that

some elements enter

into

elements in several proportions.

combination with other Thus, 8 parts by weight

•

Atoms, Molecules, and Related

Subjects.

oxygen combine with one part by weight

of

139

of hydrogen,

but in the larger number of instances 16 parts by weight

oxygen combine with various parts by weight of other Furthere.g. zinc, sulphur, and magnesium. more, sulphur combines with hydrogen in the proportion of

elements,

of 16 parts to

but in the vast majority of cases the num-

I,

ber of parts by weight of sulphur which combines with other elements

is

found

to

be

In a word, multiples of

32.

.c h

em

4a

ll.

vn

combining weights were found, and the problem then reduced itself to selecting the particular multiple to be That number which represents called the atomic weight. the combining proportion of an element in the greatest number of cases, its favorite number, so to speak, was selected as the atomic weight of that element. The number, then, which we call the atomic weight represents not an absolute weight, but a relative weight,

heavier the atom

Its

i.e.

how many

absolute weight of an atom of hydrogen

weight

arbitrarily

is

w

The atomic theory

times

than the atom of hydrogen.

w w

The

in question is

is

not known.

chosen as one.

is

viewed

at the present time as a

explanation of the laws of combination of

tp ://

satisfactory

matter revealed by experiment.

It is

generally adopted

as a working hypothesis, not as a fact.

An atom

ht

according to the present views

is

that particle

of matter which has not yet been subdivided into smaller particles.

It

combines with

itself or

with other atoms and

thereby forms molecules.

Atomic Weights. therefore,

is

that

— The

atomic weight of an element,

number which represents how many times

heavier the atom of an element is than the atom of hydrogen (see " Various Figures for Atomic Weights," page 142). Hence, the numbers hitherto called the equivalents of

Experimental Chemistry.

140

the elements are also, in the respective elements.

many

cases, the atomic weights of

Thus,

23

is

the atomic weight of sodium.

108

is

the atomic weight of silver.

80

is

the atomic weight of bromine.

127

is

the atomic weight of iodine.

The determination

vn

the atomic weight of chlorine. of exact atomic weights

operation, and no single

is

a difficult

ll.

is

method furnishes

sufficient data

4a

35.5

for a final selection of the numbers.

If

atoms combined

veal the proportions, and

if

em

in only one proportion, atom for atom, analysis would

one were the standard, or

re^

if its

terms of the standard were known, the relative weight of the other could be easily calculated. For example, Stas, a Belgian chemist who made masterly determina^

.c h

in

w w

weight

tions of atomic weights, found that 121.4993

gm.

of silver

It

was known to him atom of chlorine

tp ://

chlorine.

w

chloride were formed by burning 91.462 gm, of silver in unites with one

and that the atomic weight

to

form

of chlorine

he calculated the atomic weight of

ht

that an

is

atom

of silver

silver chloride,

35.453.

silver thus:

—

Hence,

121.4993

91.4620 30.0373 weight of chlorine used.

91.462: 30.0373 ::,r: 35.453

X Since

number

=

107.95, atomic weight of silver.

many atoms combine

in several proportions, the

selected as the atomic weight

is

based on consid-

Atoms, Molecules, and Related Subjects

141

erations such as vapor density, agreement with the periodic law, specific heat, etc.

Only one

check methods, however,

Law

of Specific Heats.

nounced the

Law

will

— Dulong

and

of Specific Heats, viz.

product of the atomic

TJic

of these

approximate or

be considered.

zveigJit

and

Petit in 1819 an-

:

—

the specific heat of

not perfectly accurate, since in

cases

only approximately 6.4

is

by Dulong and

lected

many

— the number constant — as appears

ll.

is

product

se-

4a

This law this

vn

the solid elements is a constant quantity.

Petit as the

em

from the

.c h

Table of Specific Heats. ^ Specific Heat.

.

Calcium

.

.

Copper

.

.

Iron

.

.

tp ://

.

Lead Magnesium .

w

Aluminium

w w

Element.

.

Potassium

Atomic Weight.

Product.

0.214

27.0

5.8

0.170

39-91

6.8

0.095

63.18

6.0

0.114

55.88

6.4

.

0.031

206.4

6.4

.

0.250

24-3

6.1

.

0.166

39-03

6.5

.

0.057

107.66

6.1

Sodium

.

.

0.293

23.00

6.7

Sulphur

.

.

0.178

Tin

.

.

.

0.055

118.8

6.5

Zinc

.

.

.

0.094

65.1

6.1

ht .

Silver

.

An

example

will

make

this

specific heat of silver is .057;

iFrom Meyer's "Outlines

31.98

law more if

6.4

is

intelligible.

divided by this

of Theoretical Chemistry," p. 22.

5-7

The num-

Experimental Chemistry.

142

ber, the quotient

is

1

12.2.

This

is

not the accepted atomic

checks the other determinations, since 112.2 points to 108 and not to any of its multiples. weight of

silver,

but

it

the other hand the specific heat of mercury is .032 if divided by this number, the quotient, 200, is the atomic 6.4 weight of mercury, and this number is confirmed by other

On

;

is

Various Figures for Atomic Weights. figures for the atomic weight of the

— Obviously

the

vn

methods.

will

same element

4a

ll.

Hence different atomic weight vary with the standard. on one standard, some on some found, will be tables recently, the generally until was, Hydrogen another.

being replaced by the oxygen standard, i.e. But as the is the standard atomic weight.

is

.c h

gen standard 16 and not i

em

adopted standard. Since many atomic weights" are now directly determined with reference to oxygen, the hydro-

oxygen

if

w w

atomic weight of hydrogen becomes only 1.008,

taken as exactly 16, the variation in the usual table of atomic weights is very slight, especially when whole numAppendix C contains a table of atomic bers are used.

w

is

tp ://

The approximate atomic on both standards. the most common eleof Table I.) C, weight (see App. but by constant slavishly, not ments should be learned,

ht

weights

association.

Molecular

Weights.

— Since

atoms

combine

to

form

molecules, a molecular weight is the sum of the weights of If the molecule is the simple the atoms in a molecule. combination of two atoms, then the molecular weight is

the

sum

of the respective atomic weights.

Thus

experi-

mental evidence points conclusively to the fact that sodium chloride contains one atom of sodium and o.ne atom of chlorine,

hence

its

formula

is

NaCl and

its

molecular

Atoms, Molecules, and Related weight

58.5 (23

is

+

35.5).

Subjects.

Since molecules

may

143

theoreti-

any number of atoms, the molecular weight and formula are rigidly connected. It is customary to assume the simplest formula until evidence reveals an Thus HO was formerly regarded as the formula error. but when the density of steam showed that the of water molecular weight must be 18, this fact, together with other data of a similar value, led to a change from HO to the present formula, H2O. cally contain

ll.

— Various

have con-

generalizations

4a

Avogadro^s Law.

vn

;

tributed to the solution of the problem of molecular weight

determination. is

The

oldest of these

is

Avogadro's Law,

em

which

—

is an equal number of molecules in equal volumes gases at the same temperature and pressure. of all

w w

.c h

There

tp ://

w

This law was announced by Avogadro, an Italian physicist, in 181 1, but was not recognized .by chemists and physicists as a fundamental law of science until about 1868. It has been repeatedly verified experimentally and

ht

deduced mathematically (from the kinetic theory of gases). This law means that the weights of equal volumes of gases are in the

same proportion as the molecular weights of Thus the weight of a liter of oxy-

the gases themselves.

gen was found by Exp. 17 to be approximately 1.43 gm. A liter of hydrogen under the same conditions weighs But .0896 and 1.43 are in the same ratio as .0896 gm. 2 to 32, the accepted molecular weights of hydrogen and oxygen, since it is believed that these gases, like most ele-

The denin a molecule. compound gases has been calculated, and the of some appear in the following table

mentary gases, have two atoms sity of all

relations

:

—

Experimental Chemistry.

144

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

Gas.

Atoms, Molecules, and Related The same

Subjects.

145

student verified this result by finding the

magnesium to be 11.95. The atomic weight magnesium is twice the equivalent, hence the atomic weight becomes 23.9 {i.e. 2 x 11.95), a result agreeing equivalent of

of

The approximate

fairly well with 23.7 previously found.

atomic weight of magnesium

is

24.

Again, from the results of the

Weight of oxygen

*

Hence the proportion

Weight of magnesium oxide

:

{i.e. .2.5

.62

.

.

' '

:

—

Thus

-f-

.37) of

mag-

Atomic weight of oxygen

.

'

Molecular weight of magnesium oxide

16

::

\

x

^r

= 397

.c h

.25

.

gm.

vn

oxide.

.62

4a

of

oxygen formed

em

gm. nesium .25

experiment the mo-

first

magnesium oxide may be found.

ll.

lecular weight of

w w

The molecular weight of magnesium oxide is 40 {i.e. 24 + 16), which is in fair agreement with the above experimental determination. It is generally accepted that a molecule of magnesium oxide contains one atom each of

w

oxygen and magnesium.

tp ://

The atomic weight

obtained these results

of zinc :

—

is

A

similarly found.

student

gm. of zinc united with .26 gm. of oxygen to form gm. of zinc oxide. Using the same form of proportion as in the case of magnesium, we may write

ht

1.05

1.3

1

.26

:

1.05

:

:

16 \x

x=

An

64.61

average of the determinations of a large class work-

ing in the same laboratory on the equivalent of zinc was 32.45. lent,

zinc.

Since the atomic weight of zinc

is

twice the equiva-

the second result gives 64.9 as the atomic weight of

The approximate atomic weight

of zinc

is

65.

Experimental Chemistry.

146

A

student

performing Exp. 16 obtained these results

in

:

Grams.

Weight Weight

of potassium clilorate used 1.500

Weight of potassium

Now

....

of oxygen lost

chloride

.585

.915

left

chemists believe that a molecule of potassium

we may

chlorate contains three atoms of oxygen, hence

potassium chlorate

48

or

X

:

'

'

Weight of oxygen

Weight of

potassium chlorate

'

4a

'

vn

Molecular weight of

three

atoms of oxygen

—

.585

::

1.5

:

X=

123.07

em

Weight of

:

ll.

write the proportion

The molecular weight

48

:

X

the

Weight of oxygen .585

Weight of '

potassium chloride

.915

:

,r= 75.07 of potassium chloride,

atomic weights,

ht

its

"

::

The molecular weight adding

'

potassium chloride

tp ://

or

Molecular weight of *

w

Weight of three atoms of oxygen

—

w w

:

.c h

of potassium chlorate, found by adding the approximate atomic weights, is 122.5. Again, the molecular weight of potassium chloride may be found by the proportion

is

74.5,

it

found by

being assumed that

molecule contains one atom each of potassium and

chlorine.

The molecular weight

of water

A

may be

calculated from

student found that .905 gm. of oxygen formed 1.021 gm. of water. Hence:

the result of Exp. 44.

Weight of oxygen

—

Weight of

or ,905 ;r-= 18.05

Atoms, Molecules, and Related

Subjects.

147

This result agrees closely with 18, the molecular weight These results are ouly approximate, but they of water.

some

serve to illustrate

methods employed

of the

in the

determination of atomic and molecular weights.

power

— Investigation

to hold in

shows that each element has

combination a definite number of atonis

of other elements,

and that the power varies with the

elements which interact.

Thus

chlorine, oxygen, nitrogen,

vn

Valence.

;

with four, tetravalent

w w

valent

.c h

em

4a

ll.

and carbon, under certain conditions, combine respectively This capacity is with I, 2, 3, and 4 atoms of hydrogen. called valence. It is measured by the number of hydrogen atoms with which one atom of the element combines to form a molecule. Hydrogen and all elements combining with one atom of hydrogen, or its equivalent, are called univalent elements, e.g. sodium and potassium those combining with two atoms are called bivalent with three, tri;

;

;

with

five,

pentavalent, or

Elements of the same valence replace each If the valence is different, such a other atom for atom. number of atoms or groups of atoms must be taken that

tp ://

w

quinquivalent.

the valence of the interchanging parts will be equal.

Cu(N03)2

is

Thus

the formula of copper nitrate, because in this

ht

compound copper has the valence two and

is

equivalent to

NO3

groups which are univalent, since they combine Similarly, Na20' is directly with one atom of hydrogen. the formula of sodium oxide, but CaO is the formula of calcium oxide, the valence of oxygen and calcium being

two

two, while the valence of sodium of an

element

is

the same in the

is

one.

The valence

same compound, but

often varies in different compounds, according to circum-

and character of the other Valence must not be assumed, but learned by

stances, such as temperature

element.

Experimental Chemistry.

148

experience, since the whole theory

is

not a sharply defined

conception.

—

The formula of a compound Percentage Composition. is not only an abbreviation of its name, but also an expresThus H2SO4 means that in every sion of its composition.

then

—

—

are hydrogen.

^

are sulphur.

em

98

4a

98

ll.

cule,

vn

molecule of sulphuric acid 2 parts are hydrogen, 32 are sulphur, and 64 are oxygen, if the parts are taken by As there are 98 parts (2 + 32 + 64) in the moleweight.

.c h

-A are oxygen. 98

Should the composition

in per cent

w w

be calculated thus

—

:

ht

tp ://

w

2:

be desired,

it

can

Atoms, Molecules, and Related of each clement in the

compound.

composition of sulphuric acid

is

—

H=

2.04.

=

32.65.

S

Subjects.

149

Thus the percentage

0=65.31. each percentage is divided by the proper atomic write (approximately)

we may

:

of sulphur atoms.

=

I

= number

=

4

= number

of oxygen atoms.

.c h

^'^

of hydrogen atoms.

em

52.6c

= number

ll.

-^ = 2

—

vn

if

4a

Now weight,

position

is

w w

Hence the simplest formula of sulphuric acid is H2SO4. The simplest formula calculated from the percentage comnot always the molecular formula, that

is,

it

in a

tp ://

w

does not always express the composition and number of atoms which are in a molecule of the compound when

gaseous

state.

Since every formula

a molecular formula,

it

is

is

designed to be

usually necessary to determine

ht

from independent experimental data. The molecular weight of a compound is twice its vapor density, hence if the density is known or can be determined, then the molecular formula can easily^be calculated from the simFor example, the simplest formula of plest formula.

it

water based on gravimetric analysis is HO, but since its vapor density is 9, its molecular weight is 18, a number Again, the formula which requires the formula H2O.

H2O

is

supported by numerous facts independently

dis-

covered, such as the atomic weight of oxygen, the divisi-

Experimental Chemistry.

i^o

hydrogen into two equal parts, and the ratio of Another illustration will the volumes of the components.

bility of

make the subject still clearer. The simplest formula of a compound of carbon and hydrogen was found to be CH2. Therefore its Its vapor density was found to be 81.4. molecular weight must be 162.8, or nearly twelve times that corresponding to CH2, hence the molecular formula is

C12H24.

Molecular formulas of other compounds

may

vn

be similarly found.

ll.

Until recently the vapor density was the only reliable check on molecular weight determinations, but, as will

now

applicable.

em

are

4a

presently be seen, newer and more comprehensive methods

Elevation of Boiling Point and Depression of Freezing It has long been known that a solution of common

—

.c h

Point.

a higher temperature and freezes at a lower temperature than pure water. (See Exp. 31.) The elevation of the boihng point and depression of the freezing point are controlled by laws, which are easily determined by methods appHcable to many compounds, and molecular weights are

now

tp ://

w

w w

salt boils at

studied by these methods, especially by the depres-

sion of

the freezing point.

of

Investigation

molecular

ht

weights determined by the latter method shows that the depression of the freezing point of a solution is proportional to the weight of the substance dissolved in a given volume, and that the same number of molecules of any dissolved substance produces the

of

different substances but of

depression of the freezing point to the molecular weights.

found experimentally

to

same

fall in

the solution;

of the freezing point of

i.e.

temperature for solutions

equal concentration, the is

Thus

inversely proportional if

X

is

the depression

be produced by a one per cent

Atoms, Molecules, and Related

Subjects.

151

and V the depression produced by a one per cent solution of urea, the following proportion may

solution of sugar,

be written

:

—

V: X:: mol.

wt. of sugar

:

mol. wt. of urea.

known

be 342, and the molecular weight of urea calculated from the above a number agreeing closely with the proportion is 60 molecular weight found by other methods. This method

The molecular weight

of sugar

is

to

used to determine whether a molecular weight

number

or

its

is

a given

multiple, a question often arising in the case

ll.

is

vn

—

compounds having the same percentage The method is applicable, however, only in

those cases in which (i) there the solvent and the solute,

is

.c h

decompose.

no chemical action between and (2) the solute does not

em

composition.

4a

of different organic

The molecular weights

w w

Ions and Ionization. -^

of

many

older by methods agree with the values obtained by the newer methods. There is a marked disagreement, however, in the case of solutions of strong acids, strong bases, and salts,

had

been

determined

tp ://

w

substances which

the

or in general, in the case of ehxtrolytes,

i.e.

all

substances the

ht

aqueous solutions of which conduct electricity. In some instances the molecular weight is only half of the molecular weight found by other methods, i.e. the solution acts as if twice as many molecules were in solution. Thus the molecular weight of sodium chloride was found by two experi-

An extensive to be 29.4 and 30.2, instead of 58.5. experimental study of solutions, supplemented by keen ments

conclusions, derived from facts of the most varied kind,

— known as — that —

has led to the general adoption of the theory the

Theory

of Electrolytic Dissociation

Experimental Chemistry.

152

When

acidsy bases,

and

cules partly split up into

salts dissolve in

water their mole-

iojis.

Ions are atoms, or groups of atoms, charged with elec> they are carriers of electricity, which they give up

tricity

;

when they reach

the electrodes of the battery, or source of

There are always two kinds in every ions or anions, and positive ions or Hydrogen, metals, and metallic radicals (Hke cations. ammonium) form positive ions salt radicals, like SO4, and Potassium the hydroxyl group OH, form negative ions. electric current.

— negative

vn

solution,

chloride in solution

is

largely split

up

into the ions, +

K

and

4a

-

ll.

;

.

potassium nitrate becomes largely K and NO3. This dissociation, or ionization, increases as the dilution increases, and in the case of strong acids, bases, and their salts the dissociation is

concentrated solutions.

some

nearly complete even in moderately

The percentage

of dissociation of

familiar substances (normal solutions at 18°)

w w

the following —

w

Table of

tp ://

Substance.

ht

in

em

;

.c h

CI

Ionization.

is

shown

Atoms, Molecules, and Related

Subjects.

153

Thus, when soluand sodium chloride are mixed, inThe two solutions before soluble silver chloride is formed. mixing contain the ions of sodium, chlorine, silver, and the group NO3; when mixed, the ions of silver and chlorine

interpreted in the light of this theory. tions of silver nitrate

unite to form silver chloride, a

compound

insoluble in water,

the solution still and hsnce not decomposed contains ions of sodium and of NO3, together with the ions If solutions of silver nitrate of the salt added in excess. and potassium chlorate are mixed, no silver chloride is Poformed, because no chlorine ions are available. ;

ll.

vn

or ionized

+

tests are tests for ions.

German chemist, Ostwald, to the many fundamental facts of analytical

of

.c h

chemistry.

em

widely applied by the explanation

Explain and

w w

CLASS-ROOM EXERCISE. 1.

•

4a

Ordinary

-

K

and CIO3. This theory has been

tassium chlorate dissociates into the ions

illustrate the following:

XIX.

—

Equivalent, atomic weight, molecular weight.

tp ://

{b)

w

(«) Atom, molecule, mass.

{c)

Specific heat.

2.

ht

(^) Ion, anion, cation, ionization, electrolytic dissociation, depression of freezing point, elevation of boiling point. Historical.

{a) Essential facts in the (J?)

The

contributions

life

of Dalton.

of Berzelius

to

the

subject

of atomic

weights. {c)

The work

of Stas on atomic weights and

its

value at the

present time.

{d) Dulong and Petit and their joint labors. (e)

Avogadro, Ampere, and Cannizzaro, and to Avogadro's Law.

their contributions

Experimental Chemistry.

1^4 3.

The modern

theory of solution.

(a) Historical development. (d)

Brief but exact statement of the theory.

(c)

The hydrate

theory.

(d) Application to simple reactions.

Valence. (a) Give the valence of in

sodium chloride.

vn

Sodium

—

calcium chloride.

Calcium

in

Oxygen Oxygen

in water.

ll.

4.

4a

in calcium oxide.

Nitrogen in ammonia gas (NH..).

em

Nitrogen in nitric acid (HNO,). Sulphur in sulphur dioxide (SO2).

sulphur trioxide (SOo).

in

Sulphur

in sulphuric acid.

Carbon Carbon

in in

.c h

Sulphur

carbon dioxide. carbon tetrachloride (CCl^).

w w

Zinc in zinc sulphate. in

magnesium

w

Magnesium

XIII.

tp ://

PROBLEMS.

sulphate.

of hydrogen

1. If 0.34 gm. of sodium yields 165 cc volume), what is the equivalent of sodium ?

If

0.48 gm. of magnesium yields 443 cc. of hydrogen (corrected is the equivalent of magnesium ?

ht

2.

(corrected

volume), what 3.

A

4.

If

gm. evolved 670

piece of zinc weighing 1.95

from sulphuric

0.48 gm.

cc. of

hydrogeii

Calculate the equivalent of zinc.

acid.

of zinc replaces

1.6

gm. of

silver,

calculate

the

equivalent of silver. 5.

A

gram of aluminium

yields

interaction with hydrochloric acid.

1271 cc. of hydrogen at lo^C. by

What

is

the equivalent and the

atomic weight of aluminium ? 6. When 0.5 gm. of aluminium was warmed with potassium hydroxWhat is the atomic ide, 660 cc. of hydrogen at 13' C. were liberated. weight of aluminium

?

Atoms, Molecules, and Related

Subjects.

155

7. If 0.3697 gm. of aluminium liberates 0.04106 crm. of hydroiijen from sodium h3^droxide, what is the atomic weight of aluminium ? 8. A chemist found that 8.2144 gm. of alum, (NH,)._,SO,Al.,(SO^)...

24 H^,0, dried at 2i''-25"C., yielded 0.9258 gm. of aluminium oxide, AUO;.. What is the atomic weight of aluminium ? (Assume O- 15.961,

S

=

31.966,

N =

14.01.)

The same

9.

chemist found that 6.9617 gm. of aluminium bromide, 8.4429 gm. of silver to precipitate all the bromine. (Assume Ag ~ T07.649, the atomic weight of aluminium ?

AlBi'y, required is

and Br

=

79 754.)

vn

What

magnesium liberates 195.5 cc. of hycu^ogen at 13^ C, magnesium ? 11. A compound of silver and chlorine weighing 121.4993 gm. was produced by heating 91.462 gm. of silver in a current of chlorine gas. What is the atomic weight of silver ? (Assume CI = 35-5, and that one atom of silver unites with one atom of chlorine.) 12. A molecule of calcium oxide contains one atom of calcium and one atom of oxygen. The percentage composition is 71.43 per cent of calcium and 28.57 per cent of oxygen (O = 16). What is the atomic 10.

is

0.2 gpi. of

the atomic weight of

weight of calcium

?

Calculate the percentage composition of

w w

13.

.c h

em

4a

ll.

what

Ii

—

(a) Water.

Magnetic oxide of iron, Fe.jO^. sodium carbonate, Na^^CO;,. io^H.>0. (rt') Ca,(PO,),.Ca,,(PO,)F. (e) Alum, Al.K,(SO,)4 24 H,0. (/) Zinc blende, ZnS. (g) Calamine, zinc carbonate, ZnCOo.

w

(d)

Crystallized

tp ://

{c)

ht

.

14

(/i)

Feldspar, K.^Al,

(/)

Cu,(P0,),.3H,0.

(/•)

Ca,,,(P0,),.CaC03.

S{^p^^..

Calculate the percentage composition of

(a) Potassium chlorate. (d) (c)

Sugar, Ci.H.sO^. Calcium sulphate, CaSO^.

{d) Zinc sulphate. {e)

Magnesium

oxide.

(/) Copper oxide, CuO.

—

Experimental Chemistry.

156

Calculate the simplest formula of the

compound

:

—

=

Hydrogen Oxygen =

(a)

(c)

11. 11

Calculate the simplest formula of the

27.27 72.72

(a) Nitrogen

=

:

—

(c)

82.353

Iron

=

70

Potassium

=

Oxygen =

47.95

em

(d)

Hydrogen = i.o Carbon = 11.99

4a

Hydrogen = 17.647 Oxygen = 30

compounds which have

ll.

16.

=

— 32.39 Sulphur = 22.54 Oxygen = 45.07

the indicated percentage composition

of the atomic weights

(a) Copper sufphate. (d)

Barium

(^)

Manganese

w w dioxide.

w

liter

molecular weight If

1500

is its

20.

A

cc.

of carbon

molecular weight

(^)

Sodium carbonate.

(//)

Potassium

What

is its

1.

Carbon = 73.8 Hydrogen = 8.7

=

(b)

80.2

Carbon = 92.3 Hydrogen = j.j Vapor density = 38.8

15° C.

and 740 mm.

?

compouads having the

and vapor density (c)

17.1

Vapor density =

at

molecular weight

Calculate the molecular formula of the

Nitrogen

What

monoxide gas (CO) weigh 1.8816 gm.,

Indicated percentage composition

(a)

nitrate.

?

volume of gas measures 5.40675

and weighs 7.616 gm. 21.

(/) Potassium hydroxide.

?

ht

19.

Sodium hydroxide.

of sulphurous oxide gas (SO^,) weighs 2.8672 gm.

tp ://

A

:

(e)

chloride.

(d) Calcium oxide. 18.

—

.c h

sum

39.06

compounds by

Calculate the molecular weight of the following

ly.

finding the

what

Carbon

Oxygen =

88.89

Sodium

(^)

is its

compounds which have

percentage composition, and give the name of the

indicated

vn

15.

the

:

—

Carbon = 39.9 Hydrogen = 6.7 Oxygen = 53.4. Vapor dens'tv -

3^-S

CHAPTER

X.

CHLORINE AND HYDROCHLORIC ACID.

—

It

has been shown in previous experiments

vn

Chlorine.

that hydrochloric acid contains hydrogen, but as hydro-

must contain something Chemists have shown that hydroelse besides hydrogen. chloric acid is a compound of two elements, and confirmanot an element,

it

ll.

is

4a

chloric acid

em

tory evidence of this fact will be obtained later.

Obviously,

then, to obtain this other constituent of hydrochloric acid, treat hydrochloric acid with

.c h

we must

and

will

at the

w w

the hydrogen.

something which

same time combine with Several experiments have shown that

liberate this constituent

ht

tp ://

w

oxygen combines readily with hydrogen, hence if hydrochloric acid is heated with some substance which yields oxygen easily, this other element in the acid will be liberated, provided it does not combine easily with oxygen. It has also been shown that some oxides when heated yield oxygen, and, as a matter of fact, manganese dioxide was used by early chemists to prepare oxygen.

Furthermore, Scheele,

the discoverer of this other constituent of hydrochloric acid, actually prepared

it

by heating hydrochloric acid with ores

(mainly oxides) of manganese.

He

did not recognize the

new product as an element and it was not until about 1810 that Davy proved its elementary nature and gave it the name Chlorine, by which it is now known. Chlorine should not be inhaled, as

and

it

irritates the sensitive lining of the throat

nostrils. 157

Experimental Chemistry.

158

THE PREPARATION OF CHLORINE FROM HYDROCHLORIC ACID AND MANGANESE DIOXIDE. Perform Experiment

56.

this

— Put

Experiment

Hood.

in the

a dozen small pieces of manganese dioxide

in a test tube, cover with concentrated hydrochloric acid,

and heat gently.

Describe the action and enumerate the characteristic properties of the

vn

most apparent product.

57. 52.

Experiment

— Apparatus The

flask

A

Hood.

in the

4a

Experiment

this

Construct an apparatus

:

that

like

holds 500 cc. and stands on a sand

bath

;

em

Perform

ll.

PREPARATION AND PROPERTIES OF CHLORINE.

the connecting tube a

cm. long and the ends of 5

cm. apart;

.c h

about

C

is

a

E

is

about 7

B

and

are

wooden block

with a hole in the center large enough to

w w

admit B, which reaches to the bottom of To remove D, hold C in the bottle D.

D

ht

tp ://

w

aside, one hand and with the other pull bending at the same time the whole delivery tube at the point a.

Supplies: ranged,

When

provide

manganese dioxide, powdered antimony, iron,

bundle of

strip of calico,

and Fig. 52.

— Apparatus

for

the

preparation of chlorine gas.

the apparatus

gm. six

a

is

ar-

of granulated bottles, little

a

little

powdered

fine brass wire, a taper,

a

paper with writing in black

in red ink, litmus paper, short glass

tube drawn out to a fine point, deflagrating

spoon, turpentine.

Caution

—

Process:

Put the manganese dioxide

-

30

Turpentine

is

inflammalde. in the flask, insert the stopper,

and slowly pour through the safety tube enough concentrated hydroHeat gently and finally chloric acid to cover the manganese dioxide. stand the burner under the sand bath so that the flame just touches the

Chlorine and Hydrochloric Acid.

Collect

plate.

and passes into D, which should by the color) and covered with a glass bottles and proceed at once with the following

Chlorine

iron pan.

be removed when experiments

:

—

59

is

full

six

rapidly evolved

(as seen

powdered antimony into a bottle of Heat some powdered iron in a deflagrating spoon and pour

{a) Sprinkle a pinch or two of chlorine. it

Into a third bottle thrust a loose bundle of very

into another bottle.

fine brass wire

which has been slightly heated.

Describe the action,

giving especially in each case the evidence of chemical action and of products.

vn

new

Into a bottle of dry chlorine put a piece of calico, litmus paper

(^)

remain undisturbed if

Add

any.

and describe the change.

water,

Hold a burning taper

{c)

verify

it

thus

in a bottle

of chlorine

Draw

a conclusion

result.

.c h

and

few minutes and then

several drops of

Draw^ a general con-

clusion from the whole experiment.

long enough to observe the

for a

4a

to

em

Allow the whole

describe the change,

ll.

(both colors), and paper containing writing in black and in red ink.

Attach the pointed glass tube to

:

a rubber tube connected with the gas cock, light the

of

the

above conclusion ? The Fold a- strip paper (about lo cm. wid^) into the shape result verify the

result

filter

shown

may be shown

as follows

:

w

Does same

w w

gas and lower a s>nall jet into a bottle of chlorine.

tp ://

in Fig. 53; cautiously heat ^ about 10 cc. of turpentine in a large test tube saturate the paper with

the hot turpentine

When

result.

ht

Describe the

and drop

;

into a bottle of chlorine.

it

the action

is

over,

exam-

Fig.

53.— Fluted

paper

fo

r

Exp. 57 (c). draw a conclusion regarding the action between hot turpentine and chlorine. Wax (in the taper), illuminating gas, and turpentine are mainly compounds of hydrogen and carbon.. Explain the result in {c).

ine

the

paper, and

BLEACHING BY CHLORINEo

—

Put a little bleaching powder into a test tube Experiment 58. and add enough water to make a thin paste. Add a few drops of dilute 1

Hold the

easily.

test

tube with the holder.

If the turpentine catches

fire,

Remember that turpentine damp towel over it.

press a

ignites

Experimental Chemistry.

i6o

sulphuric acid to the paste, and then dip a strip of bright colored calico

Remove the

into the mixture.

calico

and wash

it

Describe

with water.

the change. If

time permits, repeat with a piece of unbleached cotton cloth and

describe the change.

A

liter

under standard conditions weighs

chlorine

of

3.18 grams.

kind of bleaching (J))

The phenomenon chemical change

in ?

or newspaper ink

{c)

Why

{d)

What

is

ll.

is

made

it

?

For what

?

Exp. 57 {b) is due to what general Will chlorine bleach a lead pencil mark

Why

?

?

Predict the result

when

red

thrust into a bottle of chlorine.

in Exp. 57 (<:)? the per cent of "available chlorine" in bleaching

was the turpentine heated is

w w

powder?

Additional study of chlorine.

Summarize the physical properties of chlorine. What is its most striking property? Is it heavier or lighter than air? How do you know? The method in Exp. 57 is called " collecting a gas by dozvnward displacement." Why so

tp ://

w

{a)

called?

{b^

What class of chemical compounds is formed in Exp. Name others in this class already used or studied.

ht

2.

How

?

commonly used

.c h

hot charcoal

is it

4a

Bleaching and bleaching powder. {a) What is bleaching powder

em

1

vn

CLASS-ROOM EXERCISE. XX.

chlorine be collected over mercury?

{c)

57 {a)

?

Could

Why?

does Exp. 57, as a whole, show regarding the chemical In what respects does its activity activity of chlorine?

What

resemble and

Is from the activity of oxygen? uncombined? Why? Does it form Are they in general stable or unstable ?

differ

chlorine ever found

many compounds ?

(^) For what chemical element has chlorine a strong attraction? What experiment shows this? {e) How may chlorine be quickly distinguished from all other gases previously studied?

(/) The industrial preparation of chlorine.

(^) Uses.

i6i

Chlorine and Hydrochloric Acid. 3.

The

equation for the interaction of hydrochloric acid and man-

ganese dioxide

+ +

4HCI 146

Name of

all

—

is

MnO^

=

Clo

87

=:

71

How much

the products.

+ +

MnCl. 126

chlorine can be

+ +

2H2O 36-

made from 247 gm.

manganese dioxide ? 4.

A

bottle of chlorine water

was exposed

to the sunlight until all

What two products were formed? Write the equation for the reaction.

{c)

What

is

necessary to form 20 gm. of the

gaseous product?

{d)

What volume

of chlorine

{a)

Name

{b)

Write the equation

(^)

How may

the gases.

for the reaction.

the gases be separated?

w w

Historical.

{a)

The

(J))

Essential facts in the

{c)

7.

.c h

If dry steam and chlorine are passed through a red-hot porcelain two gases are formed.

discovery of the elementary nature of chlorine.

w

6.

necessary to form 20 gm. of

life

of

Davy ?

tp ://

5.

tube,

is

em

the other product?

4a

weight of chlorine

ll.

{b)

(a)

vn

the chlorine disappeared.

A

brief account of Faraday's contributions to chemistry.

Liquid chlorine.

ht

{a) Faraday's work. (J?)

Present method of liquefaction.

{c)

Transportation.

{d) Uses. 8.

Nascent

state.

{a) Definition. {b)

Illustration.

(^)

Theoretical value of the conception. is sometimes prepared by heating a mixture of sodium chloride, sulphuric acid, and manganese dioxide. Interpret the reaction from the standpoint of the nascent Write the equation for the reaction. state.

{d) Chlorine

1

Experimental Chemistry.

62 9.

Miscellaneous.

(^)

Atomic weight of manganese. Molecular weight of manganese dioxide, and of manganese

(<:)

Symbol

(a)

chloride.

of antimony, carbon, and manganese.

—

synthesis of the acid.

know

be necessary, however,

the characteristic properties of hydrochloric acid,

as

may be

readily recog-

should be remembered that hydrochloric acid,

It

we have used

it,

is

a water solution of the gas, and that

em

nized.

4a

so that the product of the synthesis

ll.

to

It will first

vn

It was shown in Exp. 19 that Hydrochloric Acid. hydrochloric acid contains hydrogen, and in Exp. 56 that These results should be verified by a it contains chlorine.

the

same term, hydrochloric

and

its

acid, includes

both the gas

.c h

solution.

w w

CHARACTERISTIC PROPERTIES OF HYDROCHLORIC ACID GAS.

—

is

w

Heat a little concentrated hydrochloric acid in Experiment 59. a test tube, and observe the white fumes and pungent odor. The gas so soluble in water that

it

draws the moisture from the

tp ://

ened litmus paper and on a burning match.

ammonium

hydroxide, hold

ht

the striking result. gas,

This

it

is

air,

forming

Try the action of the gas on moist-

thereby dense white fumes.

Moisten a glass rod with

near the mouth of the test tube, and note a confirmatory test for hydrochloric acid

and should always be used

to verify its presence.

Sunnnarize the

characteristic properties of hydrochloric acid gas.

SYNTHESIS OF HYDROCHLORIC ACID GAS.

Remember

that a mixtiire of hydrogen

if broiigJit 7iear

Experiment

60.

and

air expiodes

aflame.

— Construct a hydrogen generator (see Exp. 19) and

cm. of rubber tubing to the delivery tube. Before generating the hydrogen, collect a bottle of chlorine from a generator stand and If heat is necessary, clamp A \.o

attach about

15

tx.

Chlorine and Hydrochloric Acid.

B

iengthen

and

let it

(see Fig. 82).

Generate a rather rapid current of hydrogen

run about three minutes

13) to the rubber tube,

and

minutes longer; then light

<-he

§

;

attach the platinum tip (see App. A,

the gas run two hydrogen and lower let

the flame well into the bottle of chlorine. action

and

163

h

Let the

continue long enough to observe the

color

and the color and quantity of the product;, tiien extinguish the flame by pinching the rubber tube. Cover the bottle with a glass plate and. after the action in the hydrogen generator has been stopped or the generator removed to a safe place, test the contents of the bottle as the gas was tested in Exp. 59. Do the results agree in every

vn

size of the flame,

removed or explained. Summarize the evidence of the chloric acid gas.

ll.

If not, repeat until the

disagreement

is

4a

?

54-

— Simple °^

fworine^^ras

qualitative composition of hydro-

em

particular

\^

^^^-

.c h

It was shown in Exp. 57 (<^) that chlorine unites easily with metals, forming chlorides, just as oxygen forms oxides.

ht

tp ://

w

w w

There are many compounds of chlorine and metals, the most common being sodium chloride, which would have been formed in Exp. 57 (<^) if sodium, instead of iron and antimony, had been burned in chlorine. It is expensive and inconvenient to prepare large quantities of hydrochloric acid by a synthesis, so the chlorides are allowed to interact with a compound which yields hydrogen easily. Sulphuric acid and sodium chloride are usually used. PREPARATION AND PROPERTIES OF HYDROCHLORIC ACID. Experiment

— Construct

and arrange an apparatus like Fig. 52 apparatus shown in Fig. 55 is used to prepare a solution of the gas, and is the same as shown in Fig. 52, except that 61.

to collect the gas.

B

The

passes into the absorption apparatus, /^G.

bath,

Instead of /% the appa-

shown in Fig. 56. may be used. The flask A stands on a sand and the gas is collected in D by downward displacement, exactly

ratus //,

as in the collection of chlorine.

Experimental Chemistry.

164

add slowly and with constant stirring While the mixture is cooling put 40 gm. of sodium chloride in the flask A, arrange the apparatus to collect the gas, and then pour the

To

I.

15 cc. of cold water

40 gm. of concentrated sulphuric ackl.

cold acid through the safety tube

upon the

Heat gently with

salt.

Collect four bottles,

a low flame.

as in the preparation of chlorine,

cover with glass plates, and set

Disconnect

needed.

— Apparatus

Fig. 56.

preparing

for

w w

Fig. 55.

.c h

em

4a

ll.

vn

aside until

and replace

D

by

FG

(or

w

at a,

— Apparatus replace

hydrochloric acid.

HG).

The

flask

F in

F

//,

which may

Fig. 55.

(or

H)

contains

tp ://

about 50 cc. of water, and the tube reaches just to the surface of the Pass the gas into the water, but in G the tube dips into the water. absorption apparatus, until the mixture in A seems exhausted, or for

ht

a reasonable time. II.

Meanwhile proceed

to study the hydrochloric acid gas already

collected.

{a) Invert a bottle, and hold

matic trough. result illustrate

?

How

its

result.

would a

mouth beneath

What

under similar conditions.

the water in a pneur

property of the gas does this

temperature aff"ect the result ? oxygen, hydrogen, nitrogen, and

rise of

this property with that of

Compare air

Describe the

Apply the litmus

test to the liquid in

the bottle, or to the liquid beneath the mouth of the bottle. {b) Insert a burning stick into another bottle of the gas. the result. ide,

and

air

How

Describe

do oxygen, hydrogen, nitrogen, chlorine, carbon dioxact under similar conditions ?

Chlorine and Hydrochloric Acid. (c)

Hold

of the gas.

a piece of wet

Describe the

165

paper near the mouth of another bottle

filter

What

result.

the cause

is

?

(d) Drop in the remaining bottle of hydrochloric acid gas a piece of filter paper saturated with ammonium hydroxide. The dense white fumes are ammonium chloride, and are formed by direct combination of

ammonia gas and hydrochloric

NH3

+

HCl

The equation

acid gas.

gas

—

NH.Cl

==

Ammonia

is

Ammonium

vn

Chloride

ll.

Determine the solubility of the ammonium chloride in water. (e) Enumerate other properties of hydrochloric acid gas which you

4a

have observed.

IV.

.c h

em

III. Disconnect J^G and continue to heat the flask (in the hood) until Save the contents of the flask for Exp. 62. no more gas is evolved. Meanwhile study the general properties of the solution of hydrochloric Record the results. acid gas in /^according to Exp. 48.

Every acid has properties peculiar to itself. To a solution of add a few drops of nitric acid and then a little of the

hydrochloric acid is

Determine

made in /^. Expose a

formed. its

solubility

A

white, curdy precipitate, called silver

little

of this precipitate to the sunlight.

by adding separate small portions

w

chloride,

w w

silver nitrate

to

cold

and warm ammonium hydroxide. Tabulate the propThis whole experiment (IV.), solubility erties of silver chloride. The same test included, constitutes the test for hydrochloric acid. (Compare Exp. 29 (<^).) answers for chlorides. Try it.

ht

tp ://

water, hot water,

It

when zinc and sulphuric acid new compound is formed, and (2) a definite

has been shown that

interact (i) a

weight relation exists between. the zinc and hydrogen. It is possible, though not so convenient, to prove that similar

between the factors and products when Hydroand sulphuric acid interact. chloric acid gas is not so easily collected as hydrogen furthermore, the chemical action between sodium chloride and sulphuric acid is not always complete. However,

relations exist

sodium

chloride

;

Experimental Chemistry.

(66 extensive

work by chemists has shown

stance besides hydrochloric acid action

is

complete.

It

is

is

that only one sub-

formed,

if

the chemical

only necessary, therefore, in a

qualitative test, to confine our examination to this substance

study of

in a

THE INTERACTION OF SODIUM CHLORIDE AND SULPHURIC Experiment

I.

Add enough warm

vn

ACID. 62. —

A

water to the flask

to

ll.

loosen the sohd, and pour a portion of the contents into a casserole or Evaporate to complete dryness slowly over a piece evaporating dish.

4a

of wire gauze and then heat strongly (in the hood) until

II.

{a) Dissolve a

little

Test part of the solution {b)

of the residue from

for a chloride

fumes of

all

off.

in distilled water.

I.

and the remainder

for a sul-

a general conclusion from the result.

.c h

Draw

phate.

em

sulphuric and hydrochloric acids have been driven

Test another portion thus

:

Moisten the platinum

wire

test

App. A, § 14) with water, dip the loop into the solid, and hold it Note the intense color. Clean the wire with in the Bunsen flame. hot water or sandpaper, and repeat with any compound known to contain sodium, or which you have made from sodium. (Compare Exp. 42

w

w w

(see

What

(
does this result prove qualitatively about the under examination ? Give the name

tp ://

specific nature of the substance

of the substance.

State

the

chemical

changes which

led

to

its

ht

forifiation.

COMPOSITION OF HYDROCHLORIC ACID GAS.

This experiment, including the preparatio:: ^f the sodium amalgam, should be done in the hood.

—

Method: The composition ot hydrochloric may be found by decomposing a known volume of the gas

Experiment 63. gas

sodium amalgam.

Hydrogen

ured directly in the tube used

amalgam takes no Supplies:

The

is

the only volatile product, and

in the

experiment.

acid

with

is

meas-

The mercury

in the

part in the reaction.

apparatus shown

for the tube £", tall jar, crucible

in Fig. 57; a tightly fitting cork (Hessian), 100 gm. of mercury, 5 gm.

of sodium,

A

is

Chlorine and Hydrochloric Acid.

167

iron wire, iron pan, glass-stoppered bottle.

In Fig. 57,

stiff

a 500 cc. flask,

^

a small dropping funnel,

is

with fragments of glass

drenched with concentrated sulphuric

.c h

em

4a

ll.

vn

filled

a U-tube to be

(7 is

is

a delivery tube reaching to the bottom' of die tube E.

E is graduated

I.

and

its total

tp ://

tube

w

acid, Z?

— Apparatus for determining the composition of hydrochloric acid gas.

w w

Fig. 57.

Preparation of

sodiitni

The

capacity should be known.

amalgam: Put 100 gm.

of mercury in a

ht

rather large Hessian or iron crucible, slip the crucible into a ring, clamped to an iron stand, so that about two-thirds of the crucible is below the

Cut crucible should have an iron, porcelain, or sand cover. gm. of sodium into pieces the size of a bean and slide all Cover the the sodium at once from a piece of paper into the mercury. Hold the crucible immediately and stand a lighted burner under it. rubber tubing between the thumb and forefinger and stand aside from As soon as the heat is sufficient, the reaction takes the apparatus. The instant a place suddenly, often accompanied by a flash of light.

ring.

The

about

5

flash or noise occurs,

pinch the tube to extinguish the burner flame,

and stand back until the fumes of mercury disappear. Extinguish the gas, remove the cover, and stir the amalgam vigorously with a stiff Before the amalgam cools, pour it into a shallow iron pan. iron wire.

Experimental Chemistry.

68

1

Allow

it

to solidify, then

break

into a glass-stoppered bottle. is

it

quickly into small pieces and put

it

Preserve carefully, as sodium amalgam

decomposed by moisture. II.

Process: {a) Arrange the apparatus so that the hydrochloric

acid gas will pass from the generator through the drying apparatus to Generate the the bottom of the graduated tube, as shown in Fig. 57.

gas by allowing concentrated sulphuric acid to drop slowly from the funnel into concentrated hydrochloric acid. completely with dry gas free from air. Allow the (/;) Fill the tube generator to run. moderately fast, and occasionally test the escaping gas at the

vn

E

open end of the tube with moist blue litmus paper. As the operadraw the graduated tube away from the delivery it

Do

as nearly vertical as possible.

not touch the tube

4a

tube, keeping

ll.

tion proceeds, gradually

with the hands, but use a test tube holder.

Have ready about

10

gm.

thrust the sodium

amalgam

with the sodium amalgam.

all

As

the gas to

insert the stop-

come

in contact

the action proceeds, a white deposit

and the sodium amalgam slowly

liquefies.

w w

coats the inside of the tube

When

and instantly

into the tube

Invert the tube repeatedly to allow

.c h

per.

em

of powdered sodium amalgam, wrapped in a small piece of thin paper, and when the tube is full of gas, withdraw it from the delivery tube,

If the the action seems complete, uncork the tube under water. preceding part has been correctly performed, the water will rush into

Clamp the tube so that the water is at the same level within and without, but not so that the tube is over the stream of hydrogen After arising from the excess of amalgam at the bottom of the jar.

tp ://

w

the tube.

has stood five minutes, adjust the levels (if necessary) without What is touching the tube with the hand, and read the volume.

it

ht

the relation between the original and the final volume? {c) Unclamp the tube, place the thumb over the open end,

lift it

from

the water, invert, remove the thumb, and instantly hold a lighted match at the mouth. What gas was in the tube?

(^) Summarize the evidence of the composition of hydrochloric Sketch the apparatus.

acid gas.

— The

Exp. 63 between shows approximately the volumes of hydrogen and chlorine derived from hydroIt has been proved by many experimentchloric acid gas. Discussion of Experiment 63.

result of

that a simple relation exists

Chlorine and Hydrochloric Acid. ers that these

volumes are equal.

169

This result has been

confirmed by decomposing hydrochloric acid by an electric furthermore it has current, just as water was decomposed ;

been shown chlorine

that

when equal volumes

allowed to combine,

are

of

hydrogen and

hydrochloric

acid

formed without a residue of either component. the gases so combine, the equation for the reaction

+ Cl2=

is

:

—

2HCI.

vn

H2

is

When

The Formula

of Hydrochloric

4a

be subsequently explained.

Acid Gas

em

will

ll.

This simple relation, together with the equally simple relation revealed by the volumetric composition of steam,

rivative of hydrochloric acid

hydrogen or

is

is

HCl.

— No

de-

known which contains less Hence HCl is a molecule.

w w

.c h

less chlorine in of the facts. Again, the molecular expression the simplest gas is 36.5, since its density is acid weight of hydrochloric

18.25.

CLASS-ROOM EXERCISE.

w

I.

equation for the complete interaction of sodium chloride and

tp ://

The

sulphuric acid

is

—

NaCl + H.SO,

= Na,SO^ +

ht

2

(«) {d) (c)

2

HCl

Sodium

•j

Sulphate 117

n.

XXI.

Theoretical.

+

98

=

+

142

Why is this equation correct ? Why does contain 2 NaCl instead of How would you prove this equation ? it

73

NaCl

?

Further study of hydrochloric acid. (a)

How made

(c)

Cause of

industrially

its

?

(^)

Its

yellow color.

(d) Commercial name, and

why

so called?

usual impurities.

\

Experimental Chemistry.

lyo

Explain the statement,

(e)

"The

coefficient

hydrochloric acid gas at o° C.

3.

(/)

What happens when

(g)

The

absorption ol

of

is 503.'"

a solution of hydrochloric acid

is

boiled?

liquefaction of hydrochloric acid gas.

Historical.

(a)

The

(d)

Priestley's work.

(<'/)

The

history of hydrochloric acid up to Priestley's time.

various

Davy's work.

(c)

names of chlorine and hydrochloric

acid,

and

their significance.

Miscellaneous.

Name and

(a)

describe any

vn

4.

compounds of chlorine not already

ll.

considered.

4a

I

PROBLEMS. XIV.

grams of chlorine can be obtained from the complete manganese dioxide ?

em

How many

1.

action of hydrochloric acid on one kilogram of

absorbs twice

it

A

3.

weight) will 3.6

volume

1.

of water absorb, pro-

?

1. of commercial hydrochloric acid, sodium chloride and sulphuric acid are

manufacturer needs 10

How much

1.174.

sp. gr.

its

w w

vided

.c h

How many liters of chlorine ? 2. How much chlorine (by

?

w

necessary

of chlorine would be obtained at 13° C. and 740 mm. 4. by heating 10 gm. of manganese dioxide with an excess of hydrochloric acid

?

tp ://

What volume

How much

6.

A

manganese dioxide

ht

5.

liter

will yield a liter of chlorine

of commercial hydrochloric acid, sp. gr. 1.16,

How m.'jch sodium chloride, sulphuric must be used ? 7.

How many

liters

hydrochloric acid gas 8.

Assume

acid,

and

is

?

required.

waiter (in the receiver)

of hydrogen gas can be obtained from

i

1.

of

?

(i) 100 parts of potassium chlorate yield 60.85 parts of

potassium chloride, (2) 100 parts of potassium chloride yield 192.4 parts of silver chloride, (3) the formulae KCIO.,, KCl, and AgCl, (4) O = 16,

and (5) 100 parts of

silver

combine with 32.87 parts of chlorine.

From

these assumptions, find the atomic weights of chlorine, potassium^ and silver.

Chlorine and Hydrochloric Acid.

A chemist

9.

found that 91.462 gm. of

silver,

when heated

a volume of dry chlorine measares 22.32

If

1.

in a cur-

What

rent of chlorine, yielded 121.4993 gm. of silver chloride. atomic weight of chlorine ? (Assume Ag = 108.09.) 10.

171

at o

C.

is

the

and 760

measure at 17° C. and 730 mm.? The simplest form of the equation for the interaction of chlorine

1 1

and water

will

is

it

—

H,0 + (a)

How many

=

CI,

2

of hydrochloric acid gas can be

liters

from 875 gm. of water

If 20

12.

How many How many

liters

of oxygen will be produced

liters

of chlorine will be required

of hydrogen are mixed with 10

I.

Hydrogen and

(I?)

how

which gas

mixed and exploded, and the prod-

gm.

of hydrogen

necessary to unite with one

is

gram

w w

of chlorine

(d)

What weight of each gas was used? What volume of each gas was used?

What volume

14.

and

.c h

(a)

?

of chlorine, (a)

em

uct weighed 73

chlorine were

I.

are produced,

many liters of hydrochloric acid gas and how much remains in excess ? 13.

?

ll.

{c)

made

?

4a

(d)

HCl + O.

vn

mm., what

?

percentage composition of Hydrochloric acid gas.

(a)

w

15. Calculate the

(^)

Sodium Sodium

(c/)

Silver chloride.

(t')

Potassium chloride.

chloride.

sulphate.

tp ://

(^)

ht

(/) Potassium chlorate. (g) Acid sodium sulphate,

How much

16.

sodium chloride

HNaSO^.

is

necessary to

make a kilogram

of

hydrochloric acid gas ? 17.

How many

pounds of sodiu;n chloride are necessary

to

make 150

of available lb. of hydrochloric acid solution containing 31.5 per cent acid

?

to

make

100 gm. of chlorine from hydrochloric acid? necessary to 19. How many grams of manganese dioxide are

make

18.

40

1.

How many grams

of chlorine

at 37*^

of

C?

manganese dioxide are necessary

CHAPTER XL COMPOUNDS OF NITROGEN.

means either the gas ammonia gas is, more

is

loosely used to include

just

as hydrochloric acid

aviuiojiia

solution,

or

vn

its

The solution ammonium hydroxide,

solution.

its

strictly,

ll.

— The word

4a

Ammonia.

both the gas and

of

as

appear from subsequent experiments. Ammonia is best prepared from its compounds.

.c h

em

will

PREPARATION OF AMMONIA.

— {a)

chloride

Mix and grind together in a mortar a little and lime (calcium oxide). What product is re-

vealed by the odor? Dissolve a

little

ammonium chloride in water, add a little sodium warm gently. What is the most ajDparent

w

(Jj)

w w

Experiment 64.

ammonium

product?

tp ://

hydroxide solution, and

ht

PREPARATION AND PROPERTIES OF AMMONIA GAS AND AMMONIUM HYDROXIDE. Experiment 65.

Method: Prepare the gas and the

solution sub-

stantially as in the case of hydrochloric acid.

Apparatus : Prepare the gas in a modified form of the apparatus shown in Fig. 52. The gas is collected by upward displacement in the apparatus shown in Fig. 58. B-C-D part It is an inverted form of the ''

of Fig. 52; 79

is

connected with

ammonium hydroxide

—

E

by

«, as before.

The

solution

—

prepared in the apparatus shown in Fig. 55. This experiment must be performed without interruption, and all parts is

of the apparatus must be constructed and before the experiment proper begins. 172

ready for immediate use

Compounds of

Nitrogen.

173

Supplies : 30 gm. of ammonium chloride, 30 gm. of quicklime which has been exposed to the air long enough to make it crumble easily, 5 bottles, 4 glass plates, litmus paper, stick or splint of wood, pneumatic

trough or dish

filled (as

usual) with cold water,

paper.

filter

Process: chloride

Mix thoroughly the ammonium

I.

and

Slip the mixture into the

lime.

A^ insert the stopper and its tubes, and add a little water through the safety tube to moisten the mass. Connect the collection apHeat paratus, and see that all joints are tight. flask

full,

and covering with a glass

plate.

when It

vn

Collect four bottles

:c

ll.

gently with a low flame.

of gas (in dry bottles), removing each

t

can

4a

A

[HO=i

be told when the bottle is full by holding a piece of moist red litmus paper near the

em

easily

.c h

mouth. Do not smell at the mouth of the bottle. Disconnect at a, attach the absorption apparatus FG^ and allow the ammonia gas to be and G, while absorbed by the water in both the collected gas is being studied, remembering shake II.

The

general properties of

ing experiments

:

—

Try the action of a

tp ://

{a)

Fig. 58.

— Apparatus

collecting

for

ammonia gas.

F occasionally.

w

to

w w

F

ammonia gas .are found by

bottle of the gas

the follow-

on moist litmus paper

the action on a burning stick or taper (having a small flame) also, the color,

;

try

notice,

and very cautiously the odor by wafting the gas gently Is it heavier or lighter than air, chlorine, and hydro-

toward the nose. chloric acid gas?

ht

;

Has

it

acid or alkaline properties?

Will

it

burn or

support combustion ? {p) Hold a bottle with its mouth just below the surface of the water Watch the result. Describe it. in a pneumatic trough or other vessel.

W^hat property of the gas does it reveal? Is it a marked property? Test the liquid in (or just below) the bottle with litmus paper (both What has become of the gas? colors). {c) Pour a few^ drops of concentrated hydrochloric acid into an

Cover it with a glass plate, invert it, and stand upon a covered bottle of ammonia gas. Remove both plates at once, and hold the bottles together by grasping them firmly about their necks. empty, warm, dry bottle. it

Experimental Chemistry.

1*74

Give all the evidence of chemical action. If heaV where and why. Allow the white product to settle, then scrape out as much as possible upon a paper, transfer it to a test What tube, and warm gently with a little sodium hydroxide solution. Describe the action.

was evolved,

state

formed? What was the white product? (If the last question cannot be answered from the evidence here presented, consult Exp. 6i {d)

is

and Exp. 64

{b).)

Disconnect the absorption apparatus, and remove the generator as Study the properties of the ammonium hydroxide in to a hood. III.

F

:

—

the general properties

{a) Determine

by repeating Exp. 49 («)

{b).

ll.

and

vn

follows

What

Try the

effect

The

of

ammonium

made

is

hydroxide on a grease spot.

of this property

em

{c)

practical application

gas

4a

{b) Boil a little of the liquid gently in a test tube.

evolved ?

is

What

?

ammonium

equation for the interaction of

.c h

and lime — calcium oxide — —

chloride

is

w w

2NH4CI + CaO - 2NH3 + Calcium

Chloride

Oxide

+

56

tp ://

107

w

Ammonium

_ Ammonia

=

Calcium

Gas

34

CaCl2+H20 ^^. ^

Chloride

+

III

+

18

—

ht

Ammonia gas is a comComposition of Ammonia Gas. and a quantitative qualitative pound of two elements. examination of the gas

A

will

reveal

its

components and

their relations.

QUALITATIVE EXAMINATION OF THE COMPOSITION OF

AMMONIA

—

GAS.

Method: Pass dry ammonia gas over heated Experiment (id. magnesium powder and test the two products. Apparatus: The apparatus is shown in Fig. 59. A is a 500 cc. flask, provided with a safety gauge tube and a delivery tube connected

Compounds of

Nitrogen.

175

B. The left-hand limb of B is to be empty, the bend loosely plugged with cotton, and the other limb filled with lumps of quicklime. CC is a glass tube about 25 cm. long and 2 cm. in diamit is loosely filled with soda lime, except at the ends, where the eter

directly with a U-tube

;

soda lime

is

replaced by loose plugs of cotton.

justment, this tube should be tapped along

Before the

final

ad-

entire length to insure

its

an unobstructed channel for the ammonia gas. These tubes, B and CC, serve to dry the ammonia gas a precaution absolutely essenIf the ammonia gas is evolved tial to the success of the experiment.

—

calcium chloride drying

CC

and

.

The

tube

CC

is

;

but

if

haste

is

necessary, then

a

with lime, should be placed between

attached to

B

and

DD'

,

as

shown

in the

ffl=H]

»f

w w

.c h

em

4a

ll.

B

jar, filled

vn

slowly, these tubes are sufficient

w

— Apparatus for determining the qualitative composition of ammonia gas.

tp ://

Fig. 59.

DD'

figure.

per wires at

is

ht

fracture of the

partly

shown

a

combustion tube from 12 to 15 cm. long. Two copD'^ arranged as usual, serve to prevent accidental

D and as

A delivery tube, tube or melting of the stoppers. passes from the combustion tube into a glass dish,

£",

arranged, as usual, to collect a gas over water.

The

apparatus

is

sup-

ported by iron stands provided with clamps which may be attached at Various modifications may be and-Z?'. convenient points, such as

C

economize space, but such changes should not shorten the drying tubes. The flask A stands on a sand bath or asbestos board, and the ammonia gas is evolved by heating concentrated ammonium hydroxide over a low flame, which is controlled by a Hofmann screw

made

to

attached to the gas tube (lengthensd, if necessary) near the operator. The combustion tube is heated with a wing-top burner. Two or three

empty

bottles will also be needed.

Experimental Chemistry.

1-76 Process:

Fill

A

half

powder §

in

II.)

DD'

to

make

ammonium hydroxide and

of concentrated

full

connect securely with the tubes

B and CC

a thin layer from

.

5 to 7

Put enough magnesium cm. long. (See App. A,

Connect DD' with the drying and delivery tubes. Fill the enough dilute sulphuric acid to submerge the end of

glass dish with

the (lengthened) delivery tube E.

Fill the bottles (preferably of 125 cc.

and stand them conveniently near the dish, Heat the flask A inverted, if necessary. instantly may be they that so gently, and begin to heat the combustion tube. Search for leaks, which may be detected by the odor, as soon as any ammonia gas is known to (i) the safety gauge tube, have been evolved. Watch three points (2) the magnesium, which will reveal any excessive back pressure and (3) the end proceeds experiment as the in color change will which of the delivery tube, where the gas which is to be collected rises, and

vn

capacity) with cold water,

;

ll.

—

of evolution of the latter gas. free

from

and,

finally,

When

indicates, approximately, the rate

em

where the escape of the ammonia gas

4a

;

it is

judged that the apparatus

is

heat the combustion tube throughout its entire length, A slow current of ammonia heat the magnesium strongly.

.c h

air,

bottle over the

end of the delivery tube and

magnesium

collect the gas.

until the evolution of this

w

to heat the

w w

gas should be kept passing all the time. As the temperature rises, the magnesium changes to a greenish yellow color, and a gas is evolved which does not dissolve in water. When this color appears, slip a

new gas

Continue slackens.

them aside temporarily. Cool the combustion tube slowly, and, when cool enough to handle, disconnect the combustion tube from the delivery tube and the drying and

set

tp ://

Collect three bottles of the gas evolved

ht

apparatus, and quickly pour the contents of the combustion tube into a Preserve for subsesmall dry bottle provided with a glass stopper.

quent examination.

Test each bottle of gas with a lighted match. What is the gas? What, then, is one component of ammonia gas? is its source? Test the greenish powder formed in the combustion tube thus Pour a little into a test tube half full of water. What gas is evolved?

What

Repeat, reserve

if it

the observation for

is

not specific.

Record

this observation,

and

subsequent explanation.

This experiment reveals one component, of ammonia gas, and the product of the interaction of the greenish yellow powder and water suggests the other.

Compounds The

other component of

of Nitrogen.

177

ammonia gas may be found

as

"the residual gas" by

THE QUANTITATIVE EXAMINATION OF THE COMPOSITION OF AMMONIA GAS.

—

Method: Decompose ammonia gas in a measured Experiment 67. volume of chlorine. The method depends mainly upon the fact, already shown, that chlorine will withdraw hydrogen from compounds of

vn

that element.

Apparatus: In addition to the special apparatus shown in Fig. is needed a chlorine generator, arranged as shown in Fig. 52, cept that the " B-C-D part " is replaced by a tube shaped A/ like E in Fig. 30, and long enough to reach to the bottom

60,

ex-

;

temperature of the room

a ;

tall

a

jar filled with water at the

little

(about 25-30 cc.) con-

em

of a pneumatic trough

4a

ll.

there

hydroxide, and dilute sulphuric acid. The apparatus shown in Fig. 60 consists of the graduated it is provided with a gastube A, of known capacity tight, one-hole rubber stopper, carrying the small drop;

The

is

never removed from the stopper. sealing a piece of tubing

w w

ping funnel B, which

.c h

ammonium

centrated

may be made by

latter

cm. long and 2 cm. in diameter) to a stop-cock tube the other end is then cut off at any desirable, though not necessary, is It point. desired The dropping funnel that the tube A be graduated.

w

(5

shown

in

Fig. 32

may be used

instead

of B, but

it

—

not so satisfactory.

ht

is

;

tp ://

near the stop-cock

Process

:

Generate the chlorine in the hood

as directed

Meanwhile ascertain the total capacity of the tube A (see App. A, § 22). Then fill it with water, at the temperature of the room, invert, and clamp it in the pneumatic trough so that the open end is over the hole in

in

Exp.

57.

the shelf.

By

this time the chlorine generator

ApFig. 60. paratus for determining the

quanti-

tative

com-

position

of

ammonia gas.

should be

this condition, however, can be told only by experience, absolutely essential to an accurate result, the generator must, time in case of doubt, be allowed to run at least fifteen minutes after the When the the chlorine bubbles from the end of the delivery tube. chlorine is believed to be free from air, slip the end of the delivery tube

free

from

but since

air

it is

;

Experimental Chemistry.

lyS under the

and pass a rapid stVeam of gas up into the tube

shelf,

tube will soon be

filled,

any appreciable extent.

When

utes until the water runs

before removing

it

;

the

since the gas will not dissolve in the water to

down

the tube ;

is full, let it

be sure the tube

stand a few minis

completely

full

from the trough.

.c h

em

4a

ll.

vn

Meanwhile, fill the dropping funnel half full of concentrated ammonium hydroxide, open the stop-cock, and allow the liquid to fill the lower Close the stop-cock and stand the funnel in a beaker or bottle tube. in another hood, or in some convenient place not far from Ihe chlorine Unclamp the tube, cover the open end with the thumb or apparatus. second finger, invert, and quickly insert the stopper with its funnel. Push in the stopper gas-tight. Fill the funnel with concentrated ammonium hydroxide, cautiously open the stop-cock, and allow a drop or two of the ammonium hydroxide to enter the tube. Considerable heat, and sometimes a faint flash of light, together with dense, white fumes, Add ammonium hydroxide, drop by drop, indicate chemical action. until the reaction seems complete. Take care not to let any gases out of Now add dilute or any air into the tube when the stop-cock is opened. sulphuric acid through the funnel until at least one-third of the tube full.

Fill the funnel

with water, cover with a small piece of

filter

is

paper,

w w

and invert the whole apparatus in a tall jar of water. Remove the paper, open the stop-cock, allow the water to run in, and let the whole apparatus remain undisturbed for at least fifteen minutes. Then, without

w

touching the upper part of the tube, raise or lower

it

until the

water

is

same height within and without clamp the tube in this position and read the volume of "the residual gas." What proportion of the original volume is it? Close the stop-cock, lift the tube from the water, remove the stopper, lower a lighted match attached to a wire into the tube, and observe the

tp ://

;

ht

at the

result.

What

is

Test the gas also with lime water, as previously directed. the gas? Why? Why not any of the other gases studied?

Record the two

definite results of this experiment.

Sketch the apparatus used

for the quantitative examina':-cn of the

composition of ammonia gas.

Discussion of Experiments 66 and 67.

— When ammonium

hydroxide, which has been shown to be identical with a

ammonia gas, is added to chlorine, the chlorine withdraws the hydrogen from the ammonia gas, forming

solution of

Compounds

of Nitrogen.

hydrochloric acid gas and ''the residual gas."

179 But the hy-

ammonia

drochloric acid gas instantly combines with the

gas to form

ammonium

chloride,

dense white fumes, but which added.

which

seen at

first

as the

finally dissolves in the

water

These changes continue

is

until all the chlorine is

removed. The excess of ammonia present, both as gas and in solution, is neutraHzed with sulphuric acid, and the solid product ammonium sulphate also dissolves in

—

Hence

—

end of the experiment only "the residual gas" is present as agaSy and the volume and nature may be found as directed. It was shown in Exp. 63 that chlorine combines with its own volume of hydrogen. Therefore there must have been three times as much hydrogen as nitrogen in the ammonia gas, since there was three times as much chlorine at the beginning as there was nitrogen at the end of the experiment. Since it has been shown that ammonia is a compound of hydrogen and nitrogen, the yellowish green compound formed in Exp. 66 must be a compound of magnesium and nitrogen. It is, in fact, magnesium nitride, Mg3N2. When added to water the interaction yields ammonia gas as one

vn

at the

tp ://

w

w w

.c h

em

4a

ll.

the water.

product, thus confirming the evidence of the composition

ammonia gas furnished by Exp.

6^.

ht

of

Equations for the Chemical Action in Experiments 66 and 67. The following equations represent in the simplest form the chemical action in these experiments. In Exp.

—

66-^

2NH3

+

3Mg

=

MggN^

+

3H2

+

3MgO

Magnesium Nitride

MgsNa

+

3H2O -

2NH3

t 1

Experimental Chemistry.

80

In Exp. 6^

—

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

NH3

Compounds of Nitrogen. The

factor

the gas

is

H must be subtracted

i8i

from the barometer reading because

supporting only that column of mercury which

is

the

dif-

ference between the barometer column and the column extending from

the surface of the mercury in the trough to the upper surface of the

—

found by actual measurement with a meter stick. mercury in the tube Read the volume again roughly, noting also the barometer and

Continue to pass sparks through the gas. Read again is any marked change in volume, continue to pass

thermometer. soon, and

there

if

The sparking must continue

the sparks.

When

there

is

no further change

in

until the

volume

is

constant.

volume, disconnect the wires, allow

vn

the whole apparatus to stand undisturbed for ten or fifteen minutes, then

Reduce the observed volume to standard relation between the original and final

read accurately as before. the

?

Discussion of Experiment 68.

4a

volumes

is

ll.

What

conditions.

— The

result of this experi-

is

necessary to determine the nature of the

.c h

consideration

em

ment simply shows that when ammonia gas is subjected to the action of electric sparks the volume is doubled. Further chemical change, which

and

A

volume

may be

best

explained by an

ammonia gas measured lOO cc, residual volume was 200 cc. Then of

w w

illustration.

after sparking, the

ht

tp ://

w

90 cc. of dry oxygen were added, the mixture was exploded, and 65 cc. of gas remained. It is known, of course, from previous experiments, that ammonia gas yields by decomposition the two gases, hydrogen and nitrogen. Hence the total volume of hydrogen and oxygen which disappeared as a result of the explosion must have been But two-thirds of this volume must 225 cc. {i.e. 290-65). have been hydrogen, and the remainder oxygen, since these gases unite in the proportion of two to one by volume to form water. Therefore, 150 cc. (f of 225 cc.) of hydrogen must have come from the decomposed ammonia gas and since only 200 cc. of mixed gases were formed by the sparking, the remaining 50 cc. must be the nitrogen. These two gases hydrogen and nitrogen ;

—

—

Experimental Chemistry.

i82

combined in ammonia gas in the proportion of three parts to one by vohmie. The facts revealed by Exp. 68 are most simply expressed

therefore, arc

by the equation

—

:

One volume

Three volumes of hydrogen

of nitrogen

ammonia gas under standard

conditions xveighs

gi"i^-

tion of

— The

gravimetric composi-

ll.

of Ammonia Gas. ammonia gas reveals

Formula

the fact that fourteen parts

4a

77

liter of

(17)

_ Two volumes of " ammonia gas

vn

A

2NH3

=

3H2

+

N2

is

.c h

em

The of nitrogen combine with three parts of hydrogen. vapor density of ammonia gas is 8.5 (approximately on the hydrogen standard), and hence its molecular weight is 17. The simplest formula which meets all these requirements NH3.

—A

Law

w w

comparison of the volumetric of Gay-Lussac. composition of water vapor (steam), hydrochloric acid gas,

Two

tp ://

w

and ammonia gas (see pages loi and 169) reveals the fact that in each case the volume relations can be expressed by whole numbers. Thus volumes of hydrogen

—

'

ht

unite with"

to

form two volumes of water vapor.

^

^

one volume of oxygen

One volume

of

hydrogen .

;

1

to

'^

unites with

1

'

one volume of chlorine

J

Three volumes of hydrogen

1

to form

unite with

one volume of nitrogen

^

,

.

form two volumes

r
^'

two volumes

or

;„ uydrochlonc

^

i

1

1

-

of

ammonia

gas.

J

between the volumes of the comThe ponents, and between the components and their compounds in the three cases examined, is just as simple in all cases. simple relation

Compounds of The law was

first

pointed out by Gay-Lussac,

the relation substantially as follows

Gases combine in volumes each other

and

to

183

Nitrogen.

:

—

who

stated

bear a simple relation

zvhicJi

to

the product.

—

When

two or more the compound, form a gaseous

The law may be expanded elementary gases unite to

thus

''

—

It

has been shown in several

ll.

Ammonium Compounds.

vn

volume of a fixed quantity of the compound stands to the volumes of the combining elements in a ratio which can be expressed by whole numbers."

same way

as

any other

salt.

^

.c h

in the

em

4a

experiments (Exp. 64 {b) and Exp. 65 {c)) that ammonium chloride is formed by direct combination of ammonia gas and hydrochloric acid gas. This compound may be formed

INTERACTION OF AMMONIUM HYDROXIDE AND

w w

HYDROCHLORIC ACID. Experiment 69.

— Put

about 50

cc.

of

ammonium

tp ://

w

hydroxide in an evaporating dish or casserole, and add dilute hydrochloric acid, drop by drop, until the solution A convenient dropis just neutral or faintly alkaline. ping apparatus

is

shown

in Fig. 61.

Evaporate to dry-

ht

ness on a water bath or very slowly over a piece of wire gauze. Test the residue as follows {a) Is {b)

it

:

—

an acid, base, or salt ? a little with sodium hydroxide soaition.

Warm

What is formed? Draw

a conclusion as to the nature of

the residue. {c)

Support the dish on a piece cf wire gauze and

Describe gently until a decided change occurs. the result. What compound do the fumes suggest ? {d) Verify the observations and conclusions by re-

warm

peating {b) and {c) with laboratory bottle.

ammonium

chloride from the

V Fig.6i.— Convenkmt droj){"^"1

pointed

^ube open both ends.

ai

Experimental Chemistry.

184 {e)

Draw

a conclusion from these observations regarding the main

product of the interaction of

ammonium hydroxide and

hydrochloric

acid.

in Exp. 69 was ammonium chlobelongs to a series of compounds known as the

The compound formed and

it

Ammonium

compounds.

ammonium ammonium

sulphuric acid or nitric

If

ammonium

Exp. 69, then would have nitrate

had been used

in

series of

compounds

been is

formed.

strictly

The

analogous to

ammonium and

i.e.

ll.

the sodium and other metallic series,

acid

sulphate or

vn

ride,

sodium enter into similar chemical reactions. two series of compounds are well known

—

Thus, these

4a :

NH4CI

em

NaCl

NH4OH

NaNOg

w w

Na2S04 NagPO^

.c h

NaOH

Ammonium, however,

is

NH4NO3

(NH4)2S04 (NH4)3P04

not an element, like

sodium,

tp ://

w

but a compound; and not a compound, strictly speaking, one atom of nitrogen and four but a group of atoms

atoms of hydrogen

—

— so related

to

each other and to other

atoms, that they act as one atom of a metal.

ht

group of atoms, which istence,

is

called

a radical.

radicals are exactly the

It

The chemical

relations of

as elements.

Ammonium

same

has never been isolated, or it

Such a

incapable of independent ex-

is

if

it

has,

it is

so unstable that

immediately decomposes into ammonia and hydrogen. is believed that ammonium hydroxide is a solution of

an extremely unstable compound. The other compounds of ammonium mentioned above are well defined. The symbol of ammonium is NH4, and its valence is one. The formulas of its compounds have already been given.

Compounds of Nitrogen. CLASS-ROOM EXERCISE.

XXIL

Further study of ammonia gas. (a) Source of atmospheric ammonia gas. (d)

Specific gravity.

(c)

Its relation to the subject of

Quantitative test for

(e)

combustion.

in water.

(d) Sokibility

ammonia

gas.

Liquid ammonia.

Properties.

(d) Use in manufacture of

Why

Formula.

(e)

ll.

Present method.

ice.

4a

(d) (r)

vn

(a) Faraday's work.

?

em

Historical.

knowledge of ammonia gas and

(a) Early

its

compounds.

Ammonium

hydroxide.

(a) Exact

meaning

.c h

Discovery of the gas by Priestley.

(d)

of the

name

as usually used.

w w

Source of commercial substance.

(d) {c)

Specific gravity

(d)

What

(^)

Uses

(/)

What

and strength of commercial substance. ammonia and am-

the difference between liquid

is

w

monium hydroxide

?

domestic purposes, in medicine, and in agriculture.

tp ://

for is

anhydrous ammonia

?

Names.

Why

ht

(^)

is

ammonia gas sometimes

called alkaline air, volatile

alkali ?

(b)

Why

should

muriate

monia

ammonium

of ammonia,

chloride be called sal-ammoniac,

sal-animoniaciun, chloride of am-

?

What different meanings may the term ammonia have ? (^) Ammonium carbonate is sometimes called sal-volatile. Why ? {e) What is liqnor ammoniac ? if) What is ammoniacal liquor ? (^) What is gas liquor ? {c)

(/i)

Is there

oxide

any difference between lime, quicklime, and calcium ? If so, what is it ?

1

Experimental Chemistry.

86 (f)

What

6.

Ammonium

aruvionia ?

(igua

is

hartshorn

water

Spirits

?

ot

sahs.

method of preparation,

{a) Give the formula,

of

Ammonia

?

ammonium

chloride,

ammonium

and uses and ammonium

properties,

nitrate,

sulphate.

Composition of ammonia gas.

Summarize the experimental evidence of the position of

ammonia

gas.

Summarize the evidence of the volumetric composition of

{c)

Why

simplest formula of

gas

is

what are the products? in regard to the

ammonia gas

passed over red-hot copper oxide,

What would

if

the copper

.c h

?

What is the valence of nitrogen in ammonia ammonium? In ammonium hydroxide?

gas?

In

w w

{a)

the experiment prove

composition of ammonia gas,

oxide and the products were weighed Miscellaneous.

?

4a

is NH3 the When ammonia

em

(^)

(J))

Calculate the atomic weight of nitrogen from data already

(<:)

Why

is

the formation of white fumes from the combination

ammonia gas and another gas

tp ://

of

w

given.

ammonium

not necessarily evidence of

chloride?

Gay-Lussac's Law.

ht

9.

com-

{b)

ammonia gas.

8.

qualitative

vn

{a)

ll.

7.

{a) Exact statement.

(^)

Illustrations.

{c)

Theoretical significance.

(^) Essential facts in the life of Gay-Lussac. Humboldt's contribution to the law.

{e)

PROBLEMS.

XV.

1. How many grams of ammonia gas can be obtained from 2140 gm. of ammonium chloride by heating with lime? (See Equation 16.) 2. What volume of ammonia gas can be obtained by heating 31.47 gm. of ammonium chloride with lime?

Compounds How many

3.

lime to 4.

the

at

Nitrogen.

of*

187

grams of ammonium chloride must be heated with

make 80 1. of ammonia gas ? Water absorbs about 50 per cent

of

its

ammonia gas

weight of

How much ammonium

ordinary temperature and pressure.

chloride and calcium oxide are needed to produce 10 kg. of

hydroxide

ammonium

?

If 22.4 1. of hydrogen at o" C. and 760 mm. weigh 2 gm., what an equal volume of ammonia gas weigh at 100' C. and 380 mm. ? 6. If 250 cc. of chlorine are measured at 10'' C. and 750 mm. and then allowed to interact with ammonia gas, what volume of nitrogen 5.

will

be liberated at the same temperature and pressure ? How many cubic centimeters of the component gases can be

vn

will

7.

of

liter

A

ammonia gas

ll.

obtained by the decomposition of a

?

em

4a

volume of dry ammonia gas equal to 29 cc. is decomposed by electric sparks, and the resulting mixture is exploded after 30 cc. of What gases remain, and what are their oxygen have been added. volumes ? 15 cc. of ammonia gas are decomposed by electricity, and 40 cc. 9. 8.

oxygen are added; the mixture

then exploded.

.c h

of

is

What

are the

produce a 11.

A

w w

gases and their volumes before and after the explosion ? 10. What weight of ammonia gas and of chlorine is necessary to of nitrogen

liter

kilogram of

(a)

cc.

of dry

What

is

ammonia gas

is

produced

heated with lime.

What

?

decomposed by

are

tp ://

180

chloride

at 12° C. is

w

volume of ammonia gas 12.

?

ammonium

the volume of each product

electric sparks.

?

130 cc. of oxygen are added and the mixture exploded, what gases and what volumes remain ? 13. 100 cc. of dry ammonia gas are decomposed by electric sparks; then 100 cc. of oxygen are added and the mixture exploded. If

ht

{d)

(a)

What

gases and what volumes remain after the decomposi-

tion of the (If)

14.

What

is

What volume

?

?

the weight of 30

temperature and pressure 15.

ammonia gas

After the explosion

1.

of dry

ammonia gas

at the

normal

?

of nitrogen

and of hydrogen can be obtained by

passing electric sparks through one hter of dry ammonia gas, and what volume of oxygen will be necessary to unite with all the hydrogen thus

obtained to form water

?

1

Experimental Chemistry.

88 16.

Calculate the percentage composition of

{d)

Ammonium chloride, NH^Cl. Ammonium hydroxide, NH^OH. Ammonium sulphate, (NH4)^S04. Ammonium nitrate, NH4NO3.

(^)

Magnesium

{a) (J?)

{c)

17.

nitride,

MgoN^.

Calculate the formula of a substance

composition

:

having the percentage

—

= 82.35 = 17-64 Nitrogen = 26.17 Hydrogen = 7.48 Chlorine = 66.35

{a) Nitrogen

How many

pints of a solution of

lb. ?

— Another

useful

ll.

compound

(sp. gr.

of nitrogen

is

.c h

Nitric Acid.

ammonium hydroxide

em

18.

0.88) weigh 4

1

4a

(J?)

vn

Hydrogen

nitric acid.

PREPARATION OF NITRIC ACID.

— Do not get concentrated sulpJmric or

w w

Precaution

nitric

acids on the skin or clotJiing.

w

—

tp ://

Prepare the acid in the apparatus shown in Experiment 70. retort supported by a clamp and resting on a tubulated A\%2i Fig. 62.

The neck

sand bath.

of the retort passes into the receiver B^ which Condensation of it distils from the retort.

catches the nitric acid as

ht

the acid fumes

facilitated

is

neck of the retort where if it

becomes

hot.

retort in position.

the fumes of

wood

;

it is

it

by wrapping wet

filter

paper around the

and upon the flask itself, tightly enough to hold the

enters the receiver,

The neck Turn B

is

clamped just

occasionally to expose a fresh surface to

advisable, though not always necessary, to place a block

against the bottom of the receiver to keep

it

in the desired

position.

gm. of sodium nitrate from a paper into the retort App. A, § 12), and pour upon it, through a funnel, stand-

Slip about 35

(see Fig. loi,

ing in the tubulure, about 25 the apparatus as

shown

pass into the receiver

cc.

of concentrated sulphuric acid.

in Fig. 62.

Distil at as

Heat gently, and

Adjust

nitric acid will

low a temperature as possible, as

Compounds of long as any

nitric acid

runs

down

Nitrogen.

189

the neck of the retort.

nitric acid into a small bottle for use in the next experiment.

Pour the Allow the

add just enough warm water to loosen the solid mass, pour the contents into any convenient vessel, and preserve for Exp. y^-

tp ://

w

w w

.c h

em

4a

ll.

vn

retort to cool,

Fig.

62.— Apparatus

for preparing nitric acid.

general properties of nitric acid have been shown They should experiment (see Exp. 48). preceding in a

ht

The

be recalled or the work repeated.

A SPECIAL PROPERTY OF NITRIC ACID.

—

Add twice Experiment 71. made in Exp. 70, and proceed as

its

volume of water

follows

:

—

to the nitric acid

nitric {a) Boil a piece of a quill toothpick in a portion of this diluted is the effect of continWhat ? first at changed quill the is How acid.

ued heating ? Pour color permanent ?

off the acid,

and wash the

quill

with water.

Is the

Experimental Chemistry.

i^o Add

(J?)

a dozen or more drops of nitric acid to a dilute solution of Will ammonium hydroxide restore the

Describe the change.

indigo.

original color

probability,

decomposition

Draw

Is the

?

is

change temporary or permanent

?

What,

in all

— combination

the general character of the change

or

?

a general conclusion from the whole experiment regarding the

action of nitric acid on organic matter, which

is

typified

by the

quill

and

indigo.

bottle of pure nitric acid

VIII.

vn

LABORATORY EXERCISE. Examine a

and of the commercial

—

and record

{a) Color of each acid.

Presence or absence of a gas above the

any.

Examine a

2.

sunlight.

acid

What

bottle of nitric acid

to the nitric

the stopper from a bottle of strong nitric acid.

very hygroscopic

?

What

other acid acts similarly

Smell of the acid cautiously, and record the

w w

4.

which has been exposed

.c h

Remove

and color of

does this observation show about the stability of

?

3.

liquid,

em

if

4a

(b)

gas,

w

A TEST FOR NITRIC

— To

tp ://

Experiment 72.

Is

it

?

result.

ACID.

full of water add five add also an equal volume of

a test tube one-fourth

or six drops of concentrated nitric acid

concentrated sulphuric acid.

Shake

cool by holding the test tube in

ht

acid,

ll.

1.

solution of fresh ferrous sulphate

;

until the acids are well mixed,

Make

nmning

water.

and pour

this solution carefully

the side of test tube upon the nitric acid mixture.

Where

then

a cold, dilute

down

the two solu-

meet a brown or black layer will appear, consisting of a compound formed by the interaction of the nitric acid and the ferrous sulphate. It is an unstable compound and will often decompose, if the test tube is shaken. Record the observation. This test is also used for a nitrate. Try it with a solution of sodium nitrate. Record the result. tions

The

—

Sodium Nitrate and Sulphuric Acid. It has already been shown that nitric acid is one product of the interaction of sodium nitrate and sulphuric acid, and Interaction of

Compounds of Nitrogen. since chemists have

shown

only one other substance its

is

that if

formed,

tJie

it

191

action is complete

remains to determine

nature.

THE INTERACTION OF SODIUM NITRATE AND SULPHURIC ACID.

—

Experiment 73. Pour the solid residue obtained in Exp. 70 into a casserole or an evaporating dish, and evaporate to dryness over a

As

the mass approaches pasty con-

vn

piece of wire gauze in the hood.

When

sistency lessen the heat to avoid spattering.

the mass

done

ll.

heat strongly as long as white, choking fumes are evolved.

is

This

dry, last

remove all traces of sulphuric acid, and to complete the chemical change. Allow the dish to cool gradually, and when cool, dissolve some of the white solid in distilled water and test separate portions for a sulphate and nitrate. Which is it ? Test another poris

to

em

4a

operation

tion for sodium, as previously directed.

Draw

?

is

the

name

of the white

a general conclusion regarding the chemical action which occurs

by the interaction of sulphuric acid and

w w

in the preparation of nitric acid

sodium

WMiat

.c h

substance

nitrate.

w

There are two equations expressing the chemical changes

tp ://

revealed by the preceding study of the preparation of nitric acid. If the temperature is low, then the reaction is

represented thus

:

—

ht

NaNOg + H2SO4 = HNO3

-f

Sodium

Nitrate

Sulphate

85

But

if

2

H-

98

the temperature

represented thus

:

—

=-

-f

98

63

is

NaNOg + H.SO^ = 170

HNaSO^ Acid Sodium

+

high, then

the reaction

HNO3 + Na2S04 = 126 + 142 2

(18)

120 is

Experimental Chemistry.

192

Composition of Nitric Acid.

— Numerous

the quaUtative composition of

facts pointing to

acid are found

nitric

by

simple experiments.

SYNTHESIS OF NITRIC ACID.

— Apparatus:

Experiment 74.

The

apparatus consists ot a small

bottle provided with a two-hole rubber stopper

through each hole and

;

a platinum wire passes

held firmly in place by a short piece of glass

also, a

Ruhmkorff

and the usual connections Process

:

Put

and a

coil

There

foil.

battery, or a static machine,

for the battery.

ll.

be needed,

vn

each wire terminates in a narrow strip of platinum

;

few drops of neutral water and a piece Adjust the platinum terminals so that they are near

in the bottle a

of blue litmus paper.

4a

rod will

is

mm. to 6 mm. apart. Connect the and pass sparks through the apparatus for

coil,

em

the bottom of the bottle and from 3

platinum wires with the

about twenty minutes, or until there

is

definite evidence of a chemical

acid

w w

.c h

change revealed by the litmus paper. What is the nature of the change ? Independent evidence has shown that the compound formed under these conditions is nitric acid. Since only air and water are present, what elements combine to form nitric ?

75.

— (a)

tp ://

Experiment

w

ANALYSIS OF NITRIC ACID. Generate hydrogen from zinc and dilute

sulphuric acid in a large test tube or small flask, and tion

is

when

brisk drop dilute nitric acid slowly into the vessel.

may be dropped

the evolu-

The

nitric

ht

from a burette or pipette, or from a glass tube A brown gas may appear at inter(15 cm. long) shaped like Fig. 61. vals. If so, it indicates a secondary and undesirable action. The diffiacid

culty

in

may be prevented by

(i) regulating the evolution of

hydrogen so

continuous but not too rapid, and (2) by adding the nitric acid slowly. The essential point of the experiment is to allow the nitric that

it

is

acid to interact with the hydrogen, but not to be

action with the zinc.

Add

about 10

cc.

decomposed by

inter-

of nitric acid, then pour off

the liquid from any excess of zinc, and evaporate the liquid to dryness

heat at

first

over the free flame in a casserole or in a dish which stands

on a piece of wire gauze, and conr,tantly

moving

finally heat

to prevent spattering.

over a low flame which

is

kept

Compounds of

Nitrogen.

193

Put a portion of the residue in a test tube and warm gently with sodium hydroxide sokition. A thick, white precipitate will be formed, hence the tube must be shaken vigorously and the heat applied with care. A gas will be liberated. Test it by determining the odor and by holding a piece of moist red litmus paper in the escaping vapor not against the side of the test tube which may have been covered with What is the gas ? What is its source ? What the sodium hydroxide.

—

evidence does (^)

furnish regarding the elements contained

it

Perform

'*^

nitric acid

.'*

this experi)neni in the hood.

grams of coarsely powdered ferrous sulphide in a test tube Allow the actLn to proceed a few minutes, and after the tube is cool, dilute with two or three times its volume of distilled water. Filter, and test the filtrate for a sulphate. Remembering the essential diflference between a sulphide and a sulphate, explain the general chemical change which has taken place.

vn

Boil a few

em

evidence of the qualitative composition of nitric acid

tributed

by

experiment

this

?

.c h

What

4a

ll.

with a litde concentrated nitric acid.

CLASS-ROOM EXERCISE. Historical.

w w

1.

(a)

The

{b)

Lavoisier's contribution to our

is

con-

XXIII.

alchemists' knowledge of nitric acid.

knowledge of the composition

Cavendish's determination of the exact composition of nitric

tp ://

{c)

w

of nitric acid.

acid.

{d^ Derivation and significance of the term aqua fortis.

Commercial

ht

2.

nitric acid.

{a)

Preparation.

(Jj)

Specific gravity.

(c)

Impurities.

\d) Uses. 3.

Composition of {a)

nitric acid.

Summarize the experimental evidence of the composition

of

nitric acid.

{b)

If nitric acid gas is

passed over heated copper, two of the

three products are water

must the

nitric acid

and nitrogen.

Of what elemen+s

have been composed

?

Experimental Chemistry.

194

If nitric acid

is

formed which vigorously supports is it, and what does formation show about the composition of nitric acid ?

its

About the If

is

What

combustion.

(d)

allowed to trickle through a red-hot porce-

a gas

tube,

lain

gas (probably)

stability of nitric acid

a mixture of dry

heated platinum sponge

num),

nitric acid is

nitric acid

Why What

beginning of a thunder-storm.

no acid

are there

?

w w

em

sulphuric acid

sulphuric acid,

tp ://

—

a power-

is

XVI.

needed for the complete trans-

if

nitric acid

?

the reaction takes place at a low

by heating with sulphuric acid

ht

(a) (^) (c)

3.

is

Five hundred grams of potassium nitrate are transformed into

nitric acid

culate

falls

w

How much

which

?

.c h

oxidizing agent."

How much

temperature 2.

Why

nitrates ?

formation of 606 gm. of potassium nitrate into {b)

(The platinum takes

the valence of nitrogen in hitric acid ? Explain and illustrate the statement " nitric acid is

PROBLEMS. {a)

?

plati-

does this fact prove

4a

((2)

(^)

ful

1.

What

in the reaction.)

Miscellaneous.

(c)

passed over

Salts of nitric acid are often found in the water at the

4.

air is

over a mass of porous

ll.

(f;

{i.e.

formed.

about the composition of

no chemical part

?

ammonia gas and

vn

{c)

What

is

The amount The amount The amount

low temperature.

at a

Cal-

of nitric acid produced. of sulphuric acid required.

of acid potassium sulphate formed.

the least quantity of sulphuric acid w^hich can be used to

decompose 500 gm. of potassium nitrate in the preparation of nitric acid? 4. How many pounds of nitric acid can be obtained by distilling 400 lb. of sodium nitrate with sulphuric acid ? 5. How many grams of nitric acid can be obtained by heating a kilogram of sodium nitrate with sulphuric acid at a low temperature ? 6. How much {a) sodium nitrate and {b) potassium nitrate are necessary to produce the maximum weight of nitric acid by heating each with 140 kg. of 97 per cent sulphuric acid

?

Compounds of 7.

Nitrogen.

195

Calculate the percentage composition of (a)

Nitric acid.

(d)

Potassium

(c)

Sodium

nitrate.

nitrate.

(^) Acid sodium sulphate. (e) Acid potassium sulphate.

The Interaction

upon

of Nitric

Acid and Metals.

and metals

is

— The

complicated.

It

interac-

depends

vn

tion of nitric acid

(i) the particular metal, (2) the strength of the acid,

4a

ll.

(3) the temperature, and (4) the presence of salts resulting from the chemical action.

Perform

experiment in the hood.

.c h

Experiment

76. — Stand

four test tubes in the test tube rack

each a few small pieces of one of the following metals

w w

slip into

this

em

THE GENERAL CHARACTER OF THE INTERACTION OF NITRIC ACID AND METALS.

Add

:

and zinc,

enough Observe the changes in each case, particularly (i) the vigor of the action, (2) the nature and properties of all the products, especially color and solubility, and (3) evidence of presence or absence of hydrogen.

copper,

tin,

and

iron.

to each test tube in succession just

tp ://

w

concentrated nitric acid to cover the metal.

ht

Tabulate these observations.

The

interaction of nitric acid

many

chemical action in

and copper

cases and

typifies the

demands

additional

examination.

THE INTERACTION OF NITRIC ACID AND COPPER. Perform Experiment arrange

it

(Exp. 19).

77.

—

I.

this experiment in the hood. Construct an apparatus like

30 and hydrogen

Fig.

to collect a gas over water as in the preparation of

Put from 10 to 15 gm. of copper borings in the

flask, insert

Experimental Chemistry.

196

the stopper tightly, adjust the delivery tube,

and

invert

them

Pour

in the trough.

three bottles with water,

fill

enough concentrated

just

nitric

acid through the safety tube int: the flask to cover the copper, taking

Dense brown fumes add a little water through the Collect three bottles of the gas which bubbles from the safety tube. Cover them with glass plates and stand them aside delivery tube. bend of the

care to seal the

safety tube with acid.

If the action is too vigorous,

are evolved.

tempoi^rily.

(a) Observe

as follows

:

—

em

Meanwhile study the gas

II.

bottle.

4a

be preserved in a glass-stoppered

ll.

vn

Pour the contents of the flask into a casserole or evaporating dish, and evaporate slowly to crystallization (not to dryness) on a water bath. If thc-re is much of the original copper remaining, add more nitric acid The crystals, after being dried between filter paper, should at intervals.

general properties while covered.

its

Uncover a bottle. Describe the result. Is the brown gas identical with the one observed in the generator at the beginning of the

.c h

(d)

experiment ?

not definite, or does not agree with previous observations. (rtf)

With

the third bottle determine whether the two gases will burn

tp ://

is

w

w w

(c) Uncover a bottle, pour in about 25 cc. of water, cover with the hand and shake vigorously, still keeping the bottle covered. Why has the brown gas disappeared? Uncover the bottle for an instant, then Repeat, if the result Is the result the same ? cover and shake again.

A convenient

or support combustion. to a

stiff

brown

ht

into the

Answer (i) (2)

other? (3)

Plunge

wire.

it

to the

flame

bottom

is

a burning match fastened

at first

the following:

raise

it

—

What is the source of the colorless gas? What is the general chemical relation of To the air?

Why

and gradually

gas.

is

the two gases to each

not the brown gas collected in the bottles by displace-

ment of water? (4)

Will either gas burn, or support combustion?

(5) Which gas has (other than Exp. 76) ? (6)

What

is

been observed before?

In what experiment

the general relatioa of these gases to nitric acid?

Compounds of Study the properties of the

III.

Nitrogen.

crystals

and

by determining:

(a)

Solubility in water (cold

(b)

Action of heat.

(<:)

Action of their solution upon an iron

{d) Action of their solution

when added

Discussion of Experiment 77.

copper

those of

hydroxide.

copper nitrate

— The

colorless gas

id3ntical

?

is nitric

nitrogen peroxide, and the blue

is

The

following equation

is

usually

ll.

nitrate.

ammonium

vn

the brown gas

'solid is

nail.

to

Are the two substances

obtained from the laboratory bottle.

oxide,

—

hot).

properties with

Compare the observed

197

given as the simplest expression of the interaction of copper nitric acid

:

—

4a

and

em

3Cu + 8HNO3 = 3Cu(N03)2 + 4H2O +

oxygen. equation

.c h

the nitric oxide

is

This reaction

combines with most simply represented by the

exposed

is

Oxide

to the air,

it

w w

When

Nitric

Copper Nitrate

Copper

2NO

—

w

NO + O = NO2 Nitrogen

tp ://

Nitric

Peroxide

Oxide

Nitric oxide

is

not always the only gas produced by the and copper, but it is most abun-

ht

interaction of nitric acid

dantly produced and

is

loosely regarded as the only oxide of

In the case of most metals, one or more ''Concenof nitrogen are produced. oxides of the numerous

nitrogen evolved.

and zinc yield ammonia, as well as nitric oxide, among the gaseous products, though the ammonia usually combines at once with the excess of acid to form ammonium nitrate. Some metals, such as tin and antimony,

trated nitric acid

form an oxide and not a nitrate. Nitric acid is such a powerful oxidizing agent that hydrogen which is displaced

Experimental Chemistry.

198 from

it

by metals never appears as hydrogen, but (See page 117.)

is

oxidized

to water.

Nitrates.

property,

— The

have one common and hence many

salts of nitric acid

extreme

viz.

solubility in water,

laboratory solutions are nitrates of the metallic elements. Nitrates behave in various

ways when heated.

—

Heat a

I.

high temperature

is

little

sodium

an ignition

nitrate in

necessary to produce any extensive

ll.

A

tube.

vn

ACTION OF NITRATES WITH HEAT. Jl/Xperiment 78.

What

Insert a glowing match into the ignition tube.

Dissolve the residue in water and add a few drops of

detected

is

.'*

4a

chemical change.

gas

Describe the result. Could the residue have been a nitrate? Why? If the experimental evidence is not definite enough for a final conclusion, proceed as follows Heat a mixture of 10 gm. of sodium nitrate (or potassium nitrate) and 20 gm. of lead in a sand bath pan, which stands on a tripod, or similar support.

.c h

em

dilute sulphuric acid.

melted mass with a

—

stiff

iron wire or blunt

w w

Stir the

Some

:

of the lead will disappear and a yellowish

brown powder will be seen in the molten mass. The action should proceed until most of the lead has disappeared. Allow the mass to cool, transfer to a mortar, pulverize, add hot water, and filter the clearer portion add more hot water to the residue and filter this portion. Add to the com-

w

glass rod.

tp ://

bined

filtrates

the result.

a few drops of concentrated sulphuric acid.

Compare

on a solution of sodium

in the ignition tube) a nitrate?

The led to

yellowish product

its

formation?

Describe

the result with the action of concentrated sulphuric

ht

acid

;

is

How

Is the white residue

nitrite.

(produced

Why?

lead oxide.

must the

What

nitrate

general chemical change have been changed?

Draw a general conclusion from the observations made above garding the action of heat on nitrates of the alkali metals. II.

Pulverize 8 or 10

gm. of lead

ignition tube or evaporating dish. differ essentially

Two

nitrate,

and heat the powder

Describe the result.

from the action of heat on the

obtained as follows

:

Heat the lead

nitrate in

in

an

does

it

alkali nitrates?

gaseous products are formed, though one

easily detected in the presence of the other.

How

re-

— the oxygen —

More

is

not

definite results are

an ignition tube provided

Compounds

of Nitrogen.

199

with a delivery tube passing to the bottom of a test tube half full of sodium hydroxide solution and connected by a delivery tube with an-

other test tube, or small bottle, arranged to collect a gas over water. The gas will be found to be oxygen. Add a few drops of concentrated sulphuric acid to the test tube which contained the sodium hydroxide

What compound

solution.

duced

The

it?

is

What

present?

residue in the ignition tube

these results with those obtained in Exp. 76,

Draw

is

chemical change prolead oxide.

Compare

III. {b).

a general conclusion regarding the action of heat on the

ammonium

exceptional behavior of

heated places

it

in a class

by

An

itself.

nitrate

when

examination of

ll.

The

vn

nitrates of the heavier metals.

is

another oxide of nitrogen.

em

which

4a

behavior involves also a study of the main product,

its

THE ACTION OF AMMONIUM NITRATE WITH HEAT.

the latter

;

is

apparatus

heated in A, which

is

pro-

is

is

shown

in Fig. 63.

The am-

connected with an empty

bottle,

w w

D

nitrate

.c h

— The

Experiment 79.

monium

vided with a delivery

tube, E, which dips into

pneumatic trough, as

previously

tp ://

filled,

w

a

mod-

described, with

warm

erately

^one-third

ht

Fill

water.

of crystals of

nium the

heat

nitrate,

adjust

apparatus,

A

and

gently with a

low flame.

monium

full

ammo-

,

The am-

nitrate melts

and appears

to

boil.

Regulate the heat so

Fig. 63.

— Apparatus

for

decomposing ammonium

nitrate.

that the evolution of

gas will be slow. besides the gas.

Notice the continuous formation of another product Collect three bottles of the gas,//-^^

from

air, covei

Experimental Chemistry.

200

each with a glass plate, and stand them aside until needed. As soon removed from the trough, disconnect the

as the last bottle has been

apparatus at a, and stand the generator in the hood to cool.

—

Test the gas as follows {a) Allow a jar to remain uncovered for a few seconds. this oxide of nitrogen differ from nitric oxide? :

Thrust a glowing

{h')

stick of

wood

does

same bottle of gas. Does it support com-

into the

gas combustible?

Is the

Describe the result.

How

bustion?

though

is oxygen, but it is proved by a single experiment. Put

suggest that the gas

in {b)

this fact is not easily

vn

The observations

{c)

not,

a small piece of sulphur in a deflagrating spoon, light

and lower the

ll.

it,

in a bottle of

4a

burning sulphur at once into another bottle of gas. If the experiment is conducted properly, the sulphur will not burn so brightly as it would oxygen.

not conclusive,

is

the hand, and shake.

from oxygen?

in all probability is the other

experiment?

nitrate?

full

of water, cover with

this observation help distinguish the gas

w w

What this

the bottle half

fill

Would

.c h

the result

em

(^) Stand the other bottle mouth downward in the pneumatic Describe the result. If trough, or better, in a vessel of cold water.

Could

it

product of the chemical change in

have been an impurity

in the

ammonium

tp ://

— from

w

How would you distinguish ammonium nitrate from all other nitrates ? How would you distinguish the third oxide of nitrogen — nitrous oxide {a) the other oxides of nitrogen,

{b') air, (<:)

oxygen, (^) hy-

ht

drogen, {e) nitrogen, (/") carbon dioxide?

CLASS-ROOM EXERCISE.

XXIV.

1.

Summarize the properties of the three oxides of nitrogen

2.

State briefly the effect of heat on

nitrate, 3.

{a)

ammonium

Predict

sodium

nitrate, 4.

(<:)

{e)

potassium

studied.

nitrate, (J>)

copper

nitrate.

the simplest equation for the reaction in the case of nitrate,

(J))

ammonium

Select from Exp.

The

(rt)

copper

nitrate, ']'j^

III.

nitrate,

when

{c)

lead nitrate,

heated.

(^d)

zinc

Verify the equations.

a test for copper.

fact that all nitrates, except

oxygen when heated furnishes

—

ammonium

nitrate, yield

Compounds of

Nitrogen,

20I

A SPECIAL TEST FOR NITRATES.

—

Experiment So. Heat a piece of charcoal in the Bunsen flame, lay on a board, or iron pan, and cautiously sprinkle powdered potassium nitrate upon the hot surface. Stand back when the action begins.

it

Observe and describe the action, especially

its violence and rapidity, on the charcoal, and any other

also the color of the flame, the effect characteristic result.

This kind of chemical action

is

called deflag}'ation.

—

What

causes

it?

usually stated thus

iveigJit

ll.

—

4a

A fixed

is

:

of one element so combines with different

em

This law

vn

Law of Multiple Proportions. There are two oxides of nitrogen besides the three already studied, and these five oxides aptly illustrate the Law of Multiple Proportions.

iveights of another element that the relations betiveen these

The composition per cent.

.c h

different iveights are expressed by small whole numbers. of

compounds

w w

terms of this

tp ://

is

different

clearly seen.

The

ht

multiple proportions

Name.

is

and the composition

unit, the

w

in

usually expressed in

however, a definite weight

If,

unit for one component,

between the

is

adopted as a is expressed

simple integral relation existing

proportions of the other element

following table illustrates the law of

:

—

Experimental Chemistr

202

From in

this table

it is

clear that the proportions of fixed weight of

combination with a

oxygen

nitrogen are as

This law together with the law of definite proportions has profoundly influenced the development of

1:2:3:4:5.

the atomic theory of Dalton.

CLASS-ROOM EXERCISE.

XXV.

Gunpowder. {a) Composition.

General methods of manufacture.

{c)

Kinds.

ll.

(<^)

Products of action.

Composition, manufacture, and uses of gun-cotton, nitroglycerine,

em

2.

and dynamite. Miscellaneous.

.c h

3.

« {a) Define and

What

Law

illustrate nitrification.

are etchings

and how are they made?

w w

{b) 4.

4a

\d) Uses. {e)

vn

1.

of Multiple Proportions.

{a) History.

Exact meaning.

Other

illustrations.

tp ://

{c)

w

{b)

{d) Theoretical significance.

5.

What

is

the valence of nitrogen in

HNO^?

In

Cu(NO

).,?

In

ht

N.O, NO, N2O3, NO2, and N2O5?

Aqua Regia concentrated

is

an old term

nitric

still

applied to a mixture of

and hydrochloric acids (one volume of

the former to three of the latter).

THE CHARACTERISTIC PROPERTY OF AQUA REGIA.

—

Touch a small piece of gold leaf with the end of Experiment 81. wash the gold leaf into a test tube by pouring a and glass rod, moist a few cubic centimeters of concentrated hydrochloric acid down the rod. Heat gently until the acid just begins to boil. Does the gold dissolve?

Compounds Wash

203

of Nitrogen.

another piece of gold leaf into another

test tube v;ith

concen-

and heat as before. Does the gold dissolve ? Pour the contents of one tube into the other, and warm gently.

trated nitric acid,

Draw

the gold dissolve?

Answer the following

— significance of the term

aqua

What other metals does aqua 7'egia dissolve? What is the chemical action oi aqua regia on gold? Upon what property of nitric acid does the action of aqua

regia

What

(i)

:

Does

a conclusion.

is

meaning and

the literal

(3) (4)

depend'

PROBLEMS.

4a

XVII.

ll.

(2)

vn

regia ?

Find the simplest formula of the substances having the indicated

composition

:

—

H= N=

1.58

22.22

.c h

{a)

em

1

O =

76.19

=

47-52

N= K=

38.61

What

weight of pure

tp ://

2. if

w

w w

{b~)

13.86

nitric acid

would yield 100 gm. of oxygen

completely decomposed ? 3.

The

specific

gravity of nitric

acid

is

1.522.

{ji)

What

will

weigh? {b) What volume must be taken to weigh 100 gm.? What volume is occupied by 10,000 gm. of nitric acid? (Assume

cc.

ht

100

4.

density

=

1.5.)

One gram

gunpowder yielded 280 cc. of gas at the normal temAt the instant of explosion the temperature rose to 2000° C. Calculate the volume occupied at this temperature (assuming an unchanged pressure). 5.

of

perature and pressure.

chaptp:r

XII.

CARBON AND ITS SIMPLEST COMPOUNDS.

is

It

forms

vn

living thing.

often the essential,

ll.

Carbon is a constituent of every It a vast number of compounds.

of

em

4a

and sometimes the only, constituent of the remains animals and vegetables. DISTRIBUTION OF CARBON.

— (a) Cover the bottom of a Hessian crucible with

.c h

Experiment 82.

Put on the sand a small piece of wood, a small, compact wad of cotton, a small bone, and a lump of starch. Fill the crucible loosely with dry sand, and slip it into the ring of an iron stand. Heat with a flame which extends just above the bottom of the crucible

smoking ceases (approximately a

half hour)-.

After the crucible

w

until the

w w

a thin layer of sand.

What

tp ://

has cooled sufficiently to handle, pour the contents out upon a block of wood or an iron pan. Examine the contents. What is the residue?

hereby shown about the distribution of carbon ? Heat about i gm. of sugar in an old test tube until the vapors What is the most obvious product ? cease to appear. (c) Close the holes at the bottom of a lighted Bunsen Lirner, and is

ht

(d)

hold a piece of crayon or glass tubing long enough for a thin deposit to form. its

in the

upper part of the flame it, name it, and state

Examine

source.

(d) Hold a piece of clean crayon in the flame of a candle which stands on a block of wood, and compare the result with that in (c). (e) Light a wax taper ana note the most obvious product of the flame. Explain. If time permits, heat in separate test tubes, or on an iron pan, a piece of meat, a

little

flour,

a bit of albumen, a piece of bread.

What is the most obvious product in each case? Draw a general conclusion regarding the distribution 204

of carbon.

Carbon and Carbon

Simplest Compounds.

Its

the form of

in

charcoal (often called

wood charcoal and

bone black) possesses

205

of animal

remarkable

properties.

DECOLORIZING ACTION OF CHARCOAL. Experiment

83.

—

Fill

a test tube one-fourth

full

of animal char-

App. A, § 11), add 10 cc. of indigo solution, shake thoroughly a m^'nute, and then warm gently. Filter through a wet filter paper

coal (see for

into a clean test tube.

Compare the

color of the filtrate with that of

Explain the change in color. Other organic substances besides indigo are similarly changed. Draw a general conclusion regarding the decolorizing power of charcoal.

4a

ll.

vn

the indigo solution.

Experiment gas.

84.

Fill a test

— Smell

tube half

of a

full

of

em

DEODORIZING ACTION OF CHARCOAL. weak solution of hydrogen sulphide powdered wood charcoal, add 5 cc. of

.c h

hydrogen sulphide solution, and cork securely. If the tube leaks, make Shake thoroughly. After fifteen or twenty minutes, remove the stopper and smell of the contents. Is the odor much less oflfensive? Repeat, unless a definite result is obtained. Explain the change. decolorizing

tp ://

The

w

w w

the opening gas-tight with vaseline.

largely a

physical

and deodorizing power of charcoal operation, and is mainly due to

porosity.

attraction of carbon for

ht

The

oxygen

is

its

— already shown by

experiment and often observed in various forms of combustion

— permits

REDUCTION BY CARBON. Experiment

85.

Fill the ignition

— Prepare an apparatus

tube half

full

like that

shown

in Fig. 23.

of a mixture of copper oxide (6 parts)

and powdered wood charcoal (i part) introduce the mixture by the method described in App. A, § 11. Arrange the apparatus as directed in Exp. 12. The delivery tube iii this case, however, should dip into ;

a small at first

;

dish

of lime

water.

Heat the whole ignition tube gently and finally heat strongly that part

increase the heat gradually,

Experimental Chemistry.

!2o6

of the ignition tube containing the mixture.

up the

mixture "crawls"

If the

ignition tube, tap the tube gently near the top.

Heat

evolved.

a decided change

until

is

produced

A

gas will be

in the lime water,

and then immediately remove the end of the delivery tube from the Describe the change in the lime water. What caused the change ? Draw a conclusion regarding chemical change which ocliquid.

Examine

curred in the ignition tube.

follows

:

the contents of the tube to

If the verification is not decisive,

verify the conclusion.

—

proceed as

a porcelain crucible half

vn

of the original mixture, and cover Cover the crucible and stand it on a pronged tripod, or a triangle, and heat for five or ten minutes. Let the crucible cool, still covered, and, when cool enough to handle comfortably, turn out and examine the contents. Does the observation verify the previous conclusion? If the chemical change in the crucible had been complete, and the proportions absolutely correct, what would the residue have been? Fill

full

with a thin layer of charcoal.

.c h

em

4a

ll.

it

LABORATORY EXERCISE. Complete the equation

—

w w

1.

CuO + C =

CO.,

2.

Define reduction in terms of Exp. 85.

3.

What

+

tp ://

w

other element will reduce copper oxide ?

CLASS-ROOM EXERCISE.

1.

IX.

XXVI.

Allotropism or Allotropy.

ht

(a) Definition.

(d)

Illustration

(c)

Reason

({i) Literal 2.

by means of the allotropic modifications of carbon

for existence of allotropes.

meaning and

significance of the

{a) Occurrence. (Z")

3.

word allotropy.

Diamond. Artificial preparation.

(r)

Properties.

(^d)

Famous diamonds. Properties.

Graphite. (rt)

Occurrence.

(c)

{b)

Preparation.

{d) Uses.

(
Literal

(/) What

meaning of the word. "black lead" ? Plumbago

is

?

Carbon and

(d)

Properties.

(e)

To what

(/) What

is

property

is

bone black

its ?

(,)

Average composition.

(,^)

Uses.

due

?

so called

?

efficiency

Why

Charcoal. (a) Various kinds, and (d) (c)

6.

207

Animal charcoal. (a) Preparation.

5.

Compounds.

how

obtained.

General properties. Uses.

Coal.

vn

4.

Its Simplest

Relation of kinds to each other. General mode of formation.

4a

(c)

ll.

(a) Kinds. (^)

(d)

What

(e)

Composition of typical coals (see App. C, Table XL).

and

lignite

?

em

are peat

7. Give the method of preparation (or source), properties, and of the following forms of carbon :

—

(a) Lampblack.

Coke.

9.

Miscellaneous.

w w

Experimental.

Examine a

How

section of coal through a microscope.

would you prove the chemical identity of the three

w

(a)

Gas carbon.

(^) Soot.

8.

(a)

(c)

.c h

(^)

tp ://

allotropic modifications of carbon

(b)

{c)

use.«

What What

is

black smoke

?

?

industries utilize the decolorizing po\ver of animal .?

ht

charcoal

{d) Use of charcoal as a disinfectant.

{e)

What immense in

Exp. 85

Carbon Dioxide

pounds

is

industry utilizes the principle illustrated

}

the best^ known of the simpler com-

of carbon.

PREPARATION

AND PROPERTIES OF CARBON DIOXIDE. Experiment d>6.- Method: Prepare carbon dioxide from hydrochloric acid and calcium carbonate, and study the gas water.

collected over

Experimental Chemistry.

2o8

Use the same apparatus

Apparatus:

as

in

the preparation ol

hydrogen (see Exp. 19 and Fig. 30). Other materials needed are lumps of marble, sand, concentrated hydrochloric acid, stick or splinter of wood, candle fastened to a wire, lime water, five bottles. Process: Cover the bottom of the flask with sand, add a litile water, and carefully slip into it a dozen or more small lumps ot marble. Arrange the apparatus to collect the gas over water, as previously Add through the safety tube just enough concentrated

directed.

vn

hydrochloric acid to cover the marble. Reject the first portion of Collect five bottles, cover with glass plates or wet

the gas evolved.

paper, and stand aside till needed. Allow the action in the flask to continue, and preserve tna contents

ll.

filter

4a

for subsequent examination.

—

Study the properties of carbon dioxide gas as follows Describe the («) Plunge a burning stick into one bottle.

em

I.

:

result.

and invert a bottle of carbon dioxide over it, holding the bottles mouth to mouth. Describe the result. What does this result show about the specific

Lower a

lighted candle into a bottle of

gravity of carbon dioxide

?

for that

Devise a simple experiment to verify this purpose one of the remaining bottles of

w w

conclusion, using

air,

.c h

\b)

carbon dioxide.

tp ://

w

{c) Pour a little lime water into a bottle of carbon dioxide, cover with the hand, and shake vigorously. Describe and explain the result. {d) Fill a bottle of carbon dioxide one-third full of water, cover Invert, still covered, in a with the hand, and shake vigorously.

Does the

of carbon dioxide

?

result reveal

any

facts

about the solubility

ht

vessel of water.

Filter the contents of the flask into a casserole or evaporating

II.

little warm water beforehand, if the contents is solid. Evaporate to dryness in the hood over a free flame as long as much As the residue approaches pasty consistency, add a liquid remains.

adding a

dish,

little it

water and continue the evaporation.

about rapidly to avoid spattering.

If

If a casserole is used,

an evaporating dish

is

move used,

on a gauze-covered support and move the lighted burner underHeat the residue until no fumes of hydrochloric acid are neath. Dissolve some of the residue in distilled water and test evolved.

stand

it

portions for {a) a carbonate, {b) a chloride, {c) a calcium compound If a calcium compound is found, confirm the observa(see Exp. 29). tion thus

:

—

Carbon and Dip Jt

Simplest Compounds.

209

a clean, moist platinum test wire into the solid residue,

and hold

in the

Bunsen flame.

Its

If

calciam

is

present, the flame will be colored

a yellowish red. Verify the conclusion by a simple experiment.

simplest equation for the interaction of hydrochloric

acid and calcium carbonate

2HCI

+

—

+

CO2

CaCU

Carbon

Calcium

Carbonate

Dioxide

Chloride

=

100

+

44

III

4a

The

:

Calcium

+

73

=

CaC03

is

+

vn

The

the residue?

is

+

ll.

What

qualitative composition of carbon dioxide

18

may be

em

shown by the

(20)

SYNTHESIS OF CARBON DIOXIDE.

.c h

—

w w

Exjwriment 87. Method: Draw, simultaneously, purified air over hot charcoal and the product of the reaction through barium hydroxide solution or lime water.

w

Apparatus: The essential part of the apparatus is shown in Fig. 64. Short pieces of sodium hydroxide are placed in the left-hand limb of

ht

tp ://

ir?

Fig. 64.

— Apparatus for the synthesis of carbon dioxide.

A

and calcium chloride

by a wad of cotton

;

in the other, the

two substances being separated

small wads of cotton are also placed just below the

stopper in each limb.

This U-tube removes the carbon dioxide and The tube BB^ is hard glass and from 15 to A spiral of copper wire is attached at the point B' The connected directly with the combustion tube by a glass

water vapor from the 20 cm. long. test

tube

C

is

air.

.

2IO

Experimental Chemistry.

tube passing to the bottom of the test tube

and

outlet for the excess of air

The

aspirator (see Fig. 107).

B

at the points

is

apparatus

solution.

wood

absorption tube half

Fill the

Connect as shown

connections,

as an

pump

or

charcoal in the comof barium hydroxide

full

Draw- a slow current of

in the figure.

if

Regulate the current of

necessary.

if

filter

B\

and

through the apparatus to detect the leaks,

air

D serves

the tube

may be supported by clamps

Process: Place three or four lumps of dry bustion tube.

;

attached directly to a

Readjust the

any.

air so that a

bubble

drawn through the apparatus. Heat the whole combustion tube gently at first, and finally concentrate the heat at the place where the charcoal is located. A wing-top burner is well a second, approximately,

In a few minutes (approximately 10) a

is

4a

this operation.

marked change

vn

ll.

adapted for

is

Describe

seen in the absorption tube.

it.

Since

em

the nitrogen of the air takes no part in the chemical change, explain

What

the change.

does the experiment prove about the composition

The

simplest

dioxide

is

:

.c h

of carbon dioxide.

equation

—

+

O2

w w

C

for

+

liter of

of

CO,

carbon

^

^

(21)

44

carbon dioxide under standard conditions weighs

tp ://

A

32

= =

synthesis

w

12

the

1.977 gm-

Carbon dioxide

vitally

connected with the subject of

ht

is

combustion.

CARBON DIOXIDE AND COMBUSTION. Experiment half

full

{b)

Lower a

a few minutes. bottle, {c)

88.

—

(^d)

of lime water.

Exhale through a glass tube into a

Describe and explain the

lighted candle into a bottle

Remove

the candle, pour a

and allow little

results in {a)

{[)).

and {b)^

Describe the

result.

it

to

burn

for

lime water into the

and shake vigorously. Describe and explain the Allow a stick of wood to burn for a short time

then proceed as in

test tube

result.

Does

result.

in a bottle, it

and

confirm the

Carbon and Answer (1)

the following

What

is

(2)

What

(3) How the air"?

(4)

How

Simplest Compounds.

211

—

main product of the combustion of substances

the

containing carbon

:

[ts

?

gas was formed in Exp. 14 (c)? does this experiment verify previous work on "burning in

does (a) show the relation between carbon dioxide and

combustion?

CLASS-ROOM EXERCISE. (a)

Occurrence.

(c)

Properties not

(d) Modes of formation. shown experimentally.

em

Combustion.

(d)

Carbonated mineral waters,

Historical.

Respiration and decay.

(a)

Van Helmont's work on carbon

(d)

Black's work.

(d)

Why was carbon dioxide called^^j- sylvestre

dioxide. Lavoisier's work.

(c)

a.ndyixed air ?

Miscellaneous. {a)

How

would you distinguish carbon dioxide from

{b) (<:)

for

carbon dioxide

burning stick

is

?

plunged

into

oxygen ?

Into nitrogen ?

{e)

other

Summarize the most important properties of carbon dioxide.

What is the decisive test What happens when a

ht

{d)

all

?

tp ://

gases

Into hydrogen?

What happens when Into hydrogen?

5.

(c)

.c h

(a)

w w

4.

(e)

Review.

w

3.

Solid carbon dioxide.

4a

(d) Liquid carbon dioxide. 2.

vn

Additional study of carbon dioxide.

ll.

1.

XXVII.

Into carbon dioxide?

lime water

is

Into nitrogen?

poured into oxygen: Into carbon dioxide?

Deduce the molecular weight and simplest formula of carbon

dioxide from the following data {a) {b)

A

:

—

of carbon dio^fide weighs 1.977 gm. Carbon dioxide contains its own volume of oxygen. liter

Dumas and

Stas found that 80 parts of oxygen by weight combined with 30 parts of carbon. Deduce the atomic weight of carbor4 from this fact together with the results obtained in {supra). 5 6.

Experimental Chemistry.

212

PROBLEMS.

How many

1.

15

grams of calcium carbonate are necessary

produce

to

of carbon dioxide?

1.

How much

2.

to

XVIII.

calcium carbonate and hydrochloric acid are needed

form 132 gm. of carbon dioxide? 3. What weight of carbon burned in

produce

air will

11

gm. of

carbon dioxide?

oxygen?

in

oxygen?

piece of pure graphite weighing 7 gm. is completely burned What volume of carbon dioxide is formed?

What volume

7.

of oxygen

em

A

6.

4a

its

ll.

vn

4. Twelve grams of carbon were burned in the oxygen liberated from 122.5 g"^- o^ potassium chlorate. How much carbon dioxide was formed, and what w^as the excess of oxygen? and thereby 5. An excess of air was passed over red-hot charcoal formed 21 1. of carbon dioxide. What volume of air was deprived of

necessary to burn a kilogram of

is

.c h

carbon ? How many 8. Eighteen grams of carbon are to be burned in air. liters of air are needed, and how many liters of carbon dioxide will be

formed ?

tp ://

w

w w

12° C. and 750 mm. will be 9. What volume of carbon dioxide at produced by the action of hydrochloric acid on 10 gm. of marble? 10. What weight of water must be decomposed to furnish sufficient oxygen to form, with pure carbon, 44 gm. of carbon dioxide ? 11. How much oxygen by weight and by volume is required to

unite with pure carbon to form 132 gm. of carbon dioxide? 12.

How much

carbon by weight

is

there

in

a

liter

of carbon

ht

dioxide? 13.

of a

How much

room 6 m.

carbon dioxide by weight and volume

long, 4 m. wide, and. 3 m. high,

if

there

is

is

in the air

one volume

of carbon dioxide in 1000 volumes of air?

Carbonic Acid.

— Carbon

dioxide

gas

is

carbonic acid gas, or simply carbonic acid.

that

when carbon

dioxide

bines with the water and

The case is analogous ammonium hydroxide by

is

the

formation

the solution of

called

believed it

com-

unstable

acid.

the

base

passed into water

forms a weak, to

often It is

of

ammonia gas

in

Carbon and

Simplest Compounds.

Its

213

Carbonic acid has never been isolated, but

water.

its

the carbonates, are numerous and well-defined com-

salts,

pounds.

The formula H^COg has been given

to carbonic

acid.

CARBONIC ACID.

— Construct B

is tilled

a carbon dioxide generator like that

nearly

trated hydrochloric acid (i vol. to

i

full

of lumps of marble.

vol.)

is

Concen-

The generator

put in A.

vn

Experiment 89. shown in Fig. 46.

operated as previously described.

(See Exp. 44.) Attach Z^ to a and 114) containing water or concentrated sulphuric acid to free the gas from any hydrochloric acid carried over mechanically; connect the wash bottle with an absorption apparatus is

wash

4a

ll.

bottle (see Figs. 56,65,

consisting of a

1 irge test tube or bottle the tube from the wash bottle should reach to the bottom of the absorption apparatus. A simple combined generator and wash bottle is shown in Fig. 65.

em

;

.c h

Fill the absorption apparatus nearly full of water, add a few drops of a solution of phenolphthalein and just enough sodium hydroxide solution to color the liquid a faint pink. Allow a slow current of carbon is

w

w w

dioxide to bubble through the apparatus until a definite change produced in the absorbing liquid. Describe and explain it. Sketch the essential part of the apparatus.

tp ://

Carbonates are salts of the hypothetical carbonic acid. carbonates have already been studied. Additional

Many

—

ht

experiments, however, are needed to illustrate the

FORMATION AND PROPERTIES OF CARBONATES.

Experiment 90. bottle

full

generator

— {d)

Pass carbon dioxide free

from

of lime water until considerable precipitate

shown

in Fig.

46 may

l^e

used,

if

is

acid into a

formed.

The

a wash bottle containing

water or concentrated sulphuric acid is placed between the generator and the bottle of lime water. The combined generator and wash bottle shown in Fig. 65 also gives satisfactory results. The gas 's generated in the large test tube, A^ and washed in B^ and any convenient delivery tube

is

When

may be stood in a test tube rack. has formed, disconnect the generator, and

attached to C; the apparatus sufficient precipitate

allow the precipitate to settle.

Decant the supernatant

liquid,

add a

Experimental Chemistry.

214

few drops of hydrochloric acid to its residue, ;ind test the gas evolved with a burning match and with a rod moistened with lime water. What What is the precipitate? is the gas?

:^

Complete the equations

'

^

:

—

CaCO,

+ Ca(OH), = H.O + CaCl., + HCl

{b)

Pass carbon ^\ox\d& free f?'om

CO,

vn

acid through a weak solution of sodium hydroxide (or potassium hydrox-

Add

ide) for several minutes.

a few

4a

ll.

drops of hydrochloric acid to a porDescribe and tion of flie liquid. the result, testing the main

explain

em

product of the action, In what

compound formed from

— Apparatus

for generatin

hydroxide

.c h

Fig. 65.

and washing carbon dioxide.

Heat a

ignition tube,

litde

and

:

does the

the

sodium

from calcium hydroxide? gas evolved.

test (as in {a)) the

Complete the equation

necessary.

from the one formed

differ

powdered magnesium carbonate

w w

{c)

if

respect

essential

—

=

w

MgCOg

MgO

in a test

tube or

Explain the result

+

tp ://

Magnesium Carbonate

ht

LABORATORY EXERCISE.

1.

What

2.

In what two ways

3.

How

4.

Complete the equations

is

may

carbonates be decomposed?

are carbonates formed?

{a) (b) 5.

X.

the decisive test for a carbonate?

How may

KOH

:

+

—

CO,

K.fO,

HCl

= =

KXO,

+

CO.,

lime water be easily distinguished from solutions of

sodium and potassium hydroxide?

Carbonic acid

is

carbonate, there

is

dibasic, hence, besides ordinary calcium

Carbon and

Simplest Compounds.

Its

215

ACID CALCIUM CARBONATE. Experiment

91.

— Pass

carbon dioxide free

water until the precipitate disappears. fectly clear,

and then heat.

acid into lime

Why

Describe the change.

precipitate disappear before heating (If the latter question

from

Filter, if the liquid is not per-

Why

?

should the

reappear after heating

?

cannot be answered from evidence already given,

consult a text-book.)

Na2C03

the formula of sodium carbonate, what

is

is

is

the formula

the formula of acid calcium carbonate?

4a

What

?

ll.

of acid sodium carbonate 2.

XI.

vn

LABORATORY EXERCISE. If

1.

DETERMINATION OF CARBON DIOXIDE 92.

— Method:

calcite,

Decompose

em

Experiment

bonate (preferably

which

a

IN

A CARBONATE.

known weight

of a car-

a pure variety of calcium carbonate)

is

.c h

and calculate the loss in weight as carbon dioxide. Apparatus: A 125 cc. Erlenmeyer flask is provided with a one-hole rubber stopper

show

high, and

made by

mm.

fitted

The

in diameter.

cium chloride held

trap

with a small bulb is

about 45

mm.

sealing a short tube into a bulb It

w

about 25

is

in Fig. 66.

w w

trap as

in place

filled

is

with fused cal-

by absorbent cotton.

Its

which might be carried off mechanically by the escaping carbon dioxide. The whole apparatus should not w^igh more than is

to prevent the loss of water vapor

tp ://

object

ht

60 gm. before adding the acid Process: Clean and dry the as previously directed.

flask.

Put in the

Fill

the bulb trap

flask 25 cc. of dilute

—

for

determining the proportion

of car-

bon dioxide in

a

car-

bonate.

calcium carbonate) weighing about one gram exact weight need not be known. Insert the stopper and allow

lized

the action to proceed without interruption.

liminary operation since

the

— Ap-

paratus

hydrochloric acid (one volume of acid to two volumes of water). Slip into the flask a lump of calcite (crystalits

Fig. 66.

it

is

(i)

to

fill

object of this pre-

the apparatus with

to be

liquid

amount

The

carbon dioxide, weighed finally in that condition, and (2) to allow absorb carbon dioxide, so that only a very small is

will

to

be retained in subsequent operations.

Meanwhile weigh

Experimental Chemistry.

2i6

exactly to a centigram from

to

1.3

1.5

gm. of

When

calcite.

the

evokition of carbon dioxide has ceased, open the flask for an instant, Slip in the weighed piece of calcite Allow the action to proceed until no inore gas evolved, then open the flask for an instant, close it, and weigh again. Record the results as follows

close

and

and weigh

to a centigram.

:

—

Grams.

Weight Weight

of apparatus of calcite

vn

Total Final weight of apparatus

in the calcite

em

Summary.

.c h

Per Cent of Carbon Dioxide

tp ://

w

w w

Found.

ll.

lost

Per cent of carbon dioxide

.

.

.

4a

Weight of carbon dioxide

ht

is

it,

insert the stopper.

in Calcite.

.

Carbon and Experiment

Its

— MdJiod

93.

Apparatus: The be

to

filled

test

it.

essential part of the apparatus

A carbon dioxide generator (see is

217

Pass carbon dioxide over hot charcoal,

water the gaseous product, and

collect over

which

Simplest Compounds.

Fig. 46)

is

is

shown

The combustion

with calcium chloride.

in Fig. 64.

connected with the U-tube A, tube

BB'

is

same as that used in Exp. 87. The test tube C contains a solution A delivof sodium hydroxide to absorb the excess of carbon dioxide. ery tube is connected with D and passes into a pneumatic trough the

The

arranged to collect a gas over water.

apparatus

may be supported

B

and B' or any other convenient points. It is advisable, though not absolutely necessary, to add a little sodium hydroxide solution to the water in the trough. Four or five bottles and several lumps of charcoal are also needed.

by clamps placed

4a

ll.

vn

at

Process: Put three or four lumps of charcoal in the combus ion tube

and connect the

Regulate the flow of

diiferent parts of the apparatus.

at first,

and

Collect

all

em

carbon dioxide so that the rate is (approximately) a bubble a second. Stop the leaks, if any are detected. Heat the whole combustion tube

where the charcoal is located. first two bottles, as they contain air (and possibly carbon dioxide). Collect two or three more bottles, cover with glass plates, and set them aside temporarily. Stop the generator, remove the delivery tube from the trough, and gradually cool the combustion tube. Test the gas thus

.c h

finally concentrate the heat

w w

the gas evolved, but reject the

—

w

:

it is

colorless.

tp ://

{a) Notice that

Hold a

{b)

Note the

lighted

match

flame, especially

its

at the

mouth of a

color and

how

it

bottle for

has disappeared, drop a lighted match into the bottle. a conclusion and verify

ht

Draw

resu'".

Burn another

(c)

pour a

little

it

and

bottle of gas,

by

made

in (d)

?

instant.

Describe the

{c).

after the flame

lime water into the bottle and shake.

verify the conclusion

an

After the flame

burns.

If not, repeat

has disappeared,

Does the

result

with another bottle

of gas.

LABORATORY EXERCISE. 1.

2.

dioxide 3.

XII.

Summarize the observed properties of carbon monoxide. What is the chemical li^-^tion of carbon monoxide to carbon ?

How

can each be changed into the other?

processes do the changes illustrate?

What two

general

Experimental Chemistry.

21

The

simplest equation for the action of carbon dioxide

on hot charcoal

is

+

CO2

2CO

=

C

Carbon Monoxide

+

44

weighs

1.25

56

carbon monoxide under standard conditions

of

liter

.

22)

gm.

vn

A

=

12

, f

carbon monoxide cannot be conveniently studied by Exp. 93, they may be studied from the gas prepared by the usual method, as follows :

—

em

4a

ll.

If the properties of

PREPARATION AND PROPERTIES OF CARBON MONOXIDE.

Experiment

94.

.c h

{Optional>j

— Construct

an apparatus similar to that used

for

w w

The flask should be smaller, the preparation of chlorine (see Fig. 52). the tube U should pass to and necessary, not is modification though this

w

the bottom of a wash bottle fitted with a two-hole rubber stopper. The wash bottle is filled two-thirds full of sodium hydroxide solution. A

tp ://

delivery tube passes from the wash bottle into a pneumatic trough arranged to collect a gas over water. Put 10 gm. of crystallized oxalic acid {oxalic acid is poisonous) in the

the stopper with its tubes, see that all joints are tight, and then pour 30 cc of concentrated sulphuric acid through the safety tube Heat the flask gently, and carbon monoxide will be into the flask.

ht

flask, insert

A

evolved.

small

flame must be used, because

evolved as the heat increases. It is flame as bubbles appear in the flask

— re<^ulate

cence.

Collect

all

the gas, but do not use the

the bottles with glass plates as tliey are

Disconnect the generator at a, Test the gas as directed in Exp. 93.

Add

a

little

acid to the

monoxide was produced

wash

is

rapidly

the lieat by the efferves-

two bottlc.i, covering and setting them aside and stand it in the hood

first

filled,

temporarily. to cool.

the gas

advisable to remove or lower the

bottle.

What

?

Sketch the essential part of the apparatus.

gas besides carbon

Carbon and

Its

Simplest Compounds.

CLASS-ROOM EXERCISE.

219

XXVIII.

Additional study of carbon monoxide. (a) Various methods of formation. (d)

Properties besides those revealed by experiment.

(c)

Its

{d)

What

(e)

Danger from carbon monoxide.

reducing power.

water gas

is

?

Combustion and the oxides of carbon. (a) Which oxide is formed in an excess of

2.

excess of carbon

?

vn

1.

air

?

Which

in

an

and explain the various chemical changes which occur from :he entrance of oxygen (in the air) below the grate of a red-hot coal fire to the end of the burning of the carbon monoxide at the top of the coal.

Miscellaneous. (a)

How may into

What

a mixture of the oxides of carbon be separated constituents

?

the valence of carbon in carbon monoxide and in carbon dioxide ? Is there any satisfactory explanation is

of

w w

(^)

its

.c h

3.

em

4a

ll.

(d) State

this fact ?

(0

Illustrate the

Law

of Multiple Proportions by the two oxides

w

of carbon.

tp ://

(d) Carbon dioxide

What

often called carbonic anhydride. this

Why

?

?

Calculate the molecular weight of calcium carbonate from the result obtained in Exp. 92. Compare with the theoretical weight.

ht

(e)

is

experiment proves

(/) Devise an experiment to verify the result obtained in Exp.

PROBLEM^.

92.

XIX.

gm. of carbon are heated in the presence of 44 gm. of carbon dioxide, what weight of carbon monoxide is formed, and what I.

If 20

^

weight,

if

any, of carbon remains 2.

What volume

charcoal to yield 159

?

of carbon dioxide must be passed over red-hot 1. of carbon monoxide ?

3. How many liters of carbon dioxide must be passed over red-hot charcoal to yield 84 gm. of carbon monoxide ?

Experimental Chemistry.

'i20 4.

What volume

of carbon dioxide must be passed over what weight

of carbon to produce 10 5.

What

1.

of carbon

monoxide

per cent of carbon by weight

at 14'' C.

is

and 760 mm.?

contained in carbon

monoxide ? In carbon dioxide ? 6. Carbon dioxide is passed into Hme water and forms a precipitate How much carbon dioxide can be obtained from this weighing 5 gm. precipitate 7.

?

Calculate the percentage composition of

Carbon monoxide. Carbon dioxide.

ll.

(c)

vn

(a) Calcium carbonate. (d)

ht

tp ://

w

w w

.c h

em

4a

(^) Magnesium carbonate.

CHAPTER

XIII.

COMPOUNDS OF CARBON AND HYDROGEN — ILLUMINATING GAS — FLAMES — OXIDATION AND REDUCTION.

—

em

4a

ll.

vn

Three important compounds of carbon Hydrocarbons. and hydrogen are methane, ethylene, and acetylene. They are called hydrocarbons, and are the first members of three large classes of similar compounds. PREPARATION AND PROPERTIES OF METHANE, OR MARSH GAS.

—A

when

Experiment

mixture of methane and air explodes Guard against flames and leaks.

ignited.

.c h

Precaution. violently

w w

gc,.^,-Ge7ieral Directions:

Use the same apparatus

as

Exp. 12. Fill the ignition tube nearly full of the mixture described below and insert a plug of glass wool, or asbestos between top of the mixture and the inner end of the delivery tube. Clamp the apparatus

w

in

shown

in Fig. 23,

tp ://

in the position

and

collect the gas over water.

Supplies: Heat a few grams of sodium acetate in a porcelain dish

Use a

or iron pan until the water of crystallization has been expelled.

ht

small flame and

stir

constantly toward the end of the operation.

pare one of the following mixtures {a)

Three

parts of dehydrated

:

—

sodium

acetate,

Pre-

and two parts soda

lime. (p ^ Equal parts of dehydrated sodium and quicklime.

acetate, dry

sodium hydroxide,

Process: Fill the tube with either one of the above mixtures and

arrange the apparatus as previously described. tube gently at

iirst,

Heat the whole ignition

increasing the heat gradually until a gas

is

evolved.

two small bottles of the marsh gas, and then remove the end of the delivery tube from the water. Hold a lighted match at the mouth of one of the bottles, and observe the nature Reject the

first

bubbles.

Collect

221

vn

ll.

4a

em

.c h

w w

w

tp ://

ht

+

Hydrocarbons. tube.

223

as the gas has been collected, disconnect at a^

As soon

stand the generator in the hood to cool.

When

enough

cool

and

to handle,

pour the contents down the sink or into a receptacle especially provided

dangerous mixtures. Test the gas by holding a lighted match at the mouth of a bottle. Observe and record the color and temperature of the flame, its luminos-

for

rapidity of combustion, visible products,

ity,

properties.

Add

a

little

and any other

characteristic

lime water to one of the bottles in which the

tion of ethylene?

ethylene burns, the combustion :

+

represented by

em

C2H4

is

ll.

the equation

—

4a

When

vn

gas was burned, shake, and explain the result. What evidence does this experiment present regarding the composi-

.c h

(24)

Experiment

97.

w w

PREPARATION AND PROPERTIES OF ACETYLENE.

— Put about

10 cc. of water in a test tube, stand the

tube in a rack, and drop two or three very small pieces of calcium Acetylene is evolved. After the action has carbide into the test tube.

tp ://

w

test

light the gas by holding a Observe and record the nature intensity, visible products (if any), tem-

proceeded long enough to expel the lighted match at the

mouth

of the flame, especially

ht

result suggest

of

its

its color,

Hold a cold

perature, etc.

air,

of the tube.

glass plate over the flame.

about the composition of acetylene

composition

is

Wliat does the

What

other evidence

revealed by the properties previously observed?

CLASS-ROOM EXERCISE. I.

?

XXIX.

Hydrocarbons.

meaning of term. Reason for the vast number. " homologous series." (^) Meaning of the term {d) Illustrate by hydrocarbons the terms saturated, unsaturated,

{a) Exact {b)

:

isoinerisin, polyinerisni, substitution

product.

Experimental Chemistry.

224 Methane.

2.

(«)

NameSy and why so

called.

{b) Occurrence. {c)

Properties (additional).

{d)

What

damp

is fire

?

choke damp

?

Ethylene. {a)

Names, and why so

(J?)

Equation for the reaction

{c)

Properties (additional).

called.

(^) Liquid ethylene and (^)

One

Exp.

in

96.

uses.

its

essential difference

vn

3.

between ethylene and methane.

and

historical

significance

formation.

(c)

.c h

Essential difference between methane, ethylene, and acetylene.

Miscellaneous.

5.

Law of Gay-Lussac by the combustion of methane and ethylene.

w

w w

(a) Illustrate the

What volume

carbon dioxide

and

{b) 2

facts revealed

XX.

be needed and what volume of

be formed in the combustion of {a) 2

of ethylene

by the

1.

of methane,

?

How many volumes of oxygen are required and how many volumes

ht

2.

1.

will

PROBLEMS.

of oxygen will

tp ://

1.

of

from calcium carbide.

Properties.

Id) Uses. {e)

method

em

(b) Industrial preparation

of this

4a

(a) Synthesis,

ll.

Acetylene.

4.

of carbon dioxide will be formed in burning 500 cc. of {a) ethylene and {b)

methane

3.

1000

What cc.

?

weight of

air is

necessary for the complete combuscion of

of marsh gas at 10° C. and 752

mm.

of the products measured at 300° C. and 752 4.

What

weight of

4 gm. of ethylene 5.

air is

needed

What ? mm. ?

for the

?

Calculate the percentage composition of {a)

Marsh

{b)

Ethylene, CgH^.

{c)

Acetylene,

gas,

CH^.

C^^-

are the volumes

complete combustion of

Illuminating Gas

225

formed by the destructive distillation a mixture of many gases, and its composition varies with the coal employed. The constituents are divided Illuminating Gas

of coal.

is

It is

into three classes, viz. illuminants, diluents,

The

class contains,

first

among

and impurities.

other gases, ethylene and

Marsh gas, hydrogen, and carbon monoxide, which burn with a feeble non-yellow flame, are the most common diluents. The common impurities are carbon dioxide, hydrogen sulphide, and ammonia; some of these, however, are entirely removed from the purified gas. acetylene.

—

of

—

is

often called coal

4a

Illuminating gas prepared as above

ll.

vn

all

em

gas.

PREPARATION AND PROPERTIES OF ILLUMINATING GAS.

is

wire

is

98.

— Apparatus

i

The

apparatus

.c h

Experiment

A A'

is

shown

in Fig. 67.

an ignition tube from 10 to 15 cm. long. A spiral of copper placed near A% and the tube is supported by a clamp as near this con-

bottle

is

to the

bottom

w

w w

end of the tube as convenient. An empty test tube or nected with the combustion tube by a bent tube passing

tp ://

C

B

ht Fig. 67.

a

'W C

C

— Apparatus for preparing illuminating gas.

of j5; this vessel retains tarry matter which comes from the ignition tube.

The

C and

a narrow strip of

U-tube contains moistened pink Htmus paper in the limb filter paper moistened with a lead compound

(nitrate or acetate) in the limb

sulphide.

The

bottle

D

is

C,

the latter serving to detect hydrogen

connected as shown in the

figure,

and

is

to be

Experimental Chemistry.

226 one-third

full

of lime water.

The tube

E

is

to

be connected with a

delivery tube passing into a pneumatic trough arranged to collect a gas

over water.

Three or four

Process: Fill

A A'

bottles will be needed.

two-thirds

which should be held

See that

shredded asbestos.

ignition tube gently;

if

of coarsely powdered

coal

soft

connections are gas tight by heating the

the apparatus

bubble through the bottle D.

Heat the whole

all

full

with a loose plug of glass wool, or

in place

is

Readjust,

if

ignition tube gently at

tight, the

expanded

air will

necessary. first,

and gradually increase

vn

the heat, but avoid heating either end very hot, otherwise the closed

em

4a

ll.

end may soften and burst or the rubber stopper may melt. As the heat As soon as the increases, watch for marked changes in B, CC, and D. slow bubbling shows that all air has been driven out of the apparatus, collect, as previously directed, two or three bottles of the gas evolved. Cover the bottles with wet filter paper or glass plates as fast as they are removed from the trough. When the last bottle has been removed, disconnect the apparatus at any convenient point between A' and Let the ignition tube cool. Test the gas by bringing a lighted match near the mouth of a bottle. Observe and record the color and heat of the flame, the rapidity of combustion of the gas, whether or not smoke Repeat with the is formed, and any other characteristic property. remaining gas and observe more closely any facts suggested but not by the

first

observations.

w

clearly revealed

w w

.c h

C

ht

C

tp ://

Examine the contents of the ignition tube. Does it suggest coke or some form of carbon ? Examine the bottle B for tarry matter. Does the paper in C reveal the presence of any ammonia ? If the paper in is brown or black, it is due to lead sulphide which is formed by the Did the gas interaction of hydrogen sulphide and lead compounds. contain hydrogen sulphide ? Did it contain carbon dioxide ? Record the result of each observation.

Sketch the essential parts of the apparatus.

COMBUSTION OF ILLUMINATING GAS.

—

Attach a pointed glass tube (see Exp. 57 (c)) to Experiment 99. the rubber tube connected with the gas jet and lower a small flame of illuminating gas into a cold, dry bottle. result.

Remove and

Observe the most

extinguish the flame, add a

little

definite

lime water, and

Describe the result. What do these two observations show about the composition of the main constituents of illuminating gas shake.

.''

Illuminating Gas.

CLASS-ROOM EXERCISE,

227 XXX.

Illuminating gas (coal gas). (a)

Industrial preparation, including a description of the appa-

(^d)

Constituents.

(c)

Removal of

ratus for purification

(d) By-products

Water

impurities.

— use and

value.

gas.

(«)

Industrial preparation.

(d)

Two main

(c)

Why

constituents.

often

(d) Dangers from

'^

its

enriched "

?

ll.

is it

use.

4a

2.

and storage.

Miscellaneous. (a)

Upon what does

(d)

How

(<:)

Explain the statement, "This

is its

the value of an illuminating gas depend

value determined

Review.

is

a 20 candle-power gas."

light.

(«)

Combustion.

(d)

Distribution of carbon.

w w

4.

?

.c h

(d) Describe the Welsbach

?

em

3.

vn

1.

Law

of Multiple Proportions in the light of the facts revealed

tp ://

(
w

(c) Sources of ammonia gas and ammonium compounds. (d) Source and use of (a) gas carbon, (<^)'coke.

ht

by the composition of hydrocarbons.

1.

fill

How much

PROBLEMS. XXI.

illuminating gas at 10° C. and 530

a tank having a capacity of 800 cu. m.

nating gas 2.

A

is

0.5 referred to air,

and

?

mm.

is

required to

(Specific gravity of illumi-

14.43 referred to hydrogen.)

bottle contains 53.2 cc. of moist illuminating gas at 760

and i8.5°C. What

is

mm.

the volume of the dry gas under standard conditions.^

3. When steam is passed over red-hot coal in the preparation of water gas, the simplest equation for the reaction is^

C + H.O = CO +

How many 750

mm.

liters

will

of hydrogen

H...

and of carbon monoxide

be formed from 100 gm. of steam

.''

at Io° C.

and

Experimental Chemistry.

228

Bunsen Burner.

— The

Bunsen burner which is used was devised by the

so constantly in chemical operations

German form

same

the

parts of a

The

Bunsen.

chemist,

varies,

but the principle

in

The

burners.

all

common form

are

is

shown

in Fig. 6S.

O

—Take

apart a

ll.

Experiment lOO.

vn

CONSTRUCTION OF A BUNSEN BURNER. Bun-

4a

sen burner and study the construction. Sketch the essential parts.

Write a short

description of the burner.

em

O

The theory and

practical advan-

.c h

tages of a Bunsen burner are only partly

I

shown by

its

structure.

It

also necessary to study the

w w

is

BUNSEN BURNER FLAME.

—

ht

tp ://

w

Experiment loi. I. (a) Close the holes at the bottom of a Bunsen burner Parts of a Runscn Fig. 68. and hold a piece of crayon in the upper burner. part of the flame. Note the black deposit. What is it ? Where did it come from ? Open the holes and hold the blackened crayon in the colorless flame. What becomes of the deposit ? How is the flame changed, if at all ? Does the experiment suggest a cause of the luminosity of a flame

?

What

is

it ?

Dip a glass tube a short distance into powdered wood charcoal, place the end containing the charcoal in one of the holes at the bottom of the burner, and blow gently two or three times into the other end. Describe and explain the result. I3oes it verify the answer to the last (d)

question in (a) (c)

?

Open and

Describe the

close the holes of a lighted burner several times.

result.

Pinch the rubber tube to extinguish the flame, What change is produced in the flame.''

then light the gas at the holes.

What

causes the change

?

Flames. Answer

the following

What

(i)

Why Why Why

(2)

(3) (4)

:

—

the object of the holes

is

?

and not inside of the burner? sometimes '' strike back " and burn inside ? the Bunsen flame non-luminous ?

does the gas burn does is

229

at the top

it

Hold a match across the top of the tube of a lighted Bunsen Note to burn, remove and extinguish it. it begins The ./here it is charred, and explain the result. same fact may be shown by sticking a pin through a (sulphur) match 15 mm. from the tip, suspending The it across the burner, and then lighting the gas. Turn on position of the match is shown in Fig. 69. li

{^a)

burner.

When

current of gas before lighting

it.

What

4a

full

this

does

experiment show about the structure of the Bun-

sen flame?

Verify your answer by (^).

em

a

ll.

vn

j^

Bend a glass tube about 15 cm. long into the shape shown in Fig. 70. Hold the shorter arm in

.c h

(d)

the flame about 2 cm. from the top of the burner

Hold a lighted match for an instant at the upper end of the tube. What does the result show about the structure of the Bunsen flame ? Does it

—A

(sul-

phur) match sus-

across Bun-

pended

the top of a

sen burner.

Find the hottest part of the flame, when a full current of gas is burning, by holding a platinum or copMeasure its disper wire in the flame. tance, approximately, from the top of

ht

tp ://

{c)

?

l^G. 69.

w

verify (a)

w w

tube.

the burner tube.

(d) Examine a typical Bunsen flame

— one w^hich shows of the inner part.

clearly the outlines

What

shapQ of each main part? tical

is

the general

Draw

and a cross section of the

a ver-

flame.

CANDLE FLAME.

—

Attach a candle Experiment 102. wood by means of a little melted candle wax, and proceed as fol-

to a block of

—

Fig. 70. Bent tube for examining the structure of a Bunsen flame.

lows

:

—

Experimental Chemistry.

230 Hold a

(a)

cold, dry bottle over the lighted candle.

What

result.

is

the product

What

?

is

source

its

?

Describe the .

Remove

the

and shake. Describe and explain the result. What are the two main products formed by a burning candle ? (d) Blow out the candle flame, and quickly hold a lighted match in the pour a

bottle,

little

lime water into

it,

Does the candle relight ? Why ? What is smoke? How is it related to the candle wax?

escaping smoke. nature of this

(d) contribute to the explanation of (a)

the general

How does

?

Stand a lamp chimney over the lighted candle. How is the flame Does the Prop up the chimney on two blocks of wood. candle continue to burn? Why? Now cover the top of the chimney (c)

the result?

is

ll.

What

Why?

4a

with a piece of tin or similar covering.

vn

affected?

LABORATORY EXERCISE. Sketch a candle flame.

Examine

a lamp burner.

What

3.

is

constructed according to the prin-

?

Bunsen and a cand'e

Explain the statement: "Large lamps have a powerful central

w

5.

it

any essential difference between a candle flame and a gas

Is there

4.

Is ?

the essential difference between a

?

or lamp flame

(c)

w w

flame

Exp. 102

.c h

ciples revealed in

em

1.

2.

XIII.

draft."

tp ://

CLASS-ROOM EXERCISE.

1

Essential facts in the

2.

What

life

meant by the

of Bunsen.

ignition point or kindling temperature of a

ht

is

XXXI.

flame? 3.

which 4. 5.

6.

Describe a miner's safety lamp, and state the exact principle on its

use depends.

facts about the Bunsen burner flame. Give additional facts about the luminosity of flames. Why does a draught of cool air often cause a lamp flame to smoke

Give additional

Oxidizing and Reducing Flames.

—

It

is

convenient to

consider the Bunsen flame from two standpoints,

power

to give or to take

to oxidize or to reduce.

oxygen, cr

in other

That portion

?

words

its

viz. its

power

of the flame giving

Oxidation and Reduction.

231

oxygen freely is called the oxidizing flame, and the part takA diagram of the ing oxygen is called the reducing flame. general relation of these two flames is shown in Fig. 71 A is the most effective part of the oxidizing flame, and B of the reducing flame. At A metals are oxidized, and at B oxides are reduced.

LABORATORY EXERCISE.

Borax Bead.

—A

ll.

tively

Sketch the oxidizing and reducing flames. reduction occur respec-

Why do oxidation and at A and B (Fig. 71) ?

practical

4a

2.

vn

I, '

XIV.

application

em

and reducing flames is testing with a borax bead." often made by Borax, when heated, melts and forms a clear, transparent globule, which resemoxidizing

of the

a

glass

Many

bead.

w w

bles

.c h

'*

metallic sub-

stances dissolve in melted borax and form

These beads differ in beads. and thus serve to. identify the sub-

tp ://

color

w

colored

stance or at least

its

essential elementary

ht

constituent.

—

The oxiFig. 71. dizing {A) and reducing {B) flames.

TESTS WITH BORAX BEADS,

—

Make a small loop on the end of the platinum Experiment 103. App. A, § 14), moisten it, and dip it into powdered borax. Heat it in the flame, rotating it slowly at first the borax swells, but If the bead is too small, finally shrinks to a small, transparent bead. add more borax and heat again. After use, the bead may be removed by dipping it, while hot, into water; the sudden cooling shatters the

test wire (see

;

bead, which {a)

may then be

Cobalt compounds.

easily

rubbed or scraped from the wire.

Touch a transparent borax bead

with a glass

rod which has been moistened with cobalt nitrate or chloride solution.

Heat the bead

in the oxidizing flame-

Notice the color when cold.

If

Experimental Chemistry.

2^2

is black, melt a little more borax into the bead if faintly colored, moisten again with the cobalt solution. The color is readily detected by looking at the bead against a white object in a strong light, or by examining it with a lens. When the color has been definitely deterit

;

mined, heat again

in

the reducing flame.

Compare the

color of the

cold bead with the previous observation.

Make

Copper coiiipowids.

(d)

another transparent bead, moisten

with copper sulphate solution, and heat

it

first

it

in the oxidizing flame,

4a

ll.

vn

and then in the reducing flame. Compare the colors of the cold beads, and draw a conclusion. {c) Manganese cojupounds. Make another transparent bead, moisten it with manganese sulphate solution, or touch it with a minute quantity of manganese dioxide, and proceed as in {b). Compare the colors of the cold beads, and draw a conclusion.

em

Tabulate the results of this experiment.

(^)

Differently colored hot and cold beads are characteristic

is

compounds

of different elements,

and the bead

test

.c h

of the

often used to confirm other observations or to suggest

w w

a further special examination.

The Blowpipe and

— Sometimes

it is not connor to hold a substance directly in the flame. It is then customary to study the action of a substance when heated on charcoal in a small

its

Use.

test,

tp ://

w

venient to apply the bead

much Hke

the

Bunsen flame and produced by

ht

flame,

Fig. 72.

a blowpipe (Fig. 72).

—A

A

blowpipe.

blowpipe tube

is

put inside

the burner tube (Fig. 73) to produce a luminous flame. The tip of the blowpipe rests on this tube (Fig. 74), and

when

air

is

slender flame

gently blown through the blowpipe, a long, is

produced (Fig.

75), exactly like a

Bunsen

Oxidation and Reduction.

oxidizing and reducing powers are conis the Fig. 75, A is the oxidizing and

flame as far as

In

its

B

reducing part,

Fig. 74.

— The blowpipe

Fig. 75.

—The blowpipe flame.

tip in position.

w w

—

a blowpipe Fig. 73. tube in position.

.c h

em

4a

ll.

vn

cerned.

'^33

i.e.

these points are the most effective for

tp ://

w

these respective operations.

USE OF THE BLOWPIPE.

—

ht

Slip Experiment 104. the gas and lower the flame

the blowpipe tube into the burner, light Rest the tip it is about 4 cm. high.

until

placing of the blowpipe on the top of the tube, as shown in Fig. 74, beblowpipe the of end other the Put the tip just within the flame. tween the lips, puflf out the cheeks, inhale through the nose, and exhale into the tube, using the cheeks

somewhat

as a bellows.

Do

not blow

and easy inin puffs, but produce a continuous flow of air by steady if haling and exhaling. The operation is natural and simple, and, not make one out of breath. The flame surrounded by an outer and almost incone blue inner an should be varies visible cone, somewhat as shown in Fig. 75, though its shape produced is flame the until Practice with the method of production. properly performed, will

Experimental Chemistry.

234

and without exhaustion.

voluntarily

tinguish the two parts, so that they

Watch the flame and learn may be intelligently utilized.

to dis-

Sketch a blowpipe and a blowpipe flame.

REDUCTION WITH THE BLOWPIPE. Experiment 105. one end of the

— (a)

Lead compoimds.

Make

side of a piece of charcoal.

flat

Fill

a shallow hole at

the hole with a

mixture of equal parts of powdered sodium carbonate and lead oxide, and heat the mixture in the reducing flame. The sodium carbonate

vn

melts and assists the fusion of the oxide, but the former is not changed In a short time bright, silvery globules will appear on the

chemically.

ll.

Let the mass cool, and pick out the largest globules. Put Are they soft and in a mortar, and strike with a pestle.

charcoal.

4a

one or two

and hard? State the result when a globule is drawn across or rubbed upon a white paper. How do the properties compare with those of metallic lead ? What has become of the oxygen ? Of what chemical use is the charcoal ? together in a mortar a little sodium sulphate and wooO (J)) Grind charcoal, adding at intervals just enough water to hold the mass together. Heat this paste for a few minutes in the reducing flame as in {a). Scrape the fused mass into a test tube, boil in a little water, and If a dark brown put a drop of the solution on a bright silver coin. is

produced,

it

is

evidence of the formation of silver sulphide.

w

stain

w w

.c h

em

malleable, or brittle

no such stain is produced. State all tli^ chemical changes which led to the production of the silver sulphide, explaining at the same time how the experiment illustrates reduction. if

tp ://

Repeat,

ht

OXIDATION WITH THE BLOWPIPE.

— {a)

Heat a small piece of zinc on charcoal in Observe and record the is the product? color of the product, and the color of the coating on the charcoal when both hot and cold. (See OO-) lead as in (<^), and note and record the presence (J)) Heat a piece of or absence of fumes, as well as the color of the coating wlien hot and

Experiment 106.

the oxidizing flame.

What

cold. {c) Heat a small piece of tin in the oxidizing flame, and observe and record the presence or absence of fumes, and the color of the coat-

ing, if any.

Oxidation and Reduction.

23c

{d) Tabulate the above results, stating in each case (i) color of the coating on the hot charcoal, (2) color of the coating on the cold charcoal? (3) presence or absence of fumes, (4) name of product.

CLASS-ROOM EXERCISE. 1.

What

2.

Does

3.

Review.

XXXII.

is made of the principle shown in Exp. 105 {b) the chemical action in Exp. 106 differ essentially from combustion in the air? Then why use a blowpipe?

industrial use

vn

.?

{a) Oxidation and reduction.

blowpipe.

ll.

Compound

ht

tp ://

w

w w

.c h

em

4a

{b)

CHAPTER

XIV.

SOME COMMON ORGANIC COMPOUNDS.

subdivision

''

now made

Organic Chemistry." for

Such a

convenience, not for any

chemical properties of these carbon compounds, or

em

intrinsic

is

of

title

4a

comprehensive

ll.

vn

Carbon forms a vast number of compounds. Many of them were first obtained directly or indirectly from living things, and they naturally came to be considered under the

;

.c h

organic compounds, as they are often called. Several organic compounds have already been studied

these will be reviewed from a broader standpoint, and a

The common

o-

:

ht

tp ://

1.

The Composition partially

be examined.

ganic compounds are members, or deriva-

the classes

w

tives, of

fa.niliar will

w w

few others which are

shown.

Hydrocarbons.

2.

Alcohols.

3.

Acids.

4.

Carbohydrates.

of

Organic Compounds has already been usually contain carbon and hydro-

They

gen, with or without oxygen, or nitrogen, or both

;

contain sulphur, phosphorus, and other elements.

a few

When

burned or heated they yield carbon, or carbon dioxide, water vapor, ammonia gas, sulphur compounds, etc., according to their composition. typical organic

The

general character of

compounds may be shown by a study 236

of the

Some Common Organic Compounds.

237

COMPOSITION OF ORGANIC COMPOUNDS,

—

{a) Carbon. Experiment 107. ments which showed that carbon

is

(O

Recall or repeat the experi-

a

constituent of wood, cotton,

bone, starch, sugar, illuminating gas, candle wax, meat, flour, bread, albumen. (2) Heat 2 or 3 cc. of turpentine in a porcelain or iron

and then set fire to it. Does it contain carbon? Hold over the flame long enough to collect any product, and then does the observation verify the contents for carbon dioxide Does it contain conclusion? (3) Repeat with alcohol.

a bottle

dish,

;

test the

previous

carbon?

ll.

vn

Burn a small lump of camphor in a dish or on a block of wood. Does it lamp long contain carbon? (4) Hold a bottle over a burning kerosene enough to collect any product, and test as in (2). Does kerosene

4a

contain carbon?

em

(i) Set fire to i or 2 cc. of the following liquids ir {b) Hydrogen, a porcelain dish (or crucible), and hold over the flame a cold dry bottle long enough to allow the condensation of the water vapor which is

always one product of the combustion of organic compounds which

starch, flour,

will

condense on the upper part of the

w w

water vapor

.c h

(2) Heat in separate contain hydrogen: alcohol, turpentine, kerosene. little test tubes the following dry solids, and if they contain hydrogen, a

wood, paper,

hair.

(3)

Hold

test

tube

:

sugar,

a cold, dry bottle, for a few

w

seconds over a burning kerosene lamp, a Bunsen flame, an ordinary gas flame, a burning candle, a burning taper. Is hydrogen a component

and wax? The oxygen, which unites with the hydrogen to form the water, may come from the substance, as in the case of sugar, starch, wax, wood, No simple experiment will deterpaper, or it may come from the air.

ht

tp ://

of kerosene, illuminating gas,

mine the source of the oxygen.

Mix a little granulated gelatine (one part) with dry (^) Nitrogen. soda lime (two parts) and heat the mixture in a test tube. Hold a It will be piece of moist red litmus paper In the escaping vapor. turned blue by escaping ammonia gas. Gelatine (also horn, glue, and leather) contains nitrogen which is liberated in combination whh hydrogen as ammonia gas. (i) Put a (rt') Sulphur,

The brown

stain

is

little

mustard paste on a clean

silver sulphide.

Explain.

(2)

Why

silver coin. is

a silver

spoon tarnished by a cooked egg?

Draw

a general conclusion

compounds.

regarding the composition of organic

Experimental Chemistry.

238

—

These compounds of hydrogen and Hydrocarbons. carbon have already been considered in Chapter XIII.

LABORATORY EXERCISE. 1.

XV.

Recall or repeat the experiments illustrating the preparation and

properties of methane, ethylene, and acetylene. 2.

What

3.

Write the equations

are the products of the combustion of these hydrocarbons?

combustion of methane and ethylene.

vn

for the

CLASS-ROOM EXERCISE.

a.

Give the components

ll.

mixture) of kerosene, petroleum, natural gas, illuminating gas,

em

(if

Review Class-Room Exercise xxix., Chapter XIII., page 223. (if a compound) or the main constituents

4a

1.

2.

XXXIII.

naphtha, gasoHne, turpentine, benzine, benzene.

Review Problems XX., Chapter

Alcohols.

XIII.,

w w

I.

.c h

PROBLEMS. XXII.

— These are

compounds

page 224.

of carbon, hydrogen,

ht

tp ://

w

and oxygen. Ethyl alcohol is the best known member of this class, and is therefore called alcohol, just as sodium Alcohol is formed by the ferchloride is called salt. mentation of glucose, or grape sugar.

PREPARATION OF ALCOHOL.

Experiment 108. mixtures {a)

:

—

— Prepare

300 gm. of grape sugar. 2

500

1.

of water.

cc. of yeast.

{c)

alcohol

one of the following

from

{b)

50 gm. of grape sugar. i

60

1-

of water.

cc. of yeast.

25 gm. of grape sugar. 150 cc. of water. A of a compressed yeast cake.

Put I. Dissolve the grape sugar in the water and add the yeast. the mixture in a large bottle or flask provided with a one-hole rubber

Some Common Organic Compounds.

239

stopper fitted with a delivery tube which reaches to the bottom of a small bottle half full of lime water. Pour enough kerosene down a rod upon the lime water to prevent it

from interacting with the carbon dioxide of the air. Stand the appawhere the temperature is

ratus in a dark, or moderately dark place,

25°-30°C.

Fermentation begins at once, and carbon dioxide, one of the prodExamine the stopper for a bubbles through the lime water. The operation should be leak, if no change occurs in the lime water.

ucts,

ll.

vn

allowed to conf'nue at least a day, and longer if possible. The flask will then contain mainly water, unchanged grape sugar, alcohol, and some products of minor importance. Decant the liquid, agitate it with

4a

The alcoa httle bone black to remove the odor and color, and filter. hol, which varies in quantity with the conditions, is dissolved in a large

The

distillation is

the flask half

full

stem (or granulated distil about 50 cc.

performed with the apparatus used in Exp. 30. I., add a few pieces of pipe-

of the liquid from

zinc, or glass tubing) to prevent

.c h

II.

Fill

em

excess of water and must be separated by distillation.

"bumping." and

tp ://

w

w w

Replace the residue in the Save the distillate. flask by more liquid from I., distil again, and repeat this operation Replace the one-hole stopper with until all the liquid has been used. a two-hole stopper, insert a thermometer in one hole so that the bulb just touches the surface of the combined distillates which should now be Heat gently, and collect in a separate receiver the distillate distilled. which is formed when the liquid boils between 80° and 93° C. This contains most of the alcohol. Note the odor. Drop a little into a warm dish, and hold a lighted match over it. If it does not burn, it shows that the alcohol is too Put a little in a dish, warm gently, and light the vapor. Dedilute.

ht

distillate

scribe the result.

If this

experiment

character of alcohol

is

indifferently successful, the general

may

be learned by a study of

THE PROPERTIES OF ALCOHOL.

—

(a) Determine cautiously the odor and taste of Experiment 109. Drop a little on a glass plate or on a piece of paper, and watch Is its rate of evaporation more rapid than that of water ? evaporate.

alcohol. it

Experimental Chemistry.

240 (b)

and

{c)

a measured quantity (about 25 cc.) of 95 per cent alcohol

Weigh

calculate

its

specific gravity.

Try camphor, pow-

Alcohol dissolves many organic substances.

dered shellac, or rosin.

{d) Burn a {e)

What

alcohol in a dish and observe the nature of the

little

are the products of combustion

?

Cautiously add a few drops of concentrated sulphuric acid to

equal volumes (about carefully,

5 cc.

Shake

each) of acetic acid and alcohol.

The

and then warm gently.

vn

flame.

pleasant fruit-like odor

is

due to

Its

nature will be subsequently considered.

4a

acetic acid.

ll.

the vapor of ethyl acetate, a volatile liquid which is always formed under Its formation is a simple test for either alcohol or these circumstances.

Summarize the properties of Complete the equation

C.H,p

=

+

CO2

H.O.

w w

Fermentation

+

XVI.

alcohol.

.c h

1.

2.

em

LABORATORY EXERCISE.

is

a destructive process caused, probably,

The equation

for the reaction

tp ://

ism.

w

by various organisms, and the products vary with the organ-

QHi^Oe

=

2

when sugar ferments

CsHgO

+

2

CO2.

Alcohol

ht

Glucose

Cane sugar (ordinary sugar) does not ferment. with acid,

it

changes thus

C12H22O11 Cane Sugar

+

H.p

:

—

=

C.HiPe

+

Glucose

and fermentation may then occur as

The Formula

is

If boiled

C.HiPe, Fructose

usual.

of Alcohol is often written

C2H5.OH,

be-

cause conclusive evidence shows that this general grouping

atoms exists in the molecule. The radical C2H- is called ethyl. Like ammonium, it exists only in combination. The

of

vn

ll.

4a

em

.c h

w w

w

tp ://

ht C2H5.OH+ HCl

Experimental Chemistry.

242 6.

Ethereal

salts.

(a) Occurrence in flowers and fruits. (3)

General properties.

(c)

Artificial preparation.

(d) Uses.

is a compound of carbon, hydrogen, and oxygen, made from alcohol by heating with sulphuric acid. In its narrow sense the term ether means the best known member of an homologous series of organic compounds

Ether

and

analogous to the metallic oxides. Ordinary ether C2H5 O C2H5.

is

ethyl oxide, (C2H5).p or

.

.

4a

is

ll.

which

vn

is

Ether vapor

is

em

PROPERTIES OF ETHER.

easily ignited, and should never be brought

.c h

near a flame, unless special directions are so given.

—

tp ://

w

w w

(a) Pour a little ether into a dish or test tube Experiment no. and observe the odor and volatility. Taste cautiously. Pour a drop upon a glass plate or a block of wood. How does its rate of evaporation compare with that of alcohol ? (d) Recall or repeat the experiment (see Exp. 33 (d)) illustrating the solubility relations of ether and water. The result (c) Add a bit of wax to a few cubic centimeters of ether. draw a conclusion. is typical

ht

;

1.

LABORATORY EXERCISE.

From what has

already

XVII.

been shown about ether, predict

its

approximate boiling point. 2.

Explain the statement, ''ether

is

miscible with

alcohol in

proportions.^' 3.

Complete the equation

for the

combustion of ether

(C.H^),© + 6O0 =

+

CO.,

CLASS-ROOM EXERCISE. I.

:

-

H,,0.

XXXV.

Additional study of ether. (a) Industrial preparation. (t/)

(3)

Properties.

Formula, constitution, and equations for

its

(c)

Uses.

preparation.

all

Some Common Organic Compounds.

243

Miscellaneous. (a) Ethers. (d) {c)

Significance of the terms e^/iyl ether and sulphuric ether. Explain the expression, " ether is prepared by a continuous process."

(^) Anhydrous

ether.

PROBLEMS.

XXIII.

3.

If 10

ll.

sugar, CjoHoaOi^.

gm. of pure alcohol

One and

are burned,

w w

formed?

what weight of each product

a half kilograms of absolute alcohol are burned.

HowMiiany

liters

{b)

How many

liters (at

w

{a)

of oxygen are needed?

standard conditions) of carbon diox-

and of water vapor are formed?

tp ://

ide

6.

em

Cane

.c h

(c)

5.

obtained from a

C^H^o^

{b) Acetic acid,

4.

may be

Calculate the percentage composition of {a) Alcohol, C,H,;0.

is

are the

4a

2. Calculate the weight of alcohol which kilogram of cane sugar.

What

vn

i. Ether boils at 34.9^0. and alcohol at 78.4'^ C. corresponding points on the Fahrenheit scale?

Calculate the simplest formula of the substances possessing the

ht

indicated composition {a)

Carbon

:

—

Experimental Chemistry.

244

Aldehyde is a compound of carbon, hydrogen, and oxygen, which is formed by the oxidation of alcohol. Aldehyde, like alcohol and ether, is the name both of an homologous series and of its best known member.

PREPARATION AND PROPERTIES OF ALDEHYDES,

— («)

Add

Acetic Aldehyde.

little

to a

Warm

concentrated

few cubic centi-

gently,

and observe

ll.

meters of potassium dichromate solution. It the peculiar-smelling gaseous product.

aldehyde vapor, aldehyde

is

being a colorless, extremely volatile liquid which boils at 20.8° C.

4a

itself

a

vn

Experiment iii.

hydrochloric acid and a few drops of alcohol

See Exp. 183.

Put a few cubic centi-

Formic Aldehyde or Formaldehyde.

em

{b)

meters of methyl alcohol in a test tube and stand the test tube in a Wind a piece of copper wire into a spiral around a glass rod or rack.

.c h

Slip the spiral from the rod, grasp one end in the forceps, and heat the wire red-hot in the flame. Then quickly drop it into the methyl alcohol. The pungent vapor which is suddenly produced is the

w w

lead pencil.

vapor of formaldehyde.

preparation of formaldehyde

tp ://

equation —

CH3.OH

4-

O

ht

The formula

H.CHO + H2O

=

Formaldehyde

Methyl Alcohol

1.

of acetic aldehyde

is

CHg CHO. .

LABORATORY EXERCISE.

Complete the equation

for the

C^H^.OH 2.

Derivation of the term

3.

Why may

XVIII.

formation of acetic aldehyde

+

O

=

^Z^.?/^/^.?.

acetic aldehyde be called ethaldehyde?

CLASS-ROOM EXERCISE. 1.

XXXVL

Formaldehyde. {a) Preparation. {c)

2.

represented by the

is

w

The

{b)

Properties.

Uses as disinfectant and germicide.

Use of aldehydes

in

formation of mirrors.

:

Some Common Organic Compounds. Acetic Acid

The

pound.

245

an exceedingly important organic com-

is

and

acid

its

derivatives find

numerous

appli-

cations.

PROPERTIES OF ACETIC ACID. Experiment 112.

— Recall

or determine again the general proper-

ties of acetic acid.

Warm

a

little in

a test tube and compare the odor with that of other

acids.

Experiment 113.

name

— Repeat

product of the reaction

Vinegar

is

dilute,

and describe the

result.

compound which corresponds

to the

Exp. 109

of the sodium

(^),

ll.

the

?

impure

4a

main

is

acetic acid.

em

What

vn

TEST FOR ACETIC ACID.

PROPERTIES OF VINEGAR. experimentally that vinegar

is

(i) an

acetic acid.

w w

acid,

.c h

— Show

Experiment and (2) contains 114.

Acetates are salts of acetic acid.

w

PREPARATION OF ACETATES.

tp ://

Most

acetates are poisonous.

—

—

ht

Prepare one or all of the following acetates: Experiment 115. Dissolve 20 gm. of sodium carbonate in 10 cc. acetate. {a) Sodium slowly add 30 cc. of of water in a large porcelain or agate dish, and

commercial acetic acid, with constant

stirring.

If

the solution

is

not

not clear. add a little more acetic acid. Filter the solution, if remove formed, have crystals Evaporate to crystallization. When the contain water they that Prove crystals. the Describe and dry them.

acid,

Test the acetate as follows: (i) Dissolve a little sulphuric acid, and boil. in water, add a few drops of concentrated What does the odor show is present? What other acids have been drops of alcohol (2) Dissolve as in (i), add a few similarly prepared? conclusively odor the does What boil. and acid, and of sulphuric

of crystallization.

bottle, or Preserve the crystals, finally, in a glass-stoppered paraffine. with in one having a cork covered

prove

?

Experimental Chemistry.

246

To

Lead acetate {poisonous^.

(/;)

gm. of

10

After

during the addition of acid. gently until the action ceases.

If

litharge

add

18 cc. of

Stir the mixture constantly

commercial acetic acid in small portions.

the acid has been added, heat

all

the solution

green or bluish,

is

it

is

due to a copper compound. The copper may be precipitated and removed mechanically by standing a strip of lead in the solution for an

Decant the clearer

hour or more.

crystallization on a water bath.

and dry

liquid

and then

Remove

filter.

Evaporate to

the crystals from the liquid,

moderate temperature. Preserve the crystals finally as in Test them for lead (see Exp. 98, last paragraph, and Exp. 134 {/) (i)), and for an acetate.

vn

at a

Describe the crystals.

ll.

{a).

COOH.

4a

The Formula of Acetic Acid is C.^H^Og or CHg. is formed by the oxidation of ethyl

thus

alcohol,

em

This acid :

The change

due

is

.c h

CsHeO + 02 = C2H4O2 + H2O. Acetic acid

to fermentation.

basic.

w w

CLASS-ROOM EXERCISE. lo

mono-

XXXVII.

Additional study of acetic acid.

(^) UseSo

w

{a) Industrial preparation. Glacial acetic acid.

ic)

(^)

tp ://

{b)

2.

is

Test.

(/") Constitution.

Properties.

Acetates.

General method of preparation.

Chemical name and formula of iron

ht

(d;)

(^)

gris,

{c)

liquor, red liquor, verdi-

sugar of lead.

Formula

of

sodium, lead,

silver,

chromium,

ammonium,

aluminium, and calcium acetates.

(^) Uses of acetates. 3.

4.

Vinegar. {a)

What

{Jj)

Chemistry of

{c)

is it ?

its

Industrial preparation

(^) Uses.

formation.

Oxalic acid. {a) Preparation. (^)

Formula and

(<'/)

What

{b^

constitution.

experimental use has been

do the

results

Properties.

-

show about

its

made

of oxalic acid?

composition

?

What

Some Common Organic Compounds. Show by

5.

formulas the relation

247

between ethyl alcohol, acetic

aldehyde, and acetic acid, and by equations the possibility of passing from one to the other.

Soap is a mixture of alkaline mainly palmitic and stearic acids.

It is

The

caustic soda or potash with fats. saponification,

of organic

salts

and consists simply

in

made by process

acids,

boiling called

is

decomposing an

or-

ganic salt (fat) into the corresponding alcohol (glycerine)

Fats are analogous to ethyl

salt (soap).

vn

and an alkahne and

oleate.

4a

stearate,

ll.

acetate, ordinary fats being mixtures of glyceryl palmitate,

PREPARATION OF SOAP.

—

:

in

an iron or a

em

Experiment 116. Prepare soap of the following methods

—

by one

tin dish

Boil a few minutes.

w w

tion of the salt.

.c h

(a) Dissolve 10 gm. of sodium hydroxide in 75 cc. of water, add 30 gm. of lard, and boil until the mixture begins to solidify. Then add 20 gm. of fine salt in small portions. Stir constantly during the addi-

remove the soap, which

will

form

in

Let the mass cool, and then

a cake at

.the surface.

Dissolve 13 to 15 gm. of sodium hydroxide in 100 add 100 cc. of castor oil, and boil for about half an hour. (d)

Add 20 gm. and then proceed as in (a). Dissolve 8 gm. of potassium hydroxide in 150 cc. of alcohol, gm. of lard, and stir constantly while the mixture is being heated

w

salt,

tp ://

of

(c)

ht

add 10 on a water bath to syrupy consistency.

The

cc. of water,

jelly-like

product

is

Allow the contents

to cool.

soap.

Preserve a sample.

PROPERTIES OF SOAP. Experiment 117. several days. in the

soap

(c)

Leave soap shavings exposed to the air for does the result show about the presence of water

?

Test a yellow soap for

(d)

pared

What

— (a)

free alkali.

Is

such a soap carefully pre-

?

Add

considerable dilute sulphuric acid to a soap solution.

greasy precipitate, which finally rises to the top, palmitic and stearic acids.

is

The

a mixture mainly of

Experimental Chemistry.

248

(d) To a little soap solution in separate test tubes add calcium sulphate and magnesium sulphate solutions. Describe the result. Boil Prepare a solution of acid for a few minutes and describe the result. into lime water until the dioxide carbon passing by carbonate calcium precipitate

is

Add some

redissolved.

and describe the

of the solution to a soap solution,

Boil, as above,

result.

and describe the

result.

agent, since

is

it

is

useless

as a cleansing

4a

nesium compounds, the soap

ll.

vn

Hardness of Water is illustrated by Exp. 1 17 (^)- Magnesium and calcium sulphates and calcium carbonate (in solution as the acid carbonate) form insoluble salts with As long as water contains these calcium and magsoap. immediately transformed into a sticky

hardness cannot be removed by boiling, as in the case of water containing magnesium and calcium sulHeat decomphates, the hardness is called permanent. poses acid calcium

.c h

em

If the

solid.

carbonate, the calcium carbonate is

is

liberated; hence hard-

w w

precipitated and carbon dioxide

or calcium salts.

tp ://

magnesium

w

ness due to calcium carbonate can be removed by boiling, and is therefore called temporary. Soft water contains no

CLASS-ROOM EXERCISE.

Additional study of soap. {a) Industrial preparation.

ht

1.

\b)

2.

Chemistry of

its

XXXVIII.

(0 Kinds.

preparation.

(rtf)

Uses.

Glycerine (or Glycerol). {a) Industrial preparation.

3.

{b)

Properties.

(rtT)

{c)

Relation to soap industry.

ie)

Miscellaneous. («) Stearin,

Formula and composition. Uses.

— preparation and uses.

{b)

What

{c)

Organic acids related to stearic acid.

is

saponification?

Carbohydrates are compounds of carbon, hydrogen, and oxygen.

Sugar and starch are familiar representatives.

Some Common Organic Compounds. LABORATORY EXERCISE. 1.

Examine sugar and summarize

its

249

XIX.

general properties.

What happens when it is heated? When treated with concentrated sulphuric acid ? What do these experiments show about its 2.

composition? 3.

Examine sugar through a

lens.

What

crystal

is its

form?

FEHLING's test for SUGAR. 153.

vn

Experiment 118. —Perform Exp.

LABORATORY EXERCISE.

ll.

starch through a microscope,

differ

it

and describe the

4a

2.

acid?

Examine does

from sugar?

result.

What is the effect of heat on starch ? Of concentrated sulphuric What does it contain, according to these experiments?

em

1.

How

XX.

Summarize the general properties of Is starch soluble in cold

1

Sugars.

starch.

.c h

3.

4.

water?

w w

CLASS-ROOM EXERCISE.

XXXIX.

(a) Distribution of sugars. Industrial preparation

(c)

Cane

w

(d)

and properties of glucose.

— distribution,

tp ://

sugar,

source, industrial preparation,

properties.

(
Review " Fermentation." Formula and composition of

ht

(
2.

3.

several sugars.

Miscellaneous. (a)

What

(d)

Beet root sugar industry.

is

molasses?

Sugar of milk?

Fructose?

Starch.

(a) Distribution and source. (d)

Industrial preparation.

(d) Uses. (e) Formula.

(c)

Properties.

(/) Kinds.

4.

Chemistry of bread-making.

5.

Dextrine

— preparation,

properties, uses,

and

and dextrose. 6.

Glucose?

Cellulose

— distribution, properties, and uses.

relation to starch

CHAPTER

XV.

The

elements hitherto studied suggest Httle or no

resemblance

Chlorine,

bromine and

to

and the experiments

iodine,

in this chapter are intended to reveal,

among

other things,

em

this relation as well as to present the special facts

bromine and iodine and

about

compounds.

.c h

their

rela-

however, bears a strong

ll.

each other.

to

4a

tion

vn

BROMINE, IODINE, AND HYDROFLUORIC ACID.

PREPARATION AND PROPERTIES OF BROMINE.

— Bromine

a corrosive liquid

is

w w

Precaution.

ivhicJi

at the ordinary temperature, a suffocating vapor.

hood

all experimejits

w

in the

— Bend

tp ://

Experiment 119 shape shown

in Fig. 76.

ivJiicli Jtse

or evolve bromine.

a glass tube about 30 cm. long into the

The

lower end passes through the hole of a

rubber stopper which should tightly

ht

Put

five

forms,

Perform

fit

a large test tube.

or six crystals of potassium bromide in the test

add an equal quantity of manganese dioxide and Insert the stopper and tube securely, and boil gently. Do not hold the test

tube,

10 cc. of dilute sulphuric acid.

its

tube in the band, but use the test tube holder.

fumes soon appear

in the test

Brown

tube and pass out of the

delivery tube.

Regulate the heating so that this vapor condense and collect in the lower bend of the delivery tube. Both vapor and liquid are bromine. When no further boiling produces bromine vapor in the test tube, pour the bromine into a bottle of water. Observe and record the physical properties of this bromine, especially will

—

Fig. 76. Apparatus for

preparing

the color, solubility in water, specific gravity, volatility,

bromine.

and physical

state.

Try the action of the contents 250

of

Bromine, Iodine, and Hydrofluoric Acid.

251

if the action is not marked, push the paper Determine the odor by smelling cautiously As soon as these observations have been of the water in the bottle. made, pour the contents of the bottle into the sink and flush with Wash the test tube free from water, or pour into a jar in the hood.

the bottle on litmus paper

down near

all

;

the bromine.

none on the hands.

traces of bromine, taking care to get

Answer the following

:

—

How

other elements previously

ll. simplest equation for the reaction in the preparation

bromine

KBr +

2

is

—

H2SO4+ Mn02=

Br^

+ MnS04 + K2SO4 + 2 H2O

Bromine Manganese Potassium

Potassium

+

+

^7

=160+

w w

196

151

^^^^

Sulphate

Sulphate

Bromide

238

all

em

2

essentially different from

4a

The of

is it

?

.c h

2.

studied

In

?

vn

1. In what ways does bromine physically resemble chlorins what ways does it differ from chlorine ?

+

174

+

36

w

PREPARATION AND PROPERTIES OF HYDROBROMIC ACID.

Experiment 120.

The

white product

properties

paper. lar

— Put three or four crystals of potassium bromide

a test tube, and add a few drops of concentrated sulphuric acid.

ht

in

experiment in the hood.

this

tp ://

Perform

is

hydrobromic acid. Observe Test the gas with both

— cautiously.

Does

enough

this

to

its

.most apparent

kinds of litmus

product resemble hydrochloric acid ? Are they simiGive any evidence of a secondary ?

be closely related

reaction.

Since 2 NaCl

+ H.SO^ =

2

HCl + Na.SO^

preparation of hydrochloric acid, what tion of

hydrobromic acid

is

the equation for the

?

Hydrobromic acid forms bromides, acid forms chlorides.

is

the equation for the prepara-

just as hydrochloric

Experimental Chemistry.

252

PROPERTIES OF POTASSIUM BROMIDE.

— Examine a crystal of potassium bromide.

Experiment 121. color,

Com-

with potassium or sodium chloride in regard to crystal form,

it

and

Add

solubility in water.

a few drops of silver nitrate solution to potassium bromide so-

product soluble in dilute

Is the solid

lution.

Compare

Do

rides.

ammonium hydroxide

?

and chlo-

the interaction with the interaction of silver nitrate

vn

pare

the properties of bromides, typified by potassium bromide, ?

4a

ll.

suggest any marked relation to chlorides

PREPARATION AND PROPERTIES OF IODINE.

— Mix

em

and grind together in a mortar three or and an equal quantity of manganese Put the mixture in a 250 cc. Erlenmeyer flask, dioxide. add about 8 cc. of water, and about 5 cc. of concentrated Invert a dry funnel upon sulphuric acid, drop by drop. the flask, as shown in Fig. 'j'js and stand the flask on a sand bath. Heat with a low, steady flame. Too much

Experiment 122.

w w

.c h

four crystals of potassium iodide

heat will vaporize the water, or crack the flask

The vapor

w

both.

of iodine will

fill

— perhaps

the flask, and crystals

tp ://

of iodine will collect on the sides of the funnel.

heat so that the flask

late the

so that

little

is

filled

Regu-

with vapor, but

or none escapes from the funnel.

If

vapor

ht

escapes from the funnel, plug the stem with cotton or soft paper.

— Ap-

Fig. 77. paratus

for

preparing

If

Continue to heat until no more iodine sufficient iodine

iodine.

crystals of iodine collect

on the upper

portions of the flask, a gentle heat will remove them. is

evolved, or until

has been collected for the subsequent

experiments. Scrape the crystals into a dish. Observe and record the physical properties of iodine, especially the color of the Heat a solid and of the vapor, volatility, and odor (cautiously). crystal in a dry test tube, and when the tube is half full of vapor invert it.

What

vapor

?

does the result show about the specific gravity of iodine

Touch a

Will water remove iodide

?

What do

crystal with the finger. it ?

Will alcohol

these results

Preserve the crystals.

?

What

color

is

the stain

?

Will a solution of potassium

show about

the solubility of iodine

?

Bromine, Iodine, and Hydrofluoric Acid. Answer

the following

:

253

—

In what ways does iodine resemble chlorine and bromine?

1.

what ways does

How

2.

studied

it

does

differ

it

from them

differ essentially

In

?

from

all

other elements previously

?

The

simplest equation for the chemical action in the

preparation of iodine

—

is

vn

2KI + 2H2S04+Mn02=l2+MnS04+K.^S04-r2H20 Potassium

+

=254-1-151

8y

174

THE CARBON BISULPHIDE TEST FOR

— Carbon

bisulphide

.c h

Precaution.

+

4a

+

196

em

+

332

(26)

ll.

Iodine

Iodide

is

36

IODINE.

iiiflamuiable.

It

should not be nsed near flames.

— {a)

Free

w w

Experiment 123.

iodine.

Add

tal

a few drops of carbon

made by

bisulphide to a very dilute solution of iodine,

dissolving a crys-

of iodine in a solution of potassium iodide or in alcohol,

w

the color of the carbon bisulphide, which, being

tp ://

water, will sink to the bottom of the test tube.

the color of iodine vapor {b)

Combined

iodine.

much

How

and observe heavier than

does

it

resemble

?

Add

a few drops of carbon bisulphide to a Is there

positive evidence

ht

very dilute solution of potassium iodide.

Now

add a few drops of chlorine water (see App. C, Reagents), and shake. How does this result compare with the final

of iodine

?

result in (a)

from

its

?

The

result is

due to the

compounds, and the

fact that chlorine liberates iodine

iodine, being free, forms the characteristic

color.

THE STARCH TEST FOR Experiment 124.

— Grind

a

gram

IODINE.

of starch in a mortar with a

little

Pour this into about 100 cc. of boiling Allow it to cool, or cool it by holding water, and stir the hot liquid. the vessel in a stream of cold water, and then decant the clear liquid. water to creamy consistency.

Use

this starch solution to test for iodine.

Experimental Chemistry.

254

Add

(a) F7'ee iodine.

a few cubic centimeters of the starch solution

and then add a few drops of a soluis due to the presence of a compound which is always formed under these circumstances, but the composition of which is unknown. If the color is black, pour out half of the liquid and add more water, or pour some of the liquid into a to a test tube nearly

tion of iodine.

full

of water,

The deep

blue color

vessel of water. {b)

Add

Co7nbi7ied iodine.

a few cubic centimeters of the starch

pare with theJinal result

The

—

the blue

in

facts revealed

Exp. 123

com-

Com-

(]>).

by Exp. 124 are

practically utilized

em

in

Is

a few drops of chlorine water and shake.

ll.

Add

4a

pound formed.?

vn

solution to a very dilute solution of potassium iodide.

.c h

THE DETECTION OF STARCH,

— Test

Experiment 125.

the following for starch by grinding a

small portion of each with water in a mortar, and then adding a

few

w w

drops of the extract to an exceedingly dilute solution of iodine {a) wheat flour, {]?) oatmeal, {c) potato, {d^ rice, (^) beans, (/) bread, :

tp ://

w

{g) cracker, (//) pepper, (/) baking powder. Use, if possible, about the same amount in each case, and the results will then be an approximation of the relative amount of starch. Tabulate the results.

If the starch is

detected in

{Ji)

and

(/),

give a reason

ht

for its presence.

PREPARATION AND PROPERTIES OF HVDRIODIC ACID.

—

Experiment 126. Put three or four crystals of potassium iodide tube and add a few drops of concentrated sulphuric acid. Fumes of hydriodic acid are formed among other products. Observe

in a test^

the most obvious properties of these fumes as in Exp. 120, and compare with the fumes of hydrochloric and hydrobromic acids. Are the acids similar?

Record the evidence of secondary reactions in this experiment. If nothing but hydriodic acid were formed, what would be the simplest equation? Why would this method be impracticable for the prepara* tion of hydriodic agid

on a large scalQ ?

Bromine, Iodine, and Hydrofluoric Acid. acid forms bromides. and chlorides

Hydriodic

255

which correspond

iodides,

to

PROPERTIES OF POTASSIUM IODIDE. Experiment 127. pare

it

— Examine

a crystal of potassium iodide.

Com-

with potassium cliloride and potassium bromide in regard to

crystal form, color,

and

solubility in water.

a few drops of silver nitrate solution to potassium iodide solution. Compare the precipitate with the one obtained in the case of chlorides

vn

Add

4a

ll.

and of bromides. Test its solubility in dilute ammonium hydroxide. Does potassium iodide exhibit any marked resemblance to polassiun: chloride and potassium bromide?

1.

Additional study of bromine.

.c h

(a) Occurrence.

XL.

em

CLASS-ROOM EXERCISE.

(d)

Sources of commercial bromine.

(<:)

Industrial preparation.

(d)

Summary

(e)

Additional properties.

w w

of properties experimentally observed.

Additional study of iodine.

tp ://

2.

w

(/) Preparation and properties of bromine water. (g) Uses. (a) Occurrence.

(d) Industrial jDreparation from

Summary

seaweed and from Chili

(d) Additional properties.

(e)

Vapor

(/) Solubility and color of various solutions.

3.

saltpeter.

of properties experimentally observed.

ht

(c)

density.

(g) Uses.

Historical.

(a) Discovery of bromine by Balard. (d) Contributions of Courtois,

Liebig's blunder.

Davy, and Gay-Lussac to the

discovery of iodine. 4.

Prepare a table showing the relation between chlorine, bromine, The table should include the atomic weight, physical state,

and iodine.

color, typical 5.

method ofpreparation.properties.and analogous compounds. o' hydrochloric, hydrobromic, and hydri-

Tabulate the properties

odic acids.

Experimental Chemistry.

2^6 What

6.

chemical properties are possessed in

common by

chlorine,

bromine, and iodine? Miscellaneous.

7.

" drug store iodine "? Exp. 124 utilized in chemical analysis? print? {c) What is a " bromide (^ ) What is iodoform, and for what is it used ? (e) Meaning and significance of the terms " halogen," " haloid," and "hahde."

(«)

What

(b)

How

is

is

The

Stassfurt Deposits."

PROBLEMS.

The

2.

What

138.7° F.

?

specific gravity of

bromine

is

its

boiling point

What volume

is 3.

.c h

occupy ?

4a

boils at

XXIV.

em

Bromine

1.

centigrade scale

ll.

Prepare a short essay on "

8.

vn

'"'

on the

does a pound

Calculate the percentage composition of

3.

w w

{a) Potassium bromide.

{d) Hydrobromic acid. Hydriodic acid.

(^b)

Potassium iodide.

(
{c)

Silver bromide.

(/) Iodoform, CHIo.

Marignac found that 3.946 gm. of silver dissolved in pure nitric gm. of potassium bromide. What is

w

4.

tp ://

acid were precipitated by 4.353 the atomic weight of bromine?

Iodine vapor

5.

is

(Assume

K=

8.716 times heavier than

39.) air.

What

is

its

molec-

ht

ular weight ?

How much

6.

potassium iodide

is

necessary to prepare 63.5 gm. of

iodine?

How much

7.

by all the gm. of pure manganese dioxide with (Equation is 2 KI + MnO^ + 4 HCl = Ig + MnClg

iodine

is

liberated from potassium iodide

chlorine obtained by boiling 6

hydrochloric acid?

+

2

KCl +

8.

2 H2O.)

How much

potassium bromide

is

necessary to prepare 10 gm. of

bromine ?

The Element Fluorine

is

not adapted to examination in

the laboratory on account of acid,

however,

may be

studied,

its

corrosive properties.

if it is

Its

prepared with caution.

Bromine, Iodine, and Hydrofluoric Acid.

257

PREPARATION AND PROPERTIES OF HYDROFLUORIC ACID. poison. — Hydrofluoric acid gas a gas — conwtercial hydrofluoric of

An

the

aqueous solution

acid

— burns

the flesh frigh tfully.

Experiment 128. dipping

—Warm

into hot water or

it

corrosive

is

Precaution.

a glass plate about

by standing

it

near a

liable to crack.

Coat surface

4a

The

ll.

one surface with beeswax or paraffine.

should be uniformly covthin

layer.

letters, figures,

em

a

with

Scratch

or

a diagram through the wax with a pointed instrument.

Fig. 78.

Be

—a

lead dish.

sure the instrument removes the

.c h

ered

by

object, such as

vn

a radiator or drying oven. If it is held over a flame it is

10 cm. square

warm

wax

tp ://

w

w w

through to the glass, and that the lines are not too fine. just Put 5 gm. of calcium fluoride in a lead dish (Fig. 78), and add enough concentrated sulphuric acid to form a thin paste. Stir the upon mixture with a file or nail. Place the glass plate, wax side down, the lead dish and stand the whole

Fluorine. s

a

ht

M

6.

o

i

s

18

—

8

n.

Glass plate etched by Fig. 79. hydrofluoric acid gas.

apparatus in the hood for several hours, Reor until some convenient time.

Scrape the contents the plate. of the dish, immediately, into a waste jar in the hood, and wash the dish free

move

Most of the wax can be from acid. scraped from the glass plate with a The last portions can be reknife.

moved by rubbing

with a cloth moist-

If ened with alcohol or turpentine. nails time permits, the wax can be removed by supporting the plate on Do not minutes. in a dish of water and boiling the water for a few If the experiment has attempt to melt off the wax over the flame.

been properly performed, the plate will be etched where the glass Figure 79 shows an was exposed to the hydrofluoric acid gasetched plate.

Experimental Chemistry.

258

The are

—

simplest equations for the two reactions in Exp. 128

r^F. CaF2

-4-

R.^n

^

o

RF

_L.

^Q^r (27)

—

7^

+

98

=40+136

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

and

Bromine, Iodine, and Hydrofluoric Acid. PROBLEMS. .

I

.

What

is

259

XXV.

the percentage composition of

CaF2 ? Na^AlFg

(a) Fkiorspar, (^)

Cryolite,

?

2. If 100 gm. of fluorspar are heated with sulphuric acid, calcium sulphate and hydrofluoric acid are formed ?

If

is

fluoride

yield

the atomic weight of fluorine

174.5 ?

parts of calcium

(Assume CaFg and

40.)

ht

tp ://

w

w w

.c h

em

4a

ll.

Ca =

100 parts of calcium

what

vn

3.

sulphate,

how much

CHAPTER

XVI.

SULPHUR AND ITS COMPOUNDS. is

one of the most important of the non-metallic

vn

Sulphur elements.

— (a)

Examine

a piece of roll sulphur

4a

Experiment I2g.

ll.

PHYSICAL PROPERTIES OF SULPHUR.

and write

half

— and note the increase in the volume of water.

volume

is

—

This increase

Calculate the specific

equal to the volume of the sulphur.

.c h

in

full

em

a short account of its most obvious physical properties. Slip it carefully (d) Weigh a lump of roll sulphur to a decigram. about into a graduate previously filled with water to a known point

gravity of sulphur from the observed data.

w w

AMORPHOUS SULPHUR.

— Put a few pieces

sulphur in an old test and then quickly pour the This is amorphous contents of the test tube into a dish of cold water. Note its properties. Preserve, and examine it after twentysulphur.

Experiment 130. Heat carefully

of

roll

until the sulphur boils,

tp ://

w

tube.

four hours.

Describe the change,

if

any.

it

by

this

experiment.

ht

Define amorphous, and illustrate

it

Sulphur exists not only as the amorphous variet}^, but crystallizes under favorable conditions in two distinct

crystal systems.

CRYSTALLIZED SULPHUR. Experiment 131. nearly all

full

— (a)

of roll sulphur.

the sulphur

is

melted.

Monoclinic.

Fill

a small Hessian crucible

Support the crucible Let

it

cool,

in

a ring, and heat until

and the instant

crystals shoot

out from the walls just below the surface, pour the remaining melted

sulphur into a dish of cold water.

When

the crucible can be handled

The contents should open lengthwise. resemble the conventional sketch of a typical mass of crystals shown in Fig. 80. Observe and record the properties of the crystals, especially

without discomfort, crack

it

260

Sulphur and

Its

Compounds.

261

the shape, size, color, kister, l)rittlcncss or elasticity, and any other characteristic property. for a

day or two

;

Allow the best

crystals to

remain undisturbed

then reexamine, and record

any marked changes. {b)

Orthorho7nbic.

of sulphur in a test tube of carbon disulphide

Put 3 gm. of flowers and add about 5 cc.

— remember the precau-

tion to be observed in using this liquid (see

Exp. 123).

wShake until

all

the sulphur

is

a small dish to crystalHze.

It

vn

dissolved, then pour the clear solution into

advisable,

is

tion toward the end, and,

form, remove .

crystalliza-

them with the forceps

Allow the liquid

ble

— Section of a showing

crystals of sulphur.

(see

to evaporate almost entirely, then

Examine them

cruci-

monoclinic

as in {a)

and record

remove and

their properties.

ht

tp ://

w

w w

dry the crystals.

Fig. 80.

perfect crystals

.c h

Fig. 81)

if

the

4a

Watch

em

quickly removed.

ll.

though not absolutely necessary, to stand the dish in the hood, where there is no flame and where the offensive vapor will be

{c)

{d)

Fig. 81.

— Orthorhombic crystals of sulphur.

Tabulate the essential result$"in {a) and {U). Make an outline sketch of a crystal of orthorhombic sulphur.

Sulphur combines with both non-metals and metals, and forms sidphidcs in most cases.

COMBINING POWER OF SULPHUR. Experiment 132.

— {d)

Set

fire

to a

little

spoon, and lower the spoon into a bottle.

sulphur in a deflagrating

Caiitioiisly waft the

fumes

Experimental Chemistry.

262

toward the nose, and observe and dcscril)e the odor. The product is a compound of sulphur. From what has already been shown experimentally about comi)ustion, state the components of the fumes. (d)

gm. of flowers of sulphur with 3 gm. of iron powder or and heat half of the mixture in an old test tube. As there is decided evidence of chemical action, remove the test

Mix

clean iron

3

filings,

soon as When the tube has cooled, break tlie end by tube from the flame. rapping it sharply on a hard surface. Examine the contents. What the evidence of the formation of a

to the

new compound

?

V^erify the

dilute hydrochloric acid to the product

remainder of the original mixture, testing the gaseous

ll.

and then

little

vn

is

conclusion by adding a

4a

product in each case by the odor. Summarize the evidence regarding the power of sulpliur to combine

em

with iron.

Similar results are obtained with copper and other metals.

Draw

a

.c h

general conclusion regarding the combining power of sulphur.

CLASS-ROOM EXERCISE.

w w

Additicnal study of sulphur. (a)

Occurrence of

(d)

Occurrence of combined sulphur.

(c)

Theories of the volcanic and the organic formation of

free sulphur.

w

1.

XLII.

tp ://

sulphur.

(^) Extraction of sulphur from native sulphur. Other sources of sulphur. (
ht

(/) Purification.

2.

(^)

What

(//)

Additional properties,

(/)

Illustrate allotropy

is

roll

sulphur

?

Brimstone

?

Flowers of sulphur

?

e.g. solubility.

by means of sulphur.

(/) What is milk of sulphur Miscellaneous.

?

(k)

Uses.

(d)

Review of the orthorhombic and monoclinic systems of crystallization. (See class-koom kxercise. vii., 7 (^/).) Illustrate the term amorphous by sulphur.

ic)

What

(^/)

In what crystal form does free crystallized sulphur occur

(a)

part has sulphur played in the history of chemistry

—

?

?

An important compound of sulHydrogen Sulphide. phur is the gas, hydrogen sulphide. It is formed in many

Sulphur and chemical changes,

it

Its

It is

263

possesses characteristic properties,

it

an indispensable laboratory a poisonous gas, and should never be lib-

forms many compounds, and reagent.

Compounds.

is

erated in the laboratory.

PREPARATION AND PROPERTIES OF HYDROGEN SULPHIDE. Perform

this experiment in the hood,

and do

not inJiale

the gas.

rubber connector

C

being joined to

Fill

B

by the

the test tube one-third

.c h

of coarsely powdered ferrous sulphide, cover

w w

full

a.

em

in Fig. 54, the tube

4a

ll.

vn

Experiment 133.— Construct a generator like that shown in Fig. 82. The test tube A is clamped to an iron stand at such a height that the end of C reaches to the bottom of a bottle in which the gas is collected by downward disB placement and the solution subsequently prepared. The essential part of the apparatus is also shown

ht

tp ://

w

\^

Fig. 83.

— Perforated card to prevent the

diffusion of

hydrogen sulphide gas.

with dilute hydrochloric acid, and quickly insert Hydrogen sulphide gas is rapidly the stopper. evolved.

DiiTusion of the gas

maybe

prevented

^^^

82.

— Apparatus

generating hydrogen sulphide gas.

for

by covering the bottle with the block of wood used in the collection of chlorine, or with a piece of stiff paper

shown

in

Fig 83, and cut along the

line

ab to allow

it

shaped as

to be slipped

Experimental Chemistry.

264 easily

upon the delivery

Collect three small bottles, removing

tube.

each, and covering with a glass plate as soon as

warm

of gas stops or slackens,

If the evolution

full.

gently or add more hydrochloric acid.

After the bottles of gas have been collected, allow the gas from the

Hydrogen generator to bubble through a bottle half full of water. sulphide water will be formed, which should be preserved in a stoppered bottle for future use

more convenient,

or, if

;

may be poured

it

into the stock bottle.

is

(d) Test the gas from the

paper. (c)

Is

it

vn

hydrogen sulphide, and

characteristic of

the gas color

acid or alkaline

?

is

bottle with both kinds of litmus

same

?

—

ll.

This

Has

test.

:

toward the nose, and then

//Ule of the gas cautiously

describe the odor.

a decisive

hydrogen sulphide gas as follows

test the

Waft a

4a

(a)

em

Meanwhile

Bring a lighted match to the mouth of a bottle. Observe the Observe cautiously

properties of the flame as in previous experiments.

.c h

the odor of the product of the burned gas

;

to

what compound

is

the

What, then, is one component of hydrogen sulphide ? odor due (d) Burn another bottle of hydrogen sulphide and hold a cold botWhat additional experimental evidence does tle over the burning gas. this result give regarding the composition of hydrogen sulphide ?

w

w w

.'*

1

tp ://

LABORATORY EXERCISE.

Summarize the properties of hydrogen sulphide and the experi-

mental evidence of

phide:—

The

composition.

2H,S

+

for

the

O

=

combustion of hydrogen 2

SO.

sul-

+

simplest equation for the preparation of hydrogen

sulphide gas

is

FeS

—

+

2HCI

=

H^S

+

FeCl^

Ferrous

Hydrogen

Ferrous

Sulphide

Sulphide

Chloride

88

A

its

Complete the equation

ht

2.

XXI.

-I-

73

=

34

+

127

dry hydrogen sulphide gas under standard conditions weighs 1.542 gm. liter of

Sulphur and Sulphides.

Its

— Hydrogen

Compounds.

sulphide

a

is

26^

weak

acid

and

forms salts called sulphides. Many of these sulphides have characteristic colors and they vary in solubility, hence they are easily detected and separated. They are readily formed by adding to solutions of compounds of metals a usually called hydrosolution of hydrogen sulphide gas, or by passing the gas through the gen sulphide water, the moist gas itself acts immediately solution of the metal

—

— ;

vn

on some metals.

— (a)

134.

Shake the

bottle

of

hydrogen sulphide

4a

Experiment

ll.

PREPARATION AND PROPERTIES OF SOME SULPHIDES.

em

water prepared in Exp. 133 (or a similar solution), and Hold successively at the mouth or in the neck of the bottle (i) a clean copper wire or piece of sheet copper, (2) a bright strip of lead, and (3) an un-

These com-

Describe the result in each case.

.c h

tarnished silver coin.

pounds are sulphides of the respective metals. Put a gram of litharge

a test tube, cover

it

— the

Describe and explain the change. Complete the equation

—

w

:

+

H.S

The formula of pure

=

H.O

warm

litharge

— in

gently. is

PbO.

+

tp ://

PbO

(c)

brownish-yellow oxide of lead

with hydrogen sulphide water, and

w w

(d)

Prepare the following solutions in separate

test tubes

:

—

(i) Dissolve a small crystal of lead nitrate in water.

a minute quantity of arsenic trioxide in dilute hydro-

ht

(2) Boil

chloric acid.

(3) Dissolve a minute quantity of tartar emetic in water.

the metal antimony (4)

—a

compoimd

of

—

Dissolve a small crystal of zinc sulphate in water.

All the above solutions are poisonous.

about half

full.

Add

about one-fourth

its

The

water to each solution, and shake thoroughly. each sulphide, and tabulate the

The varying

test

tubes should be

bulk of hydrogen sulphide

Observe the color

results.

solubility of sulphides permits

—

of

266

Experimental Chemistry.

THE SEPARATION OF SULPHIDES. Experiment 135.

— Mix

equal

quantities

of

solutions

dilute

of

and (3) sodium chloride. Add dilute hydrochloric acid. Pass hydrogen sulphide gas through the mixture (use the same generator as in Exp. 133), or add considerable hydrogen sulphide water. In either case, warm gently, allow the precipitate to settle, and then add a few drops of hydrogen sulphide water (i) copper sulphate, (2) ferrous sulphate,

complete precipitation.

precipitation

If

is

not complete,

vn

to ensure

(i) Precipitate.

Proceed as follows

:

—

em

three parts to test.

4a

ll.

add more hydrogen sulphide water, and proceed as above. If complete, decant the clear liquid into a clean vessel by pouring it down a glass rod, and save it for subsequent examination. Add dilute hydrochloric acid to the precipitate, warm gently, and filter. There are now Stand the funnel

in a clean test tube,

with a pointed glass rod in the apex of the

filter

.c h

precipitate into the test tube with dilute nitric acid

down

upon the

a glass rod directly

solid.

Use

as

make a

paper, and

hole

wash the

by pouring the acid

little

acid as possible.

and then add considerable ammonium hydroxide. The solution should become a distinct blue, which is evidence that a copper compound is present. Had an iron compound been present, the result would be entirely different. Add ammonium hydroxide to the filtrate, and a black (2) Filtrate. precipitate will be formed. This is iron sulphide. Dissolve it in hydrochloric acid, add a few drops of nitric acid, boil, and then add is

dissolved,

tp ://

w

w w

Boil until the black precipitate

ammonium

hydroxide.

A

rusty-red precipitate of ferric h3droxide

the

ht

formed, showing that an iron

compound was

is

the main constituent of

filtrate.

(3)

Clear liquid.

Filter, if this

liquid

is

not free from particles.

Apply the flame test for sodium to this liquid. Summarize the results of the whole experiment.

The above experiment method

of separation

illustrates

and detection

briefly

of

the

general

metals employed

Sulphides are not the only compounds, however, which permit systematic separation.

in Qualitative Analysis.

A

more

explicit

treatment of this subject will be found in

Chapter XIX., page 322.

Sulphur and

Compounds.

Its

CLASS-ROOM EXERCISE. 1

267

XLIII.

Additional study of hydrogen sulphide. (a)

History.

(i>)

Names and

(c)

Occurrence.

their significance.

(d) Properties not experimentally shown. Uses.

(e)

Sulphides. (a)

Natural sulphides.

(d)

Exact name and color of sulphides of arsenic, antimony,

(c)

Why

vn

2.

ll.

zinc, lead.

does a silver spoon blacken in mustard?

{e)

Why Why

(/)

Name and

?

does silverware blacken?

formula of cinnabar, stibnite, copper pyrites,

and pyrite. Composition of hydrogen sulphide gas.

.c h

3.

does white paint often turn brown or black

In a

em

{d)

4a

cooked egg?

w w

(i) If a spiral of platinum wire is heated in a bottle of hydrogen sulphide gas, a yellow powder and an invisible gas are formed the powder burns with a pale blue flame, producing a choking vapor, and the invisible gas burns with a colorless, hot flame. W^iat evidence do these

w

facts present

;

about the composition of hydrogen sulphide?

tp ://

(2) Sulphur is often deposited in bottles of hydrogen sulphide water. Chlorine passed into hydrogen sulphide forms sulphur and

What do

hydrochloric acid.

ht

hydrogen sulphide ? (3) Give additional

these facts

evidence of

show about

the

the composition of

composition

of

hydrogen

sulphide.

PROBLEMS. XXVI. 1.

How much

diameter weigh 2.

does a stick of brimstone

Dumas heated

3.

m. long and 4 cm. in

10.000 grains of silver in sulphur vapor and obtained

1^481.5 grams of silver sulphide. phur?-

i

?

What

is

the atomic weight of sul-

(Assume Ag = 108, and Ag,, + S = Ag.,S.) How many grams of sulphur can be obtained from 600

hydrogen sulphide gas ?

cc.

of

Experimental Chemistry.

268

How many grams

4.

of ferrous sulphide are necessary to yield a

liter

of hydrogen sulphide gas? 5.

Calculate the percentage composition of (a) Galena, PbS. (d)

6.

What

Iron pyrites, FeSg.

(c)

(d) Ferrous sulphide, FeS.

Zinc blende, ZnS.

weight and what volume of hydrogen can be obtained from

vn

102 gm. of hydrogen sulphide?

The two oxides of Sulphur, sulphur dioxide ana sulphur and their related acids, are the most important compounds of sulphur.

4a

ll.

trioxide,

Perform

experiment in the hood.

— Construct

a generator like that

.c h

Experiment 136.

this

em

PREPARATION AND PROPERTIES OF SULPHUR DIOXIDE.

shown

in Fig.

tube should be clamped high enough to be conveniently heated with a free flame and the delivery tube must be long enough Put a few grams of copto reach to the bottom of an empty bottle. per borings in the test tube, cover with concentrated sulphuric acid,

The

test

w w

82.

tp ://

w

and arrange the apparatus to collect a gas as in Exp. 133. Heat gently with a low flame, and sulphur dioxide gas is evolved. As the reaction proceeds, the evolution of gas

may become

violent.

Remove

the flame

gas

slow and

at intervals, regulating the heat so that the evolution of

steady.

Remember

hot

that

sulphuric

acid

is

is

a dangerous liquid.

ht

Collect four small bottles of gas, covering each with, a glass plate as

soon as full. Then remove the stand with its attached generator to Study the sulthe hood or some place where it will not be disturbed. phur dioxide gas as follows :

—

{a) Observe the most obvious physical properties,

e.g.

co

or,

odor

(cautiously), specific gravity.

the same gas as was formed in Exp. 132

{b)

Prove that

{c)

Hold a blazing

it is

(
Will the gas burn previously acquired facts would have

stick in a bottle of the gas.

What

or support combustion?

enabled you to predict this result?

{d) Pour 10 or 15

cc.

of water into a bottle of sulphur dioxide, cover What is the evidence of solution? Is the

with the hand, and shake.

resulting liquid acid, alkaline, or neutral?

Sulphur and

269

Moisten a pink or purple flower with a few drops of water, hang remaining bottle of sulphur dioxide, holding it in place by putting

{e) it

Compounds.

Its

in the

the stem between the glass and a cork.

Observe and describe any slow or indefinite, stand a deflagrating spoon containing burning sulphur in the bottle for a minute or two. What is this operation called?

change

If the action is

in the color of the flower.

LABORATORY EXERCISE. as far as the sulphur

What

is

is

concerned.

the function of the sulphur in a burning match?

ll.

2.

XXII.

Light a sulphur match and observe and describe the entire action,

vn

1.

4a

Sulphurous Acid is formed when sulphur dioxide disSulphur dioxide is, therefore, sulphurous

solves in water.

The

simplest equation expressing this fact

SO2

is

—

em

anhydride.

+ H2O = H2SO3

.c h

Sulphurous

an unstable acid, and gradually forms sulphuric by combining with oxygen from the air. Its salts

— yield

sulphur dioxide

w

the sulphites

—

w w

It is

acid

Acid

acids.

CLASS-ROOM EXERCISE.

treated with

XLIV.

tp ://

I.

when

Additional study of sulphur dioxide.

Occurrence.

ht

{a) (J?)

Additional properties,

{c)

Relation to combustion.

e.g. solubility, specific gravity.

{d) Explanation of bleaching power. {e)

Liquid sulphur dioxide."'

{/) Composition and formula.

Sulphur Trioxide, SO3, is formed when a mixture of sulphur dioxide and oxygen is passed over heated platinized The It is the anhydride of sulphuric acid. asbestos. equation expressing the latter fact

is

—

SO3 + H2O = H2SO4

Experimental Chemistry.

270

Sulphuric acid has not, until recently, been industrially prepared in this way. Its preparation is not well adapted the laboratory, but

to

may be

properties

its

profitably

studied.

ACTION OF SULPHURIC ACID WITH WATER.

—

ll.

vn

Experiment 137. Recall or repeat that part of Exp. 36 which shows the action of sulphuric acid with water. Record the result.

4a

This experiment illustrates the necessity of always addto the zvatcr. The most obvious result is due to the formation of a compound of sulphuric acid and

The experiment

water.

em

ing the acid

which decomhydrogen and oxygen in

also proves the avidity with

This

affinity often

.c h

sulphuric acid unites with water.

poses compounds which contg.in

w w

the proportion to form water.

ACTION OF SULPHURIC ACID WITH ORGANIC MATTER.

— {a)

w

Experiment

138.

Write some

letters or

tp ://

sulphuric acid on a sheet of white paper, and

move

figures with

dilute

the paper back and

forth over a low flame, taking care not to set fire to the paper.

As

the

water evaporates the dilute acid becomes concentrated.

ht

Observe and describe the result. Paper is largely a compound of carbon, hydrogen, and oxygen, and the hydrogen and oxygen are present in the proportion to form water. Explain the general chemical change in this experiment. {b)

Dissolve 3 or 4 gm. of sugar in a test tube half

of

full

warm

and add cautiously several drops there is no decided result, add more

water, stand the test tube in the rack,

of concentrated sulphuric acid. acid.

What

is

obtained in Exp. 82 {b).

experiment?

If

the black product? Is

Compare the

final result

with that

the chemical action the same in each

Are the statements made

in {a)

about paper also true of

sugar ? {c)

Repeat

the result.

{b)^

using powdered starch instead of sugar.

How does

the result resemble that in

Predict the components of starch. diction be verified?

(Jb)

In what simple

and

in

Describe Exp. 82 {a) ?

way may

the pre-

Compounds.

271

(d) Stand a stick of wood in a test tube one-fourth Allow it to remain in the acid for

fifteen minutes,

Sulphur and

Its

trated sulphuric acid.

then remove the stick and wash off the acid.

Does

it

resemble that in (a), {b), and

{c),

and

LABORATORY EXERCISE. 1. Can sulphuric acid be used ammonia gas? Why?

of concen-

Describe the change.

Exp. 82 {a)

in

?

XXIII.

Can

to dry gases?

What

full

it

be used to dry

experiment proves this?

Is sulphuric acid volatile?

W^hat happens when concentrated sulphuric acid

vn

2. 3.

is

exposed to

ll.

moist air? 4. Determine the measured volume (25

specific gravity of sulphuric acid

by weighing a

Compare the

result with the

specific gravity of the

commercial

4a

cc.) in a graduate.

em

acid.

TEST FOR SULPHURIC ACID.

—

.c h

Devise a test for sulphuric acid. Verify it. Is Experiment 139. the same test applicable to soluble sulphates ? Devise, or find in a textbook, a test for sulphates almost insoluble in sulphite?

Is

How

it.

barium sulphate absolutely insoluble

w

CLASS-ROOM EXERCISE.

(«) Complete account of

its

a

in all reagents?

XLV.

industrial preparation.

(b)

Properties not experimentally found.

{c)

Uses.

{d) History.

ht {e)

2.

calcium sul-

Additional study of sulphuric acid.

tp ://

1

w^ater, e.g.

can a sulphate be distinguished from

w w

Verify

phate.

Significance of the term oil of vitriol.

Miscellaneous. {a) Explain and illustrate the^ statement, "sulphurous and sul-

phuric acid are dibasic." {b) (c)

Valence of sulphur in H,S, SO,, SO,, H.SO,, H,SO,. Give the chemical name and formula of gypsum, heavy spar, plaster of Paris, white vitriol, blue stone, green vitriol, Glauber's

salt, kieserite.

{d) Illustrate the Periodic

Law by

sulphur, selenium, and

tel-

lurium. {e)

What the

is

''hypo"?

latter.

What

is

sodium thiosulphate?

Use

of

Experimental Chemistry.

272

PROBLEMS. XXVII. 1.

What volume

of air

is

necessary to burn 1000 gm. of sulphur?

2.

How many

3.

Calculate the percentage composition of

grams of sulphur can be obtained from a sulphuric acid? (Assume the commercial density.)

Copper sulphate.

(d) Sodium sulphate.

Chamber

(/*)

Nordhausen

crystals,

1

SO..NO0.HO.

ht

tp ://

w

w w

.c h

em

acid, H^S^O;.

4a

{e)

ll.

Zinc sulphate.

(c)

vn

(a) Barium sulphate. {b)

liter of

CHAPTER

AND PHOSPHORUS AND THEIR COMPOUNDS.— REVIEW.

vn

SILICON

XVII.

Silicon does not occur in the free the

but

distributed.

earth's

crust

is

4a

mately one-fourth of

state,

ll.

pounds are abundant and widely

its

com-

Approxi-

silicon.

Its

.c h

em

most important compound is silicon dioxide, Si02, which is familiar as sand and quartz. The properties of some compounds of silicon are shown by the

— a porcelain or platinum crucible half — sodium carbonate (4 parts) and potassium carbonate

140.

Fill

full of

tp ://

w

Experiment a fusion mixture

w w

RELATION OF SILICON DIOXIDE TO OTHER COMPOUNDS OF SILICON,

Support the crucible on a tripod, or a triangle, and heat (5 parts). gently, until the fusion mixture is melted. Then add a pinch of clean, exceedingly fine sand, and heat with the hottest available flame

lamp flame, if possible. time to time, and finally heat suspended in the molten mass.

ht

blast

—a

Add

three or four pinches of sand from

until

no particles of sand can be seen heat must be intense and steadily

The

no undue frothing. Cool the cruand then place it in a beaker or casserole cover with water and boil gently until the mass is detached. Remove the crucible, and heat until the residue is dissolved. Filter, it the solution contains any sand. Add dilute hydrochloric acid slowly to

applied, but so regulated that there cible gradually, especially if

it is

is-

porcelain,

;

the clear liquid until the carbonates are decomposed. precipitate

the result.

is

siHcic acid.

Rub some between

The

gelatinous

the fingers and describe

Evaporate the precipitate to dryness upon a water bath

porcelain dish, or casserole, in the hood.

273

As

the mass hardens,

in a

stir it

Experimental Chemistry.

274

Toward

with a glass rod.

more

the end, add

liydrochloric acid

and

Then stand the dish on a gauze-covered The residue is silicon dioxide tripod and heat strongly for live minutes. mixed with chlorides of sodium and potassium. Rub some between the evaporate to complete dryness.

fingers or across a glass plate.

grit

detected?

apparatus required for Exp. 140

may be shown by

the same results

— " water

hydrochloric acid to a solution of sodium

The

this point as in

gelatinous precipitate

Exp.

140.

em

Proceed from

— Add

glass."

SILICIC ACID.

4a

Experiment 141.

not available,

ll.

PREPARATION AND PROPERTIES OF

silicate

is

the

vn

If the

any

Is

Discussion of Experiment 140.

— When

is

.c h

alkaline silicates are soluble in water,

acid.

silicon dioxide is

fused with alkaline carbonates, an alkaline sihcate

The

silicic

is

formed.

and when hydro-

tp ://

w

cipitate

w w

is added to such a solution, the gelatinous preformed is a siHcic acid having the formula H2Si03 This acid is decomposed by heat into silicon (probably). dioxide and water, thus

chloric acid

ht

HaSiOg

:

—

=

SiO^

Silicic

Silicon

Acid

Dioxide

+

H2O

acids are numerous and complex, and the which they form constitute a large class of important minerals and rocks.

The

silicic

silicates

CLASS-ROOM EXERCISE. I.

AL.VI.

Additional study of silicon. (a) Occurrence

and

distribution.

{d)

Preparation and properties of amorp.ious and of crystallized

{c)

Resemblance

silicon.

to carbon.

and Phosphorus and Compounds.

Silicon

275

Silicon dioxide.

2.

(a) Occurrence and distribution. {d)

Properties of various forms.

(c)

Geological significance.

(d) Uses. {e) Reason for abundance. {/) Meaning of the term silica.

Other compounds of

silicon.

{a^ Silicon tetrafliioride. Silicic acids.

Silicates.

id) Carborundum.

Miscellaneous. {a)

What

diatomaceous earth

is

?

scope.

(c)

What What

is

" electro-silicon "

is

opal

it

through a micro-

?

em

{p)

Examine

4a

4.

{c)

vn

ib)

ll.

3.

?

{d) Crystallization of quartz,

Significance of the term rock crystal.

(/)

What

{g)

Write an essay on " Glass." Prepare a short account of the manufacture of pottery and

the essential chemical constituent of

w w

(//)

is

.c h

ie)

many

rocks?

porcelain.

the equation, SiCl^

How much

ht 2.

silicofluoride? 3.

XXVIII.

Scheele found that 0.6738 gm. of silicon tetrachloride gave 2.277 silver chloride. Calculate the atomic weight of silicon. (Assume

gm. of

tp ://

1.

w

PROBLEMS.

+ 4 AgNOg +

2

HgO =

SiO.,

+

4 AgCl

+ 4 NH^NOg.)

can be obtained from 119 gm. of potassium (Assume the equation, K^,SiFg + 4 K = Si + 6 KF.) silicon

Calculate the percentage composition of {a)

Willemite, Zn^,SiO^.

{b)

Steatite,

—

Mg.Sip,, H.O. .

Phosphorus itself is not adapted to extended laboratory examination on account of its properties. It takes fire suddenly and produces dangerous burns. The element has

some

uses,

cations.

and

its

compounds have many

industrial appli-

Experimental Chemistry.

276

LABORATORY EXERCISE. Recall or read again the notes

1.

XXIV.

made about

the properties of phos-

phorus observed in Exp. 45. 2. Smell of the end of a phosphorus-tipped match, then smell of

the,

fumes arising from a bottle containing phosphorus under water.

Do

they suggest each other?

study of yellow phosphorus. {a)

History.

(^)

Significance of name.

em

A

XLVII.

4a

CLASS-ROOM EXERCISE. 1.

in the

vn

If convenient, rub the end of a phosphorus-tipped match and observe and describe the result.

ll.

3.

dark,

Occurrence and sources. (d) Manufacture. Properties.

(/) Uses. (g) Danger (//)

A

in its use.

should be kept.

study of red phosphorus. Preparation.

tp ://

(a) ((^)

Properties.

(c)

Uses.

Compounds

of phosphorus.

ht

3.

it

w

2.

How

w w

(^)

.c h

(c)

(a)

Preparation and properties of phosphorus pentoxide.

(d)

Orthophosphoric acid, H0PO4, and its salts. Metaphosphoric acid, HPO^, and its salts.

(c) 4.

Miscellaneous. (a)

Use

(d)

Fertilizer

(c)

Test for phosphorus.

of phosphates as food of plants.

— manufacture, constituents, use.

(d) Write an essay on " Matches." What is bone black? Bone ash? A cupel? Apatite? (e) Phosphate rock ? Microcosmic salt ? Disodium phosphate ? allotropy by phosphorus. Illustrate (/) (^) To what group in the periodic classification does phosphorus belong?

Silicon and

S.

A

Phosphorus and Compounds.

277

study of arsenic. {a) Occurrence.

{b)

Preparation.

(<:)

Properties.

{d) Preparation, properties, and uses of arsenic trioxide. What is Marsh's test for arsenic? (6')

(y) What {g)

" arsenic,^' white arsenic, arsenious oxide

is

?

Antidote for arsenic poisoning.

—

The foregoing part of this book contains most Review. fundamental principles of chemistry illustrated by

of the

ll.

vn

It is advisexperiments as far as such a method permits. able at this stage to glance backward and review these

from

all

sources.

4a

principles in the light of the facts gleaned

CLASS-ROOM EXERCISE.

em

1

XLVIII.

Discuss the atomic theory as an expression of the Laws of Multiple

.c h

and Definite Proportions. 2. Discuss molecules and molecular weight in the light of the Laws of Avogadro and Gay-Lussac, vapor density, vapor tension, elevation of

and depression of the freezing point. Law by the volumetric formation of water, hydrochloric acid gas, hydrogen sulphide, sulphur dioxide,

3.

Illustrate

ammonia

gas,

w w

the boiling point,

Gay-Lussac's

4.

w

and by the oxides of carbon. Illustrate the

Law

of Multiple Proportions by the oxides of nitro-

tp ://

gen, carbon, and sulphur, and by the hydrocarbons, methane, ethylene,

and acetylene. 5.

Illustrate the

Law

of Definite Proportions

by Exps.

15,

16, 22,

ht

26, 44, 54, 55, 92. 6.

Discuss the causes, accompaniments, and results of chemical

action. 7.

8.

Discuss

:

—

{a)

Heat of combustion.

{c)

{b)

Solution.

{d) Valence.

Discuss with illustrations («)

The

:

—

Periodic Law.

(J?)

Reduction and oxidation.

{c)

Equations.

{d) Elements and compounds. {^e)

Symbols and formulas.

Allotropism.

Experimental Chemistry.

278

State the test for a chloride, sulphate, sulphide, sulphite, nitrate,

9.

carbonate, and for Zn, Na, Ca, Cu, Pb, Ag, C. O, H, Sb, As, CO,, N, CI, Br,

I,

S,

H^S, SOo,

SiO^,, P,

State the chemical

10.

an

alkali,

an

acid,

name and formula

and a neutral

salt.

of lime, lime water, lime-

stone, chloride of lime, bleaching powder, marble, muriatic acid,

blue

vitriol,

ammonia,

vitriol,

soda, quicklime, slaked lime,

ammoniac, cream of tartar. sal

salt,

Prepare a chronological table of the following chemists

Stahl, Black, Cavendish,

Liebig,

Priestley,

who

Boyle, Becher,

:

Dalton, Davy, Faraday, Graham,

Gay-Lussac, Dumas, Scheele,

Proust,

Berthollet,

Lavoisier,

modern chemistry

vn

as the founders of

of

ll.

11.

may be regarded

4a

Stas, Berzelius.

Discuss the principles underlying the nomenclature of acids,

and

salts.

PROBLEMS.

How many

(Review.)

grams of hydrogen may be obtained by the interand 196 gm. of pure sulphuric acid? much mercury will remain after obtaining 48 gm. of oxygen

action of zinc

How

w w

2.

XXIX.

.c h

1.

em

12.

bases,

oil

soda, potash, caustic

What

weight of potassium chloride remains after obtaining

tp ://

4.

necessary to produce

is

w

by heating mercuric oxide? 3. What weight of potassium chlorate 144 gm. of oxygen? 8 gm. of oxygen from potassium chlorate? 5.

How much How many

zinc is necessary to obtain 2 1. of hydrogen? grams of oxygen can be obtained from 490 gm.

ht

6.

ot

potassium chlorate? 7.

If

the density of ice

A° C. occupy 8-

when

The formula

volume of steam 9.

oxide.

300° C. 10.

Ten

A

0.92,

what volume

of crystallized

gypsum

at 300° C. is liberated

liters

will a liter of

water at

is

CaSO^

.

2 H^,0.

What

by heating 100 gm. of gypsum?

of hydrogen at 30° C. are passed over hot copper

How much is

is

frozen?

copper

is

set free,

and what volume of steam

at

(The equation is CuO + Hg = Cu -f H^.) quantity of carbon monoxide was passed through a red-hot formed?

The resulting gas was absorbed (Fe^,0;5). by caustic potash. The gain in weight of the caustic potash was 0.86 gm. What was the volume of the carbon monoxide at the standard temperature and pressure? tube containing ferric oxide

CHAPTER XVIIL

vn

SODIUM — POTASSIUM — COPPER — SILVER — MAGNESIUM — CALCIUM — ZINC — MERCURY.

— Most of the elements hitherto studied are gases. The few soHds — carbon, sulphur, phosphorus, and iodine —

ll.

Metals.

4a

bear almost no resemblance to the elements called metals. The popular conception of a metal is that of a lustrous

more satisfactory and metals, but

em

possessing certain characteristics,

ductility, tenacity,

e.g.,

malleability or

varying degrees of hardness, to

make no sharp

.c h

solid,

etc.

It is

division into non-metals

tp ://

w

w w

to regard all the elements as a series, broken into related groups the members of which have a marked gradation of propierties, some elements emphasizing basic, some acid, and some both properties. If an element emphasizes basic properties at any or all times, it is then a metal. (See page 128.)

ht

PROPERTIES OF SODIUM.

Reniefnber

tJie

precautions

to be

observed in using sodium.

(See page 89.) Experiment 142. record

hard or

its

— {a)

Examine a small

most obvious physical properties,

piece of

e.g.

soft, etc.

{b)

Repeat Exp. 42, and read

(<;)

Answer

the following

:

—

its

accompanying

text.

(i) Is sodium heavier or lighter than water (2)

What

(3) Is

it

properties suggest that

it is

?

a metal

harder or softer than most metals 279

sodium, and

color, luster,

?

?

whether

Experimental Chemistry.

28o

The Principal Compounds

of

Sodium are the

chloride,

sulphate, carbonate, nitrate, and hydroxide.

GENERAL PROPERTIES OF SODIUM COMPOUNDS. Experiment

test,

sodium.

It is

is

most abundant compound of under the name salt, or com-

the

familiar to

vn

legitimate conclusions.

Sodium Chloride

all

salt.

4a

mon

determine again) the flame

(or

and color of the most common sodium compounds.

ll.

Draw

— Recall

143.

solubility in water,

Experiment 144.

— Grind

em

PREPARATION OF PURE SODIUM CHLORIDE. 50 gm. of

salt

with 150

of water in a

cc.

Fiher this saturated solution

.c h

mortar, adding the salt in small portions.

and conduct hydrochloric acid gas into it. Genby the method employed in Exp. 61 or Exp. 63. A funnel, or calcium chloride tube, or a thistle tube, should be attached to the end of into a dish or beaker,

w w

erate the gas

the delivery tube so that tion.

As

wall dip just

it

below, the surface of the

salt solu-

the operation proceeds pure sodium chloride separates, but the

w

magnesium chloride and other impurities remain

in solution.

When

tp ://

considerable sodium chloride has separated, remove the generator, allow the solid to settle, decant the clear liquid, add 15 cc. of cold water, and

decant again. it

If

;

if

a

dry the

salt

pump

filter

not, wasli

ht

water with

by heating

rod during the heating.

is available, remove the last traces of and decant once or twice as before. Finally

in a porcelain dish

Describe

;

stir

constantly with a glass

it.

Preserve a specimen in a small tube or bottle.

Sodium Hydroxide is a useful compound of sodium. have already been studied.

Its properties

PREPARATION OF SODIUM HYDROXIDE. Experiment

145.

— Dissolve

25 gm. of sodium carbonate in 150 cc. is well

of water and heat gently in an iron dish (an ordinary iron spider

adapted for this work).

enough water

td

Meanwhile slake 10 gm. of lime and add

make a milky

liquid

— " milk of lime."

Add

just

the milk

Sodium.

281

of lime to the sodium carbonate solution and boil for several minutes, Let the precipitate subside, stirring constantly with an iron wire or file.

remove a little liquid with a pipette or small tube, and if it effervesces with hydrochloric acid, add more milk o^ lime and boil if not, decant the clear liquid into a convenient vessel, let it stand for a few minutes ;

or until the solid settles, and siphon off the liquid through a glass This solution of sodium hydroxide may be evaporated to siphon.

dryness and the solid product tested and the remainder preserved, or the may be tested at once as follows

solution

excess

Rub Add

to a small portion a solution of zinc sulphate.

of sodium

hydroxide.

changes

this solution.

Try the flame

have

Add an

already

been

4a

{c)

These

Reconsider them, and state what they prove

explained (Exp. 21).

about

vn

{b)

—

ll.

{a)

:

a httle between the fingers and describe the feeling.

test.

em

{d) Determine the specific gravity by weighing a measured volume.

1.

{b)

Industrial preparation.

tp ://

w

Uses. (
Peroxide

— preparation, properties, and uses.

ht

Sodium hydroxide. {a) Names and formula. {b^

4.

Industrial preparation

Sodium

{c)

Additional properties.

(<:/)

Uses.

{b)

Purification.

chloride.

{a) Sources. {c)

-

Properties not experimentally found.

{d) Uses. 5.

Discovery.

w w

(c)

3.

XLIX.

Additional study of sodium. {a) Occurrence.

2.

.c h

CLASS-ROOM EXERCISE.

ie)

Physiological value.

Sodium carbonate. {a) Names. {b^

Industrial preparation, including the in each process.

{c)

most important equations

Uses.

(^) Chemical name and formula of soda, washing soda, soda crystals, alkali, soda ash.

Experimental Chemistry.

282 6.

Sodium bicarbonate. (a) Formula.

7.

(d)

Names and

(c)

Properties and uses.

their significance.

Other sodium compounds. (a)

Sodium

— source,

sulphate

preparation,

properties,

uses,

historical significance.

(0)

Sodium

nitrate

— names, source, properties, and uses.

Miscellaneous.

vn

8.

NaOH, Na,SO^, HNaSO,, Na.O, Na..PO^ (sodium phosphate), H^,NaPO^ (dihydrogen sodium phosHNa.PO^

(diso'dium phosphate),

salt)

HNaCNHJPO^

em

(microcosmic

4a

phate),

ll.

(a) Valence of sodium in

PROPERTIES OF POTASSIUM.

Experiment 146.

—

piece of freshly cut

w w

it

its

Touch

it

it between and drop it on Stand just near

Scrape the coating from a piece of potassium, press

w

{b^ filter

Does

Examine a very small

most obvious physical properties. suggest caustic potash and soda?

potassium, and record slightly.

(
.c h

Observe the same preeautions as in the use of sodium.

paper to remove the

oil,

cut off a very small piece,

tp ://

the water in a pneumatic trough or similar .vessel.

ht

enough to see the action. Describe the action. How does it differ from the action of sodium? Test the water as in Exp. 142. From what has already been learned about sodium and potassium, predict the main chemical change observed in {b) and write the equation. {c)

Answer

the following

:

—

(i) Is potassium heavier or lighter than water?

(rtf)

(2)

What

(3)

How

(4)

What

If possible,

properties suggest that

does is

it

reseml)le

and

it is

differ

a metal

?

from sodium?

the usual test for potassium?

examine the flame of a potassium compound

potassium chloride) through a spectroscope, and describe the

The Principal Compounds

of

{e.g.

result.

Potassium are the chlorate,

chloride, hydroxide, nitrate, carbonate, bromide,

and

iodide.

Potassium.

283

GENERAL PROPERTIES OF POTASSIUM COMPOUNDS. Experiment 147.

— Recall

(or determine again) the solubility of

Subject them to the flame

these compounds.

Draw

color the flame?

LABORATORY EXERCISE. What

2.

What happens

to potassium hydroxide

and potassium carbonate

to the air

What

ll.

is the thermal effect produced by dissolving potassium and potassium hydroxide separately in water?

em

Potassium Hydroxide has properties which are analogous those of sodium hydroxide. It is similarly prepared.

.c h

to

of potassium chlorate,

?

4a

3.

nitrate

does each

XXV.

made

experimental use has been

potassium bromide, and potassium iodide

when exposed

How

vn

1.

test.

a legitimate conclusion.

PREPARATION OF POTASSIUM HYDROXIDE. Experiment

— Proceed

as in Exp. 145, but use potassium car-

w w

148.

bonate instead of sodium carbonate.

w

hydroxide.

term

tp ://

Potassium Carbonate is

now

is

Test as

in the case of

the historical potash, though that

usually applied to potassium hydroxide.

Some

have already been considered.

ht

of its properties

sodium

PREPARATION AND PROPERTIES OF POTASSIUM CARBONATE. Experiment

149.

— {a) Heat strongly gm. of cream — in an iron dish in the hood until 5

acid potassium tartrate is

white.

filtrate

Grind

this solid with

water in a mortar, and

(i) with both kinds of litmus paper, (2)

(3) for a carbonate.

Record the

If test

(3)

Record the

is

warm

gently.

—

filter.

Test the

potassium, and

results.

ib) Fill a test tube half full of

water, shake, and

for

of tartar

the residue

wood

Filter,

ashes,

and

add half the volume of

test the filtrate as in {a).

not decisive, repeat the experiment on a larger scale.

results.

Experimental Chemistry.

284 Answer (i)

(2)

the following

What is the source of cream of tartar? What do (a) and (d) show about the distribution Of

sium? (3)

—

:

What

is

its

of potas-

assimilation by plants?

the literal

meaning of the word potash

?

little

water

in a mortar, filter,

and

test the filtrate as in {a). ?

How

has

4a

the potassium nitrate been changed

ll.

a

vn

{c) Mix 5 gm. of powdered potassium nitrate and i gm. of powdered wood charcoal. Spread the mixture on an iron dish or pan, place the pan on a tripod or ring, stand a lighted burner under it, and step aside. Wait for a decided result. As soon as the mass is cool, grind It with

1.

Additional study of potassium. {a) Occurrence and sources.

L.

em

CLASS-ROOM EXERCISE.

and

significance

w w

(/) Derivation

.c h

{c) Industrial preparation. Discovery. {e) Uses. {d) Properties not experimentally shown.

{b)

of

the

words

kaliion

and

potassium.

Potassium hydroxide. («)

Names and

{c)

Explain the statement, '-the reaction

formula.

potassium hydroxide

{d')

is

in

the preparation of

reversible."

Additional properties.

{c^

Uses.

Halides of potassium.

ht

3.

Industrial preparation.

{b)

w

tp ://

2.

{a) Sources, preparation, properties, and uses of each. (J))

Their

similarity.

4.

Potassium chlorate.

5.

Potassium carbonate.

{a) Industrial preparation.

Properties.

{b)

(«) Sources.

6.

{b)

Preparation (several methods).

(J)

What

Potassium («)

is

pearlash

Names and Preparation.

Properties.

(^/)

Uses.

Potash ?

their significance.

{d) Properties, (e)

Uses.

(/) Review the subject of gunpowder.

Uses.

{c)

nitrate.

(^) Sources. (r)

?

{c)

285

Potassium. 7.

Soduim and potassium. (a) How do they illustrate the Periodic Law ? Explain ((^) "Their molecules are monatomic." (c)

Why

are they called " alkali metals

''

this statement.

?

(d) Significance of their discovery by Davy. Miscellaneous.

(d)

What is "lye"? Valence of potassium

(c)

KBr. Elements related

(a)

to

KOH,

in

K^SO^, HKSO^,

sodium and potassium

properties. volatile, fixed,

spectroscope

—

its

their

mineral, and vegetable, have

all

construction and use.

4a

The

— especially

Explain each term.

b.^en applied to alkali. {e)

KgCOg,

ll.

(d) The terms

Kp,

vn

8.

"

with special reference to

em

" The Stassfurt Deposits (/) Review potassium compounds.

{g) Review "Fertilizer" from the standpoint of potash.

Ammonium compounds. {a)

Review the compounds previously mentioned or used. they be considered with the "alkali" compounds?

Why may

w w

{b)

.c h

9.

XXX.

PROBLEMS.

tp ://

w

acid) 1. Stas found that 100 gm. of pure silver (dissolved in nitric required 54.2075 gm. of sodiur.v chloride for complete precipitation.

(Assume atomic weights

Calculate the atomic weight of sodium.

of

and AgNOg + NaCl = AgCl + NaNOg.) silver and 2. One hundred gm. of potassium chloride give 52.42 gm. of potassium and 47.58 gm. of chlorine. Calculate the atomic weight of making two assumptions. potassium kg. of sodium car3. How much sodium can be obtained from 2

ht

chlorine

—

bonate,

if

the latter

is

The

heated with carbon?

Na^COg + C. = Na^ + 4.

How much

potassium carbonate

of potassium hydroxide?

The

K,C03 + Ca(OH),, = 5.

How much

sodium carbonate

of sodium hydroxide ?

is

equation

is

3

equation

is

—

CO.

necessary to prepare a kilogram is

—

2KOH

+ CaCO,.

necessary to prepare a kilogram

Experimental Chemistry.

286 What

per cent

How many

7.

of salt cake

pounds of

The

?

2

How much

8.

The

Glauber's

of

salt,

Na^,SO^.ioHp

sodium

is

?

equation

salt are is

—

needed to make one-fourth of a ton

NaCl + H,,SO^ = NaoSO, +

HCl.

2

sodium carbonate can be made from 500 kg. is given in problem 7, the other is

—

equation

first

Na._,S04

CaCO.5

-f

+

2 C2

=

Na,,CO..

of salt?

vn

6.

sulphate

+ CaS +

4 CO.

ll.

by heating 100 gm. of 9. How much sodium sulphide is formed sodium sulphate with charcoal? The equation is

Copper

is

2

C2

= Na,S +

4 CO.

em

Na^SO^ +

4a

—

an abundant element, and its compounds are Its properties, which are familiar, adapt the

.c h

numerous. metal to various uses.

w w

GENERAL PROPERTIES OF COPPER.

— (a) Examine several forms of copper — wire, — and observe and state the most obvious physical

Experiment 150.

w

sheet, filings, etc.

properties.

Determine the specific gravity by weighing copper in air and then by weighing it in air and comparing this weight with the water it displaces when immersed in a known volume in a volume of

tp ://

(d)

in water, or

ht

graduate.

XXVL

LABORATORY EXERCISE.

copper a good conductor of heat? evidence is your answer based? 1.

Is

2.

Is

3.

What happens

copper ductile?

Malleable?

to copper

Of

Tough?

Brittle?

when heated?

electricity?

When

On what

Hard

or soft?

exposed to the air?

TESTS FOR COPPER. Heat a copper wire in the Bunsen flame. and its compounds, though not a since the same color is produced by other substances.

Experiment 151.—

The

color

conclusive (^)

is

test,

Add

solution,

(^?)

characteristic of copper

a few drops of

and observe the

ammonium hydroxide to copper sulphate now add an excess of ammonium

result;

Copper. The

hydroxide.

bhie solution

287

a characteristic and decisive test for

is

copper.

Add

(c)

then add a few drops of acetic acid and

;

ferrocyanide

potassium

water a drop of copper sulphate

to a test tube half full of

and shake

solution

The brown

solution.

precipitate

is

of

copper

ferrocyanide.

Copper replaces some metals, of their

compounds, and

is

suspended in solutions by other metals.

if

in turn replaced

vn

Both operations precipitate or deposit a metal. INTERACTION OF METALS

COPPER.

ll.

—

it

(d)

the copper?

Put in separate

What

is

question?

How

What

has become

final color of

the solution

the deposit?

Does the

w w

last

of the zinc

After a short time remove the

.c h

some

and iron? indicate any chemical change ? of

has

copper sulphate solution a

test tubes half full of

bright nail and a strip of clean zinc.

metals and examine them.

What

Describe the change.

with a soft cloth or paper.

become of some of

em

wipe

4a

(a) Put a clean copper wire into a solution Experiment 152. After a short time, remove the wire and of any compound of mercury.

would you prove the answer

to the

tp ://

w

The Important Compounds of Copper are the copper oxides, copper sulphate, and copper nitrate.

LABORATORY EXERCISE.

1.

What

2.

Examine

ht

experimental use has been a

crystal

obvious properties. 3. ties.

How

made

XXVIL of one copper oxide?

of copper sulphate

What happens

to

it

has copper nitrate been prepared?

What

is its

and observe

its

most

when heated? Summarize

its

proper-

formula?

4.

Prove that each of the above important compounds contains copper.

5.

What

is

the color of

many copper compounds?

—

There are two oxides of copper, the Oxides of Copper. black oxide, already studied (see Exps. 9 and 151 (a)), and the red oxide. The formulas are respectively CuO and CugO, and

their exact

names are cupric and cuprous

Experimental Chemistry.

288

These oxides are the

oxides.

copper compounds

of

the metal

**

first

-ic

members

and

of

latter, or is in

farther on

two classes

In the former

-ous.

combined with a larger proportion

is

than in the

— the

of

oxygen

a higher state of oxidation

—

Other metals form similar

in the series."

classes.

vn

PREPARATION AND PROPERTIES OF CUPROUS OXIDE.

—

about

5 cc.

4a

ll.

Dissolve i gm. of copper sulphate in 15 cc. of Experiment 153. water, and 5 gm. of Rochelle salt (sodium potassium tartrate) in 10 cc. Add to this filtrate of water; mix these solutions, warm, and filter. of a dilute solution of grape sugar (or of cane suga; which

five minutes with dilute sulphuric acid), and The enough sodium hydroxide solution to dissolve any precipitate. Boil until a decided change is solution must be strongly alkaline. produced. The j^roduct is cuprous oxide. Describe it. Show by a comparative table the general properties of the two oxides of copper.

The mixture

.c h

em

has been boiled at least

copper sulphate, Rochelle salt, and sodium Fehhng's solution, and is widely used to detect the presence of sugar. of

w w

hydroxide

called

w

is

The

tp ://

Alloys are mixtures or compounds of two or more metals. properties of the alloy vary with the constituents and If mercury is one constituent, the alan amalgam. The important alloys in which

their proportions.

called

is

ht

loy

copper silver,

is

the larger constituent are brass, bronze,

and

CLASS-ROOM EXERCISE. 1.

LI.

Additional study of copper. {a)

Occurrence of native and combined copper.

{p)

Preparation from

(c)

Additional properties.

(/) What 2.

German

their allied alloys.

is

its

electrolytic

ores.

{d') (
copper and how

Uses. History. is it

prepared.'*

Oxides. {a)

Review the preparation and properties of cuprous and cupric ,

(Jy)

oxides.

Significance of the terminations -ous and

-ic.

Copper. Copper sulphate. Names. (rt) (d)

Copper sulphides. (a)

pyrites,

7.

(c)

Names and

formulas.

(a)

What

(d)

Cu(N03)2, Cu.S? Derivation of the word

is

copper in CuO,

valence of

the

ciiprinn.

Alloys of copper.

common

Alloys allied to brass. Composition, properties, and uses of (i) gun metal, (2)

bell

bronze,

(5)

metal,

.c h

(J))

Cup, CuSO^,

Composition, preparation, properties, and uses of brass.

{c)

copper

Give formula and color of azurite and malachite.

Miscellaneous.

{a)

ore,

copper glance.

vn

(d) 6.

(^) Properties.

Occurrence.

Copper compounds. (a) Give the chemical name and symbol of ruby

ll.

j.

4a

4..

Properties.

(c)

(d) Uses.

Preparation.

em

3.

289

speculum

(3)

metal,

(4)

antique

(^/)

w w

aluminium bronze.

Composition, properties, and uses of (i) ordinary German silver, (2) Chinese Pakfong, (3) white German silver,

German

w

(4) casting

silver.

Experimental.

tp ://

8.

{a)

Starting with copper,

copper

Give the steps

prepare successively

and cuprous oxide

for the transformation of

?

copper into copper

ht

(Jj)

how would you

nitrate, cupric oxide,

sulphate and cuprous oxide?

PROBLEIVIS. 1.

When

XXXI.

gm. of 1.3305 gm. of copper were heated in oxygen, 1.6675 Calculate the atomic w^eight of copper.

cupric oxide were formed.

(The equation 2.

is

How much

Cu +

O =

cupric oxide

CuO.) is

formed by heating 1467 gm. of copper

in air?

cuprous oxide is formed by boiling 100 gm. of copper hydroxide and grape sugar? (The equation is potassium sulphate with - Cup + O + I2H,0 + 2 K,SO,.) 2CuSO,.5H.O + 3.

How much

4KOH

Experimental Chemistry.

290 4.

•

Calculate the percentage composition of

CuC03.Cu(OH)2. 2CuCO..Cu(OH)2.

(a)

Malachite,

(d)

Azurite,

Silver

is

Two

familiar as the alloy of silver in coins.

compounds, silver nitrate and silver chloride, have already been considered in testing for chlorine in the form its

of chlorides.

:

—

— Prepare

(a) Fill a small dish

(e.^i^.

silver

by one or both of the following

4a

Experiment 154. methods

ll.

PREPARATION OF SILVER.

vn

of

a porcelain crucible) half

full

of silver

and add a few drops of mercury. Allow the whole to stand undisturbed for a day or more, and then examine. The delicate crystals attached to the mercury are silver. Pick them out with the forceps, wash well with water, and preserve them.

.c h

em

nitrate solution,

(d) Dissolve a ten-cent piece in

10 cc. of concentrated nitric acid,

and add hydrochloric acid until the precipitation is complete. Let the precipitate settle, and wash several times by Then filter and wash until the filtrate is neutral. If condecantation. venient, let the precipitate dry if not, scrape half from the opened

w

w w

dilute with a little water,

;

tp ://

paper with a knife or spatula, put

it

in a shallow dish, cover with dilute

sulphuric acid, and add a piece of zinc; put the other half in a cavity at the

end of a piece of charcoal, cover with sodium carbonate, and

it

with a blowpipe flame.

ht

duce

In the

first

re-

case, the silver will collect

as a grayish powder remove any excess of zinc, filter, wash with water and dry the residue. It may be preserved as a powder, or fused into a bead with a blowpipe flame. In the second case, minute globules of silver will appear on the charcoal scrape them together and fuse into ;

;

a single bead.

PROPERTIES OF SILVER. Experiment state briefly its

155.

— Examine

the silver formed

in

Exp.

154,

and

most obvious properties.

TEST FOR SILVER. Experiment

156. — Devise

previous experiments.

Verify

a test for it.

combined

silver,

based upon

291

Silver.

LABORATORY EXERCISE. 1.

What

caused the blue color of the

2.

Name

the haloid

and

compounds of

XXVIII.

filtrate in

Exp. 154 (d)

?

State their resemblances

silver.

differences.

3.

Explain the chemical change in the formation of silver in the first Does it differ fundamentally from the change in

casein Exp. 154 (d). the second case?

How may

silver sulphide

What

be formed?

CLASS-ROOM EXERCISE. (a)

ll.

Additional study of

silver.

Occurrence of native and combined

silver.

What

is

argen-

'

em

tiferous lead?

various industrial methods of preparation.

(d)

The

(c)

Properties.

.c h

(d) Uses. (e)

LIL

4a

1

What

color?

is its

"tarnishes"?

silver

vn

4.

happens chemically when

History.

silver.

Occurrence, properties, and uses of silver chloride.

(Jf)

Preparation and uses of silver bromide and iodide.

(6)

Properties

w

{a)

common

to this group.

Silver nitrate.

{a)

Names.

{b)

Preparation.

ht

3.

Halides of

tp ://

2.

w w

(/) Derivation of the word argentum.

(6-)

Properties.

\d) Uses.

4.

5.

Miscellaneous. («)

Describe the process of silver plating.

{b^

What

{c)

Compare copper and

(rt')

In what respect does gold resemble copper and silver

is

silver glance

Horn

?

silver

?

Alloys of silver. {a)

Composition of standard

((^)

What

{c)

Why

is

Lunar caustic

?

silver in the light of the Periodic

sterling silver

silver coin.

?

are coins stamped

and not

cast

?

?

Law.

Experimental Chemistry.

292

PROBLEMS. XXXII. Calculate the percentage composition of

(a)

is

53.1958 gm. of

I

gm. of

atomic weight of If

4.

nitrate

is

in

0.7526 gm. of

silver interact with nitric acid,

.''

when

— The

conduct of

ammonia, and when

it

to

.c h

ammonia gas

in

how much

magnesium when

?

silver

oxygen,

in

air,

it is

XXIX.

heated in

air, in

oxygen,

w w

and

the

was treated with hydro-

LABORATORY EXERCISE. What happens

is

magnesium has been

the element was heated in

chloric acid.

1.

what

silver,

?

em

and

silver

AggS.

Silver sulphide,

?

silver chloride yields

480 gm. of formed

Magnesium. studied

(d)

form 92.6042 gm. of silver bromide, AgBr,

the atomic weight of silver

If

3.

silver

vn

what

Silver chloride, AgCl.

ll.

If

2.

4a

1.

w

2. What is the equivalent of magnesium ? The atomic weight ? Summarize the experimental evidence on which the answers are based,

tp ://

GENERAL PROPERTIES OF MAGNESIUM.

Experiment 157. a short account of

its

— (a)

Examine a piece of magnesium, and write most obvious physical properties.

ht

(d) If a sufficient quantity

Weigh

it

first

is

available, determine

in air, then in water,

from these data.

Compare

its

specific gravity.

and compute the

specific gravity

the result with the specific gravity ot other

metals.

Magnesium Oxide is the only important compound magnesium previously considered.

LABORATORY EXERCISE. 1

What 2.

When magnesium is its

What

formula is

is

burned

?

State

in air,

of

XXX.

what compound

is

formed

?

?

magnesia

important application of magnesia.

its

observed properties.

Predict an

Magnesium.

293

TESTS FOR MAGNESIUM.

—

(a) To a solution of magnesium sulphate or Experiment 158. add successively solutions of ammonium chloride, ammonium hydroxide, and disodium phosphate. A precipitate of ammonium mag-

chloride

nesium phosphate

formed,

is

but finally crystalline.

It is

NH^MgPO^.

It is

Try

soluble in acids.

voluminous

at first,

it.

Put a litde powdered magnesium carbonate or oxide in a cavity end ot a piece of charcoal, moisten with water, and heat intensely Cool, and moisten with a drop of cobaltous nitrate in a blowpipe flame. Heat again, and when cool observe the color. If the experisolution. ment has been conducted properly, a pink or pale flesh-colored residue (d)

4a

ll.

vn

at the

em

coats the charcoal.

CLASS-ROOM EXERCISE.

LIII.

.c h

Additional study of magnesium.

compounds.

(a)

Occurrence of

(d)

Preparation.

(c)

Additional properties.

(d) Uses.

How

was magnesium

utilized in the discovery of

argon

?

w

(e)

its

w w

I.

Magnesium oxide.

tp ://

2-

(a)

Names.

(c)

(d)

Preparation.

((i)

(e)

What

?

magnesia mixture

ht

is

magnesia

3.

4.

?

Magnesium

Properties.

Uses.

Calcined magnesia

citrate

?

Fluid

?

Magnesium sulphate. Ca)

Names.

(d)

Preparation.

-^

Properties.

(c)

(^) Use.

Miscellaneous. (a)

Chemical name and formula of inagnesia

alba, magnesite,

brucite, periclase, dolomite. (J?)

{c)

5.

Valence of magnesium

in

MgO,

MgoCO.., MgClo,

Review " The Stassfurt Deposits sium compounds.

Black's work on Magnesia alba.

''

Mg(OH)..

with reference to magne-

Experimental Chemistry.

294

PROBLEMS.

XXXIII.

mm. will combine magnesium ? (Equation is 3 Mg + N^ = Mg.jN2.) 2. How many grams of magnesium will be formed by heating 100 (Equation is Kg + gm. of potassium with magnesium chloride

What

1.

volume of nitrogen at 20° C. and 780

with 50 gm. of

.-*

MgCl2=Mg + 2 3. How much

KCl.)

How much .

7

H,0

(d)

MgCa^^COa)^,

dolomite,

?

Epsom

(c)

salts,

em

MgSO,

magnesium can be obtained from 100 gm. of (a)

MgCO^,

magnesite,

ll.

similar to 2.) 4.

4a

is

vn

sodium is necessary to decompose a kilogram of magnesium chloride, and how much magnesium will be formed ? (Equation

.c h

Calcium is an uncommon metallic element, but its compounds are exceedingly widespread and important.

TESTS FOR CALCIUM.

— (a)

Subject calcium chloride to the flame

w w

Experiment 159. Record the result.

test.

Repeat Exp. 29 (d). If possible, examine a calcium flame through a spectroscope. Compare the result with the position of the potassium lines.

w

(d)

tp ://

(c)

The Principal Compounds

Calcium are the hydroxide, fluoride, and hypo-

of

carbonate, chloride, sulphate,

ht

oxide,

chlorite (bleaching powder).

LABORATORY EXERCISE. 1.

What

experimental use has been

XXXL

made

of calcium hydroxide,

calcium chloride, calcium fluoride, and calcium hypochlorite 2.

What happens

exposed to the each in water ? 3.

Give the

air

?.

to

oxide and calcium

calcium

What

thermal

common name

eff"ect

is

.''

chloride

when

produced by dissolving

of each of the above

compounds (except

calcium chloride). 4.

How

is

lime water prepared

What happens heated ? To calcium 5.

?

How

should

it

be kept

to crystallized calcium sulphate

carbonate

when

?

(gypsum) when

treated with acids

?

Calcium. 6.

Examine specimens

of selenite,

gypsum, and plaster of

Paris.

Recall or repeat the experimental study of the solu-

Describe them.

Mix a

calcium sulphate.

bility of

295

enough

plaster of Paris with

little

water on a block of wood to form a thin paste. Let it stand undisturbed Describe the change. for ten or fifteen minutes, and then examine.

What 7.

is

meant by the "set" of

Starting with limestone,

plaster of Paris?

how would you

prepare lime, lime water,

milk of lime, and chloride of lime? nearly insoluble in water

is

it is

CLASS-ROOM EXERCISE. {a) Occurrence of

LIV.

combined calcium.

Discovery.

Calcium oxide.

{c^

Properties.

{a)

Names.

{b)

Industrial preparation.

{c)

Properties.

{e)

Explain and

.c h

2.

be

em

{h)

it

4a

Additional study of calcium.

1.

how can

;

a sulphate?

vn

Calcium sulphate

ll.

8.

proved experimentally that

illustrate

the statement, "the

term

hme

is

w w

ambiguous."

{d) Uses.

Calcium hydroxide.

Names.

Properties of actual substance.

w

{a) {b) {c)

Uses.

(^)

What

tp ://

3.

is

"milk of lime"?

Slaked lime?

Plaster?

plaster.

ht

and

4.

Cement?

Mortar?

Explain the hardening of mortar, cement,

Calcium carbonate. {a)

Names.

{b)

Occurrence.

{c) ^

Crystallization.

{d) Properties.

Uses of various varieties. if) What are stalactites and stalagmites?

(e)

5.

{a) Natural sources. {b) 6.

How

are they formed?

Calcium chloride. Preparation,

Calcium

Properties.

{d) Uses.

fluoride.

(a) Occurrence. {b)

{c)

Crystallization.

{c)

Properties.

{d) Uses.

Experimental Chemistry.

296

Calcium sulphate.

7.

Names.

(a)

Plaster of Paris

(e)

Properties.

(c)

(d) Occurrence.

called

— source,

(^) Uses. properties,

Why

and uses.

so

?

Calcium hypochlorite.

Review the subject Formula.

(c)

What

is

" bleach "

as considered under chlorine

?

vn

(a) ((^)

Chloride of lime " ?

''

ll.

8.

Calcium phosphates.

Review the subject as considered under phosphorus.

(rt)

4a

9.

em

Miscellaneous.

10.

(c)

magnesium and calcium. Review "Hardness of water." (See Class-Room Exercise IX, 4 (c) and page 248.) What is the chemical name of Iceland spar? Of satin spar?

(^)

What

(e)

Valence

Of

selenite? is

the "lime" light?

w w

(d)

.c h

(a) Elements related to

calcium

of

in

CaO, CaCL,

CaCOo,

Ca(0H)2,

in the light of the Periodic

tp ://

w

CaSO^. (/) Discuss magnesium and calcium Law.

PROBLEMS. XXXIV.

How much calcium may be obtained from 100 gm. of (a) marble, gypsum, CaS0^.2Hp, (0 Auor spar, CaFg, (d) superphosphate oflime, CaH,(PO,),? 2. How many tons of limestone must be heated to form 100 tons

ht

1.

(d)

of quicklime? 3.

composition Ca 4.

what 5.

The

equation for the reaction

is

CaCOg =

CO.,

+ CaO.

Find the simplest formula of a compound having the percentage If is

—

40,

C =

12,

O =

48.

100 gm. of calcium carbonate yield 56 gm. of calcium oxide,

the atomic weight of calcium

How many

constant weight?

?

grams does a pound of

The

equation

is

CaSO^

selenite lose .

2

when heated

H,0 = CaSO^ +

2

to

H^O.

and the compounds, zinc sulphide and zinc sulphate, have been experimentally studied. Zinc

is

a familiar metal,

Zi nc.

297

GENERAL PROPERTIES OF 160. — (a)

ZINC.

Examine a

Experiment piece of zinc and record its most obvious properties. (3) Determine the specific gravity by the method previously described. (See Exp. 150 (d).) Compare the result with the specific gravity of other metals.

LABORATORY EXERCISE.

2.

Does

When

Is zinc

it is

to

when heated?

zinc

exposed

hard or soft?

Malleable?

Ductile?

melt easily?

it

— (a)

Tough?

Recall or devise a simple test for combined

em

zinc.

(d)

Brittle?

4a

TESTS FOR ZINC. Experiment 161.

Describe and name the

to air?

vn

What happens

ll.

1.

product.

XXXII.

Recall or repeat the action of zinc

when heated

in the oxidizing

.c h

flame.

one end of a piece of charcoal with zinc and heat strongly in the blowpipe flame.

(c) Fill a small cavity at

oxide, moisten with water,

w w

Cool, and moisten with a drop of cobaltous nitrate solution, then heat

A

Cool and examine. compounds.

green incrustation

is

caused by zinc

w

again.

tp ://

Zinc interacts with other metals similarly to copper.

INTERACTION OF METALS

ht

Experiment 162. phate solution, as

in

— (a)

Put a

Exp. 152.

ZINC.

zinc in copper sulDescribe and explain the result which strip of clean

soon occurs. ((^) Put a strip of clean zinc in lead nitrate or lead acetate solution, and describe and explain the resuli (c) Clean a strip of zinc and put it in a solution of any salt of mercury. Examine after a short time. What is amalgamated zinc, and for what is it used ?

LABORATORY EXERCISE. I

.

What happens when

the purified solid product.

change.

XXXIII.

added to sulphuric acid ? Describe Illustrate by an equation the chemical

zinc

is

Experimental Chemistry.

298 2.

What happens when

a

little

sodium hydroxide solution

added

is

compound (in solution)? When an excess is added? all the compounds of zinc formed in these changes. 3. What happens when a sulphide, e.g. hydrogen sulphide monium sulphide, is added to a zinc compound (in solution) ?

Name

to a zinc

characteristic property has the solid product?

acid (instead of neutral),

How may

If the zinc solution

zinc be transformed into zinc nitrate

Additional study of zinc. {a) Occurrence of combined zinc.

{a) Chemical

LV.

{c)

Properties.

4a

Compounds.

into

{d) Uses.

Industrial preparation.

em

2.

and then

ll.

CLASS-ROOM EXERCISE.

{b)

were

the result be changed?

zinc oxide?

1.

What

vn

4.

how would

am-

or

name and formula

of

calamine,

zinc

blende,

3.

Alloys.

4.

Miscellaneous.

What

alloys contain zinc?

w w

{a)

.c h

gahnite, zinc white, white vitriol, sphalerite.

{a)

What

{b)

Valence of zinc

galvanized iron? in

ZnSO^, ZnCU, ZnO, ZnS.

1.

PROBLEMS.

XXXV.

Review Problems i, 2, 4, and 6 in Chapter III., page 52. Review Problems 2, 3, 4, 1 1, 12, and 15 in Chapter IV., page Review Problem 3 in Chapter IX., page 154.

62.

ht

2.

tp ://

w

is

3.

Mercury

is

the only metallic element which

is

liquid at

the ordinary temperature, and it is more or less famiUar from its extensive use in thermometers and barometers.

GENERAL PROPERTIES OF MERCURY.

Merauy and Experiment

its

163. — {a)

compounds arc poisonous.

Examine some mercury, and Pour a drop or two

characteristic physical properties.

shallow dish, and agitate the dish for the

name

" quicksilver "

?

;

state

its

into a large

does the result suggest the reason

Mercury. (fi)

Estimate

mercury.

Lift a bottle of

299 its

specific gravity.

Verify

the estimate by consulting a book, or by weighing a measured small quantity, as in the case of sulphuric acid (Exp. 4,

Lab. Ex. xxiii.,

page 271).

Mercury them alone,

is

prepared from

compounds by

its

or with sodium carbonate or Hme.

mercuric sulphide,

compound used

the natural

is

roasting

Cinnabar, in the

vn

industrial preparation of mercury.

ll.

PREPARATION OF MERCURY. in the Hood.

Experiment

4a

Perform 164. — {a)

Recall or repeat the preparation of mercury

{b)

Put a

em

from mercuric oxide.

vermilion or powdered cinnabar near one end of

little

a glass tube open at both ends, and heat slowly at slight angle to the flame

first,

but finally

.c h

strongly where the powder

is

and

located.

rotated.

The tube should be held at a Fumes of sulphur dioxide (and

mercury times

will

be deposited in the colder portion somewhat as

Mix any dry its

will

in {a).

mercuric chloride, with three

tube may be used, but it is liable to crack or be deposited on the upper part of the tube.

ht

— The layer The

a sublimate.

subliming. tion.

e.g.

test

tp ://

A

Mercury

Definitions. is

mercury,

weight of dry sodium carbonate, and heat strongly in an

ignition tube.

melt.

salt of

w

((f)

w w

possibly of mercury) will escape from the upper end of the tube, and

A

The

of

mercury obtained

operation

is

in

Exp. 164

called sublimation, or

preparation of iodine illustrated sublima-

sublimate

usually purer than

is

its

source.

TESTS FOR MERCURY. Experiment 165.

— {a)

What

{b) Recall or devise a test for

Mercuric Oxide viously studied.

is

is

the simplest test for free mercury

combined mercury.

the only

compound

of

Verify

?

it.

mercury

pre-

Experimental Chemistry.

jOO

LABORATORY EXERCISE. 1.

oxide. 2.

Describe briefly but accurately the Write the equation for the change.

What

XXXIV.

compound

historical interest has this

heat on mercuric

effect of

?

mercurous and mercuric nitrate and chloride.

ll.

scribed, viz.,

vn

Other Important Compounds of Mercury belong to the two series ?nalogous to the copper compounds previously de-

— (a)

chloric acid to a little is

The

Note

mercurous chloride.

dilute hydrochloric acid.

black precipitate

is

a few drops of hydro-

The white

insolubility in water

its

a few drops of

w w

is

a few drops of

ammonium

Add

The

{a).

precipitate

is

mercuric

ammonium

tp ://

chloride.

little

hydroxide, or enough to produce a decided

w

Compare with

change.

in

ammonium hydroxide. Its mainly mercurous ammonium chloride.

Add

a delicate test for mercury in mercurous compounds. Add a few drops of hydrochloric acid to a Mercuric. ib) mercuric nitrate solution. Compare the result with that in {a).

formation

pre-

and

.c h

cipitate

Add

Merairoits.

mercurous nitrate solution.

em

Experiment i66.

4a

PROPERTIES OF MERCUROUS AND MERCURIC COMPOUNDS.

mercurous nitrate is Hg./N03)2, and of mercurous chloride is Hg2Cl2; some authorities write these formulas HgNOg and HgCl. The formula of mercuric nitrate is Hg(N03)2, and of mercuric chloride is HgCl2. of

ht

The formula

These compounds are analogous and -ic oxides. Thus, Mercuric oxide

corresponding -ohs

HgO

is

Mercuric chloride

Mercuric nitrate

Mercurous oxide

HgCla Hg(N03)2

is

is

HggO

is

Mercurous chloride

Mercurous

to the

is

nitrate is

... ,

.

.

.

Hg2Cl2

.

Hg2(N03)2.

Mercury.

301

CLASS-ROOM EXERCISE.

LVI.

Additional study of mercury.

1.

(a) Occurrence of free and combined mercury. (d)

Industrial preparation.

{c)

Impurities,

and how removed.

(d) Properties. (e)

Uses.

vn

(/) Significance of the common name. (£) History. Mercuric oxide.

2.

Historical significance.

Mercurous compounds. (rt)

4a

Names.

(c)

em

3.

(<^)

ll.

(a) Preparation of the varieties.

Preparation, properties, uses, formulas^ and

common name

{3)

Other mercurous compounds.

(^)

Valence of mercury in mercurous compounds.

Mercuric compounds. (a)

w w

4.

.c h

of mercurous chloride.

Preparation, properties, uses, formula, and

common name

(c) 5.

Other mercuric compounds. Valence of mercury in mercuric compounds.

tp ://

(d)

w

of mercuric chloride.

Miscellaneous.

Explain the statement, " the vapor of mercury and of zinc

ht

(a)

consists of

(d)

monatomic molecules."

Discuss the relation of zinc to mercury, and of both metals to

magnesium and calcium

in the light of the Periodic

Law. (c)

6.

meaning of word " hydrargyrum."

Literal

Amalgams. (a)

Definition of an amalgam.

(d)

Preparation, properties, and uses of sodium amalgam.

(c)

What

is

amalgamated

zinc,

and

for

(d) For what do dentists use amalgams (e)

How

is

gold often extracted from

what

is it

?

its

ores ?

used

?

Experimental Chemistry.

302

PROBLEMS.

XXXVI.

and 620 mm. are obtained by heatthe atomic weight of mercury ? 2. How much mercury is formed by heating 400 gm. of pure cinnabar ? (Equation is HgS + O^ = Hg + SO^.) 3. If 70 gm. of mercuric oxide are heated, what volume of oxygen at 21'' C. and 740 mm. is evolved ? If 177.1664 gm. of mercuric sulphide yield 152.745 gm. of mer4. cury, what is the atomic weight of mercury ? 1.

If 195 cc. of

oxygen

at 37° C.

is

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

ing 2.7 gm. of mercuric oxide, what

CHAPTER

XIX.

ALUMINIUM — TIN — LEAD — CHROMIUM— MANGANESE IRON — SEPARATION OF METALS.

methods,

is

by

to its extensive preparation

a familiar metal.

Alum

has long been

ll.

known.

elec-

vn

Aluminium, owing trolytic

4a

GENERAL PROPERTIES OF ALUMINIUM.

—

Is

?

(d)

it

ductile, malleable, soft, hard, tough, brittle

Compare roughly the weight of a

piece of zinc, pasteboard,

aluminium

If sufficient

(See Exp. 150

available, determine the specific gravity. result with' the specific gravity of

w

other metals.

is

Compare the

((^).)

?

piece of aluminium with a

and glass having approximately the same

w w

volume.

.c h

brass

em

(a) Examine a piece of aluminium (sheet or Experiment 167. Has it any "spring 'Mike wire), and observe its physical properties.

tp ://

It has been asserted that aluminium by acids and alkalies.

is

not acted upon

ht

ACTION OF ALUMINIUM WITH ACIDS AND ALKALIES.

Experiment 168.

Warm,

if

necessary.

compound (d)

is

Add

formed

only a

Add

a small piece of aluminium to separate

Describe the action. in

each case

Test the gas evolved.

little

sodium hydroxide, and

gas

is

What

?

a small piece of aluminium to a test tube half

dilute solution of If

— (a)

containing dilute sulphuric acid and dilute hydrochloric acid.

test tubes

boil.

full

of a

Test any gas evolved.

liberated, attach a simple delivery tube

and

collect

the gas over water.

Other acids and alkalies act similarly draw a general conclusion from this experiment. Is the aluminium examined in Exp. 167 tar;

303

Experimental Chemistry.

304

? Scrape the surface, and examine again. from most metals in this respect ?

Does aluminium

nished differ

Aluminium Hydroxide

is

an important compound of

aluminium.

PREPARATION AND PROPERTIES OF ALUMINIUM HYDROXIDE.

—

4a

ll.

vn

Experiment 169. {a) Add slowly a little potassium hydroxide or sodium hydroxide solution to a test tube half full of alum solution. The gelatinous precipitate is aluminium hydroxide. Now add an excess of the alkali to one half, and dilute, hydrochloric acid to the other. Describe the results. Recall or devise another simple

Add The

a

little

solution of

precipitate

is

ammonium

sulphide to a solution of

not a sulphide, but aluminium hydroxide,

.c h

{c)

alum.

method of preparing aluminium

em

{b)

hydroxide.

because aluminium forms no sulphide in the wet way.

tp ://

w

w w

{d) Add a little alum solution to a dilute solution of cochineal, then add ammonium hydroxide. The colored product is called carmine lake. It belongs to a class of dyes formed by the combination of a vegetable dye and a metallic hydroxide, usually aluminium hydroxide.

Discussion of Experiment 169. or potassium hydroxide

is

first

— When sodium hydroxide added

to a solution of a

ht

compound of aluminium, aluminium hydroxide The simplest equation for this reaction is Al2(S04)3

+ 6K0H = 2Al(OH)3 +

3

formed.

K2SO4.

Aluminium Hydroxide

Aluminium Sulphate

An

is

—

excess of alkali produces a chemical change repre-

sented by the equation

A1(0H)3

-f

:

—

3KOH =

A1(0K)3 Potassium

Aluminate

+

3H2O

Aluminium.

The chemical changes

305

are similar to the changes of zinc

compounds under the same

(See Exp. 21.)

conditions.

TESTS FOR ALUMINIUM. Experiment i*jo.— minium?

(a)

What

is

a simple test

for metallic

alu-

Verify it. test for combined aluminium. zinc? of from those distinguished be compounds aluminium How can (c) Heat a little aluminium sulphate or aluminium hydroxide on Cool and moisten with a drop of cocharcoal in the blowpipe flame. Heat again, and if the operation has been baltous nitrate solution. conducted properly, a blue residue will coat the charcoal. This color Recall or devise a

ll.

vn

(/;)

aluminium compounds. Compare this result with compounds under similar circumstances.

4a

characteristic of

is

Alum

is

by

far the

em

the action of other metallic

most useful compound

of aluminium.

.c h

PREPARATION AND PROPERTIES OF COMMON ALUM.

— (a)

Dissolve about 10 gm. of aluminium sulamount of hot water. Dissolve 3 gm. of potassium sulphate in the same way. Mix the clear, hot, saturated solutions in a small shallow dish, and allow the solution to cool undis-

w w

Experiment 171.

turbed.

and

Crystals of potassium alum will be deposited.

and examine.

tp ://

best ones

w

phate in the least possible

;

dry,

Remove

Describe them, giving color,

the

luster, size,

crystal form.

Prove by actual tests that (i) they are a sulphate of potassium and of aluminium, and that (2) they contain water of crystallization.

ht

(d)

CLASS-ROOM EXERCISE.

LVIL

"^

1.

Additional study of aluminium. (a) Occurrence. the earth's crust.

(d)

Proportion

(c)

Industrial preparation.

in

(^/) Properties.

(e) Uses.

(/) History.

(g) Derivation of the words aluminiDn and al/n/iniium. 2.

Alums. {a) General formula. {b)

Varieties.

{c)

Properties of alums.

{d) Potassium alum.

{e)

Uses.

Experimental Chemistry.

3o6 Compounds.

Chemical name and formula of corundum, ruby, sapphire,

(^?)

cryolite, turquoise, bauxite, alumina, feldspar.

Miscellaneous. (a) Valence of aluminium in AljO.^ and

(c)

(d)

Al._,

(804)3.

What is burnt alum, a mordant, red liquor? What elements are closely related to aluminium? What is aluminium bronze? Uses.

vn

(d)

complete)

:

—

=

Al

+

O

(d)

Al

+

H,SO, =

A1„(S0,),

+

3H2

(0 Al,(SO,),

+

KOH

2A1(0H)3

+

3

4a

em

=

AloO,

XXXVII.

w w

can be obtained theoretically from 100 gm.

(a)

ALOo-aSiOo?

(I?)

Cryolite, AlNagF^j?

(c)

Turquoise,

w

Al^.p^ H^AiPe .

.

2 H,,0

?

tp ://

How much aluminium can be obtained by

the interaction of a

kilogram of sodium aluminium chloride and sodium? AlCL.NaCl + 3Na = Al + 4 NaCl.)

ht

What volume

KgSO^

.c h

How much aluminium of-

3.

already

(a)

PROBLEMS.

2.

is

ll.

Complete the following equations (note that one side

of oxygen at I5°C.

is

needed

to

(Equation

burn

5

is

gm. of

aluminium to Al^Og? Half a gram of aluminium when warmed with potassium hydroxide, cc of hydrogen at 13° C. (over water). Calculate the atomic = 2 KOII + 2 (Equation is Al, + weight of aluminium. 4.

liberated 660

2 KAIO., 5.

+

Hp

3 H,.)

Review Problems

Tin

is

5, 6, 7, 8,

9 in Chapter IX, page 154.

a familiar metal owing to

protective coating for iron.

Its

its

extensive use as a

compounds

merous, though one, stannous chloride, dyeing.

is

are not nu-

widely used in

Tin.

307

GENERAL PROPERTIES OF

TIN.

—

{a) Examine a stick of tin or a piece of pure Experiment 172. and state the most obvious physical properties. Bend a stick tin, and note the crackling sound.

tinfoil,

c^

{b)

If

a stick of tin or a piece of block tin pipe

mine the

specific gravity

150 (b).

Compare

is

available, deter-

by either of the methods described

Exp.

in

the result with the specific gravity of other metals.

Experiment 173.

—

{(i)

Put a small piece of

vn

ACTION OF TIN WITH ACIDS. tin

— about

and heat

— in the hood.

at first, and when action Most of the tin disappears,

Heat gently

Save

(^).

— in the

{b) Treat a small piece of tin with concentrated nitric acid It is

advisable to stand the test tube in the rack or in a bottle as

.c h

hood.

Exp.

this solution for

em

soluble stannous chloride being formed.

174

.5 gm. add a little

4a

water,

begins regulate the heat accordingly.

ll.

in a test tube, cover with concentrated hydrochloric acid,

w w

soon as the action begins. The white, amorphous product is metastanHow does the action of nitric acid on tin differ from and nic acid. resemble its action on other metals, zinc, for example?

w

Stannous chloride has the formula SnCl2, but the formula which

it is

tp ://

of metastannic acid varies with the temperature at dried.

ht

Experiment

174. —

TESTS FOR TIN. {ci)

What

is

a simple test for metallic tin

{b) Recall or repeat the action of tin

when heated

in a

?

blowpipe

flame. {c)

Add

a few drops of mercuric chloride solution {poison) to a

small portion of the stannous chloride solution prepared in Exp. 173 {a). The white precipitate is mercurous chloride. Add a little more stannous chloride solution finally to

and heat

gently.

The mercurous

chloride

is

reduced

mercury, which appears as a grayish powder.

Discussion of Experiment 174. readily form stannic compounds,

— Stannous i.e.

compounds by an extension of

the conception of oxidation and reduction, they reduce

Experimental Chemistry.

3o8

compounds and become oxidized, though no oxygen Thus the simplest equation for the involved. be may and mercuric chlorides is stannous of interaction other

—

2

+

HgCl2

SnCla

=

+

Hg2Cl2

SnCl^

Stannous

Mercurous

Stannic

Chloride

Chloride

Cliloride

Chloride

chloride

is

reduced to mercurous chloride,

while the stannous chloride

is

oxidized to stannic chloride.

ll.

The mercuric

vn

Mercuric

broadest sense means " going lower," and oxidation "going higher" in a series of compounds. Stannous chloride is often used as a reducing agent.

4a

its

em

Reduction in

Experiment 175.

.c h

DEPOSITION OF METALLIC TIN.

— Put a

strip of zinc in a slightly acid solution of

after a short time, and the tin will be found adhering to the zinc as a grayish black deposit; sometimes it appears as minute scales. What becomes of the zinc ?

Examine

w

w w

stannous chloride.

1.

tp ://

CLASS-ROOM EXERCISE.

Additional study of

tin.

(a) Occurrence of

(c)

2.

5.

(^/)

Uses.

(e)

History.

Compounds.

tin, tin

4.

tin.

Properties.

(a) Chemical

3.

combined

Industrial preparation.

ht

.{d)

LVIII.

name and formula

of cassiterite, tin crystals, strean:

dioxide, oxymuriate of

tin.

Miscellaneous. («)

What

(d)

Valence of

Name

is

tin plate tin in

?

"Tin"?

the important alloys of

Complete the equations (a)

Sn +

(^)

SnCl^

(0

SnCl^

+ +

:

Block

tin ?

SnCU, SnCl^, SnOg, SnS. tin.

— = SnO.. = SnCl^. = SnCL +

2

HCl

Lead.

PROBLEMS.

309

XXXVIII.

Calculate the percentage composition of

1.

(a) Tinstone, SnO^,. {d)

Stannous chloride, SnCl^.

(c)

Stannic chloride, SnCl^.

If 100

2.

gm. of

tin are

heated with nitric acid, and the

stannic

oxide formed on heating the product weighs 127. i gm., what tin

Lead, both free and combined,

the

is

well known, and has

Its principal

applications.

compounds

are the

ll.

numerous

is

?

vn

atomic weight of

and carbonate.

4a

oxides, sulphide, sulphate, chromate, nitrate,

GENERAL PROPERTIES OF LEAD.

em

—

(a) Examine a piece of freshly cut lead and most obvious physical properties. Determine its specific gravity by either method described in

Experiment 176. its

(d)

Exp. 150

Compare

(d).

.c h

state

the result with the specific gravity of other

metals.

easily

2. 3.

melted and tarnished

What Draw

the result.

What

it

for its extensive use

erroneously called "black lead"

is

air?

?

ht

?

Is there

any

?

TESTS FOR LEAD.

— (a)

Recall or repeat the reduction of lead oxide

(3) Recall or repeat the action of

Add

formed.

hydrogen sulphide with the

solu-

compound.

dilute hydrochloric acid to a little lead nitrate solution until

precipitation ceases.

Warm

scribe the action. its

exposed to the

blowpipe flame.

tion of any lead

is

XXXV.

When

?

physical properties adapt

Experiment 177.

(c)

?

a piece of lead across a sheet of white paper and describe

lead in a lead pencil

in the

when heated

w

it

to lead

tp ://

Is

w w

LABORATORY EXERCISE. What happens

1.

Note the

insolubility of the lead chloride

which

Deand permits

gently as long as any decided change occurs.

This

is

characteristic of lead chloride

separation from the chloride of silver and of mercury (in the -ous

condition).

Experimental Chemistry.

jio {d)

dilute sulphuric acid to a little lead nitrate solution until

Add

The

precipitation ceases. properties. {e)

Is

precipitate

soluble in hot water

it

is

Observe

lead sulphate.

Try

?

its

it.

Repeat {d), using potassium chromate or dichromate instead of

The

sulphuric acid.

precipitate

is

Describe

lead chromate.

it,

espe-

cially the color.

test in {c) it

is

is

usually

confirmed by

ll.

vn

—

The Discussion of Experiment 177. employed as the preliminary test, and {b), {d), and (e\ or any of these three.

4a

Lead, like other metals, interacts with zinc.

INTERACTION OF METALS 178.

—

LEAD.

em

Experiment

Repeat Exp. 162

(d),

and describe the

result.

and carbon

dioxide.

w w

air

.c h

Soluble Lead Compounds are often formed when lead is subjected to the action of water containing much gas, e.g:

ACTION OF WATER ON LEAD.

—

Fill

w

Experiment 179. dioxide into

tp ://

clean lead in

a bottle half

full

of water, pass carbon

from the lungs, and shake vigorously. Put a piece of the water, cork the bottle, and let the whole stand undisit

turbed for a day or two.

Remove

the lead and test separate small por-

by Exp. 177

(c),

(d), (e).

If

no lead

is

ht

tions of the water for lead

detected, let the action continue another day, or evaporate the liquid to

a small bulk and test as above.

Ordinarily, drinking water has no action on lead, but if the solvent power is increased by the presence of an excess of gases or of organic matter containing

sodium or potassium

nitrate, enough lead compound may be taken up by the water to cause lead poisoning when the water is drunk.

Oxides

of

Lead.

— There are several oxides of lead

;

the

most important are lead monoxide, PbO, lead dioxide, PbOg, and lead tetroxide, PbgO^.

Lead,

311

PROPERTIES OF THE OXIDES OF LEAD.

—

(a) Examine the three oxides and tabulate Experiment 180. most obvious physical properties, stating the exact chemical name and formula and the popular name of each oxide. their

Repeat or

(d)

recall the

experiment in which lead was heated

What

oxidizing flame, especially the color of the coating. is

(c)

thereby formed

Warm

product

is

a

.'*

lead tetroxide with dilute nitric acid.

little

Describe

lead dioxide.

The

LABORATORY EXERCISE.

ll.

XXXVL

1.

How

2.

If lead tetroxide is

heated strongly, lead monoxide

does this

about the stability of lead tetroxide

When

is

Complete the equation

evolved.

+

PbO,

?

=

HCl

PbCl.,

+

2H2O

—

+

?

lead nitrate be formed

w

How may

w w

does this interaction resemble that of manganese dioxide and

hydrochloric acid 4.

formed.

is

lead dioxide and concentrated hydrochloric acid are mixed

and heated, chlorine

How

4a

fact reveal

?

em

3.

might lead tetroxide be prepared

.c h

What

solid

it.

vn

lead

in the

oxide of

heated strongly?

Examine

Prove that

it is

?

What happens when

it

is

a nitrate and a lead compound.

lead carbonate and state

tp ://

its most obvious properties. and contains lead. 6. Examine a lump of galena and state its most obvious properties. Prove that it is lead sulphide. Complete the equation

5.

it is

ht

Prove that

a carbonate

:

+

PbS

O

=

4-

CLASS-ROOM EXERCISE.

—

SO.,.

LIX.

Additional study of lead. (a)

Occurrence.

(c)

Properties.

(d)

Metallurgy.

(^/)

Uses.

Oxides of lead. (a) (d)

(e)

History.

Give the preparation, properties, and uses of

Lead monoxide. Lead dioxide.

(c)

Lead

tetroxide.

Experimental Chemistry.

312 3.

4.

Lead carbonate. (a)

Occurrence.

(d)

Industrial preparation

(c)

Properties.

— old and new methods. Uses.

(^/)

Lead sulphide. (a)

Properties of galena.

(d)

Properties of the

artificial

sulphide.

Compounds of lead. Give the chemical name and formula of 5.

galena, cerussite, anglesite,

lead, litharge, lead

lead, red

Miscellaneous.

PbO,

(a) Valence of lead in

lead. 7.

PbO.,,

Law by

PbS, PbCO,, PbCla, PbCl^. the compounds of tin and

em

Illustrate the Periodic

(i>)

chrome

4a

6.

peroxide,

ll.

yellow.

vn

sugar of lead, white

Alloys of lead.

.c h

(a) Approximate composition of hard and soft solder, and of

pewter; uses of each.

Approximate composition of Britannia metal and of type

(c)

Components of a

(^)

What

w w

{d)

metal.

shot

Uses.

fusible alloy.

?

tp ://

w

is

PROBLEMS. XXXIX.

1.

What

per cent of lead

is

contained in

—

ht

(a) Galena, PbS. (d)

Cerussite,

(c)

Anglesite,

PbCOg. PbSO^.

(d) Lead acetate, PbCC.H.^O.Oa

•

3

HoO

How much litharge can be made from 40.5 gm. of lead tion is Pb + O = PbO.) 3. An analysis of lead monoxide showed that 100 gm. 2.

7.1724 gm. of oxygen. 4. is

If 5

?

(Equa-

contained

Calculate the atomic weight of lead-

gm. of lead chloride give 5.16 gm. of

the atomic weight of lead

?

(Equation

AgCl + Pb(N03)2-) 5. If 100 gm. of lead form 159.9703 gm. atomic weight of lead ? (Assume Pb + 2

is

silver

chlonde, what

PbCh,

+

2

AgNOg =

2

of lead nitrate, what

is

the

HNO3 = Pb(NO,)^ + H3.)

Chromium.

3^3

Chromium is an uncommon metal, but several of its compounds, especially potassium chromate, potassium dichromate, and chrome alum, are familiar, and have numerous industrial appHcations.

TESTS FOR CHROMIUM. Experiment i8i.

— (a)

Prepare a borax bead (see page 231), touch ^.^^. chrome alum, and heat in bodi the oxidizing and reducing flame. The green „olor is it

with a minute quantity of any chromium compound,

vn

a characteristic and delicate test for chromium.

Mix equal small quantities of potassium carbonate, potassium and powdered chrome alum,, place the mixture on a platinum and hold it with the forceps in the upper Bunsen flame so that the

(d)

will fuse.

A

crucible.

If a

platinum

is

not available, use a porcelain

yellow mass, due to the presence of potassium chromate,

If the color is

results.

foil

4a

mixture

acetic acid, slowly at

not decided, dissolve the mass in water, add

first,

and

em

foil,

ll.

nitrate,

boil to expel the

carbon dioxide.

Add

mate white,

precipitated.

is it

is

.c h

a few drops of lead nitrate solution to a portion, and yellow lead chro-

(Compare Exp. 177 (e).) If the precipitate is and shows that not all the potassium car-

lead carbonate,

w w

bonate was decomposed, as intended. (c) Add lead nitrate solution Name and describe the precipitate.

Try the solubility of the and sodium hydroxide.

solution.

precipitate

tp ://

w

in acetic acid, dilute nitric acid,

to potassium, dichromate

ht

Chromium in its Compounds is sometimes metallic and sometimes non-metallic toward the other components. Thus, in chromium trioxide, CrOg, the anhydride of the hypothetical chromic acid, H2Cr04, chromium acts as a non-metal, just like sulphur in sulphuric acid;

hence in chromates the chromium is acidic, or non-metallic, in its chemical relations with the other elements. In chromic compounds, however, chromium acts as a metal. Thus

chromium hydroxide, Cr(0H)3, is analogous to aluminium hydroxide chrome alum is potassium chromium sulphate, and is analogous to aluminium alum. The two classes pass into eagh other by appropriate operations, ;

Experimenta' Chemistry.

314 Chromates.

— The two important chromates are potassium

chromate, K2CrO^, and potassium dichromate, K2Cr207.

PROPERTIES OF CHROMATES. Experiment 182.

— {a)

Examine

crystals of potassium

chromate and

From

dichromate, and state their most obvious physical properties.

previously determined facts, predict their solubility or insolubility in

Verify the prediction.

vn

(J?)

Complete the equation

Recall the properties of lead chromate.

+

K^CrO^

=

Pb(N0,,)2

:

+

PbCrO^

ll.

water.

Add

(c)

a few drops of concentrated hydrochloric acid to a dilute

solution of potassium chromate

and observe the change of

color.

This

due to the presence of potassium dichromate, which was formed from

The

the chromate.

2KXr04

equation

2HCI

is

=

K,Cr,0,

+

2

Hp.

+

KCl

w w

+

—

.c h

is

em

4a

Lead Chromate

{d)

Add

w

Potassium Dichromate

potassium hydroxide solution to 10 until the color just changes.

tp ://

mate solution

the presence of

potassium chromate, which

Thus

—

ht

dichromate.

K,Cr,0.

(e)

2KOH =

+

The chromates

cc. of

The

is due to was formed from the

2K,Cr04

are oxidizing agents.

potassium dichro-

yellow color

Add

+

HoO.

a few drops of con-

centrated hydrochloric acid to powdered potassium chromate and dichro-

mate

in separate test tubes.

of hydrochloric acid.

mate

is

—

KaCrO^

+

8

HCl

The

=

Chlorine

is

evolved, owing to the oxidation

simplest equation in the case of the chro-

3 CI

+

CrCl,

+

2

KCl

+

4 H,0.

Chromic Chloride

—

Oxidation sometimes means the withdrawal hydrogen from a compound, as well as the addition of

Definition.

of

Chromium. oxygen.

If the

315

hydrogen can be removed,

it is

ultimately

oxidized to water, hence oxidation actually occurs.

Chromic Compounds. Exp. 182 chromate

— The

chromic chloride formed in passing from a

{e) illustrates the possibility of

chromic

a

to

Here the chromate was

salt.

Conversely, Exp. 181 (d) illustrates the forma-

tion of a

chromate by the oxidation of a chromic compound.

vn

reduced.

few cubic centimeters of potassium

concentrated hydrochloric acid and a few

little

Warm

Two

gently.

The

important changes occur.

em

drops of alcohol.

to a

4a

— Add

Experiment 183.

dichromate solution a

ll.

REDUCTION OF CHROMATES TO CHROMIC COMPOUNDS.

chromate is reduced to chromic chloride which colors the solution green the alcohol is oxidized to aldehyde, which is detected by its peculiar odor. (See Exp. in (^).) The equation is

+

8

HCl +

3 C,>H,0

=

2 CrClg

w w

K.^Cr.Pj

.c h

;

+

3

C.Hp +

— 2

KCl +

7

Hp.

Aldehyde

Alcohol

w

PROPERTIES OF CHROME ALUM.

— (a)

tp ://

Experiment 184.

Examine chrome alum and

state its

most

obvious physical properties.

and describe the

Recrystallize a

(c)

Prove that chrome alum

ht

(<^)

chromium and water

little

is

crystals.

a sulphate, and that

it

contains

of crystallization.

PREPARATION AND PROPERTIES OF CHROMIC HYDROXIDE.

— (a)

Add

sodium hydroxide solution to is chromic hydroxide. Describe it. Add an excess of sodium hydroxide solution and shake. Boil, and state the result. Describe the result (6) Add a little, and then an excess, of ammonium sulphide to a Compare the result with that in (a). Docs solution of chrome alum. chromium form a sulphide? Do aluminium and zinc?

Experiment 185.

a solution of chrome alum.

a

The

little

precipitate

Experimental Chemistry.

ji6

LABORATORY EXERCISE. 1.

Compare

XXXVII.

the action of sodium hydroxide on ordinary alum and

on chrome alum. 2. riow can aluminium hydroxide be distinguished from chromic hydroxide ? 3.

Read the discussion of Exp.

1.

Additional study of chromium. («) Occurrence and source.

(d) Uses.

(d) Preparation.

Chromates.

em

2.

Properties.

4a

(c)

LX.

ll.

CLASS-ROOM EXERCISE.

vn

169.

Give the preparation, properties, and sources of (a) Potassium chromate. Potassium dichromate.

w w

3.

.c h

(d)

Chromic compounds. (a) How do these compounds differ essentially from chromates ? (d) Names and formulas of those experimentally studied. (c) Preparation and properties of chrome alum.

w

4. Miscellaneous.

chromium

in

Cr(OH)o,

tp ://

(a) Valence of

(^d)

Cr^,(S0^)3,

PbCrO,, K,Cr,0.. Chemical name and formula of chromite,

ht

yellow,

crocoite,

K^,CrO^,

chrome

Guignet's green, chrome green, chiome alum,

yellow chromate of potash.

PROBLEMS. XL. 1.

Find the percentage composition of {a) Lead chromate, PbCrO^. (d) Chromic oxide, Cr^Og. FeO. (c) Chrome ironstone, Cr^,0.5 (J) Potassium chlorochromate, KClCrOg. (e) Chromium monoxide, CrO. .

(/) Chromium trioxide, CrOg. 100 gm. of lead nitrate produce 97.576 gm. of lead chromate, what is the atomic weight of chromium? (Equation is KXrO^ 2.

If

Pb(N03)2

= PbCrO^ +

2

KNO3.)

Manganese. If 100

3.

what

is

If 36.865

4.

what

gm. of chromous

the atomic weight of

is

317

chloride, CrCl^, yield 57.5

chromium

gm. of

gm. of chromic chloride form 100 gm. of

the atomic weight of chromium

= 2Cr(N03)3 +

?

chlorine,

?

(Equation

silver chloride,

6

AgNOo

Two

of its

2 CrClg

is

+

6AgCl.)

Manganese, like chromium,

is

a rare metal.

— (n)

Subject a minute quantity of manganese

dioxide to the borax bead

test,

and note the color of the bead

4a

Experiment

ll.

TESTS FOR MANGANESE. 186.

vn

compounds, manganese dioxide and potassium permanganate, have already been used.

heating in each flame.

after

tp ://

w

w w

.c h

em

(d) Fuse on a platinum foil or in a crucible a litde manganese dioxide mixed with potassium carbonate and potassium nitrate. (See Exp. 181 The green mass is a characteristic test for manganese. It is (d).) due to the presence of potassium manganate. (c) Add. ammonium sulphide to manganese sulphate or chloride The flesh-colored precipitate is manganese sulphide. Divide solution. Add hydrochloric acid to one and acetic acid to the it into two parts. Draw a other, then add an excess of ammonium hydroxide to each. conclusion regarding the solubility of manganese sulphide.

LABORATORY EXERCISE.

For what has manganese dioxide been used in the laboratory? it an oxidizing agent? 2. For what has potassium permanganate been used in the labora-

ht

1.

(s

XXXVIII.

tory 3.

?

Describe potassium permanganate.

bility in

What

can be said of

its

solu-

water?

Potassium Permanganate

is

a powerful oxidizing agent.

OXIDATION WITH POTASSIUM PERMANGANATE.

— (a)

Experiment 187. weak solution of fresh

Add

a few drops of sulphuric acid to a

ferrous sulphate

solution of potassium permanganate.

;

then add, drop by drop, a dilute

Us color

is

changed^ owing to

Experimental Chemistry.

31

the loss of oxygen which changes the ferrous to the ferric sulphate

the decomposition of the permanganate also allows the formation of

potassium and manganese sulphates.

Pour a solution of potassium permanganate upon a piece of Describe and explain the result.

{d)

paper.

LABORATORY EXERCISE. What

XXXIX.

the formula of potassium permanganate?

is

formula give a clue to the oxidizing power?

Potassium permanganate solution is

this application

is

often used as a disinfectant.

based

?

4a

property

ll.

2.

Upon what

Does the

vn

1.

filter

LXL

(a)

Occurrence.

(6)

Preparation.

Occurrence in native

Properties.

(c)

Properties.

(d) Uses.

state.

w

Potassium permanganate. Preparation.

(d)

Properties.

tp ://

(a) 4.

(c)

(d) Use.

Manganese dioxide. (a) Names. (d)

3.

.c h

2.

Additional study of manganese.

w w

1.

em

CLASS-ROOM EXERCISE.

(c)

Uses.

Miscellaneous.

Valence of manganese in

(a)

MnO, MnO^„ Mn^Og, MugO^,

ht

KMnO^, MnS, MnClg.

1.

what 2.

If is

PROBLEMS.

manganous

sulphate,

the atomic weight of

Calculate

MnSO^,

XLL yields 42.392 per cent of oxygen,

manganese ?

how much manganese can be

obtained from 100 gm.

of— Manganese dioxide, MnOoManganese trioxide, Mn^,0.;. (c) Manganese sulphide, MnS. (d) Manganese alum, K^,Mn^,(SO^)^ 24 (a) (d)

.

3.

H^,0.

Calculate the weight of oxygen liberated from 100 gm. ol potas'

slum permanganate when heated with sulphuric acid. ?

KMnO^ +

3

H3SO4 =

50 + 2 MnSO^ +

K2SO4 +

(Equation

3 H3O.)

is

319

Iron.

How much

4.

manganese ore containing 85 per cent

needed

dioxide

is

MnO. +

4 HCl

Iron and

numerous

to

prepare

= MnClg +

many

of

2

its

300

H.O +

of

manganese

(Equation

chlorine?

of

lb.

is

Cl^.)

compounds

are familiar and have

applications.

GENERAL PROPERTIES OF

IRON.

—

em

4a

ll.

vn

Experiment 188. (^) Examine cast iron, wrought iron, and steel, and state their most obvious physical properties. Try the action of a magnet on each. Drop a pinch of iron powder into the Bunsen flame. Hold a piece of fine iron wire in the Bunsen flame. Describe the results and draw conclusions. Compare the {b) Determine the specific gravity of a piece of iron. result with the specific gravity of other metals.

.c h

LABORATORY EXERCISE.

XL.

In previous experiments iron has been (i) heated in air, (2) heated and (4) heated with sulphur. Recall

1.

What

2.

alcohol ")

is

?

What

each experiment.

" iron by hydrogen,'' and " alcoholized iron" (or " iron by

use has been

made

tp ://

3.

briefly the essential result of

w

and record

w w

in steam, (3) treated with acids,

of ferrous sulphide in the laboratory.

Ferrous and Ferric Compounds.

— Iron forms two

ht

compounds, the ferrous and ferric. cuprous and cupric compounds. in the ferric

series of

They are analogous to The ferrous compounds

presence of free acid pass into the corresponding

compound by the

oxygen, bromine.

nitric

acid,

action of oxidizing agents, e.g.

potassium

Conversely the

ferric

the ferrous by reducing agents,

chlorate,

chlorine,

and

compounds are reduced e.g.

to

hydrogen, hydrogen

sulphur dioxide, and stannous chloride. The passage from one state to the other occurs easily, especially sulphide,

from ferrous

to ferric.

Experimental Chemistry.

320

— The

Ferrous Compounds. tests of ferrous

compounds

preparation, properties, and

are

shown by the

BEHAVIOR OF FERROUS COMPOUNDS.

— (a)

a

Put a few grams (3 to 5) of iron filings in 10 cc. of dilute hydrochloric acid, and warm

Experiment 189. add about

test tube,

Ferrous chloride

gently.

is

formed (in solution)

(

.

i

)

Pour a little into

The precipiWatch the changes in color. To what are the changes due? (2) Add a second portion to potassium ferricyanide solution. The precipitate is ferrous ferricyanide. Describe it. (3) Add tube one-third

test

full

of sodium hydroxide solution.

vn

a

potassium thiocyanate solution.

absent, no change results.

The

ferrocyanide solution. scribe

it.

tests,

serve to

especially (2),

.c h

The above

If ferric salts are

(4) Add a fourth portion to potassium precipitate is ferrous ferrocyanide. De-

em

a third portion to

4a

ll.

tate is ferrous hydroxide.

distinguish

ferrous from ferric compounds, as will be readily seen by a

w w

study of the

BEHAVIOR OF FERRIC COMPOUNDS.

—

scribe

tp ://

w

To a little ferric chloride solution add (i) Experiment 190. sodium hydroxide solution. The precipitate is ferric hydroxide. Deit.

Add

to ferric chloride solution (2) a little solution of potas-

sium ferricyanide.

Add

ht

as above (3) a wine-red coloration test

distinguishes

Compare the negative little is

result with (2) in

solution of potassium

caused by the soluble

ferric

thiocyanate.

Exp. 189,

The

from ferrous compounds.

(4) a little solution of potassium ferrocyanide. Describe it. ferrocyanide.

The

Add

above

as

precipitate

rich

This

ferric thiocyanate.

is

ferric

Tabulate the results of Exps. 189 and 190.

REDUCTION OF FERRIC COMPOUNDS. Experiment 191.— Put a piece made slightly acid by hydrochloric

of zinc in ferric chloride solution

duces the

After the operation has proceeded

for

ferric to ferrous chloride.

about fifteen minutes,

and a

ferric

compound.

acid.

test a portion

If

The

nascent hydrogen re-

of the liquid for a

ferrous

the tests are not conclusive, continue the

Describe the result.

Iron.

321

OXIDATION OF FERROUS COMPOUNDS.

— (a) To

Experiment 192.

add a

ferrous sulphate

crystals of potassium chlorate.

add a few

test portions of the liquid for

{b)

Add

warm

After heating a short time,

10 cc. of concentrated nitric acid, drop by drop, to a hot

boil.

sulphuric acid 'las been

little

Test portions of the liquid for a

ll.

LABORATORY EXERCISE.

a crystal, which has been exposed to the the more Examine specimens of

scribe each.

piece of

ground

glass,

6.

It is

w

ties.

Examine

ferric

Test

and ferrous

first

the formula of each (pure) 5.

both

hematite, limonite, and magnetite. Detwo across a sheet of rough paper or a and describe the "streak-' made by each. What

the

iron pyrites

Examine specimens

What

compound?

and

Significance of each

name?

most obvious physical properthe formula? For what is it used?

state its

What

iron disulphide.

tp ://

is

Draw

physical properties.

stable form, ferrous or ferric?

w w

4.

Explain.

Which seems

its

air, for

.c h

compounds. 3.

XLI.

4a

Read the discussion of Exp. 174. Examine ferrous sulphate, and state

em

2.

and a ferrous

Recall a third illustration of the oxidation of a ferrous to a ferric

compound.

1.

ferric

vn

compound. {c)

gently,

a ferric and a ferrous compoun.L

solution of ferrous sulphate to which a

added, and

washed and then

a solution of fresii or freshly

hydrochloric acid,

little

is

of siderite.

Describe them.

How

Siderite

is

formed in the earth's crust? Try the action of warm hydrochloric acid on a little powdered siderite. How does iron get into clay banks and :Xo the soil ? is

the formula?

is

it

ht

ferrous carbonate.

CLASS-ROOM EXERCISE. I.

LXIL

Additional study of iron. (rt)

Occurrence of

(^b)

Ores of

free

and of combined

iron.

iron.

Metallurgy of iron and steel. {d) Properties of cast iron, wrought iron, and steel. {e) Composition of the three common kinds of iron. (c)

(/")

What

{g)

Uses of the various kinds.

is

passive iron?

Experimental Chemistry.

322 2.

Explain the general relation of ferrous to ferric compounds, and by equations the method of passing from one to the other.

illustrate 3.

Compounds of

iron.

Give the chemical name and formula of red hematite, iron magnetite, loadstone, copperas, green vitriol, iron liquor. 4.

Miscellaneous. (a)

What

(c)

and how

Valence of iron in Fe.fi.^, Fe^O^, FeCOs, Fe(OH)3, FeO, FeSO^, Fe,,(SOJ,, FeS, FeS,. The group CN, known as cyanogen, has the valence one.

Common

ink?

is

rust?

bluing?

Calculate the atomic weight of iron.

Fe,03.) 2.

gm. of iron formed 2.265

A

(Equation

gram of iron

w

tp ://

ferrous oxide to ferric oxide?

What volume

reduce 63 gm. of

H = 3 H,0 +

ht

6

(Equation

ferric

Iron

of ferric

Fe +

oxide to metallic iron?

3

O

and

oxidation of 100 gm. of

FeO + O = and 780 mm.

is 2

of hydrogen at 13° C.

Fe^,03.) is

(Equation

needed to is

Fe.,03

+

2 Fe.)

Separation of Metals.

ments

2

liberated 389.74 cc. of hydrogen at 14° C.

820mm. What is the equivalent of iron? 3. What volume of oxygen is used in the 4.

g'""-

is

w w

=

Galvanized iron?

XLII.

.c h

PROBLEMS. Berzelius found that 1.586

oxide.

in ferrous ferricyanide,

In ferric ferrocyanide Fe^(Fe(CN)^)3?

em

What

4a

What is the valence of the iron atoms Fes (Fe(CN ),;).?

(d)

closely

this relation emphasized.''

vn

is

ll.

(/;

What metals are

elements are related to iron ?

related to iron,

1.

pyrites,

— Many

of the foregoing experi-

fundamental principles of quahtative analysis. The experiments, however, emphasize only the detection of elements or groups, e.£: zinc and the sulphate group when testing zinc sulphate. In many instances the illustrate the

various tests would be interfered with by the presence of

Hence it is necessary to separate the compounds before applying tests. It is custom-

other substances. essential

ary to speak of the separation of metals, though usually a

compound

of the metal

is

meant.

Thus,

if

a mixture

Separation of Metals.

and

of lead chloride

^'^3

silver chloride is boiled

with water,

the lead chloride dissolves, and filtration separates the lead chloride from the silver chloride, or, loosely, the lead from

the

silver.

Once

A

but others are complex. is

illustrated in

and behave

in

Exp. 135, since sulphides are usually solids various definite ways.

following experiments illustrate simple separations,

vn

The

may be used Some separations are simple, common method of separation

separated, the special tests

to detect the various metals.

Such a course

is

beyond the scope of

this

4a

book.

ll.

but are in no respects a substitute for a course in qualitative analysis.

SEPARATION OF LEAD AND SILVER.

em

—

Mix 5 cc. each of lead nitrate and silver nitrate Experiment 193. and add dilute hydrochloric acid drop by drop, until precipitation ceases. Allow the mixed precipitates of lead chloride and silver chloride to settle, decant the supernatant liquid down a glass rod, add a little water to the precipitate, and boil. Filter. Test portions of the filtrate for lead (see Exp. 177 (d) and (e)). Test the precipitate for silver

w w

.c h

solutions,

by (a) fusing a portion

ammonium

w

the solubility in

in the

blowpipe flame, or (d) determining

hydroxide, or (c) exposing

it

to the sunlight

tp ://

(a change to purple indicates silver chloride).

SEPARATION OF LEAD, SILVER, AND MERCURY

(-OUS).

Experiment 194. — Mix

ht

5 cc. each of lead nitrate, silver nitrate, and mercurous nitrate solutions, and add dilute hydrochloric acid drop by

until precipitation ceases. Separate and test the lead as in Exp. 193. Pierce a hole in the point of the filter paper with a glass rod, and wash the mixed precipitates of silver and mercurous chlorides Warm gently and into a test tube with dilute ammonium hydroxide.

drop,

shake.

Filter,

and

test the filtrate for silver as in

Exp. 193.

residue (see Exp. 166 (a)).h a sufficient test for mercury.

may be confirmed

thus

agua

with water, and add a clean copper wire

regi'a, dilute

:

The Its

Dissolve the black precipitate in a very

wire in a few minutes, wipe gently, and mercury will wire as a bright silvery coating.

black

presence little

remove the be seen on the ;

Experimental Chemistry.

324

SEPARATION OF SILVER AND COPPER, OR ANALYSIS OF A SILVER COIN. ,

Experiment

195. — Repeat the

and the

precipitate for silver,

and

first

filtrate

part of Exp. 154 {b).

Test the

copper (see Exp. 151

for

{b)

{c)).

SEPARATION OF COPPER AND OF BRASS.

vn

— Dissolve

a few grams of fine brass wire in a

ll.

Experiment 196.

dilute nitric acid, evaporate nearly to dryness, dissolve the residue

4a

little

OR ANALYSIS

ZINC,

add 10 or

in water,

and pass hydrogen

15 cc. of hydrochloric acid,

siderable hydrogen sulphide water.

sulphide water to see

The

if

complete, continue the

filtrate

Test the

filtrate for

warm

not, proceed as

filtration.

;

the precipitate

zinc (see Exp. 21 (a)).

and

dilute nitric acid,

filtrate for

if

;

filter, if

is

Dissolve

the solution

copper (see Exp. 151 {b) and

(<:)).

w

Test the

and add hydrogen

little,

complete

w w

the copper sulphide in

not clear.

is

contains the zinc as zinc chloride

copper sulphide.

is

Filter a

precipitation

.c h

before, but

if

em

sulphide gas into the solution for about twenty minutes, or add con-

tp ://

SEPARATION OF LEAD AND TIN, OR ANALYSIS OF SOLDER.

—

ht

Dissolve a gram of solder filings in as small a Experiment 197. quantity of hot aqua regia as possible, evaporate nearly to dryness, dissolve the residue in water,

add 10

to 15 cc. of hydrochloric acid,

precipitate the metals as sulphides as in

hot water, pierce a hole in the a test tube with yellow

and shake.

sulphide,

The

filtrate

The

precipitate

and

is

paper,

196.

Filter,

wash

and wash the precipitate into Add more ammonium

sulphide.

ammonium

sulphostannate

;

add

to

it

and yellow stannic sulphide appears.

lead sulphide.

Dissolve

it

in hot dilute nitric acid,

test the filtrate for lead.

SEPARATION OF COPPER. IRON, AND SODIUM. Experiment 198.

and -with

Filter.

contains the tin as

dilute hydrochloric acid,

filter,

filter

ammonium

Exp.

— Repeat Exp.

135

Separation of Metals.

325

SEPARATION OF ZINC AND IRON.

—

Mix 5 cc. each of zinc sulphate and ferric add an excess of sodium hydroxide drop by drop, and shake vigorously. Filter a little, and add sodium hydroxide to see Experiment

199.

chloride solutions,

precipitation

if

continue the tate

is

complete

filtration.

not,

if

;

Test the

proceed as before, but

filtrate for zinc.

if

complete,

Scrape the piecipi-

from the paper into a dish, dissolve in dilute hydrochloric Exp. 190).

ac'd,

and

vn

test portions for ferric iron (see

— Mix

ll.

SEPARATION OF ALUMINIUM AND IRON.

each of alum (common) and ferric and separate as in Exp. 199. Test the aluminium (see Exp. 169 (a)) and the precipitate for iron as 5

cc.

4a

Experiment 200. filtrate for

in

Exp.

em

chloride solutions, precipitate,

190.

.c h

SEPARATION OF ZINC AND ALUMINIUM.

— Mix

each of zinc sulphate and alum (comand redissolve the hydroxides of zinc and aluminium with sodium hydroxide solution. Pass hydrogen sulphide gas into the solution, or add considerable hydrogen sulphide water. The precipitate is zinc sulphide, which may be further tested, Filter. if desired, though the formation of zinc sulphide under these condiThe aluminium is in the filtrate as tions indicates the presence of zinc. sodium aluminate. Add to the solution of sodium aluminate hydrofilter, if necessary, and test the chloric acid to acid reaction, and boil

Experiment 2GI.

5 cc.

Precipitate

w w

solutions.

tp ://

w

mon)

;

ht

filtrate for

aluminium.

CLASS-ROOM EXERCISE. I.

LXIII,

Devise and describe a method for the separation and detection of

the metals in a mixture of

—

Manganese sulphate and chrome alum. (^d) Silver nitrate and alum. (c) Copper and aluminium (aluminium bronze). (d) Lead sulphide and silver sulphide.

(a)

vn

ll.

4a

em

.c h

w w

w

tp ://

ht

vn

ll.

4a

em

.c h

w w

w

tp ://

ht APPENDIXES,

vn

ll.

4a

em

.c h

w w

w

tp ://

ht

APPENDIX

A.

MANIPULATION — WEIGHING AND MEASURING. Hard Glass Tubing

infusible in ordinary flames, and which require intense heat. It is cut in the same manner as soft tubing, though the scratch must be deeper. It can be bent b}^ using the hottest possible flat flame of a Bunsen burner. Ignition tubes and combustion tubes are made of hard glass tubing and unless they are heated and cooled slowly they will surely crack. Constant care should be taken in using such glass. It is advisable to heat the whole tube gently at first, before directing the flame upon any particular part. Combustion tubes may be safely heated by either (i) winding a piece of fine wire gauze (iron or copper) around the part of the tube to be heated, or (2) winding a piece of copper wire (No. 20) once or twice around each end of the tube so that is

in all operations

tp ://

w

w w

.c h

em

4a

ll.

used

vn

I,

is

pieces of the wire project like

and

The

59.

ht

Figs. 45

used

Avith

success in

spokes of a wheel.

latter device all

See

has been repeatedly

the experiments

in

this

book

demanding such a precaution.

MAKING IGNITION TUBES.

—

Experiment 6. Ignition tubes have thick walls and are made of Read again the precautions to be observed in heating hard

hard glass. glass.

Select a piece of hard tubing about 20 centimeters long and of the

desired internal diameter (from 7 to 10 millimeters

Warm

it

by holding

it

over the

flat

Bunsen

329

flame,

is

a convenient size).

and gradually lower

Experimental Chemistry.

330

so that the middle

the tube into the flame

Rotate

and

pull

When

slowly and evenly.

it

it

soft,

shown

apart a short distance, as

the hottest part.

in

is

remove

from the flame,

it

Then

Fig. 84.

in

so that the flame will melt

along the dotted line B

yields

to

a

will

pifich

a

it off"

little

it

Do

separated.

more-

and B the two

A

not pull

portions apart too quickly, or the glass

made.

may have

little

vn

are

tube, partially

out a

it

operation until

Heat

thread or bit of glass on the end.

with the forceps

if

;

The

be thin at the end.

ll.

— Ignition

this

large,

it

4a

84.

Fi(^.

soon as

as

A

part

gentle pull, remove from

the flame, and draw

Continue

;

heat

that

may be pulled

off,

part

A

end and

this

but this opera-

remove too much glass and make the end thin. If the closed end is not symmetrical, heat it, and then blow gently into the Heat tube, heating and blowing until the desired shape is produced. liable to

at the

em

B

is

narrower part and proceed as with

If a blast

lamp

same procedure.

is

.c h

tion

^i.

available, better results

Hard

may be obtained by

the

glass tubes, after heating, should always be

Heating.

beakers,

retorts,

and

all

glass

should never be heated when empty, nor over a

tp ://

vessels

— Flasks,

w

2.

w w

coated with soot from the yellow flame and thus allowed to cool slowly.

direct or free flame

somethin^:,

if

they

unless

the

ht

contain

even

Fk;

f

wire "auze.

directions so indicate.

Fig. 86.

— Porcelain dish.

They should be placed on

a piece of

by a tripod or the ring of an iron stand, and heated gradually from beneath. Porcelain dishes (Fig. S6) should be heated with even

iron or brass wire gauze (Fig. 85) supported

more precaution than large

glass vessels.

They should

Appendix A.

33

always be placed on a piece of gauze, or similar protection, and heated and cooled gradually. They should never be

on a cold surface when they are hot, but on a block of unfinished wood, a piece of asbestos board, or a straw

ring.

— Covered porcelain crucible. Porcelain

Triangle.

Fig.

em

Fig. 87.

4a

ll.

vn

laid

crucibles (Fig.

Sy),

however, owing to

and small size are usually supported on a triangle (Fig. 88), or a pronged tripod (Fig. 21), and heated

.c h

their thin walls

safely with a low, free flame.

The

covers of crucibles

snap, and should be heated with

w w

often

than the crucibles themselves, especially

w

been weighed, since the

loss of a

more precaution if

the cover has

weighed cover means a

ht

tp ://

repetition of the experiment.

Fig. 89.

— Casserole.

An

exceedingly convenient and inexpensive porcelain vessel for general use is a casserole (Fig. 89). It is a deep, It is thin-walled dish with a handle and a flat bottom.

made

in

several sizes,

and the one containing 125 cubic

Experimental Chemistry.

33^ centimeters

is

best adapted to ordinary use.

heated over a free flame,

kept in motion, though

if

it

is

may be

It

and employ a piece of

partly filled with liquid safer to

gauze.

Evaporation

vapor.

flame

It is

the slow conversion of a liquid into

is

may be accomplished

in several

A

ways.

vn

3.

best suited for rapid evaporation, but

it

free

should

used for concentrated solutions or semi-fluid masses, as loss or accident may occur by spattering, deAs the concentration increases, composition, or breakage.

4a

advisable to transfer the vessel to a water bath (Fig. 90),

em

it is

ll.

never be

which

^^^__

intended to ac-

.c h

w w w

tion. sel,

iron,

The

containing ves-

which has

copper or

is

a

top

tp ://

consist-

ing of movable concentric rings to adapt

it

of various sizes.

two-thirds

— \\'aterl)atn

evapora-

slow

full

to dishes It is filled

of

water,

supported on a tripod or

ht

Vir.. 90.

is

complish

ring of an iron stand, and heated underneath, the vessel meanwhile having been so placed on the bath that it is

The temperature of the almost entirely in the steam. slowly raised to nearly thus is evaporated be solution to never be alloweU must 100° C. bath the in The water run dry." Equable heat at a higher temperature than 100° C. may be conveniently obtained by using a sand batho This is simply a shallow iron pan (Fig. 91) filled with

to evaporate entirely or

dry, clean

*

sand and supported on the ring of an iron The dish to be heated is partly

stand or on a tripod.

Appendix A

333

imbedded in the sand, and heat is suppHed by a burner A small tin pan serves the purpose, under the bath. though iron pans of all sizes m ay be obtained from dealers.

Evaporation is also performed by placing the vessel containing bestos

meters

square.

15

The

centi-

Fig. 91.

— Sand bath pan.

asbestos

in the same way as the sand bath. An air sometimes used for evaporation (Fig. 92). It is

supported is

4a

bath

ll.

is

about

board

as-

vn

the solution on a piece of

also called a dry-

em

ing

is

oven, for

it

really nothing

ht

tp ://

w

w w

.c h

but a small copper

oven

supported

on four hole

A

legs.

the

in

top

contains

a

cork

carrying

a

ther-

mometer allows

which tem-

the

perature

the

of

bath to be noted

without

opening

the door.

An

oil

stove and

its

ac-

companying baking Fig. 92.

— Air bath

a

oven

make

convenient

air

bath. 4.

Filtration.

— The folded paper should rest firmly on the

walls of the funnel so that the weight of the added liquid

Experimental Chemistry.

334

If moistened with water or will not tear the filter paper. the liquid to be filtered after being fitted to the funnel, the paper will keep its place more securely and filter more rap-

The paper should never project above the edge funnel. The stem of the funnel should be near the wall

idly.

the vessel and just above

down

It is better, also, to

a rod

upon the

pour the liquid

side of the paper, as

to

be

shown

tp ://

w

w w

.c h

em

4a

ll.

filtered

of

the surface of the liquid to pre-

vn

vent spattering.

of

ht

Fkj. 93.

in Fig. 93,

— Filtering —correct

otherwise the liquid

of the containing vessel, as is

Fig. 94.

used for rapid

filtration,

— Filtering -

may run down

shown

in Fig. 94.

the apex of the

mcorrect.

the outside If a filter

pump paper

should be protected by a platinum cone, by a small cone of parchment paper pricked with holes, or by a small square of cheese cloth folded into the point of the

filter

paper.

—

Rubber Stoppers, Corks, Joints, and Safety Tubes. recommended. are holes two with and stoppers with one 5.

They

are decidedly superior to corks.

If

corks are used.

Appendix A.

335

they should be free from cracks and be softened by rolHng convenient way is to wrap the cork in or pressing.

A

paper to protect it from dirt, and then roll it under the Holes of any size are made in corks foot on the floor.

A

by a cork borer.

The

set of

cork borers

is

shown

in

Fig.

which accompanies each set of cork borers serves as a handle when passed through the holes in the cap of the borer, and also as a piston to remove the cyUnder of cork which often remains in the borer after the stout wire

vn

95.

— Set of cork borers.

.c h

Fig. 95.

em

4a

ll.

operation.

w w

To bore a hole in a cork proceed as follows Select a cork free from cracks or channels and use a borer which Hold the cork is one size smaller than the desired hole. :

in Fig. 96, press the

ht

tp ://

w

between the thumb and forefinger, as larger end against a firm but soft board, and slowly push the borer by a rotary movement through the cork, taking care to

Fig. 96.

— Boring a hole in a cork.

keep the borer perpendicular to the cork.

with a round

file.

If the hole is too small,

enlarge

it

If corks are used instead of rubber

stoppers, the apparatus should always be tested before use into it, stopping of course all legitimate outpoor cork often means a failure, to say nothing

by blowing lets.

A

of wasted time.

Rubber stoppers to be used in quantitative experiments should be boiled in dilute sodium hydroxide solution, rinsed

Experimental Chemistry.

jj6

with water, then boiled in dilute hydrochloric acid, and This operation removes all finally washed with water. particles of matter which might adhere to tubes and thereby introduce into the final result a needless error. Glass tubes are joined by short pieces of rubber tubing called rubber connectors.

Such

joints should

be gas-tight.

vn

Before experiments begin leaks should be discovered by Dj not stop testing the apparatus at the necessary points.

ll.

leaks by wax, vaseline, or any temporary makeshift. Rubber connectors pieces of apparatus which fit.

Select

may be

end

of the tube

em

4a

tightened by tying them to the glass tube with a waxed Joints are often made tighter by having on thread. the end of the glass tube a flange, made by heating the

and pressing

while hot upon a hard

.c h

surface.

it

w w

Safety tubes are recommended in place of the ordinary See Fig. 30. They should fit perstraight thistle tube.

and always have enough liquid in the lower bend to If the liquid to be prevent a backward escape of gas. introduced will not run down, loosen the stopper slightly. the If the straight thistle tube is used, it must dip into

tp ://

w

fectly

ht

liquid in the flask or bottle.

6.

To Cut

off

the Bottom of a Bottle.

— Select a bottle with

Tie a piece of cotton string walls of uniform thickness. point where it is to be cut. the at bottle the loosely around enough to stay in place tight just be The string should little kerosene on the a Pour and the knot very small. turning the bottle slowly at the same time, until The kerosene should follow the string is saturated. the string and in no case be allowed to run down tne Light the kerosene at one point and side of the bottle. string,

rotate the bottle slowly so that the flame will heat the glass

Appendix A. beneath the

When

string.

plunge the bottle into a

the circle

337 complete, quickly

is

and

pail of water,

it

will

crack

The edges should be smoothed Both parts of the bottle may be utilized with emery paper. The ordinary five-pint acid bottle, in many experiments.

evenly at the desired point.

or Hthia bottle,

is

well suited to this method.

Rubber Tubing. -- Cut the rubber tubing at an angle, as shown in Fig. 97, moisten the smoothed end of the glass tube with water, place the end of the glass tube in the angular shaped cavity so that both To Insert a Glass Tube

into

— Rubber tube cut at an angle

.c h

Fig. 97.

em

4a

ll.

vn

7.

(exact size).

w

w w

tubes are at about a right angle, and then slip the rubber tube If the glass slowly up and over the end of the glass tube. tube is large or the rubber tube stiff, the rubber tube

To Fit a Glass Tube

ht

8.

tp ://

must be held firmly between the thumb and forefinger keep it from slipping off until it is securely adjusted. to

a Stopper.

edges of the tube in the flame. the end with a

little

— First

When

it is

to

round the

cold,

moisten

water, glycerine, or vaseline (preferably

about an inch from the end, hold the stopper between the thumb and forefinger of the other hand, and work the tube into the hole by a gradual rotary Proceed in the same manner, if the tube is to be motion. pushed through the stopper. Never point the tube toward Never the palm of the hand which holds the stopper. grasp a safety tube or any bent tube at the bend when the

first),

inserting

grasp

it

it

firmly

into a stopper

—

it

may

break.

Experimental Chemistry.

33^

To Dry the Inside of a Tube or Bottle.— Moisten the inside with alcohol, and then with a bellows force in air through a glass tube reaching to the bottom of the vessel hold the bottle mouth downward and withdraw the glass Never stand a wet bottle tube as the alcohol evaporates. 9.

tedious.

—

ll.

is

vn

on a hot support, for a drop of water may be jostled down upon the heated bottom and shatter the bottle. The inside will dry if the bottle is exposed to the sun, but the operation

Partly fill the bottle To Clean the Inside of a Bottle. shot, or sand, and paper, soft with water, drop in wads of shake the bottle vigorously. This device is also applicable to the large tube of a condenser, and to large flasks,

w w

.c h

em

4a

10.

w

stage.

Introduce

into a

a

Tube. —

narrow strip smooth paper so that

First fold a

it

— Introducing a powder into a tube first

Powder of

tp ://

Fig. 98.

To

11.

will slip into the

easily.

tube

Place the pow-

der at one end of the troughUke holder, and

ht

slowly push the paper into the tube, as far as necessary,

moving the tube rather than the paper. operation Fig. 98.

is

This

shown

in

Rotate the tube

or turn the paper, and

the powder will be deposited

at

the

desired

Fig. 99.

second

point (Fig. 99). Carefully withdraw the paper.

way, whether the tube

is

Introducing a powder into a tube

Introduce

open

all

—

stage.

powders

in this

or closed, large or small.

Appendix

A

339

—

Liquids Pouring Liquids and Transferring Solids. a vessel without spilling, by moisten-

12.

may be poured from

ing a glass rod with the liquid and then pouring

down the rod as is shown in Fig. lOO. The

it

angle at which the rod held varies with

cumstances.

a

is

Fig. ioo.

way

— Pouring a liquid down a rod.

pour

to

ll.

convenient

cir-

This

vn

is

4a

a liquid from a vessel containing a solid without disturbing

the

Solids should never be poured directly from a

solid.

em

large bottle into a test tube,

retort,

Fig. ioi.

w w

.c h

vessel.

— Pouring a solid

method

A is

or

similar

convenient as

follows

Rotate the bottle slowly so that the solid will roll

into a vessel with

out in small quantities

a small opening.

tp ://

w

catch this solid on a narmiddle, and slide the the folded along paper row strip of vessel. ' The last into the desired solid from the paper

is

the operation

ht

part of

shown

in Fig.

lOi.

Liquids can often be

poured from a bottle

by holding the bottle as shown in Fig. 102. Notice that the stopper

and

bottle are held in

the same hand.

This

pjg. 102.

—The

way

in

which a glass stopper

should be held while a poured from a bottle.

liquid

is

being

by accomplished holding the palm of the hand upward and removing the

is

Experimental Chemistry.

340

stopper by grasping it between the fingers before the botAll stoppers should be removed this way, is lifted. when possible, and never be laid down, because the im-

tle

purities adhering to the stopper

may run down

into the

Never return any taken, throw it been has much if too bottle to a reagent mixed if become will not bottles and away. Stoppers label. similar has a each bottle and stopper and contaminate the

bottle

solution.

To Make a Platinum

A

is

Tip.

— The steps arc shown

in

piece of glass tubing about 12 centime-

1

A

D

B

.c h

em

4a

a.

ll.

13.

Fig. 103.

vn

;

w

w w

:>c

ters

tp ://

Fig. 103.

long and

middle

ht

in the

5

B

tip.

millimeters in internal diameter. Heat this Bunsen flame and draw it out into the

in the

shape shown in

Cut

— Stages in making a platinum

B

;

draw

it

slowly at

at the point indicated

first,

then rapidly.

by the dotted Hne.

Roll a

about 25 millimeters square begin at one corner and in shown as tube, into a conical file, gradually shapround of a end small roll it around the piece of thin platinum

foil,

D

;

ing the platinum tube so that it will slip into the larger end where the Heat of C but not out of the smaller end.

B

dotted line is drawn, and the glass and platinum The completed tip is like B, though it unite.

will firmly

may vary

Appendix A.

J41

It is used in burning hydrogen and with circumstances. other gases and is attached to the generator by a rubber conThis tip is more expensive than the customary nector.

form, but

safe

is

it

and durable.

A

short piece of pipe-

stem or capillary tubing may be used instead of the num tip, but these are not so satisfactory.

plati-

—

Rotate To Seal a Platinum Wire into a Glass Rod. long, centimeters about 10 rod, glass of piece of a one end a piece grasp time same the At softens. in the flame until it forceps about

to 7 centimeters long firmly in the

5

centimeter from the end and hold it in the the rod is soft enough, gently push the hot

i

When

em

flame.

from

4a

of platinum wire

ll.

vn

14.

Cool the rod gradually by rotating

.c h

wire into the rod.

The completed

w

in the flame.

If a glass

tube to

is

-o test wire.

wire

is

used, instead of

a very small

tp ://

drawn out

— Platinum

w w

Fig. 104.

it

shown a rod,

diameter (see

in Fig. 104. it

should be

Fig.

103,

B)

before inserting the platinum wire, but in other respects

ht

the two operations are practically identical.

—

Gases are usually collected over 15. Collecting Gases. water by means of a pneumatic trough, a common form of which is shown in Figs. 23 and 25. The vessel to be filled with gas

is first filled

with water, covered with a piece of

paper, inverted, and placed

the trough, which the shelf.

is

mouth downward

previously

The paper

is

filled

filter

on the shelf of

with water just above

then removed and the vessel

Glass plates placed over the hole in the shelf of the trough. filter paper may be used to cover the bottles

instead of

Experimental Chemistry.

34^

Figure 105 is a conventional sketch of a cylinder in position pneumatic trough. It is represented partly filled with gas which comes through a delivery tube and bubbles up

in a

through the water into the cylinder. As the gas rises, water is

forced

down

out of the bottle Bottles are

into the trough.

inders,

vn

usually used in place of cyl-

and the delivery tubes

4a

ll.

have various shapes. All gases insoluble in water may be collected over water in this way.

em

Some heavy rine,

gases, like chlo-

hydrochloric

and

acid,

.c h

sulphur dioxide, are collected

—

by allowing the gaS tO flow ^^^^^^^^^^ ^^,^0 an empty ^ J bottlc and displace the air in the See Fig. 52. Ambottle, i.e. by dowmvard displacement. monia gas, being a light gas, is collected by allowing the gas to flow upward into a bottle, i.e. by upward displacement. See Fig. 58.

•

ht

tp ://

w

w w

Cylinder partly filled with Fig. 105. gas in position in a pneumatic trough.

16.

A

Gas Holder.

as follows

:

—A

A bottle, as

small gas holder

large as available,

is

is

constructed

provided with

a two-hole rubber stopper through which pass two tubes, each bent at a right angle one tube, B, reaches to the ;

even with the stopper. Attach about 20 centimeters of rubber tubing to each glass tube and provide each rubber tube with a Hofmann screw (Fig. All joints must be 106) near the end of the glass tube.

bottom, the other. A,

air tight.

The

is

holder

and tubes with water,

just

is filled

close

A

as follows

:

Fill the bottle

with the screw about

5

cen-

Appendix A.

343

timeters from the end, and put the outer end of

B m

a

When the apparatus which generates or vessel of water. contains the gas to be introduced is ready, pinch B with the thumb and forefinger, loosen the screw on A, connect the

and im-

delivery tube with A,

mediately remove the press-

The gas

water out through B. initial

pressure of

tering

gas

The en-

Fig. io6.

— Hofmann screws.

must be strong start the flow through B, and once started

4a

to

the

operation

When

em

enough the

will

and the

vn

A

flow in through

ll.

ure from B.

proceeds smoothly.

the holder

is

and comfull, press A firmly with the screw a few centimeters from the Attach the end of B to the lower opening of an end.

.c h

pinch A, instantly slip off the delivery tube,

w w

aspirator bottle or to a large funnel supported above the

holder to force out the gas.

is

is

loosely

tp ://

holder

B

clamped or

holder by loosening the screw attached to A. attach

B

to the faucet, to force out the gas, as air is

ht

water pipe 17.

left

clamped, the flow from the reservoir to the The gas is driven from the easily controlled. if

w

open, but

Do

not

from the

apt to pass into the holder along with the water.

Aspirators.

—

It is often

necessary to draw (or force)

may be done by a filter pump, or by an aspirator. The former may be obtained from the dealer, the latter is easily constructed. A common form is shown in Fig. 107. A five-pint acid bottle is provided with a two-hole rubber stopper carrying two open

a gas through

tubes.

The

a tube.

shorter

is

This

bent at a single right angle,

tends just within the bottle, and

is

it

ex-

called the inlet tube.

Experimental Chemistry.

344

The longer tube is bent at a double right angle, the inner arm of which extends nearly to the bottom of the bottle, while the other arm terminates at any convenient point below the bottom

A Hofmann

of the bottle.

screw,

attached to a piece of rubber tubing,

A, near the end of this outer tube, serves to regulate the flow of water.

the

An

replace the greater portion of outer

arm

the

of

outlet

ll.

may

vn

more convenient, the rubber tube

aspirator bottle

may

4a

If

tube.

be obtained

em

from the dealer, but one made as above serves the purpose. To draw

— or aspirate — a

gas,

the bottle

fill

Fig. 107.

— Aspirator.

.c h

with water and insert the stopper with

w w

arm

tubes,

its

to

the

screw, start the water flowing,

the

shorter

loosen

the

and regulate the flow by

tp ://

w

the screw.

attach

apparatus,

ht

18. The Metric System originated in France during the French Revolution, and its use has since been required or The fundamental legalized in most civilized countries. unit of the system is the meter, which is approximately equal to the ten-millionth part of the distance from the equator to the north pole. This distance was ascertained

by actual measurement of an arc of a meridian passing through Barcelona in Spain and Dunkirk in France. The legal equivalent of the meter in the United States is 39.37 inches. The superior advantage of the metric system

is its

deci-

mal character, which allows rapid transformations from

Appendix A. volume

into weight

and

vice versa,

345

and between denomina-

same unit. Each unit has multiples and subwhich are designated by prefixes attached to the

tions of the

multiples,

particular unit. hccto-,

and

1000.

The

kilo-,

The

prefixes denoting multiples are deca-^

equivalent respectively to

submultiple prefixes are

which correspond respectively to .1, The meter the unit of length chemistry, but the centimeter

is

and

and

milli-,

and .001. seldom used in often employed to express .01,

—

is

vn

—

100,

10,

deci-, ccnti-,

vessel.

The

ll.

the length of a tube, or the linear dimensions of a large

height of the barometer

stated in centi-

is

The has

its

unit of weight

is

em

4a

meters or millimeters, and the length of the smallest pieces of apparatus is often expressed in the latter denomination. the gram, which, like the meter,

vacuum

.c h

a

The gram

multiples and submultiples.

actually derived from the kilogram,

which

is

itself

is

the weight in

of a cubic decimeter, or 1000 cubic centimeters, its

maximum

w w

of pure water at

density.

Y{Q.xiZQ^ 07ie

gram

The weights of one cubic centimeter of zvater. If of small masses are expressed in terms of the gram.

w

is the zveigJit

ht

tp ://

an object weighs, for example, 2 grams, 2 centigrams, and 5 milligrams, the weight is written 2.025 gi'ams, though the two small weights may read 20 and 5 milligrams. Two milligrams is more often written as .002 gram than as The decimal 2 milHgrams, though both forms are used.

form of the fraction is always used in the metric system. Thus, 4 decigrams is not written -^^ grams, but .4 gram, or often, 0.4 gm. The unit of volume is the liter, which is used for both dry and liquid measure. It is equal to the capacity of the vessel containing the standard kilogram. tains 1000 cubic centimeters,

A

liter of

i.e.

it

is

water weighs looo grams.

It

therefore con-

a cubic decimeter.

Volume

is

usually

Experimental Chemistry.

346 expressed

in

cubic centimeters, and most graduated volu-

described by this denomination.

metric apparatus

is

a

often

liter

flask

burettes are

is

made

marked

to deliver 50 cubic centimeters, 01

cubic centimeters, and pipettes from meters.

The

i

following tabular view will

between the

units, their multiples,

to

make

clear the rela-

and submultiples

ht

tp ://

w

w w

.c h

em

4a

ll.

Length.

100

100 cubic centi-

vn

tions

Thus

looo cubic centimeters;

:

—

Appendix A.

347

To counterpoise a balance proceed as follows Clean the pans with soft paper or cheese cloth, and allow them to swing freely to ascertain the exact condition of the 19.

:

balance.

If the

make

pointer does not

equal excursions

on each side of the middle or zero point, then add to the Do lighter side weight sufficient to restore equilibrium.

come

not wait for the pointer to

left.

to rest, but estimate dis-

Balls of paper, bits of wire

vn

tances to the right and

to the proper pan of the hern Often a piece of wire equilibrium. secure pan balance to to the beam, if attached is spring bent in the form of a

may be added

balance

is

persist-

Weight is added to the lighter pan of the trip scales by properly

.c h

ently ''off."

em

the

4a

ll.

or of match,

the

adjusting

may be

w w

screws near the pointer. The horn pan balance

protected from

w

by hanging the balance from the top of a box shaped like an

tp ://

drafts

balance

ht

ordinary

The box

is

open

but the rear

is

case.

in front,

covered

Fig, io8.

— Horn pan balance in a case.

with cheese cloth, held firmly in place by half-round moulding. The box and its enclosed balance are shown in

Fig. io8.

Weights from the kilogram to the gram are made of iron or brass, and the smaller weights of platinum or 20.

some other durable metal. They may be obtained in sets A set from 50 gm. to possessing any degree of accuracy.

Experimental Chemistry,

348 I

large

eg. is

See Fig. 21.

the

enough

for the exact

work

this book.

in

109.

Weighing.

center of

— The object

the

left-hand

to

be weighed

pan

placed in

counterpoised

the

of

is

balance, and in the

other pan a weight

which

placed,

is

vn

is

assumed

to

be the

ll.

approximate weight the

4a

of

object.

weight

the

em

heavy,

If

too

is

return

it

to

box and place on the pan a weight or several weights smaller in amount. Proceed thus, addand removing

— Set of weights.

ing

tp ://

w

Fig, 109.

w w

.c h

the

balance

judged

is

to

weights,

be

in

equilibrium

until

the

then allow the

;

pointer to swing freely several times, and note the dis-

they are unequal, adjust the weights accordthey are equal, the balance is in equilibrium and

If

ht

tances.

ingly;

the

if

sum

of the weights

is

the weight of the object.

Record

the weight immediately in the proper place in a note-book

— not

on a scrap of paper.

of determining the correct as follows

:

Add sum

The most satisfactory method sum of the individual weights is

the weights missing from the box and

then add the weights on the 'oalance and compare with the amount recorded finally, as the weights are replaced, beginning with the largest, add record their

;

;

again and check the

first

result

This operation takes

Appendix A. time, but

349

assuredly less time than that consumed by a

repetition of the weighing or of an experiment.

Certain precautions must be observed in weighing. ( 1 )

Substances should not be weighed on the bare pan,

but on a piece of smooth paper creased on the sides or

some counterpoised

the middle, or in

vessel, e.g. a

in

watch

glass, beaker, crucible, tube, or flask.

(2)

Never touch the weights with the

This

is

ll.

Arrange the weights symmetrically about the center

of the pan.

on the

Use

especially necessary with large weights

4a

(3)

fingers.

vn

clean forceps.

trip scales.

e.g.

Never attempt to weigh the exact amount specified, 1.49 gm., but weigh accurately an approximate amount,

e.g.

1.47 gm., or 1.50 gm., unless, of course, the directions

em

(4)

.c h

The expression "from 2.1 to exactly 1.49 gm. gm." means any weight between these two, but the 2.9 weight, whatever it is, must be exactly known; the two amounts, 2.1 and 2.9 gm., are simply limits adapted to So also the expression, ''weigh about the experiment. 2.4 gm.," means an exact amount which approximates 2.4 gm. (5) If the same object is to be weighed more than once, it should be weighed, if possible, with the same balance and weights. If the balances are carefully counterpoised,

ht

tp ://

w

w w

state

this precaution

(6)

is,

however, not absolutely necessary.

The balance and weights must always be

usable condition

— and they

will

left in

a

always be so found.

—

Measuring Liquids and Gases. Liquids are measured in graduated cylinders, or graduates, tubes, burettes, and pipettes. Vessels of various capacities are used, depending upon the volume of liquid to be measured. A 22.

Experimental Chemistry.

350 liter

lOO

graduate cc. is

is

shown

A

in Fig. lie.

graduate holding

Small volumes are

best adapted to general use.

more conveniently measured

in a burette, or in a pipette

Burettes and pipettes also hold

(Fig. 40).

most

various volumes, though the burettes often used hold 50

cc.,

and pipettes ic cc.^ The method cc.

25 cc, and occasionally 50 is

explained in the ex-

vn

of using a burette

periment on neutralization (Exp.

53).

are wanted, such as 10 cc, or from

pointed end

i

to 5

cc

4a

The

The

used when definite small volumes

is

ll.

pipette

dipped into the liquid, which is then gently sucked up into the tube to a point just above the mark on the stem,

em

is

and the top

the tube

.c h

of

with the forefinger.

hand and pipette

w w

the

in Fig. 40. Fig. no.

— Liter

mark on

relative position of

at this stage is

w

Pipettes hold the indicated

tp ://

shown

If the pressure of the finger is

the stem, and

the extreme lower end. its

quickly closed

lessened, the liquid will slowly fall

graduate.

or

The

is

farther

volume between

this

if

to

the

desired.

mark and

Occasionally flasks holding a

liter

fractions are used to obtain exact volumes.

ht

Gases are measured roughly by collecting them over water in a vessel the capacity of which is known or subsequently determined by filling the space occupied by the gas with water from a graduate or burette. In accurate experiments, the gas is collected in a graduated tube called a gas measuring tube (see Figs. 32 and 48), or in a graduated tube having two platinum wires sealed into the walls near the closed end, and called a eudiometer (see Figs.

and

44).

The

latter is

electric sparks are to

111

used only in those cases in which

be passed through the contents of

Appendix A.

35^

the tube. Often the capacity of a plain tube may be found by a burette and used instead of the more expensive

graduated tube. Certain essential precautions must be observed in reading volumes of liquids or gases, (i) Notice the exact value of a unit space

Thus one space may, and

does, equal o.i

i

often

cc, 2 cc, and

on different vessels.

The

4a

5 cc.

(2)

cc, 0.2 cc,

ll.

capacities.

even

vn

on the graduated scale, since single spaces often vary in value with vessels of different

surface of most liquids in a tube,

em

especially in a small tube,

but concave.

not horizontal

is

column

w w

of the

.c h

This curved surface is called the meniscus. It is customary to call the lowest point of the meniscus the correct height of water, or depth of the

of gas, as the case

the meniscus

ht

tp ://

though garded

Fig. III.

— Eu

diometer.

is

Thus

re-

erroneously

as

more

or less,

were

at II., or III., in-

if

11,,11

the eye 12-

stead of at

column

in Fig. 112

ii./cc,

may be

it

be..

reading of

correct

w

the

may

I.,

the

--III

cor-

The eye tangent to the low-

rect position.

must be

in a line

est point of the meniscus in order to determine the correct reading. The reading 11.7 cc. is the depth of the gas column in Fig. 112. If the

Fig. 112. rect

—

Meniscus. Correading is along the

line I.

height of the water column is desired, as is often the case, then 1 1.7 must be subtracted from the graduated capacity

Experimental Chemistry.

352

if the graduation is from the Usually the graduation of top downward. begins at the bottom, graduate or cylinder a meniscus is then the the of height and the

of the vessel,

actual height of the water column.

Some-

A Thermometer

23.

(Fig.

1

13)

is

vn

times tubes are graduated in both directions, and the reading is then simple.

an instru-

There measuring temperatures. the one in scientific are two kinds in use use is the Centigrade, the one in general

ment

ll.

for

change

in

is

the Fahrenheit.

temperature

em

use in this country

4a

;

The

measured by

is

ex-

.c h

pansion and contraction of the mercury, or popularly speaking, by " rise and fall of the

w

w w

thermometer." The abbreviation for centigrade is C. and for Fahrenheit is F. The point where the mercury stands when

tp ://

held for a time in boihng water is called the boiling point of water, and the point where the mercury stands

held in melting ice

is

the thermometer

called the freezing

ht

is

when

point of water.

the centigrade thermometer the boiling point is 100, and the freezing point is on the Fahrenheit thermometer the zero

On ;

boiling point is 32. is

is

212,

and the freezing point these two points

The space between

divided into equal portions called degrees. abbreviation for degrees is °, s,g: 212°.

The

Between these two points on the centigrade scale, as the

space

is

called, there are

100

^

Appendix A.

^^^

equal portions; but on the Fahrenheit scale there are i8o Hence lOO degrees centigrade equal i8o equal portions.

degrees Fahrenheit.

Since

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

.

APPENDIX

B.

GAS LAWS.

I.

—

ll.

be stated more explicitly thus

:

—

given volume of gas under constant pressure expands or

em

A

may

4a

the Lazv of Charles,

vn

It has been found that all gases 1. Law of Charles. under constant pressure expand or contract uniformly for This law, known as the same change of temperature.

273 of its volume at zero degrees centigrade for every degree through wJiich it is heated or cooled.

.c h

co}itracts

—

w w

This law means that 273

cc. at 0°

become 273 +

i

=

274

cc. at

1°

C.

273

cc. at

become 273 +

2

=

275

cc. at 2°

C.

3

=

276 cc. at 3° C.

w

o"^

become 273 +

tp ://

273 cc. at 0°

273 volumes at

or

ht

Let

and

become 273 +

V= the

F'

Then This proportion

thus —

t°

=

V\

volume

t

volumes

/°

V ::273

+

may

273

C. t.

be solved for either

+/

273

273 354

C.

at 0° C.

the volume at :

at f"

V

or

V ^

;

^

Appendix From

we can

B.

355

volume a gas would For example, suppose a volume of gas at 17° C. measures 245 cc, its volume at 0° C. would be found thus occupy

(i)

if

easily calculate the

at 0° C.

:

—

245x273 _Ho r, ^ ^ 230.6 cc. y= 273

And from

(2)

17

the volume at any temperature may be at 0° C. is known. Thus if the

the volume

if

vn

found,

+

17° C. (2).

ll.

volume is 230.6 cc. at 0° C, the volume at be found by substituting the proper values in

—

4a

^,^230.6(273+17)^2

would

Thus

^^

em

273

— Since the volume varies

Correction for Temperature.

2.

.c h

with the temperature, gas volumes to be comparable must

be at the same temperature.

This situation is not always hence it is customary to reduce the observed volume by formula (i) to the volume it would occupy if it were to exist at o^ C, which is the normal or standard

w

w w

possible,

temperature.

The

operation

is

called ''reducing to standard

The

sig-

and the correction for temperature the solution of some typical problems.

will

tp ://

temperature," or "correcting for temperature." nificance of the law

ht

be clearer after

/?i

tJie

PROBLEMS.

fcllowing- problems

f/ic

III.

pressure

is to

be regarded

as co7istant. 1.

Find the volume which 173

cc. of

gas at

12''

C. would occupy at

o°C. 2.

If

a gas volume measures 466 cc. at

ure at 0° C. 3.

14''

C, what would

it

meas-

?

What would

measures 706

be the volume at

cc. at 15°

C..''

o'^

C. of a volume of gas which

Experimental Chemistry.

2^6

A certain

4.

be

volume

its

What would

cc. at 27^ C.

?

Two gases are equal in volume one is at — 20" C, What would each volume be at 0° C. ?

5.

+ 20°

volume of a gas measures 25

at o" C.

;

the other

is

at

C.

6.

A

would

its

gas volume measures 3 1. at 0° C. At what temperature volume be 4 1. ? What would be its 7. A volume of gas at 13° C. measures 100 cc. volume at - 130^ C. ? At - 13° C. ? At + 130° C. ? 8. If 1000 cc. of gas are heated from o^ C. to 39^^ C what is the new volume ? 9. If 1000 cc. of gas are heated from —39' C. to 52"" C, what is the new volume? 10. Suppose 10 cc. of gas are measured at 15' C. What volume will the gas occupy at 150° C. ? 11. If 500 cc. of nitrogen at 27'' C. arc cooled to —5" C, what is the new volume? 12. A volume of gas measured 120 cc. at 15° C. What will be the volumes at 30" C, o" C, and — 10° C. ? 13. If 743 cc. of gas are heated from 47 C. to 83^0., what is the new volume ? 14. One thousand cubic centimeters of air at 13" C. w^ill occupy what volume at 65° C? 15. If 155 1. of air are cooled from 150° C. to 0° C, what will be the new volume? 16. A liter of oxygen is heated from 14'' C. to 42" C. Find the new

tp ://

w

w w

.c h

em

4a

ll.

vn

,

volume.

A

17.

be

(d)

volume of carbon dioxide measures 1500 cc. at o" C. What volume at each of the following temperatures (a) I5°C., C, (c) 100^ C, (<'/) 30o''C. ? At what temperature will it its

50"^

measure a 18.

If

liter?

a volume of hydrogen measures 100

be the volume at 19.

heated 3.

cc. at 100"

C, what

will

— 100'' C. ?

Twenty-five volumes of

they occupy 30 volumes.

its

:

ht

will

air

measured

To what

at

—

10"'

C. are heated until

temperature must they have been

?

Absolute Temperature.

volume

— Since a gas contracts 273

at zero C. for every

cooled, then at

—273°

degree through which

C. the gas

it

of is

would have no volume!

Appendix

B.

j^y

This condition is not possible, and as a matter of fact as gases approach this point (which has not yet been reached), they deviate from the law. However, for convenience the

—273"

poinc IS

C.

is

regarded as a starting or zero point, and Absolute temperature is reckoned

called absolute zero.

from this point, just as centigrade temperature is reckoned from zero on the centigrade scale. Degrees on the absolute scale are found by adding 273 to the readings of the

—

=0°

274^ absolute

= + 1° = — 1°

of Boyle.

4a

em

— The

tp ://

it

often stated thus

effect of pressure

was not

Boyle announced his Law:

—

ht

The volume of a gas at a

inversely as

tJie

:

—

until

on gases was

about

1662 that

c oustant tempei^ature

varies

pressure.

This law means that 200

or,

C.

.c h

is

C.

absolute temperature.

w

Law

its

early discovered, but

125

C.

volume of a gas undei' constant pressmr varies

directly as

4.

of Charles

w w

TJie

Law

the

ll.

273° absolute

272° absolute

Hence

vn

Thus

centigrade thermometer.

mm. become

—

cc. of

gas under a pressure of

100

cc.

under a pressure of

250 mm.

50

cc.

under a pressure of

500

mm.

25 cc. under a pressure of 1000

mm.

200 X 125

= 25

X 1 000.

vn

ll.

4a

em

.c h

w w

w

tp ://

ht

358

E>

Appendix B.

359

read directly from the barometer, and then to reduce the observed volume to the volume it would occupy if at 760 mm., which is the standard

existing pressure,

which

is

This operation

or normal pressure.

called ''reducing to

is

standard pressure," or ''correcting for pressure."

PROBLEMS.

760

at 755

?

mm.

mm.?

A

3.

.

gas volume at 780

gas holder contained 4.5

What would

mm.

is

200

25 cc,

is

1.

What

cc.

is

the volume

what would the volume be

em

at

mm

If a

2.

be re-

of oxygen

when

the volume be at 762

the barometer stood

mm.

?

.c h

760

mm.

of a gas at 740

ll.

The volume

1.

at

constant.

eis

is to

4a

gardeei

problems the temperature

vn

the folloiving

/;/

IV.

when the barometer stood at 4. A tube contained 137 cc. of air What 766 mm. The next day the barometer reading was 757 mm.

A

5.

530

w w

was the new volume?

measures 1000

gas

mm- ?

cc.

at

770

mm. .What

is

its

volume

at

w

A volume of hydrogen measures 467 cc at 756 mm. What would volume be at the normal pressure ? found to be 195 cc when 7. A volume of gas was measured and should be increased volume If the mm. at stood 740 the barometer to 200 cc, what would be the barometer reading? What would the volume 8. A gas volume was 467 cc. at 756 mm. have been at 29.92 in. by the barometer?

ht

tp ://

6.

its

CLASS-ROOM EXERCISE. 1,

II.

Historical.

{a) Essential facts in the

life

of Charles.

{b) Essential facts in the

life

of Boyle.

share in the discovery of Boyle's Law. (J) Mariotte's 2.

Experimental. {a) Proof of Boyle's Law. {b)

Proof of Charles's Law.

Experimental Chemistry.

360

—

When different gases are confined Aqueous Tension. same vessel, each gas exerts its pressure against the Hence, when a gas is collected over atmospheric presstire. water, as many gases are, it is saturated with water vapor 6.

in the

and does not bear the full pressure of the atmosphere, Hence the volume since part is borne by the water vapor. The vapor. water of pressure the of a gas is increased by pressure of water vapor, or aqueous tension, as

it

is

usu-

be regarded as existing

is

—

4a

to

the pressure under which a dry gas

Hence

eter reading. is

ll.

vn

ally called, has been calculated. in terms of miUimeters of mercury, and may be subtracted directly from the barom-

really ?'

a,

a being the

.c h

em

symbol commonly employed to designate aqueous tension. The amount of water vapor present in a volume of saturated gas varies with the temperature, hence the pressure exerted by this confined water vapor in its effort to escape varies with the temperature.

vapor

is

significance of the tension of aqueous

w w

The conception and

not always grasped by students.

—

The

fact

may

tp ://

w

be illustrated as follows Take a glass tube about 90 cm. long and closed at one end, and dry and warm it. Fill it with dry, warm

mercury and invert

ht

The mercury

will

in a

fall

:

mortar containing the same liquid. Introduce a little in the tube.

a

water by means of a small pipette or by a medicine dropper, and the mercury will soon fall sHghtly, owing to tension of aqueous the pressure of the water vapor Httle

vapor —

—

in

the

space

above

the

mercury.

Warm

the

upper end of the tube with the hand and the mercury falls still lower. If it were possible to boil water in the tube, the pressure of the vapor would be equal to the pressure of the atmosphere at that instant, since water boils when it just overcomes atmospheric presor a lighted candle,

Appendix The

sure.

correction

pected and must be

is

J6i

often larger than might be sus-

made

Gases are assumed

B.

to

work.

in all accurate

be

saturated

when measured when dry.

over water, but their volumes are compared

Hence

a ''correction for aqueous tension" as well as for

temperature and pressure must be made before the vol-

umes

are comparable.

following

is

a

—

vn

The

4a

ll.

TABLE OF THE TENSION OF AQUEOUS VAPOR (REGNAULT).

ht

tp ://

w

w w

.c h

em

i.

Experimental Chemistry.

362

corrected for temperature, pressure, and aqueous tension

reduced

make

to

standard conditions),

convenient to

is

it

the corrections simultaneously by the formula

V^

—

In tnis formula

V—

:

—

V\P'--) (5)

760(1 +.00366/)

the corrected volume.

vn

{i.e.

V — the observed volume. =

the observed pressure.

/

=

the observed temperature.

a

=

the aqueous tension at

4a

ll.

P'

em

/°

C.

.c h

" Corrected " means " under standard conditions," and "observed" means "under any other conditions." This formula is so important, its derivation should be

w w

mastered.

—

Since all gases expand Temperature Correction. oj 33 of their volume at zero for each rise of a degree centigrade, then

w

(a)

tp ://

;

= F+ -^

ht

V'

—

But

.00366 X A

(

X

F

V273

Hence

the above equation becomes

273 V'

= V+

(.00366 X

= VX

(i

.•.F= (l -f

(b)

+

F

.00366 t)

"^ .00366

Pressure Correction.

X

f)

— Since

volumes of gases are

inversely proportional to pressure, the volume relations of

Appendix

B.

2^3

may be expressed

the same gas under two different pressures

—

V: Therefore

VP =

V'P'

^"^

"7^

or

P = 760,

VP' — V=— ^

.'.

760

ll.

and since

V ::P' :P.

vn

by the proportion

—

Combined Corrections for Temperature and Pressure. To reduce a gas volume to 0° and 760 mm. it must first P' I and then by -— by be multiplied ^ 760 (i + .00366 t)

em

——

;

V

—+

.c h

V=

Hence

4a

(c)

x

^

w w

(i

VP

(i

(6)

is

760

—

(6)

+ .00366/)

used when there

tp ://

Formula

.00366 t)

r>l

I

w

760

—— x —P'

T

^

is

710

correction

for

aqueous tension.

—

ht

Since the correction for (d) Combined Corrections. from the observed subtracting by aqueous tension is made pressure the aqueous tension in

(found in the Table in

§ 6),

760

An

example

will

formula (6) becomes-

V'(P'

V=

(i

make

milHmeters of mercury

+

-

a)

.00366 /)

the formula more intelHgible.

A

student actually found that a mixture of potassium chlorate and manganese dioxide yielded 2192.4 cc. of

oxygen when the barometer read 757.8 mm. and the

ther-

Experimental Chemistry.

364 mometer

The aqueous

21.5° C.

was taken the formula becomes tension

Substituting these vakies,

19.097.

as

—

^^^ 2192.4(757.8- 19-097) 760

=

(

I

4-

.00366 X 21.5)

2192.4 ^^ ^ ^ ^ ^ X 738.703

=

^

„

1980.6+

CO.

760(1 +.07869)

vn

Therefore, 1980.6 cc. is the volume which would be occupied at standard conditions by 2192.4 cc. at the ob-

ll.

served temperature and pressure.

4a

In this solution notice (i) that the aqueous tension subtracted from the barometer reading and

is

remainder

multiplied by the observed gas volume, and (2) that the

temperature

is

em

is

tJiat

multipHed by .00366 and

is

added

to that

by 760.

.c h

result before multiplying

i

PROBLEMS problems the gas

w

Reduce

be regarded as dry, unless

is to

to standard conditions the following:

—

tp ://

1.

w w

/;/ tJiese

otherwise stated.

V.

mm. and 136.5° C. measured at 950 mm. and 91'^ C. (c) 480 cc. measured at 380 mm. and 68.25° C. {d) 25 cc. measured at 780 mm. and 27° C. 14 cc. measured at 763 mm. and 1 1'' C. (
147 cc. measured at 570

ht

{b) 320 cc.

2.

A

vessel 10 cm. long, 5 cm. wide, mm. and 100° C. What

gas at 770

and

cm. deep, is filled with volume under standard

3.5

is

its

gas under standard conditions has

its

conditions? 3.

A

temperature raised until the volume

What

is

the final temperature?

is

pressure doubled and

its

the same as the original volume.

Appendix 4.

A

would

its

B.

365

vn

gas volume measures 12 liters at o'^C. and 760 mm. What volume be at 800 mm. and 17^ C? 10'' C. and 500 mm. What would be 5. A gas measures 150 cc. at its volume at 16.4° C. and 520 mm. ? 6. If 852 cc. of hydrogen are measured at 1 1° C. and 760 mm., what would be the volume at 27^ C. and 900 mm. ? 7. A certain volume of hydrogen measures 250 liters at 745 mm. and — 15" C. What would be its volume at 20'^ C. and 765 mm. ? 8. What volume under standard conditions would be occupied by 200 cc. of gas at 14° C. and 756 mm. ? 9. Reduce to standard conditions 1328 cc. of gas saturated with water vapor and measured under the following conditions

mm.

Aqueous

mm.

em

Temperature, 18" C.

4a

Pressure, 765

—

ll.

:

tension, 15.357

10. Correct 99.5 cc. of air for pressure, temperature, and aqueous tension from the following data:

.c h

—

mm.

w w

Pressure, 756.3

Temperature, 20.5° C. tension, 17.943

mm.

w

Aqueous

What would be the corrected volume of ']'].'] cc. of saturated measured at 17.5" C. when the barometer stood at 755.5 mm., allowing 14.889 mm. l"or aqueous tension?

tp ://

11.

air, if

ht

12. Reduce to standard conditions in the following cases the gas volume measured under the given conditions

{a) 97.2 cc. 20.3° C.

756

mm.

17.65 a. {b)

^7 cc.

17.5^0.

755

mm.

14.89 a.

:

{c)

81.2 cc.

746^ mm. 19.5''

C.

16.87 ^-

{d) 100

cc.

755.3

mm.

—

{/)

100 cc.

756

mm

24° C.

22.18 a.

(/) 99.8

cc.

753.2

mm.

18.5° C.

20.3° C.

15.85 a.

17.65 a.

Experimental Chemistry.

^66

(/) 786CC.

(g) 79 cc.

754

mm.

758.4

i9.5°C.

16.35

20.29^.

16.87 «.

97-8 cc.

756-3

mm.

19.5° C.

a.

16.87 a.

PROBLEMS.

A

certain

volume of

On

mm.

air

measures 150

the following clay

the barometeT

A

em

3.

when

volume had decreased

Calculate the change in the height of the barometer. 146 cc. of air at 10^ C. and 730 mm. are measured over water. would the dry air measure under standard conditions?

1.52 cc.

What

cc.

its

4a

stands at 760

(REVIEW.)

VI.

vn

0)

mm.

ll.

rt.

20.5° C.

17.94

2.

mm.

22.5^C.

756.5

1.

a

'/58.4

I9.5°C.

98.8 cc.

(/i)

(k) 77

mm.

certain quantity of nitrogen measures 155 cc. at

lo""'

C, and

5.

A

liter

if

heated to 100° C.

w w

the air expand

.c h

under a pressure of 530 mm. What will the volume become at 18.7° C. and under a pressure of 590 mm. ? 0° C. How much will 4. A certain weight of air measures a liter at of air at 39° C.

134

6.

1.

w

volume.

tp ://

7.

50

cc.

?

cooled to

of air are heated from

volume.

8.

is

of air at

10''

100 cc. of air at

-

ht 10.

will

A

volumeat

C. are heated until

Find the new temperature. 9. yoo cc. of air at 77^ C. and 1000

and 872 mm.

26° C.

Find the new

30" C. to 60° C.

C. occupy what 12''

—

Find the new

24' C.

?

they occupy 145

mm. measure what

at

cc.

163° C.

?

quantity of air which measures 230 at 0° C. and 760 mm. ?

1.

at 14° C.

and 740

mm.

measure what

II.

MANIPULATION OF GASES.

Certain facts, simple in themselves but easily overlooked,

render work with gases somewhat (i)

Most gases are

easily discovered.

colorless

difficult.

and

their escape

is

not

Appendix B.

367

They are difficult to dry and purify. Their volume changes quickly and considerably with changes of temperature and pressure. (2) (3)

They cannot be weighed

(4)

directly without delicate

apparatus and equable surroundings, hence their weight

must be

indirectly determined.

(5) Several exact readings

must be made.

and

vn

Nevertheless, gases present a most fruitful field of study, certain precautions are heeded, fairly accurate results

if

Inasmuch as many of the exact experiments book deal with gases, the difficulties above mentioned

warrant further discussion.

4a

in this

ll.

are possible.

(i) Since most gases are collected over water, the whole system should be watched height of water, bottle, or tube, and space occupied by the gas. The water level is an indicator of the gas level, and the eye should lead the to

regard this water level as the essential indicator of

w w

mind

.c h

em

—

the conditions.

Again,

all

apparatus used

in

gas experi-

ht

tp ://

w

ments should be rigorously tested before the experiment begins, or, better still, as the arrangement of the apparatus proceeds. If the gas is to be under increased or diminished pressure at any time, the connections should be perfect. Stoppers 7niist fit and tubing must be the exact size. Do not use wax to stop leaky joints. Never use vaseline unless (2)

it

is

Each gas has

prescribed in the directions. its

pai:ticular

drying or purifying

agents, and these agents vary in efficiency.

Water vapor most common ingredient to be removed. It is customary to pass a gas through a bottle or U-tube containing the purifying agent. The two substances used for the removal of water vapor are concentrated sulphuric acid and calcium chloride. The Either may be put in a U-tube. sulphuric acid drier is more efficient if both limbs are is

the

Experimental Chemistry.

368

nearly but loosely filled with glass beads or fragments of glass tubing and then enough acid poured into each limb This device to drench the glass but not seal the bend.

exposes a large surface of acid, permits a steady current of gas, and relieves the pressure on the generator, since the gas

to overcome acid in heavy the

have

not

does

the pressure of

the bend of the U-tube. is

unnecessary, then a

vn

precaution

If the last

is

114)

ll.

Drechsel drying bottle (Fig.

a convenient substitute for the

em

4a

The Drechsel bottle may U-tube. be replaced by the apparatus shown in Fig. 56.

If

calcium chloride

is

should be the fused variety and be free from powder, as the latter hardens when moistened and

used,

.c h

it

w w

Often the U-tube may be successfully replaced by a calcium chloride tube or jar, or even an ordinary glass tube. All drying apparatus must be protected

Fig.

tp ://

w

clogs the tube.

114.

— Drechsel

drying

ht

(or washing) bottle.

plugs (Fig. 47). or soda lime.

from the

Ammonia

is

air

by

tight corks or glass

dried by passing

it

over lime

and (4) Since gases cannot be easily weighed, their If the volume weight is calculated from their volume. or not ignored changes and the change in conditions is revealed by the thermometer or barometer, the weight will apparently change, while the mass is constant. The heat of the hand or even of the body will often alter a gas volume, yet the thermometer shows no appreciable change. Hence, tubes contaiimig gas to be measured must never be (3)

Appendix touched

zvitJi tJu

hand.

If

it is

B.

369

necessary to

move them, do

paper wound around the tube, or a piece of straw matting, or a test tube holder. The temperature of a gas is taken either by hanging a so

by the clamp, or with a

slip of

vn

thermometer beside the gas tube, or finding the temperature The latter way is of the water over which the gas stands. more reliable. Nevertheless, errors lurk in this method. The gas must stand over the water at least fifteen viiniites before the temperature is taken so that the whole system

may be

em

4a

ll.

It is convenient to at the same temperature. measure gases over the water in tall jars which have been standing in the laboratory for several days before The thermometers may remain in the jars all the use. time and the tubes containing the gas may stand in the

.c h

water over night, readings being taken at the close of the session or on the following morning before the regular

Again, the reading of the gas volume and the temperature must be made simultaneously, and the thermometer must be read while the bulb is in the

A lens

is

often necessary to read the exact height

w

water.

w w

laboratory period.

of the mercury, especially

tp ://

if

the reading

is

estimated to

the fraction of a degree.

A

ht

barometer reading taken at the beginning of the laboratory period and posted in plain sight is sufficiently accurate for several hours, unless violent atmospheric changes are in operation. All readijigs should be verified,

by the teacher or a student, and any disagreement remedied before the calculations are made. either

CLASS-ROOM EXERCISE. 1.

Define law, hypothesis, and theory, as the terms are used

science. 2.

IV.

Of what

Why

value

is

each

?

should gas volumes be reduced to standard conditions

?

in

APPENDIX familiarity with the

tions are only suggestive;

language of Chemistry

Many

and note-taking.

all

should be interpreted by the larger and more

substance

which

neu-

a base, decomposes a car-

tralizes

Amalgam,

Alloy in which mer-

n.

em

Sour; reddens blue litmus,

A

n.

4a

recent text-books.

Acid, adj.

indispensable to

is

of the following defini-

ll.

WORKING

intelligent reading, speaking,

vn

GLOSSARY OF CHEMICAL TERMS.

I.

A

C.

cury

a constituent,

is

sodium

e.g.

amalgam.

and reddens blue litmus. Amorphous, ailj. Non-crystalline, eg. Same as Acid (adj.). amorphous sulphur. Often applied See Attraction. to powders, as amorphous carbon. Affinity, n. To shake; to mix by Analysis, n. A separation a partial Agitate, v.

.c h

bonate,

violent shaking.

Alkali,

Popularly a

mination by a chemical operation of the presence of a substance, as

w

acid,

tp :// Having the

adj.

qualitative analysis, or of the

ht

of

Allotr5p'-ic, adj.

sulistance,

Anhydride,

in

the

physical

acid,

called

an

anhydrous copper sulphate.

A

compound

" water-free "

or mixture

of metals having metallic properties, brass.

which unites e.g.

acid

Anhydrous, adj. Applied to a compound from which water of crystallization has been removed, e.g.

carljon. n.

t)xide

anhydride.

Vari-

properties

amount

quantitative,

form an

Often

hydride.

ropy,

assumed by some elements, especially sulphur, phosphorus, and

as

sulphurous anhydride, carbonic an-

Illustrating Allot-

n.

An

n.

with water to

allotropic form,

Allotropism, A115t'-ropy,

e.g.

a

gravimi;tric, or volumetric analysis.

properties

Basic.

An

Allotrope, n.

Alloy',

deter-

and turns

of an alkali,

ation

The

The

A strong hydroxide. substance, A narrow use

of the term Base,

Alkaline,

;

complete decomposition.

opposite of synthesis.

red litmus blue. caustic

or

substance

n.

which neutralizes an

A

w w

Acidic, adj.

Any

substance, as anhy-

drous alcohol or ether.

Anion, 370

n.

A

negative or acidic ion.

Appendix C. To

v.

render less

brittle

by

Aqua,

Latin

n,

means

?-t'gia

Cation,

A

n.

positive or

metallic

ion.

slow cooling. for

Aqua

water.

royal water.

Caustic, e.g.

Aqueous, adj. Relating to water, as aqueous vapor, aqueous tension, or an aqueous solution as distinguished from an alcoholic solution. To draw or force air Aspirate, v. or any other gas through an ap-

Burning,

adj.

caustic

(silver nitrate).

Chemical,

Relating to chemis-

adj.

Implies

chemical change.

try, e.g.

deep-seated action.

Chemical

n.

agent

compound

any substance used

;

laboratory.

paratus.

corroding,

lunar

potash,

caustic

re-

;

in the

vn

Anneal,

371

A Combustible, adj. Inflammable, burns pump. with flame, ignites easily. force or draw a gas bottle to Chemical action Combustion, n. through an apparatus. and heat. light by accompanied the to Relating Atmospheric, adj. A

n.

filter

4a

ll.

Aspirator,

em

Attraction,

Force which

Affinity.

n.

and maintains combination

ment.s,

Commercial,

of elements.

pure;

Bare

flame."

as

free

in

" free

w w

Bare,

Same

adj.

oxygen; broadly, a burn-

ing.

.c h

causes

a union with certain ele-

Strictly,

atmosphere.

flask is

one not pro-

adj.

Not

Compound,

Product of the com-

n.

ing.

in

Base,

w

bination of two or

A

tp ://

See Alkali and Acid.

hydroxides.

A

ht

synonym of of Acid

opposite

Mono-,

Acidic.

the

dicate

Often

means the opposite of mixture. OppoStrong. general Concentrated, adj.

an acid. A loose term including metallic oxides and

The

more elements

proportions.

definite

substance which neu-

tralizes

Basic, adj.

alkaline.

(adj.)

and

di-.tribasic, etc., in-

number of replaceable

site

of Dilute.

Abbreviation of " chemically

C. P.

Free from impurities.

pure."

Crystal, n.

A

solid,

bounded by geo-

metricaUy arranged surfaces and deposited usually from a vapor or

saturated solution. hydrogen atoms in a molecule of Applied to a class of Crystalline, adj. Consisting of an acid. tals or

salts.

Bi-.

A

prefix

meaning two.

Same

adj.

Applied to a compound

of two elements.

Bump,

V.

site

of

resembling a

.crystal.

Amorphous. To change v.

Crystallize,

as Di-.

Binary,

by

dealer.

tected by a gauze or a similar cover-

n.

chemically

furnished

ordinarily

as

Loose term meaning sud-

den or violent

boiling.

form

crys-

Oppo-

into or to

crystals.

Having the form Not powdered, or dis-

Crystallized, adj. of crystals.

solved, or amorphous.

Experimental Chemistry.

372

To pour

v.

a supernatant

liquid from a vessel without disturb-

as " to

Act of decanting,

n.

To

v.

separate

into

Act of decom-

n.

Deflagrating,

Dyad,

suddenly.

Applied to a spoon

adj.

Deflagration,

A

bivalent element.

Rapid and sudden

n.

To

v.

rapidly from the

Deliquescence,

absorb moisture

Liquefaction

or

air.

w w

Applied to sub-

adj.

stances which deliquesce.

Mixing, intermingling,

w

Diffusion, n.

See

ll.

The bubbling of a The result of

n.

To

V.

moisture

soften

to

;

heat

by heat and in

to

closed

a

chemical

ht

preparatory

Weak. See Concentrated.

To weaken,

usually

by addi-

tion of water.

Displacement, by alltjwing

n. it

Collection of a gas to fall or rise into a

The former method

is

E.g. the escape of car-

A^ot hoiliug.

bon dioxide from the decomposition of a carbonate by an acid.

Effloresce,

v.

To

lose easily water of

crystallization.

A

Efflorescence, n.

turning to powder

at the ordi-

nary temperature.

Applied

Efflorescent, adj.

to

sub-

stances which effloresce.

Electrode,

operations.

Dilute, adj.

chemical action, and usually occur-

water of crystallization

Bi-.

tp ://

prefix.

vessel.

Boiling or bubbling of

or loss of luster due to escape of

especially of gases.

V.

Effervescence,

.c h

n.

ture from the

Deliquescent,

vessel

n.

due to escaping gas.

ring without the application of heat.

air.

dissolving due to absorption of mois-

A

lifiuid

gas through a liquid.

Deliquesce,

Digest',

Ebullition, a

burning.

Di-.

two.

into wire.

Element with valence of

n.

4a

times applied to a mixture, or to a

often ap-

wood.

which deflagration occurs. Some-

single substance.

is

vapor.

distilling.

May be drawn

em

in

To burn

v.

of

manufacture of various

the

liquids from

Ductile, adj.

posing.

Deflagrate,

Act

n.

plied to the preparation of coal gas, or to

simpler parts.

Decomposition,

The condensed

Distillation,

Destructive distillation

wash by decantation."

Decompose,

by subsequent condensa-

it

tion.

Distillate, n.

ing the sediment.

Decantation,

recover

vn

Decant,

n.

Pole or terminal of a

wire conducting an electric current.

Element,

A

n.

substance which has

not yet been

decomposed by any

means known

to science.

Equivalence,

down- Evaporate,

v.

n.

See Valence.

To

convert into vapor.

To heat until all liquid has been ward displacement, the latter is upturned into vapor; eg. "evaporate ward displacement. Substitution of to dryness," means to heat until no one element for another in a comliquid remains. pound replacement. Distil, V. To evaporate a liquid and Evolve, v. See Liberate. ;

Apperxdix C. Evolution,

Liberation; escape as

n.

a result of chemical action, as evolu-

oxygen

of

tion

from

potassium

A

n.

a

is

necessr.ry to

Extract,

little

"A

slight

more than

produce certain

To remove

v.

More

large quantity.

than a given quantity. excess "

Generate,

is

results.

the essential

See Liberate and Evolve.

v.

Generator,

Apparatus

n.

which

in

gases are generated.

Gram,

chlorate.

Excess,

373

Unit

n.

weight

of

Metric System.

Equal

looo mg. and to

the

of water at

cc.

i

in

weight to

in

4°C.

Granulated,

In sma'l

adj.

pieces

varying in size from a single crystal

part of a mixture, usually by dissolv-

of sugar to a hazel nut.

ing

to zinc usually used to generate hy-

and then

special solvent,

a

drogen.

filtering.

Gravimetric, separate a solid from a

liquid; to purify.

apparatus by which

filtration

complished. liquid

bers

sodium

group

the

n.

of

It is

of this group salts

times

a

•

etc.,

halogen

sea

sal.t.

are somesalts,

or

halides.

Hard,

adj.

Applied

to

water v/hich

contains salts of calcium or

Plural of formula.

mem-

because their

resemble

called

pro-

salt

applied to the

Chlorides, bromides,

symbols

composition

tp ://

Formulas,

of

w

expressing

)

Halogen means a " sea

Opposite of

volatile.

A

n.

compound. Formulae,

mine, iodine, and sometimes fluorine.

which passes

w w

Not

adj.

ac-

.c h

The

Precipitate (n,).

Fixed,

is

ducer."

through the paper.

Formula,

n. and adj. A group of elements consisting of chlorine, bro-

em

filter

paper, or sometimes to the whole

Filtrate, n.

weight.

Halogen,

Loosely appHed to the

n.

By

adj.

4a

To

Filter, v.

Applied

vn

in hot water, or alcohol, or

ll.

it

mag-

nesium, or both.

n. Used inaccurately as a synonym of hydroxide. touches the object. Free channel Hydrated, adj. Combined with water, for gases has no obstruction. opposite of dehydrated and anhyFuse, v. To melt. drous. "Opal is hydrated silica." Fusible, adj. Capable of being Hydro-. Prefix meaning («) an acid

Hydrate,

i

Not opposed.

Free flame

ht

Free, adj.

melted.

containing no oxygen, or

{b')

a com-

Popularly, a mixture of gases, eg.

pound containing hydrogen, the word hydrocarbon. Hydroxyl, n. The radical OH.

illuminating gas.

Hygroscopic,

Gas,

n.

The

Gelatinous,

aeriform state of matter.

adj.

See Vapor.

Like

to precipitates like

droxide.

jelly.

Applied

aluminium hy-

as in

adj. Applied to bodies which readily absorb moisture from

the atmosphere,

bonate.

e.g.

potassium

car-

Experimental Chemistry

374 A

Hypo-.

meaning

prefix

below.

Applied tJ a compound in which the distinctive element has a low,

and usually the lowest, valence,

6 g.

Limb,

An arm

n.

tube,

or portion

of a

limb of a U-tul)e.

e.g.

Unit of volume in the Metric

Liter, n.

A cubic decimeter, equiva-

System.

lent to looo cc, a kilogram, 2.2

hypochlorous acid.

lb.,

or 1.06 quarts of water.

Ending of binary compounds. vapor

Ihe

vapor of such liquids as carbon bisulphide, ether, alcohol, naphtha,

and benzine

Not

Infusible, adj.

fusible; not easily

on

set

to burn, to

fire,

with tube,

The e.g.

act of igniting.

Used

ignition tube, a tube

will not melt at a

high tem-

Opposite of organic;

Inorganic, adj.

w w

relating to mineral substances, as in-

Applied

organic or mineral acids. to all

compounds except the com-

w

plex derivatives of carbon.

Not

They

To

v.

react,

chemical action, to Interaction, n.

to

ht

that chemical action in

which there

consisting of both

position

Tlie

re-

decom-

electrically

or atomic group.

charged atom

See Chapter IX.

are

Ionization, n.

The

solid

A

temperature.

An

ment.

Molecular,

base-forming ele-

Applying

adj.

molecular

mole-

to a

A

weight. or

proportional

weight

ordinary

the

at

alloy.

as

cule,

mer-

except

All,

electricity.

equal

to

proportions.

act of breaking

group

atoms

of

The smallof a compound pos-

est

particle

sessing the properties of the

com-

pound.

fluid,

adj.

Melted,

thick, viscous.

fluid

or semi-

Applied to a

hot mass.

Element with a valence

n.

A

of one.

Monatomic,

ions.

A

n.

chemically combined.

Monad,

See Anion and Cation.

up into

and

Molten,

and combination.

An

reflect light,

they are good conductors of heat

Molecule,

Especially

double decomposition.

action

undergo

act.

Reaction.

characteristic

are usually hard,

the molecular weight, as molecular

soluble.

tp ://

Insoluble, adj. Interact,

Ion, n.

substance, generally an

possessing

smooth surfaces

their

cury,

perature.

is

A

n.

element,

.c h

which

part of an experiment.

properties.

kindle.

Ignition, n.

into

Experimenting.

n.

4a

To

V.

be rolled

bar.

Manipulation,

Metal,

melted. Ignite,

May

adj.

Compare Germ, hdiiimer-

sheets.

" Handling " apparatus. The manual

inflammable.

is

Malleable,

vn

to a

readily.

ll.

Applied

adj.

which burns

or gas

em

-ide.

Inflammable,

univalent element. adj.

One atom

to

the

molecule.

Liberate,

v.

To

set

free, to

evolve,

eg. to liberate hydrogen from an acid.

Mono-.

A prefix

as Uni-.

meaning one.

Same

Appendix C. Nascent,

Applied to an ele- Oxide,

adj.

ment the

instant

evolved

Oxidize,

e.g.

The

n.

of oxygen with

To change to an oxide. To increase the To withdraw hydrogen.

v.

To add

active state.

Neck,

Compound

n.

one other element.

or

An

compound.

from a

released

is

it

375

slender part of a vessel,

oxygen.

valence.

the long stem of a retort, the

A compound

Oxidizing Agent.

part of a bottle or flask to which a

yielding oxygen easily, as nitric acid

stopper

or potassium chlorate.

is fitted.

Neutralize,

A

chemistry.

Physical,

physical change.

An

seen or detected by physical means.

Pneumatic, adj. Relating to gases, e.g. pneumatic trough, a vessel for col-

element not a

acid-forming element,

lecting gases.

w

tp ://

is

one measured

these

conditions.

at or

reduced to

Salt

containing

ht

Notation,

The

n.

chemistry,

Precipitate,

the

adj.

vegetable

complex

often

symbols

falls to

Proto-. )

Applied to natural or

A

the bottom of the vessel.

meaning

prefix

i

first

or

lowest.

life. More specifically, compounds of carbon. Qualitative,

Act of causing

The

in filter-

Denoting the first of a series of compounds, as protochloride, protoxide. Sometimes used synonymously with Mono.

products from animal or

n.

by the paper

Literally, a substance thrown down, because the insoluble solid

Opposite of Inorganic.

Oxidation,

solid so produced.

ing.

Prot-.

artificial

insol-

as

and formulas. Organic,

The

solid retained

written language of

especially

To produce an

v.

uble solid by mixing solutions. n.

no replaceable hydrogen, such K2SO4.

by

the discovery of several gases.

= 760 mm. Normal Tem= o" C. Normal volume

perature

The Pneumatic Period

of chemistry was characterized

Normal

Standard.

adj.

Pressure

e.g.

Implies a change

of properties which can be readily

of ele-

such as sulphur or nitrogen.

Normal,

— the

Relating to Physics,

adj.

of

w w

An

metal.

highest

compounds.

in similar

system of terms and

ments and compounds. n.

beyond.

element has a higher valence than

The naming

terminology.

Non-metal,

in the

salt.

To make neutral. n. The language

v.

Nomenclature,

the

which sulphur has the highest valence. Often denoting that an acitl in

interaction

and base resulting

formation of a

denoting

4a

of an acid

The

n.

meaning

prefix

valence, as persulphuric acid

neutral."

is

Neutralization,

A

Originally

"sodium

as,

em

chloride

alkaline,

Per-.

Neither

neutral."

is

nor

ll.

"v^'ater

as,

acid

litmus,

vn

Indifferent to

adj.

.c h

Neutral,

adj.

Referring only to

the kind of matter. c>

com-

Quantitative,

bination with oxygen. j

adj.

weight or volume.

Referring to exact

Experimental Chemistry.

376

changed on the addition of more State in which all chemical

n. A group of different atoms acting as a single element in

solid.

a series of compounds and incapa-

attraction

Radical,

independent existence, as to

change,

chemical

Behavior

toward

reaction.

Loosely used as syngny-

mous with

equation.

A

acid

as

*'

n.

Any vessel which

A

Reducing Agent. oxygen

compound

easily,

ab-

such

as

w

stracting

tp ://

hydrogen or carbon. Reduction, n. Act of reducing, or v.

Whatever remains,

as

n.

A

solid left after

tion or evaporation.

A

is

to close

meaning one and

Applied to compounds

ment and two of another, Soluble,

as Fe^O.s.

Applied to

adj.

sub-

all

stances which dissolve (usually

in

Opposite of Insoluble.

water).

The

n.

solid

which the

liquid

dissolves.

n.

The

which the

liquid in

solid dissolves.

Stable,

Not

adj.

Sublimate,

A substance sublimed.

n.

Sublimation,

Act of

n.

distilling

a

Usually, converting a soUd

solid.

into

decomposed.

easily

See Normal.

Standard.

a vapor

which

immediately

purer state higher up

Substitute,

v.

To replace one element

or group by another.

"residual gas."

Residue,

is

in the containing vessel.

See Substitute.

adj.

ht

Residual,

seal a flask

prefix

solidifies in a

removing oxygen. Replace,

seal a tube

air tight.

one-half.

.c h

To remove oxygen. To valence. To add hydro-

See Oxidize.

gen.

catches

w w

lower the

A

Sesqui-.

Solvent,

or receives a distillate. v.

— usually

Solute,

chemical."

Receiver,

Reduce,

a

e.g.

Often applied to

group reagent. any

change,

chemical

To

together. it

To

containing three atoms of one ele-

mixture or compound,

often in solution, used to produce a

desired

close.

4a

n.

litmus,

To

V.

melt the open end (or ends)

em

A

usually applied to a complete change.

Reagent,

Seal, to

n.

A compound

added, such as water. chemically,

act

interact.

Reaction,

is satisfied.

which nothing can be chemically

vn

NH4, OH, CN. To V.

React,

to

ll.

of

ble

filtra-

A final product.

Substitution,

Sulpho-.

remainder.

n.

Replacement

in a

compound. Prefix denoting a

compound

of sulphur.

Salt, n.

A compound

formed by the

replacement of the hydrogen of an Popuacid by the metal of a base. lar

name

Saturated,

of sodium chloride. adj.

mum A saturated

Containing a maxi-

amount under given conditions. solution

remains un-

Supernatant,

adj.

Applied

to a liquid

standing over a solid, especially a precipitate.

See Decant.

Supersaturated,

adj.

solution containing

Applied to a

more

solid

than

would contain if an undissolved portion were present.

it

Appendix in the phrase " in

Suspension, n. Used

C.

377

Tubulure,

A short

n.

tube-like open-

suspension" to describe a solid distrib-

ing in the bulb of a retort or side of

uted in fine particles through a liquid.

a bottle.

Symbol, n. The abbreviation name of an element. Synthesis,

of the

Same

Uni-.

Op- Unstable,

Putting together.

n.

as

Mono-. Easily decomposed.

adj.

posite of Analysis.

Valence,

A

tetravalent or quadriv-

alent element.

Same as Sulpho-. Treat, v. To add to, to mix e.g.

with, to

"treat with

means

hydrochloric acid "

Tubulated,

three.

A trivalent

element.

Loosely,

Applied to

adj.

all

sub-

vessel, e.g. a retort.

w

tp :// A

-yl.

Suffix

some

of

radicals,

e.g.

hydroxyl.

BIBLIOGRAPHY.

Successful experimental work use of the best books.

See

tu-

Applied to a glass-stop-

II.

By volume.

adj.

Gravimetric.

Provided with a

adj.

air.

vapor.

w w

pered

moisture in the

any cloud-like substance.

Element with the valence Volumetric,

of three.

bulure.

larly,

gas

Popu-

stances which easily change into a

meaning

prefix

its

.c h

n.

Any

solid.

condensing point.

near

add Volatile,

to

hydrochloric acid.

A

Gaseous form of a substance

n.

em

allow to react with;

Triad,

of hydrogen.

Vapor,

normally liquid or

Thio-.

Tri-.

replacing or com-

vn

n.

of four.

The

n.

bining power of an element in terms

ll.

Tetrad,

meaning four. Element with the valence

prefix

4a

A

Tetra-.

is

enlivened and fixed in mind by intelligent

chemical library should be in every laboratory

;

pupils should have free access to books, and should be encouraged to consult

them frequently

ht

at all stages of the

work.

The

following

list

contains only a

portion of the books which the author regards as useful to both teacher and

The

pupil in elementary work.

intended for the teacher's use. simple in statement,

full

such a discrimination

is,

are subject to discount.

under separate chapters

but not ponderous, and new, of course, largely personal.

* 2.

in its

A

Dictionary of Chemical Solubilities, Comey.

515 pp.

$5, net.

list;

DICTIONARIES.

Co.

vols.

own

some cases

Teacher's Supplement.

&

4

which are

accurate and

prices in

Dictionary of Chemistry, Watts, Morley, and Muir.

I.

Green,

Co.

is first

The

is

Special books, monographs, and pamphlets are noted in the I.

*

starred (*) titles indicate books

In most cases the book which

Longmans,

$65.

The Macmillan

Experimental Chemistry.

378 3.

New

Co.,

(Contains 12,500 useful receipts.)

$^.

Kalendar, BiedenTiann.

CilEMiKER

*4.

Munn &

American Cyclopedia OF Receipts.

Scientific

York.

Berlin

Springer,

(annually).

(Contains numerous tables.)

LARGE DESCRIPTIVE.

II. I.

682 pp., 146

Treatise on Chem'STRy, Roscoe and Schorlemmer.

* 2.

Co.

^1.75..

illus.

2 vols.

Chemistry (Advanced Course),

3.

;^i.i2.

&

Co.

Greenaway. Boston.

Bacon,

SMALL DESCRIPTIVE.

Co.

453 pp.

w w

Elementary Manual of Chemistry,

3.

Book

Allyn

by

&

Elements of Chemistry, Shepard. D. C. Heath & Co. 366 pp. $1.40. Chemistry (Briefer Course), Remsen. Henry Holt & Co. 435 PP-

.c h

2.

&

em

(Includes experiments.) III.

1.

Edited

4a

Longmans, Green, & Co. 2 vols. ^10. 5. General Inorganic Chemistry, Freer. ^3-

Henry Holt

Remsen.

(Includes experiments.) 850 pp. ^2.80. 4. Principles of Chemistry, Mendeleeff.

559 PP-

D. Appleton

(Inorganic.)

^8.

vn

Co.

Longmans, Green, &

Textbook of Inorganic Chemistry, Newth.

ll.

$1.

Elements of Chemistry,

American

Williams.

Ginn

&

Co.

397 pp.

^i.io.

w

4.

Storer and Lindsay.

$1.20.

THEORETICAL AND PHYSICAL.

tp ://

IV.

ht

Physical Chemistry for Beginners, Van Deventer. Translated I. 154 PPby Boltwood. John Wiley & Sons, New York. $^-S^*2. Outlines of General Chemistry, Ostwald. Translated by Walker.

The Macmillan

386 pp.

Co.

^3.50.

Translated by Outlines of Theoretical Chemistry, Meyer. Bedson and Williams. Longmans, Green, & Co. 232 pp. $2.50. Principles of Theoretical Chemistry, Remsen. Lea Bros., Phila4. * 3.

delphia. * 5.

Sons.

*6.

$2.50.

John Wiley

&

^i.

Elements of Physical Ciikmisiry, Morgan.

299 pp. * 7.

361 pp.

Outline of the Theory of SolutioNj Morgan.

John Wiley

&

Sons.

$2.

Scientific

The Macmillan

Co.

Foundations 216 pp.

^2.

of

Analytical

Chemistry,

Ostwald,

Appendix C.

236 pp.

{/>)

wm.

96 pp.

$1.

D, Appleton

class are constantly appearing.

special, but exact;

12

is

the latest

4.

and 8

em

HISTORICAL.

544 pp. $4-50The Macmillan Essays in Historical Chemistry, T. E. Thorpe. (Biographies of eleven famous chemists.) 381 pp. $2.20.

w w

Co.

2, 3,

History of Chemistry, Venable. D. C. Heath & Co. 172 pp. $1. History of Chemistry, von Meyer. Translated by M'Gowan. The

Macmillan Co. * 3.

the above,

.c h

I.

Of

Ths Macmillan

good, though brief; 7 and 10 are and from many standpoints the best for a is

i

study of the whole subject.

V.

$i-50.

344 PP-

$3-

in this

are excellent, though not the latest;

2.

Co.

vn

332 pp.

*

&

Lntroduction to Physical Chemistry, Walker.

Books

first

American Book Co.

Ames, Editor.

J. S.

Modern Theory of Solution, Jones, 134 pp. ^i. Fl'ndamental Laws of Electrolytic Conduction, Good-

*ii. Atomic Theory, Wurtz.

Co.

The Mac-

$.70.

Scientific Memoirs, (a)

*i2,

Longmans, Green, & Co,

Aluir.

Chemical Theory for Beglnners, Dobbin and Walker.

millan Co. 10.

[ry

^2.

ll.

9.

Translated

Solutions, Ostwald.

4a

*8.

310 pp.

379

Gases of the Atmosphere, Ramsay.

The Macmillan Co.

240 pp.

Co., Easton, Pa.

^.50 each.

tp ://

Alembic Club Reprints, Chemical Bub. 1.

2.

3.

Experiments on Magnesia Alba. Foundations of the Atomic Theory. Experiments on Air.

4.

Foundations of the Molecular Theory.

5.

Extracts from Micrographia.

ht

5.

w

(Covers pneumatic period.)

$2.

6.

Decomposition of the Fixed Alkalies.

7.

Discovery of Oxygen.

Part

i.

8.

Discovery of Oxygen.

Part

2.

9.

Elementary Nature of Chlorine.

10.

Researches on the Arseniates, Phosphates, and Modifications of

Phosphoric Acid. 11. Increase in

Weight of Tin and Lead on Calcination.

12.

Liquefaction of Gases.

13.

Early History of Chlorine.

14.

Researches on Molecular Asymmetry.

Experimental Chemistry.

jSo

Century Science Series. The Macmillan 1. Humphry Davy, T, E. Thorpe.

6.

4. Justus

von Liebig, Shenstone.

— Chemists,

Heroes of Science

N.Y.

$1.25 each.

John Dalton, Roscoe. Michael Faraday, Thompson.

2.

3.

7.

Co.

350 pp.

$1.50.

Muir.

&

E.

Young

B.

J.

Co.,

&.

Popular but accurate.

—

(Same as 7.) Physicists, Garnet. Heroes of Science History of the Warfare of Science with Theology, White. D. Appleton & Co. 2 vols. ^5. Vol. i. Chap. 12, contains a valuable account 8.

9.

vn

*

of the growth of chemistry.

VI.

D. Appleton

em

552 pp. (2

$2.

vols.).

D. C. Heath

&

Laboratory Manual of Organic Chemistry,

.c h

Organic Chemistry, Remsen.

3.

78 experiments.

w w

* 5.

The Macmillan

Co.

2.

5.

VII.

Co.

Vol.

C.

Gattermann.

Chp:mistry,

330 pp.

II.,

D.

accompany 2 (supra).

to

$1.60.

Translated by E. F. Smith.

$3.

$1.30.

364 pp.

Orndorff.

671 pp.

P. Blak-

$3.

MISCELLANEOUS. F.

H. Thorp.

The Macmillan

^3.50.

Shenstone.

Longmans, Green,

&

Co.

Houghton,

&

Co.

^.50.

Physical Properties of Gases, Kimball.

238 pp. 4.

Richter.

625 pp.

Methods of Glass Blowing,

96 pp.

Sons.

I.,

Co.

Outlines of Industrial Chemistry,

528 pp.

* 3.

Vol.

tp ://

&

ht

1.

Son

w

Organic Chemistry,

iston's

Co.

Designed

$.40.

The Practical Methods of Organic

* 4.

Translated by Shober.

171 pp.

B. Lippincott Co., Phila-

J.

2.

Heath & Co.

Co.

ORGANIC.

Organic Chemistry, Perkin & Kipping.

1.

delphia.

&

ll.

Tyndall.

4a

Faraday as a Discoverer,

10.

Mifflin,

$1.25.

Minerals and 368 pp.

how

to study Them, E.

S.

Dana.

John Wiley

&

^1.25.

Questions ON Chemistry, Jones.

The Macmillan Co.

^.75.

(About

1500 unanswered questions.)

D. Appleton

6.

Fermentation,

7.

Chemistry of Daily Life, Lassar-Cohn.

Schiitzenlierger.

J.

&

Co.

331 pp.

^1.50.

B. Lippincott Co. ^1.75.

Appendix C. Aluminum and Aluminum Alloys.

8.

266 pp.

Pittsburg (Pa.) Reducing

The

^1.50.

Chemical Pub. Co,

Development of the Periodic Law, Venable.

*g.

321 pp.

^2.50.

of

Chemistry

10.

592 pp.

Common

Life,

568 pp.

Co.

&

Co.

^7.50.

13.

The New Chemistry, Cooke. The Chemistry of Cookery,

14.

Story of a Piece of Coal, Martin.

12.

D. Appleton

Manual of Chemical Technology, Wagner.

* II.

&

Appleton

D.

Johnston.

$2.

D. Appleton Williams.

&

D. Appleton

$.75.

Inorganic Chemical Preparations, $1.50.

&

Houghton,

4a

16.

238 pp.

Coal and the Coal Mines, Green.

F.

H. Thorp.

em

15.

$2.

393 pp.

&

Co.

Co.

^1.50.

165 pp.

ll.

$.40.

240 pp.

Co.

D. Appleton

vn

Co.

381

D. Appleton

&

Co.

Mifflin,

&

Co.

Ginn & Co. 192 pp.

$1.

17.

Laboratory Practice,

18.

Liquefaction of Gases, Hardin. The Macmillan Co. 244 pp. $1.50-

.c h

Cook.e.

APPARATUS AND CHEMICALS.

w w

III.

specific directions regarding laboratory supplies are given in the

Various

list

w

Teacher's Supplement, in the

The subjoined

periments.

lists

of Reagents, and in the directions for the ex-

are inserted simply to assist in the preparation

tp ://

Quantities and prices have been intentionally omitted, since it is and purchaser will make more fehcitous arrange-

of an order.

believed that both dealer

No teacher if both are unrestricted by a list unavoidably incomplete. and no author conditions, working the knowing without another fcr judge can has a right to insist that a dealer shall always furnish an article for a fixed sum.

ht

ments,

The market as with the

price fluctuates,

method

and prices vary with quantity and quality as well

of ordering.

The

author, at his

own

suggestion, has lodged

with the L. E. Knott Apparatus Co., 16 Ashburton Place, Boston, Mass., information regarding the quantities of apparatus and chemicals used by his own classes.

It is

hoped

that teachers will avail themselves of the opportunity to

correspond with both author and dealer in the preparation of order

I.

lists.

INDIVIDUAL APPARATUS.

This list includes the apparatus constantly used by a single student, who should be provided with each piece, and be held responsible for its return in

Experimental Chemistry.

382

The

usable condition.

apparatus, as JtcmizeJ below, should not cost

more

than $6.75. Flask, 500 cc. Two-hole rubber stopper,

Test tubes, 6xf.

Test tubes, 8x1.

One-hole

Test tube rack.

fit

rubber stopper, to

fit

above.

Test tube brush.

Evaporating dish, 3

Bunsen burner. Feet rubber tubing,

\ in. int.

Crucible block.

No.

Blowpipe.

Casserole, 125 cc.

o.

vn

Wing-top burner.

Pair iron forceps.

Horn spoon,

Triangular

ll.

Blowpipe tube. 5 in.

100 Filter papers, 4 in. salt mouth, 250 5 Bottles,

file.

Mortar and

cc.

pestle, 3 in.

Ignition tube, 4

(8 oz.)

in.

x

^ in.

Deflagrating spoon.

em

Funnel, 2|

in.

Crucil)le with cover.

diam.

4a

I

to

above.

Test tube holder.

in.

Towel.

Safety tube.

SPECIAL APPARATUS.

.c h

II.

This list includes the apparatus used occasionally, but of such a nature that should be given only when demanded, and returned as soon as used. The only items costing over $2.00 in this list are the burettes (if with glass

w w

it

stop-cock) and the platinum crucible.

The

latter

need not cost over $8.00

In some cases cheaper forms than those called for

w

(see Exp. 140).

it

is

equipment.

Marchard

Beads.

tube.

Pinchcock, Mohr.

2.

ht

Beakers,

Ilofmann

Bottle, Drechsel.

Burettes.

Pipe, iron.

Calcium chloride tube. Chlorine decomposition tube.

Pipette.

Platinum crucible.

Condenser.

foil.

Crucible, Hessian.

wire.

Thermometer.

Dish, lead. glass (shallow).

Eudiometer, 100

Thistle tube top.

Trap, bulb (for Exp. 92).

cc.

Flask, Erlenmeyer, 250 cc and 125 cc.

Funnel, dropping-

Gas

tube, 100 cc.

steam. U-tube.

and 50

cc.

may

answer,

imprudent to economize on permanent

tp ://

but in the author's judgment

Appendix C. GENERAL APPARATUS.

HI. This

$io

includes

list

or over arc

apparatus inte nded for general use.

all

marked with a

Items costing

*.

Jars, battery, 6 x 8 in.

*Air bath.

3 x 15 in.

tall,

pump.

*

3^3

Asbestos boards,

6x6

waste.

in.

Aspirator bottle.

Labels (Dennison, 223, 205, 219, 201).

Balance, horn pan.

Magnets.

Barometer.

Magnifying

Battery.

Meter

vn

wide mouth, 2

oz.

and 4

oz.

Rule, 30 cm.

ll.

Pneumatic troughs.

Blast lamp. Bottles,

glass.

stick.

Sand bath pans, 4

Chimneys, student lamp.

Scales, trip.

Scissors, 6 in.

em

furnace, 10 burner.

Combustion

Shears, 12

Corks, assorted.

*

borers, set.

Cylinders, graduated (set)

Dowel

Stoppers, rubber, with

7.

and

w w

paper.

File, round.

pump.

Triangle, porcelain.

Tripods.

Tubing, rubber (ordinary and pressure),

w

*Gas holder.

i,

diam.). t\, i in. (int.

tubing, soft.

Water baths, 5 in. Weights (for horn pan and Wire cutter.

tubing, hard.

Wood

in.

6x6

in.

tp ://

Gauze, iron, 6x 6

rod.

coil.

Iron stands, with 3 rings and 2 clamps IV.

This

blocks,

See Cylinders.

Graduates.

list

includes

Acid, acetic. citric.

hydrochloric nitric.

all

I

6x6x1 6x6x f 4x4x1

Woulff bottle, 2-neck.

CHEMICALS.

chemicals needed

trip scales).

(splints).

Wooden

ht

Glass plates,

Induction

2 holes.

Thread, cotton.

Electrolysis apparatus, io| in.

P'ilter

i

Tapers, box.

rod.

Emery

in.

Spectroscope.

.c h

Cork

in.

4a

Candles.

for this

book.

Acid, oxalic. sulphuric, tartaric,

in. in.

in.

Experimental Chemistry.

384 Alcohol, ethyl.

sulphate (dehydrated).

methyl.

wire.

Alum, chrome.

Cotton (absorbent).

Cream

potassium.

of tartar.

Aluminium, metal. Ether. sulphate. chloride.

Galena.

hydroxide.

Gelatine.

nitrate.

Glass wool.

oxalate.

Glycerine.

sulphide.

Gold leaf (book).

Antimony, metal.

vn

Ammonium,

Hematite.

ll.

Arsenious 'oxide. Indigo

Asbestos, shredded. chloride.

Iron,

hydroxide.

by hydrogen.

em

chloride (2V).

Beeswax.

filings.

Bleaching powder.

pyrites.

.c h

Borax (powd.). Brass wire. No. 24. Calcite (lump).

sulphate (ous), sulphide (ous).

w w

Kerosene.

Calcium carbide.

carbonate (marble),

w

chloride, fluoride,

tp ://

oxide (lime),

sulphate.

Carbon bisulphide.

ht

Charcoal, animal (powd.).

lump.

wood (powd.).

Cogl, scft.

Cobalt nitrate. Cochineal.

Coin

4a

Iodine.

Barium

Lead

acetate.

carbonate. dioxide (peroxide). nitrate.

monoxide tea.

tetroxide.

Limonite. Litmus, cubes, paper.

Magnesium carbonate (magnesite), oxide.

(silver).

Copper borings,

powder. ribbon.

nitrate,

oxide (granulated), sheet,

sulphate (cryst.).

(litharge).

sheet,

sulphate.

Manganese

dioxide.

sulphate.

Appendix C.

385

Mercury.

Soda

Mercuric chloride.

Sodium, metal.

lime.

nitrate.

acetate.

oxide.

bicarbonate.

sulphide (cinnabar).

Mercurous

carbonate.

nitrate.

chloride.

Mustard.

hydroxide.

Phenolphthalein.

nitrate.

Phosphorus, yellow (worm-shaped), Picture cord (iron).

nitrite.

phosphate phate). silicate.

carbonate,

sulphate.

Stannous chloride

chlorate (cryst,).

Starch.

(tin crystals).

em

chlorate (powd.).

Sugar, cane,

chloride.

grape.

chromate.

.c h

Sulphur, flowers.

dichromate. ferricyanide.

roll.

Tartar emetic.

w w

ferrocyanide.

Tin, granulated.

Turpentine.

w

nitrate.

4a

bromide.

hydroxide.

(disodium phos-

ll.

Potassium, metal.

iodide.

vn

hyposulphite (thiosulphate).

Parafifine.

Vaseline.

permanganate.

tp ://

Vinegar.

sulphate.

Water,

sulphocyanide.

Sand.

Wood

ht

Selenite (g}'psum, cryst.).

Zinc, dust.

Shellac.

granulated.

Siderite.

oxide.

Silver nitrate.

pure.

Soap.

sheet.

Solder.

sulphate.

IV.

The

distilled.

ashes.

following apparatus

Porcelain dish, 14

Funnel, 7

in.

Graduate, 1000

in.

is

REAGENTS. helpful in the preparation of reagents I I

cc.

I

Graduate, 500 cc. Iron dish (frying dish).

Tin dish (8

in.

sauce pan).

:

—

Experimental Chemistry.

386 I

Mortar, 7

I

Set of hydrometers.

Filter paper, 12 in.

in.

pump,

Filter

and Witt

flask

plate.

Glass rod (i cm. in diam.).

Lithia bottles.

Glass wool.

Glass stoppered bottles (5 pint acid),

Asbestos, shredded.

quantities of a solution in the

No.

5

(November, 1899),

The

following

p.

Vol.

22,

those required for this book.

A

407.

of reagents includes

list

hastened by using a

is

American Chemical Journal, all

vn

The preparation of large One is described

dissolver.

Reagents not mentioned

few others have been inserted for completeness.

are either unimportant or are fully explained in the experiments requiring

C2H4O0.—

commercial acid (2)

Add

1000

Use the

(i)

of glacial acetic

— Use

the commer-

(sp. gr. .815

;

Alum.

—

Solid.

See Ap-

w w

95 per cent of alcohol). pendix C, Table X.

contains

Use the commercial

crystals.

w

commercial alum

looo

tp ://

in

water.

This proportion answers

any alum.

Chloride,

ht

Aluminium

AICI3.

Dissolve 100 gm. of the

1000

cial salt in

(2)

cc.

of for

— (i)

commer-

Precipitate

ll.

water.

aluminium

Filter.

Ammonium

hy-

ammonium hysolution of alum. Wash

Use the commercial

Add

Dilute.

water to one volume of commercial

ammonium

hydroxide.

Ammonium Molybdate,(NH4)2Mo04.

— (i) Add oxide

100 gm. of molybdenum

(M0O3)

400

to

ammonium

stir until

000

(sp. gr. 1.2), using

(2} in

I

OCX) cc. of

Ammonium

Carbonate, (NH4)oC03.

.(i vol.

cial salt in

icxx) cc. of water, with-

salt in

out heating, and add

100

cc.

of

com-

Cool, and

cc.

add

of nitric acid

no heat.

Dissolve 150 gm. of the salt

solution into

— Dissolve 250 gm. of the commer-

1

cc. of

hydroxide, and

dissolved.

droxide to a

the precipitate free from acid, and slight excess of concentrated

,96).

volumes of

three

all at once

hydrochloric acid.

=

liquid (26° or sp. gr.

droxide by adding

add a

NH4OH. —

Hydroxide,

Concentrated.

mercial

cc. of water.

100 gm. of

Dissolve

Solution.

Solid.

salt.

the commercial salt in 1000 cc. of

Dissolve 100 gm. of the

Solution.

hydroxide.

tightly stoppered.

Ammonium Chloride, NH4CI.

.c h

cial liquid

ammonium

Keep

Use the commercial

acid to 2500 cc. of water.

Alcohol, C2HCO.

consult the index.

commercial Filter.

(sp. gr. 1.04). cc.

list,

em

Acetic Acid,

not mentioned in this

is

4a

If a reagent

their use.

1

water and potir this

000

acid to

I

cc.

of nitric acid

vol. water).

(3) Dissolve 60 gm. of the dry

400

monium

cc.

of commercial am-

hydroxide, add 400 cc. of

Appendix C. add slowly 500

Ammonium Oxalate,

(NH4)2C204.

commercial

—

Ammonium (i)

salt in

1000

Barium

of water.

cc.

400

saturated,

is

—

The

and then add

ammonium

hy-

Keep

tightly stoppered

may

in the

hood, where the bottle can-

the saturated solution gives no pre-

when heated

to the air

The

w w

soon forms the yellow aiiujiouiuin sulphide.

latter

may be

pared by dissolving a

sulphide.

tp ://

Sulphide

(NH4)2Sx.

— Saturate

ammonium

flowers

little

ammonium

(Yellow),

1500

hydroxide (sp.

ht 100

of

cc.

(sp. gr. .90)

ammonium

and 2500

in the

Dissolve

cc.

gr.

with hydrogen sulphide gas. 1

pre-

w

of sulphur in

Ammonium

of

NH4SCN.

— Dissolve

—

Solid.

work use

Keep

variety.

tightly stoppered, or preserve in a

quick- sealing jar.

100 gm. of

Dissolve

Solution.

the commercial salt in 1000 cc. of

day,

75 gm. of flowers of sulphur. Filter." Sulphocyanide (or Thi-

for quantitative

cial salt;

lumps of the fused

water.

above from 50 to

CaClo.

Chloride,

For ordinary work use the commer-

.90)

of water.

satu-

40 gm.

liter.

Add

hydroxide

cc.

Ammonium

ocyanate),

to the

Ammonium Calcium

sulphate.

when exposed

sulphide

rated solution contains about

.c h

magnesium

gently with

A

em

of the solution, or by the fact that

and stand

not be accidentally upset.

be found either by the intense odor

cipitate

cc. of

water with a few drops of bromine.

saturation point

of dilute

cc.

droxide.

Keep tightly stoppered. Shake 500 Bromine Water.

hydroxide until the so-

4a

lution

of hot water

Let the solution stand a and then filter if not clear.

day,

of dilute

cc.

cc.

vn

ammonium

looo

in

bonates.

Pass purified hydrogen sul-

phide gas into 600

—

from carbon dioxide and car-

free

solution to 500 cc. of water.

(2)

Ba (0H)2.

Hydroxide,

compound

of the commercial

cc.

sul-

Dissolve 50 gm. of the commercial

(NH4)oS.

Sulphide,

Add 500

of water

cc.

Filter if not clear.

phates.

Should be made as needed.

Filter.

1000

salt in

from sulphuric acid and

free

Dissolve 40 gm. of the crystallized

commercial

Dissolve 50 gm. of the

Solution.

cc.

of commercial nitric acid.

ll.

water, and then

387

Let the solution stand a

and then

filter if

not clear.

Calcium Sulphate, CaS04. For

water

of

gypsum

crystallized

—

Solid.

crystallization (selenite).

use

For

other work use the powdered variety.

Make

Solution.

a saturated solu-

lOOO

10 gm. of the commercial salt in

tion by allowing

1000

water to stand over 10 gm. of the

of water.

cc.

powdered

Barium Use salt.

Chloride, the

BaClo.

crystallized

—

Solid.

commercial

salt.

then siphon

off

Shake

cc.

of cold

often,

and

the clear supernatant

liquid.

Chlorine Water.

— (i)

Pass chlorine

Experimental Chemistry.

388

—

Dissolve Ferrous Sulphate, FeS04. 100 gm. of the clean, fresh, or strongly of the gas. freshly washed, commercial salt in (2) Slowly add concentrated hyinto water until the solution smells

drochloric acid to a few grams of

dark

a

in

This solution does not keep place. well, and should be made as needed.

Chrome Alum. solve 10

1000

— See Alum.

Co(N03)-2.

Nitrate,

Cobalt

— Dis-

gm. of the commercial

salt in

Filter if not clear.

cc. of water.

wire

in the

sionally

bottle,

(once

it,

If

keep iron

and add occa-

day)

a

solu-

a drop

two of concentrated sulphuric

or

acid.

—

Mix four parts of Fusion Mixture. anhydrous sodium carbonate and

—

of

parts

five

bonate.

vn

and

stoppered

tightly

The

as needed.

dry

potassium

car-

ll.

then add 500

made

necessary to preserve

Keep

of water.

cc.

locK) cc. of cold water.

tion should be

and

crysfallized potassium chlorate,

em

Grind a few pieces

of cochineal, or a

powder,

little

in

water, and dilute with water to the tint.

Digest

(2)

gm. of cochineal

w w

desired

5

powder with 50

cc. of alcohol

(25

w

dix C.)

—

tp ://

Dissolve Copper Sulphate, CUSO4. 100 gm. of the crystallized commercial salt in

1000

cc. of

ht

Dissolve 100 gm. of the crystallized commercial salt in 1000 cc. of water.

Chloride,

FeCls-— (0

Dis-

solve 50 gm. of the commercial

salt

ferrous

sulphate

solu-

add ammonium hydroxide, filter, wash the

tion

with

precipitated

nitric

ferric

from acid and

volume of volumes of

water.

—

Use the Hydrogen Peroxide, H2O2. Keep in a commercial solution. and occasionally loosen

cool place,

the cork for an instant.

Indigo. cial

—

Use the

^i^//^.

commer-

substance. (i) Dissolve

Solution,

a

little

acid,

cc.

of water. (2) Slowly

add 10 gm. of pow-

dered commercial indigo to 25 of concentrated sulphuric acid.

cc.

Let

the mixture stand a day, then add it

slowly, with constant stirring, to

1000

in 1000 cc. of water.

(2) Boil

one to four

commercial indigo paste in looo

hot water.

Disodium Phosphate, HNa2P04.—

Ferric

commercial acid

(See Table X., Appen-

per cent).

Add

Dilute.

— (i)

.c h

clear.

Cochineal.

4a

Dissolve Cobalt Chloride, C0CI2. ConcenHydrochloric Acid, HCl. 50 gm. of the commercial salt in Use the commercial acid trated. Philter if not 1000 cc. of water. (sp.gr. 1.2).

Iodine,

cc. of water. I.

—

Solid.

Use the commer-

cial crystals.

Solution.

— (i)

Grind

to

com-

hydroxide free

plete solution in a mortar 10 cc. of

and dissolve

water, 12 gm. of commercial iodme, and 20 gm. of potassium iodide,

alkali,

in concenr.rated hydrochloric acid.

Appendix C. and then add the solution

1000

to

cc.

of water.

1000

cc. of water.

Let the

solution stand a day, then

filter

if

not clear.

100 gm. of the commercial

1000

cc. of water.

stand

until

salt

in

Let the solution then decant or

clear,

filter.

salt

Manganous

Chloride, MnCl..

—

Mercuric Chloride, HgCl2. Dissolve 50 gm. of the commercial salt in 1000

cc. of

Mercurous

warm

iron

or

tin

dish,

make

add

" milk

of

then

let

clear

for several days,

and siphon

stand,

off the

supernatant liquid.

the same solid.

— Solid.

Use the commer-

tp ://

cial blocks.

Solution.

Grind

(i)

in

salt

blocks of litmus, with a

gm. of the

little

few water,

(2) Dissolve metallic mercury

warm

moderately acid,

tric

concentrated

mercury undissolved.

little

—

Nessler's

Reagent. Dissolve gm. of potassium iodide in 10 dissolve 1.6

curic chloride

Add ally

30

in

and with constant

ht

teen

minutes,

Extract

once

pour or

off

the Hquid.

twice

more with

Then add

cc.

of water.

HXO3.

bottle.

A

stoppered

few drops of chloroform

occasionally

added

formation of mould.

will

prevent the

in

60

tightly

— Concentrated.

Use the commercial acid

commercial acid

loosely

redis,

stoppered.

Nitric Acid,

and

a

be

Keep

Filter.

1.42).

in

to

a solution of 6.^

gm. of potassium hydroxide

hot distilled water, dilute the liquid with about 150 cc. of distilled water,

keep

of water.

stirring until

solved.

blocks,

cc.

gm. of mer-

cc.

sired color.

logm. of litinus

3.5

the latter to the former gradu-

the precipitate ceases

(2) Grind

ni-

taking care to leave a

in a mortar, and add the paste to enough water to produce the de-

with hot distilled water, in a mortar, and, after the mass has stood for fif-

crystal-

of distilled

cc.

water, add 75 cc. of concentrated nitric acid and a little mercury.

of water; a

Poison.

Hg2(N03)2.—

1000

be added to

w

Litmus.

Several

w w

may

portions of water

lized

.c h

lime," pour into a stoppered bottle,

shake occasionally

water.

Nitrate,

em

lime in an

water enough to

— Dis-

100 gm. of the commercial in 1000 cc. of water.

solve

(i) Dissolve 50

Lime Water, Ca(0H)2.— Slake quick-

— Dis-

100 gm. of the commercial in 1000 cc. of water.

solve

salt

— Dissolve

Lead Nitrate, PbCNOs) 2.

of water.

cc.

Chloride, MgCl2.

vn

100 gm. of the commercial

solve

1000

Magnesium

ll.

— Dis-

salt in

4a

solution.

Lead Acetate, Pb(C2H302) 2. salt in

Magnesium Sulphate, MgS04.— Dissolve 100 gm. of the commercial

Use the commercial

(2)

389

Dilute.

Add

one to

(sp. gr.

volume four

of

volumes

of water.

Phenolphthalein.

gm. of the

— (i)

Dissolve

i

solid in 100 cc. of alco-

Experimental Chemistry,

390

mate), KoCtoOt.

C.)

of the

in (2) Dissolve I gm. of the solid cc. of alcohol (95 per cent).

1000

100

precipitate

redissolve

to

enough alcohol

mercial

the

Keep

precipitate.

Use the commercial

(3)

Platinic Chloride, PtCU. a

solution

or

1000

in

salt

of water.

cc.

stoppered and in a

tightly

dark place.

solution.

— (0

desired

of

salt in

water.

—

then add just

forms;

powdered commercial

cc. of

Potassium Ferricyanide,K3Fe(CN) 6. Dissolve 75 gm. of the com-

until a

Dilute with distilled water

(or Bichro-

— Dissolve 50 gm.

Buy Potassium Ferrocyanide,K4Fe(CN)6. Dissolve 75 gm. of the commerknown

—

cial salt in

strength.

vn

Appendix

Potassium Dichromate

(See Table X.,

hoi (50 per cent.)

1000

cc. of water.

platinum in

em

4a

scrap

ll.

Potassium Hydroxide, KOH.— Use the stick form. Solid. drypasty to evaporate aqua regia, Dissolve 100 gm. of Solution. ness, and dissolve the residue in the commercial lump potash in 1000 distilled water. Use an iron dish, and Dissolve cc. of water. Potassium Bromide, KBr. (2) Dissolve

—

—

commercial

dry

w w

Use the which should always be kept

Solid. salt,

K2CO3.

Carbonate,

Potassium

stir

If the solution

constantly.

clear,

.c h

50 gm. of the commercial crystals in 1000 cc. of water.

Keep

shredded asbestos.

solution containing 500 liter (sp. gr.

w

Dissolve

Solution.

100 gm.

of

looo

cc.

tp ://

salt in

ht

50 gm. of the commercial cc. of water.

Fiker

— Dissolve salt in

lOOO

gm.

to the

1.27 approximately).

Potassium Iodide, KI.

—

Solid.

Use

the commercial crystals.

Dissolve 50 gm. of the

commercial

Potassium solve

not clear.

if

=

Solution.

of water.

Potassium Chloride, KG.

tightly

dioxide in quantitative work, use a

quick-sealing

the dry commercial

not

For absorption of carbon

stoppered.

tightly stoppered, or preserved in a jar.

is

through glass wool or

filter

salt in

1000

Nitrate,

cc.

of water.

KNO3.

— Dis-

100 gm. of the commercial

Filter. salt in 1000 cc. of water. Potassium Chromate, K..C'r04.— KMn04. Dissolve 100 gm. of the commercial Potassium Permanganate, Dissolve 5 gm. t)f the commercial Filter if salt in icxx) cc. of water.

crystals in

not clear.

Potassium solve salt in

lution

be

Cyanide,

100 gm. of the

1000 is

commercial

cc. of water.

This so-

a violent poison,

and should

small

quantities,

prepared

in

plainly labelled,

1000

cc. of water.

KCN. — Dis- Potassium Sulphate, K2SO4.

and kept where

it

cannot be promiscuously handled.

solve salt in

1000

cc.

of water.

Potassium Sulphocyanide cyanate),

KSCN.

(or Thio-

— Dissolve

gm. of the commercial cc. of water.

— Dis-

commercial

100 gm. of the

salt in

10

lOOO

Appendix C. Nitrate,

Silver

— Dissolve

AgNOs-

391

hydrogen ceases.

through glass wool, or better, siphon off the clear supernatant

mercial

(3)

Keep

This solution should be kept free from dust and organic matter. Dissolve 10 Soap Bubble Solution. gm. of thin shavings of castile soap

vn

a few pieces of tin in

Stannous chloride solution does

Solid. crys-

4a

—

not keep unchanged, and should be

made

as needed.

Paste.

Starch

tals as directions require.

— Grind

10

Dissolve 100 gm. of the

starch to a paste with a

crystallized

commercial compound

water in a mortar.

in 1000

of water.

is

made

430 gm. in 1000

Sodium

saturated

Sulphuric

NaCl. — Dissolve

w

salt in

Filter.

cc. of water.

NaOH.

tp ://

Sodium Hydroxide,

— Solid.

gm. of the commercial lump caustic soda in Use an iron 1000 cc. of water. dish, and add the solid slowly to the

ht

liquid with constant stirring.

through asbestos.

glass

wool

Keep

or

Filter

shredde^l

—

DisSulphite, NaoSOs. 200 gm. of the crystallized commercial salt in 1000 cc. of water.

solve

Stannous Chloride, SnClo. the commeicial

Add

—

(i)

Use

solution.

in an (2) Dissolve granulated tin

excess of hot concentrated hydro-

of

cold

the paste

Use

Boil.

water.

trated.

Acid,

— Concen

USO^.-

commercial acid

the

.Use

(sp.gr. 1.84).

Slowly pour one volume Dilute. of commercial acid into four volumes Stir constantly

Cool and

operation.

commercial acid

is

during the

filter,

the

if

not colorless.

Tartar Emetic, K(SbO)C4H406.— Dissolve 100 gm. of the commercial salt in

1000

cc. of water.

tightly stoppered.

Sodium

gm.

little

cold.

of water.

stick form.

Solution. Dissolve 100

of

cc.

water.

cc. of

Chloride,

Use the

200

when

100 gm. of the commercial

1000

to

by dissolving about

w w

solution

A

.c h

Solution.

cc.

the

in

ll.

the solution.

63.

Use the commercial powder or

Keep

water.

filter

of glycerine.

—

acid.

of tin

pieces

a few

em

Add 50 cc.

if .lot clear.

hot

of

cc.

hydrochloric

the com(4) Dissolve 112 gm. of mercial salt in 200 cc. of hydrochloric acid (i to i) and add 800 cc. of

Shake

See Exp. Sodium Amalgam. Sodium Carbonate, Na2C03.

1000

in

salt

solution.

—

complete, and

volumes

5

Dissolve 500 gm. of the com-

concentrated

Uquid.

until solution is

Add

of water to the solution.

filter

in 100 cc. of distilled water.

of

chloric acid until the evolution

in 50 gm. of the commercial crystals 1000 cc. of distilled water. Let the solution stand a day, and if not clear,

Zinc Chloride, ZnCL..

— Dissolve

gm. of the coimiiercial cc. of water.

Zinc

Sulphate,

ZnS04.

— Dissolve

100 gm. of the commercial

1000

cc.

solution

is

of water.

not clear.

50 looo

salt in

Filter

salt in if

the

Experimental Chemistry.

39'^

V.

TABLE

I.

— IMPORTANT

TABLES.

ELEMENTS AND THEIR ATOMK

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

WEIGHTS.

Appendix C.

393

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

TABLE L — IMPORTANT ELEMENTS AND THEIR ATOMIC WEIGHTS — {Continued)

Experimental Chemistry.

394

III.

— COLORS

OF BORAX BEADS.

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

TABLE

Appendix C. TABLE

395

— SPECIFIC

GRAVITY AND MELTING POINT (APPROXIMATE) OF METALS.

VII.

Melting Point.

Specific

Metal,

.

2.6

625

"57

.

.

8.9

1054 1600

2912

Iron (wrought)

7.8

....

Mercury

"•35

326

13-59

-38.5

-

1775

3227

Platinum

.

.

21.5

Silver

.

.

IO-53

.

7-3

Zinc

.... TABLE

6.86-

VIII.

— SOLUBILITY

w w

Salt.

Copper sulphate

(cryst.)

Potassium chlorate

.

.

.

.

w

Potassium chloride

.

.

tp ://

Potassium dichromate Potassium nitrate

.

Potassium sulphate

.

.

Sodium chloride Sodium sulphate (anhyd.) Sodium sulphate (cryst.)

ht

.

.

619

954

7.2

37-3

1749

232.7

450-9

433

811.

em

...

.

OF SALTS IN WATER.

.c h

.

Tin

1929

vn

Lead

Fahrenheit.

.

ll.

.

Centigrade.

4a

Aluminium Copper

Gravity.

Grams soluble 20°

c

in 100 gm.

at

Experimental Chemistry.

?^9^

TABLE

X.

— FORMULA

FOR PREPARING AN ALCOHOLIC SOLUTION OF DESIRED STRENGTH.

_ ac X= a

d := c

vol, required.

= % of =

%of

solution used.

solution desired.

vol. of stock solution used.

vn

TABLE XL —COMPOSITION OF TYPICAL COALS.

ht

tp ://

w

w w

.c h

em

4a

ll.

Kind.

Appendix

397

y.\\.— {Conliimed).

ht

tp ://

w

w w

.c h

em

4a

ll.

vn

TABLE

C.

Experimental Chemistry.

j^S

VI.

SUGGESTIONS FOR A SHORT COURSE.

The experiments in chemistry.

incorporated in this book constitute a liberal course fact, however, that conditions, often tem-

In view of the

integrity,

:

—

ht

tp ://

w

w w

.c h

em

4a

ll.

be made

vn

all the porary or unavoidable, may prevent the pupil from performing its experiments, this course may be shortened without detriment to experiments of apportionment and if the following selection

INDEX Tests

ADbreviaiious of metric denominations,

Exp. 170.

for,

Amalgam,

Sodium, Exp.

Acetic acid, 245.

gas, composition, 174.

Formula, 182.

(a).

Preparation and properties, Exp. 65.

Qualitative examination, 178, Exp. 66.

Acid, definition, 117, 128.

Quantitative examination, 178, Exp. 67. Volumetric composition, 181, Exp. 68.

.c h

97.

Acids and bases, interaction of, Exp. 52. Quantitative examination of, Exp. 53.

117.

w w

Acids, bases, and salts, 116. Acids, general properties, 117, Exp. 48.

w

Air bath, 333. Air, composition, 105. Quantitative examination, Exp. 45.

Weight of liter

Ammonium,

Compounds,

183, 184.

69.

Preparation and properties, Exp. 65.

Ammonium

tp :// of,

of, 182.

184.

Ammonium hydroxide, 172. And hydrochloric acid, Exp.

action with

nitrate,

heat,

Exp. 79.

See Atmosphere.

Weight of liter

63.

Preparation, Exp. 64.

Ammonia

preparation and properties,

Nomenclature,

172.

4a

Ammonia,

em

Formula, 246. Properties, Exp. 112. Test for, Exp. 1 13. Acetic aldehyde, Exp. iii Exp.

ll.

properties, 304, Exp. 169. 288.

Acetates, 215. Preparation, Exp. 115.

Acetylene,

vn

Aluminium hydroxide, preparation and

lO.

Exp. 47.

Analysis, definition, 33.

Alcohol, 238, 240.

ht

Formula, 240. Preparation, Exp. 108. Properties, Exp. 109. Alcoholic solution of desired strength,

Anhydride, definition, 129. Anhydrous, definition, 67. Annealing, 4. Apparatus, lists, 381-383.

Aqua

regia, 202.

Characteristic property, Exp. 81.

396.

Aqueous

tension, 360.

Aldehyde, 244. Aldehydes, preparation and properties, Exp. III.

Table of, 361. Argon, 105, 397.

Alloys, 283.

Aspirators, 343.

Alum, common, preparation and proper- Atmosphere, Exp. 171. Chrome, Exp. 184. Aluminium, action with acids and alkalies, Exp. 168. Equivalent, Exp. 55. General properties, Exp. 167.

105.

Other constituents See Air,

ties,

of,

Exp. 46.

Atom, 53, 140, 141. Atomic and molecular weights, tion

Atomic

399

of, 144.

theory, 136.

calcula-

Index. 139.

Various figures lor, 142. Table of, 392. Avogadro's law, 143. Balance, counterpoising

a,

Hornpan, 12, 347. Barium chloride, water of

347. crystallization

Exp. 26. Barometer, 353. in,

Using

353, 369.

a,

Base, definition, 128. Bases, general properties, 118, Exp. 49.

Nomenclature, See Acids.

119.

123.

Carbon

Basic oxides, 129. glass, 2-6, Exps.

dioxide, 207.

Action of hot charcoal on, Exp. 93. And combustion, Exp. 88. Determination of, in a carbonate, Exp.

2, 3.

4a

Bending

Calcium, compounds of, 294. Tests for, 221, 294, Exp. 159. Candle flame, Exp. 102. Carbohydrates, 248. Carbon, 204, 236. See Charcoal. Distribution of, Exp. 82. In organic compounds, Exp. 107 (a). Reduction by, Exp. 85. Carbonate, acid calcium, Exp. 91. Determination of carbon dioxide in a, Exp. 92. Carbonates, 213. Formation and properties, Exp. 90. Carbon bisulphide test for iodine, Exp.

ll.

Atomic weights,

vn

400

Bertholiet, 35. Berzelius, 138.

Bibliography, 377-381. Black, 137. {e).

Weight of liter of, 210. Carbon monoxide, 216, Exp. 93. Preparation and properties, Exp. Weight of liter of, 218.

w w

.c h

Bleaching by chlorine, Exp. 58. By sulphur dioxide, Exp. 136 Blowpipe and its use, 232. Blowpipe flame, 233. Oxidation with, Exp. 106. Reduction with, Exp. 105. Blowpipe tube, 232. Blowpipe, use of, Exp. 104.

em

92.

Preparation and properties, Exp. 86. Synthesis of, Exp. 87.

of, 150.

w

Boiling point, elevation 31.

tp ://

Of water, Exp. Bone black, 205. Borax bead,

231, 232.

ht

Tests with, Exp. 103. Bottle, Drechsel, 368. Drying (or washing), 368. To clean the inside of a, 338. To cut off the bottom of a, 336. Boyle, 105.

Law

of,

357.

of, Exp. 196. Bromides, 251. Bromine, preparation and Exp. 119.

Brass, analysis

Bunsen burner,

1-2, 228.

Construction of, Exp. 100. Flame, Exp. loi. Burette, use of, Exp. 53. Burner. See Bunsen.

Wing-top,

2.

properties,

Carbonic acid,

212, 214,

Exp.

94.

89.

Casserole, 331.

Cavendish, 38, 51, 83, 137. Changes, physical and chemical, 15. Charcoal, action of carbon dioxide on hot, Exp. 93. Animal, 205. Decolorizing action of, 205, Exp. 83. Deodorizmg action of, 205, Exp. 84. Charles, law of, 354.

Chemical action, 22. Chemical compounds, 27, 29, 30, 3^" Chemical reaction. See Reaction. Chemical terms, glossary of, 370-377Chemicals, list of, 383-385. Chemistry, definition, 15-16. Organic, 206. Chloride, definition, 34. Test for, FIxps. 29 {d), 61 Iv. Chlorine, 157, 250.

Bleaching by, Exp. 58. Decomposition of water by, Exp. 41. Preparation and properties, E.xps. 56, 57-

Index. Class-room Exercises,

160.

of,

Chromates, 314. Properties, Exp. 182. Reduction of, to chromic compounds, Exp. 183. Chrome akim, properties, Exp, 184.

Chromic compounds, reduction mates

of chro-

Calcium and

its

Carbon, 206-207.

Carbon

dioxide,

Chromium,

Chemical

313.

Exp. 181. Cinnabar, Exp. 164 {d).

action, 23, 26, 277.

Chemists, 278.

for,

Chlorides, 72. Chlorine, 160-161.

Chromium and

its

compoundi,

316.

ll.

Coal, 207. Collecting gases, 23.

Combustion,

36.

4a

Compound

blowpipe, 51.

Compounds, 36, 55, 277. Copper and its compounds, 288-289.

em

Class-room Exercises. Acetates, 246. Acetic acid, 246. Acetylene, 224. Acids, bases, and salts, 129-131. Air, 109-111, 113. Alcohol, 241.

Courtois, 255.

Alkali, 130.

Allotropy, 206, 276, 277. Alloys, 289, 291, 298, 308, 312.

Aluminium, 305. Alums, 305. Amalgams, 301.

.c h

170, 255.

Dextrine, 249.

Ammonium compounds, Ampere, 153. Animal charcoal,

w

207.

185, 186, 285.

tp ://

Aristotle, 109.

Dalton, 153.

Davy, 87, 130, 161, Deliquescence, 72.

185, 186.

Apparatus, 52.

Crystallization, 51.

w w

Ammonia,

211.

Cellulose, 249.

Charcoal, 207. Charles, 359.

Tests

no,

Cavendish, 193.

Exp. 183. Chromic hydroxide, Exp. 185. to,

compounds, 295-296.

Cannizzaio, 153.

vn

Weight of liter

401

Diamond,

206.

Diffusion of gases, 52. Distillation, 73.

Dulong and

Petit, 153.

Effervescence, 52. Efflorescence, 72. Electrolytic dissociation, 153.

Atmosphere. See Air. Atomic theory, 277. Atomic weights, 162. Atoms, 153. Avogadro, 153.

Elements, 36, 55, 277. Equations, 277, 306, 308.

Balard, 255. Becher, 36.

Faraday, 161, 185. Fermentation, 241.

Berzelius, 153.

Fertilizer, 276, 285.

Black, 211, 293.

Filtration, 73.

Bleaching by chlorine, 160. Bleaching powder, 160.

Fluorine, 258.

ht

Arsenic, 277.

Ethereal

salts, 242.

Ethylene, 224.

Flames, 230.

Formaldehyde, 244. Formulas, 55, loi, 246,

Boiling, 74.

Boyle, 359.

Bread-making, 249. Bromine, 255. Bunsen, 109, 230.

Bunsen fiame,

Ether, 242-243.

23.

271, 277, 278,

312, 316.

Freezing, 75. Gas, illuminating and water, 227. Gases in the atmosphere, iii.

Index.

402

Class-room Exercises. Molecular weight, 162, 277. Molecules, 153, 277. Multiple proportions, law of, 202, 227,

Class-room Exercises. Gases, solubility in water, jj.

Gay-Lussac, 255.

Law

of, 186,

224.

Glass, 7, 275. Glycerine, 248,

Nascent

Graphite, 206.

Nitrates, 200, 202,

Nitric acid, 193, 194.

202.

Heating glass and porcelain, History of

air,

Ammonia,

23, 36.

Oxides of, 200. Nomenclature, 130, Organic acids, 248. Organic matter, 72.

109.

185.

Bromine, 255.

Carbon

Nitrogen, 108.

dioxide, 211.

278.

vn

Gunpowder,

state, 161.

Neutialization, 129, 130.

Hydrochloric acid, 170.

Oxalic acid, 246. Oxidation, loi, 235, 277.

Hydrogen,

Oxygen,

51.

gases in

Nitric acid, 193.

Phosphorus,

109, 276.

em

Physical and chemical changes, 23.

Potassium and its compounds, 284. Potassium permanganate, 51.

Hydrofluoric acid, 258.

.c h

Precipitation, 51. Priestley, 36, 170.

50, 130.

Reduction, loi, 235, 277. Relation between chlorine, bromine,

Sulphide, 267.

w w

Hydroxyl, 131. Hypothesis, 369.

and

iodine, 255, 256.

Review, 277. Rocks, 275.

Iron and its compounds, 321-322. Lavoisier, 36, 51, 109, 130, 193, 211.

Salts, ethereal, 242.

w

Illuminating gas, 227. Iodine, 255-256.

369. definite proportions, 36.

tp ://

Law, Of

Scheele, 36. Separation of metals, 325.

and its compounds, 274-275. and its compounds, 291.

Silicon

Of Gay-Lussac, 186, 224. Of multiple proportions, 202,

Silver 227.

ht

Laws, 277.

Lead and its compounds, 311-312. Lead in water, 73. Liebig, 255.

Soap, 248.

Sodium and its compounds, Sodium and potassium, 285.

281-282.

Solids, solubility of, in water, 82.

Solution, 277.

And

Litmus, loi.

Magnesium and Manganese,

271, 276,

277, 285, 291, 296, 301, 312.

Oxygen, 36. Water, 87, loi. Hydrocarbons, 223, 238. Hydrochloric acid, 169-170.

Hydrogen,

36, 109.

Periodic classification, 258,

air, 113.

4a

New

ll.

Chlorine, 161.

its

compounds,

293.

Mariotte, 359. Matches, 270, Matter, 23, 72. its

of,

154.

Standard conditions, 369. Starch, 249.

compounds,

Metals, separation

Methane, 224.

theory

Specific heat, 153. Stahl, 36.

162, 318.

Mercury and

taste, 82.

Modern

of,

325.

301.

Stas, 153. Stassfurt deposits, 256, 285, 293.

Mixture, iii.

Sugars, 249. Sulphates, 72.

Moissan, 258.

Sulphide, hydrogen, 267,

Index. Compounds

Class-room Exercises. Sulphides, 267. Sulphur, 262. Sulpliuric acid, 271. 55, loi, 162, 277.

Tests, 278.

and pressure, 363. For aqueous tension, 361, 363. For pressure, formula for. 358, 363. For temperature, formula for, 354, 362.

Theory, 369.

Tin and

its

compounds,

287.

of,

General properties, Exp. 150. Interaction with metals, Exp. 152, Oxides, 287. Tests for, Exp. 151. Corrected, definition, 362. Correction, combined, for temperature

Sulphur dioxide, 269. Symbols,

403

308.

Valence, 154, 186, 194, 202, 271, 277, 282, 285, 289, 293, 296, 298, 30X,

Counterpoising a balance, 347. Crucible block, 19.

Vapor

Crystallization, 42.

Of

4a

ties, Exp. 153. Cutting glass, 2, Exp.

standard, 75.

Composition

Formula

of,

Dalton, 137, 138, 202.

loi.

Davy, 83, 157. Decomposition,

.c h

Gas, 227. 72.

in, 73.

Of

density

w w

Lead

of, 75.

crystallization, 72, 73.

w

Relation to temperature, 75. Solubility of gases in, 77.

342. Distillate, definition, 71.

29S.

Distillation,

ht

Electrolytes, 151. 236,

of, 99.

See Cuprous-

of,

151,

Element, definition, 15. Elements, table of, 392.

Emergency

set,

397.

Equations.

Combination

of

calcium oxide and

water, 131.

Hydrochloric

Corks, 334. (-opper, 286.

Electrolytic dissociation, theory 152.

Exp. 107.

Section of inner, 21. Cork, boring a, 335.

Petit, 141.

Efflorescence, 68, Exp. 27.

33.

Components, definition, 33. Composition of organic compounds,

Composition, percentage, 148. Concentrated, definition, 75. Condenser, 71. Connector, 338.

Exp. 30.

Dulong and Dumas, 83.

Closing tubes, Exps. 5, 6. Coals, composition of, 396.

Composition of water, summary

Dilute, definition, 75.

Dissociation, definition, 67.

9.

Combination, definition,

Dehydrated, definition, 67. Deliquescence, 68-69, Exp. 28. Determination, definition, 34. Displacement, downward and upward,

tp ://

Solvent power of, 82. Weighing, 36. Zinc and its compounds, Cleanliness,

definition, 33.

Deflagrating spoon, 25, 26. Deflagration, 211.

History of, loi. In atmosphere, no.

Maximum

i.

em

of, 87, loi.

Drinking, 72.

Hard,

for, 43.

Cuprous oxide, preparation and proper-

Water, 72.

As a

zinc sulphate, Exp. 20.

Rules

ll.

tension, 361.

Vinegar, 246. Volumetric composition, 277.

vn

306, 308, 309, 312, 316, 318, 322. Van Helmont, 211.

monia

acid

gas, 182.

gas

and

am-

Index.

404

Equations.

Equations.

Chromic Cuprous

Hydrogen and chlorine, 171. Hydrogen and nitrogen, 184. Oxygen and magnesium, 56, 58, 61. Oxygen and phosphorus, 115. Sulphur trioxide and water, 131. Sulphuric acid and ammonia, 182. Combustion of ethylene, 223.

chloride, 314.

oxide, 289.

Formaldehyde, 244. Hydrofluoric acid, 258,

Hydrogen,

Hydrogen

56.

sulphide, 264.

Iodine, 253.

Lead chromate,

Methane, 222. Decomposition of ammonia gas by

316.

Nitric acid, 201.

Nitric oxide, 207.

chlorine, 182.

vn

Nitrogen peroxide, 207. Potassium aluminate, 304, 306. Potassium chromate, 314.

59.

Silicic acid, 274.

Potassium dichroinate, 314. Potassium hydroxide, 285.

Water by carbon, 227. Water by chlorine, 173.

4a

Sodium,

285.

Sodium carbonate, 286. Sodium sulphate, 286. Sodium sulphide, 286.

em

Fermentation of glucose, 240. Formation of steam from hydrogen and oxygen, 102. Water from hydrogen and oxygen,

ll.

Mercuric oxide, 59. Potassium chlorate,

Sulphuric acid, 269,

100.

and acids, 241. Ammonia gas and magnesium, 181. Copper and nitric acid, 207. Hydrofluoric acid and silicon diox-

Sulphurous acid, 269. Reduction of ferric oxide, 322.

w w

.c h

Interaction of alcohol

ide, 258.

Problems based on, 60-61.

Quantitative interpretation

tp ://

Stannous and mercuric

chlorides,

ht

Sulphuric acid and potassium permanganate, 318.

Neutralization, 129.

Of aluminium, Exp. 55. Of magnesium, Exp. 54. Of zinc, Exp. 22. Ester, 241.

Ether. 242. And water, Exp. 33 {b). Properties, Exp. no. Ethyl, 240.

Oxidation of carbon to carbon dioxide,

Acetate, 241, Exp, 109 {e).

60, 220.

Alcohol. See Alcohol. Chloride, 241. Ethylene, combustion of, 223. Preparation and properties, Exp. 96. Eudiometer, 351, Exps. 43, 68.

Ferrous oxide, 322. Iron, 322.

Sulphur to sulphur dioxide, 60. Preparation of aldehyde, 315.

Ammonia

Evaporation, 332. Experiments, form of record

Bromine, 251.

Fats, 247.

304.

gas, 177. Ammonium chloride, 167.

of, 13.

Fermentation, 240, 246, Exp. 109. Ferric compounds, behavior of, Exp. 190

Carbon dioxide, 219. Carbon monoxide, 228. Chlorine, 163, 319.

57-59-

Etching, Exp. 128.

308.

Aluminium, 306. Aluminium hydroxide,

of,

Equivalent, definition, 48, 132.

w

Lime water and carbon dioxide, no. Magnesium nitride and water, 181. Sodium and water, 91. Sodium chloride and sulphuric acid.

Equations, chemical, 55-57. 59-6o.

,

Reduction

of,

Exp. 191.

index. Ferrous and ferric compounds, 319. Ferrous compounds, behavior of, Exp Exp. 192.

Filter, folding a, 8.

334, 343.

Hydrobromic

Filtrate, definition, 8.

Filtration, definition, 8, 333.

Flame, Bunsen,

Luminous and non-luminous, i, 2. Oxidizing and reducing, 230-231.

Formula

Fluorine, 256.

Hydrogen,

Gas from the red powder,

identification

13.

holder, 342.

38.

water, 86, 90, Exp. 40,

em

of, 150.

Flame, Exp.

23.

Generator, 39. In organic compounds, Exp. 107 (d). Preparation and properties, Exps. 18,

.c h

Freezing point, depression Of water, Exp. 31.

19.

w w

Product of burning, Exp.

Gas, how to light, 1-2. Gases, collecting, 341,

w

Drying agents for, 367. Manipulation of, 366-369. Measuring, 349. Solubility of, 76, Exp. 32. Gay-Lussac, 83.

23.

Weight of liter of, 50. Hydrogen sulphide, 262. Preparation and properties, Exp. Weight of liter of, 264.

133.

tp ://

Hydroxides, 119. Hydroxy!, 129.

182.

Generator for producing steady current of gas, 96. Glass stopper, holding a, 339. Glass tube, to fit a, to a stopper, 337, To insert a, into a rubber tube, 337. Glass working, 2-5.

Glossary of chemical terms, 370-377. Glycerine, 247.

Gram,

Synthesis of, Exp. 60. Hydrofluoric acid, preparation and properties, Exp. 128.

And

396.

of,

169.

ll.

(d).

Calculation of, 149. For preparing an alcoholic solution,

Law

of,

Properties, Exp. 59.

Formaldehyde, Exp. iii Formulas, 54.

Gas

and

Preparation and properties, Exp. 61. Hydrochloric acid gas, composition of, 168, Exp. 63.

Flat, 2.

Exp.

preparation

Hydrocarbons, 221, 236, 238. Hydrochloric acid, 162.

2.

Bunsen burner, Exp. loi. Candle, Exp. 102.

of,

acid,

properties, Exp. 120.

ht

.

83.

4a

Pump,

screw, 343.

vn

of,

Hofmann

Humboldt,

Hydrate, definition, 119. Hydrated, definition, 67. Hydriodic acid, preparation and properties, Exp. 126.

189.

Oxidation

405

Combustion

of,

Exp.

99.

Preparation and properties, Exp. 98. Iodide, potassium, properties of, Exp. 127.

Iodides, 255. Iodine, 250.

Carbon bisulphide test for, Exp. 123. Preparation and properties, Exp. 122.

345.

Hard glass tubing, 329. Hardness of water, 248, Exp. 117 Heating glass and porcelain, 330. Heating glassware, 7. Heating hard glass, 329. Hofmann apparatus, Exp,

Ignition tubes, making, 329. Illuminating gas, 225.

38.

(d).

Starch test for, Exp. 124. Ions and ionization, 151. Iron, 319. See Ferrous and Ferric. General properties, Exp. 188.

Joints, 336.

Index.

4o6

Solubility

Laboratory Exercises. Acids, bases, and salts, 123.

Lucretius, 137.

Air, 27, 108. cf,

294.

Magnesium, 292. Atomic weight of, 144. Combination of, with oxygen, Exp.

action, 108.

Chromium, compounds

316.

of,

Copper, 286, 287.

Equivalent of, Exp. 54. General properties, Exps.

Ether, 242.

Flames, 230, 231. Hydrocarbons, 238.

Tests

41.

for,

Magnesium Magnesium

Sulphide, 264. Iron, 319, 321.

Lead, compounds

of,

14

{e),

157-

Exp. 158. nitride, 179.

oxide, molecular weight

145-

311,

Magnesium and its compounds, Manganese, compounds of, 317. Mercury, compounds of, 300.

292.

Manganese, 317. Tests

Marsh

for,

of,

vn

Hydrogen,

9,

15.

Exps. 103

(t), 186.

ll.

Calcium, compounds

Chemical

Exp. 33.

of,

Liter, 9, 10, 345.

gas, Exp. 95.

Matter, 15.

Nitrogen, 108.

Conservation of, 55. Organic, 69, 310, Exps. 29 (a), 138. Meniscus, 351. Mercurous and mercuric compounds 300, Exp. 166. Mercury, 298.

Oxides, 23, 26. 108, 276.

Potassium, compounds Reduction, 206.

of,

283, 318.

.c h

Oxygen, 26. Phosphorus,

Compounds

Silver, 291.

Starch, 249.

compounds,

297.

tp ://

its

w

Sulphur dioxide, 269. Sulphuric acid, 271.

w w

Sugar, 249. Sulphide, hydrogen, 264.

Zinc and

Lavoisier, 51, 55, 83, 86. Law of Avogadro, 143.

ht

Boyle, 357. Charles, 354. 357. Conservation of matter, 55. Definite proportions by weight, 34.

Gay-Lussac,

em

4a

Nitric acid, 190.

182.

Multiple proportions, 201. Specific heats, 141.

Lead, 309. Action of water on, 310, Exp. 179. General properties, Exp. 176. Interaction with metals, Exp. 178. Tests for, Exps. 98, 177. Lead acetate, preparation, Exp. 115 {b). Lead oxides, properties of, 310, Exp. 180. liquids, measuring, 349. Pouring, 339.

300.

of,

General properties, Exp. 163. Preparation, 299, Exp. 164. Tests for, Exp. 165.

Metal, definition, 15, 16, 128, 279. Change in, when heated, 16, Exp. Effect of heating a, covered

9.

and un-

covered. Exp. 10. Result of heating known weight

Exp.

of,

II.

Metals, separation

of,

Methane, combustion

322. of,

222.

Preparation and properties, Exp. 95. Meter, 344. Metric system, 9-10, 344. Mixture, definition, 35. Molecular weights, 142. Multiple proportions, law

of,

201.

Neutralization, 125, 127, Exps. 52, 53.

Newton, 137. Nicholson and

Carlisle, 83.

Nitrates, 198.

Action Special

Test

of,

with heat, Exps. 78, 79.

test for,

for,

Exp.

Exp. 80.

73,

Index.

Potassium chlorate, molecular weight

Nitric acid, analysis, Exp. 75. Interaction with metals, 195, 197, Exps.

Per cent of oxygen in, Exp. 16. Potassium chloride, molecular weight

Preparation, 198, 201, Exps. 70, 73. Special property, Exp. 71.

Potassium hydroxide, preparation, 283^ Exp. 148. Potassium iodide, properties, Exp. 127. Potassium permanganate, oxidation with, Exps. 29 (a), 187. Powder, to introduce a, into a tube, 338. Precautions in bending glass, 5.

Nitrogen, oxides

of, 197,

Exps.

'j'j,

79.

Non-metal, 128. Observed, definition, 362. Organic chemistry, 206. Organic compounds, composition of, 236, Exp. 107. Organic matter, 69, 310, Exps. 29 {a) 138. Ostwald, 153. Oxidation, 34, 308, 314. With blowpipe, Exp. 106. With potassium permanganate, Exp. 187.

.c h

24.

Precipitate, definition, 8.

water, 88.

Combination

of,

with magnesium, Exp.

w w

And

15-

Density

of, 102.

w

In the air, 105, Exp. 45. Per cent in potassium chlorate, Exp.

tp ://

16.

Preparation and properties, Exp. 14.

Weight

reading volumes, 351. using carbon bisulphide, 253. using ether, Exp. no. using phosphorus, 106. using sodium, 89. using thermometers, 353.

In using turpentine, 158, 159. In weighing, 349.

Oxide, definition, 22.

Oxygen,

cutting glass, 3.

generating hydrogen, 39, 48. preparation of methane, Exp. 95. preparation of ethylene, Exp. 96. reading the barometer, 353.

em

,

In In In In In In In In In In In

vn

(c).

liter of, 113.

ll.

of

4a

Weight

of,

146.

Synthesis, Exp. 74.

Test for, Exp. 72. Nitrogen in the air, Exp. 45. In organic compounds, Exp. 107

of,

146.

n-

76,

407

of

liter of, 30,

Exp.

17.

ht

Palmitic and stearic acids, 247. Percentage composition, 148.

Phosphorus, 275. Precaution in using, 106. Pipette, use of, -jt, 352, Exp. 33. Platinum test wire, 341. Platinum tip, 340, Exps. 23, 60. Platinum wire, to seal a, into a glass rod, 341-

Pneumatic trough,

21, 24, 344.

Potassium, properties, Exp. 146. Properties of compounds, Exp. 147. Potassium bromide, properties, Exp. 121. Potassium carbonate, preparation and properties, 283, Exp. 149.

Pressure, correction

for, 358,

363.

Priestley, 83, 137.

Problems. Air, 114-115, 212, 224. Alcohol, 243.

Aluminium,

Ammonia

154, 155, 306. gas, 186-187.

Ammonium

compounds, Atomic weights, 154, 155.

187. 170, 171, 256,

259, 275, 285, 289, 292, 296, 306, 312, 316, 318, 322.

Barium

chloride, 67.

Boyle, law

of,

359.

Bromine, 256. Calcium, 155, 296. Calcium carbonate, 212. Carbon, 62, 115, 211, 212. Carbonates, 214, 215.

Carbon

dioxide, 62, 63, 211, 212.

Charles, law

of, 355-356. Chlorine, 170-171.

Chromium, 316-317. Composition of water, 102-104.

Index.

4o8

Qualitative analysis, 266, 342.

Problems.

Copper,

103, 289.

Radical, 184, 240.

Ether, 243. Equivalents, 154. Fluorine, 259.

Formula, 156, 188, 203, 243. Gas volumes, reduction of, 364-366, Hydrocarbons, 224. Hydrochloric acid, 170-171, 212.

Hydrogen,

52, 62, 102, 103, 114, 171.

Reducing agents,

Sulphide, 268.

vn

Iodine, 256. Iron, 322. Lavk' of Boyle, 359.

ll.

Of Charles, 355-356-

Residue, definition, 155, 294.

8,

34.

Safety tubes, 336.

Salt, ethereal, 241.

171, 172.

em

Magnesium, 37, 154, Manganese, 318. Manganese dioxide,

4a

Lead, 312.

Salts, 121, 128.

62.

General property Nature of, 125.

Metric system, lo-ii. Molecular weight, 156.

.c h

Nomenclature

of,

of, 120,

Exp.

120-121.

bath, 332. Saturation, 79.

Nitric acid, 194, 203.

224.

Scales, trip, 12, 347. Scheele, 157.

188,

Separation of aluminium and iron, Exp.

w w

Nitrogen, 114, 187.

Oxygen, 37, 62, 63, 102, 103, 114,1115, Percentage composition, 155, 171,

w

195, 224, 243, 256, 259, 268, 272,

275, 290, 291, 309, 316.

tp ://

Phosphorus, 115. Potassium, 170, 285. Potassium chlorate, Review, 278, 366.

37, 62.

ht

Silicon, 275,

Silver, 155, 170, 292. 103, 154, 285.

200,

Copper,

iron,

Lead and

and sodium, Exp.

Exp. 193. Lead, silver, and mercury, Exp. Zinc and aluminium, Exp. 201. Zinc and iron, Exp. 199. Silicic acid,

preparation and properties,

Silicon, 273. of, to

Sulphur dioxide,

Silicon tetrafluoride, 258.

pounds of silicon,

274,

Sulphuric acid, 62, 194.

Silver, 290.

Thermometers,

Analysis of, coin, Exp. 195. Preparation, Exp. 154. Properties, Exp. 155. Tests for, Exp. 156. Smelling and tasting, 8. Soap, 247, 248. Preparation, Exp. 116.

14, 243, 256.

Tin, 309. Water, 102-104, 212. Water of crystallization, 67. Zinc, 52, 62, 154.

Problems based on equations, 60-61.

194.

Exp. 141. Silicon dioxide, relation

63.

198.

silver,

Sulphide, hydrogen, 268. Sulphur, 267, 272.

Proust, 35.

50.

Sand

Nitrates, 194.

Sodium,

102.

Reduction, 102, 308. By carbon, Exp. 85. Of gas volumes to standard conditions, 361-364. With blowpipe, Exp. 105.

Illuminating gas, 227.

Mercuric oxide, Mercury, 302.

Rayleigh and Ramsay, 105. Reaction between zinc and sulphuric acid, Exp. 22. Reaction, chemical, 41. Reagents, list of, 385-391. Red powder, products obtained by heating the, Exp. 12.

•

Properties, Exp. 117.

other com*

Exp. 140.

409

Index. Separation 88, 90, 91,

Exp. 42. General properties of compounds of, Exp. 143. Precautions in using, 89. Properties, Exp. 142. Sodium acetate, preparation, Exp. 115 {a).

Sodium amalgam, Exp. 63. Sodium chloride, preparation of Exp.

pure,

144.

Sodium hydroxide, preparation, 280, Exp. 145-

Sodium

nitrate

action

and sulphuric

of, 190, 191,

acid, inter-

Exp. 73.

Exp. 197. Solids, solubility of, 78, Exp. 34.

Solder, analysis

of,

Transferring, 339. Solubility,

terms for expressing, 75.

Solute, definition, 75. Solution, 75. And chemical action, Exp. 37.

Solutions,

list of,

Of gases,

76,

Exp. 32.

liquids, 77, 78, Exp. 33. solids, 78, Exp. 34.

w

Solvent, definition, 75. Specific heats, law of, 141.

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Standard temperature, reducing to, 355. Standard pressure, reducing to, 359. Starch, detection of, Exp. 125. Test for iodine, Exp. 124. Stirring rods, Exp. 4. Steam, density of, 99. Volumetric composition of, loi. Sublimate, definition, 299. Subliming, definition, 299. Substitution, definition, 45.

Sugar, Fehling's test for, Exp. 118. Sulphate, definition, 45. Test for, Exp. 2i{l>). Sulphide, definition, 45. Sulphide, hydrogen, 262. Preparation and properties, Exp. 133.

Weight

of

liter of,

264.

Sulphides, 261, 265. Preparation and properties of some,

Exp.

134.

Sulphur, amorphous, Exp. 130. Combinmg power of. Exp. 132. Crystallized, Exp. 131.

In organic

Oxides

of,

compounds, Exp. 107

(d).

268.

Physical properties of, Exp. 129. Sulphur dioxide, preparation and properties, Exp. 136. Sulphur trioxide, 269.

Sulphuric acid, 270. Action with organic matter, Exp. 138. Action with water, 270, Exp. 137. Test for, Exps. 21 {d), 139.

Sulphurous acid, 269. Supersaturation, 79, Exp. Symbols, 53.

35.

List of, 392. Synthesis, definition, 33.

Colors of borax beads, 394.

Exp. 36.

385-391,

Exp. 135.

Tad/es.

w w

Of Of

of,

266,

Of coatings on charcoal, 393. Of flames, 394. Of residues moistened with

.c h

Thermal phenomena

of,

Sulphites, 269.

vn

of,

ll.

88.

water, interaction

4a

And

em

Sodium,

cobalt

nitrate, 394.

Composition of

Of

air,

108.

typical coals, 396.

Conversion of thermometric readings, 394-

Densities

and molecular weights

of

gases, 144.

Equivalents and atomic weights, 136. Freezing and boiling points, 74. Important elements, symbols, and atomic weights, 392. Ionization, 152.

Metric equivalents, 9. System, 346. Transformation, 346. Periodic arrangement of the elements, 396. Solubility of carbon dioxide, 76.

Of salts in water, 395. Of some liquids, 78. Of typical solids, 79. Specific gravity

and melting point

metals, 395. Specific heats, 141.

of

4TO

Index. Deposition of metallic, Exp. 175. General properties, Exp. 172. Tests for, 307, 308, Exps. 106 (a),

Tables.

Tension of aqueous vapor, 361.

Weight

of a liter of gases, 395.

174,

Triangle, 331.

Temperature, 352.

Tube, gas measuring, 350, 369. Marchand, Exp. 44.

Absolute, 356. Correction for, 355, 362. Tension, aqueous, 360.

Vapor,

To

dry the inside of a, 338. U-, 367, 368, Exps. 23, 44.

68, 69.

Test, definition, 42, 44.

U-tube, 367, 368, Exps. 23, 44.

Tests.

Valence, 147. Vinegar, 215.

Acetic acid, Exp. 109 {e). Alcohol, Exp. 109 {c). Alkali, 90, Exps. 42 {d), 49.

Calcium, Exps. 29

vn

ll.

170.

{d), 86 II, 159.

Carbon

dioxide, Exps. 46, 86 1. Chlorides, Exps. 29 (<^), 61 IV.

Chromium, Exp,

4a

Aluminium, Exp. Base, Exp. 49.

Properties, Exp. 114.

Water, action of, on lead, 310, Exp. 179. And hydrogen, 86, 90, Exps. 40, 42. And oxygen, 88, Exp. 41. And sodium, 88, Exp. 42. Bath, 332.

of, by chlorine, P2xp. 41. Exp. 40. Electrolysis of, 83, Exps. 38, 39, Freezing and boiling points of, Exp. 31. General distribution, Exp. 24. Gravimetric composition of, Exp. 44. Hardness of, 248, Exp. 117 {d). Impure, 69.

Decomposition

181.

iron,

em

By

.c h

Cobalt, Exp. 103 {a). Copper, Exps. 103 {b), 151. Hydrochloric acid, Exp. 61 IV. Iodine, Exps. 123, 124. Iron, Exps. 189, 190.

w w

Lead, 310, Exps. 105 (a), 106 (/'). I77Magnesium, Exp. 158. Manganese, Exps. 103 {c) 186. Mercury, Exps. 165, 166, 174. Nature of common substances, Exp. 51. Nitrate, Exps. 72, 78, 79, 80. Nitric acid, Exp. 72. Organic matter, Exps. 29 (a), 72, 138. Potassium, Exp. 146. Silver. See Exps. 29 {b), 61 IV. Sodium, 90, Exp. 42. Starch, Exp. 125.

ht

tp ://

w

,

Sugar, 153. Sulphate, Exps. 21 {b), 105 {b). Sulphides, Exp. 124. Sulphuric acid, Exp. 21 {b). Tin, Exps. 106 {c), 174. Zinc, Exps. 21 {a), 106 {a), 161.

Mineral, 69. Molecular weight

solution,

Exp. 36.

Thermometer, 352. Using a, 353, 369. Tin, 306.

Action with acids, Exp. 173.

146.

of, 70,

91.

Relation to temperature, 73, Exp. 31. Tests for impure, Exp. 29.

Volumetric composition

of,

95,

Exps.

38, 39. 43Water of crystallization, 65-67.

Detection of, Exp. 25. Determination of, Exp. 26.

Weighing, Exp. 7. And measuring, Exp. Rules for, 348. Weights, 347.

8.

Zinc, 296.

Atomic weight

Thermal phenomena of

of,

Exp. 30. Quantitative composition of, Purification

81,

of,

145.

Equivalent of, 45-48, 145, Exp. 22, General properties, Exp. 160. Interaction of, with metals, Ex;). 162. Tests for, Exps. 21 {a), 161. Zinc sulphate, crystallization of, Exp. 20.

Test

for, Elxp. 21,

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