An elementary chemistry, by George Rantoul White

Preface

This book is little more than a reproduction of the course in elementary chemistry as now given at Exeter Academy. The course itself has been developed, little by little, during several years of observation and experi¬ ment on the part of the writer, to meet the needs of all classes of students, — those who are preparing for a further course of study at college, those who expect to enter a scientific school, and those who go from the academy directly to their life-work. The majority of all these students take chemistry merely as a part of a liberal education, some intend to follow the paths of science ; a few will become chemists.

In planning this work for beginners the writer has tried to prepare a course that will meet the needs of one class as well as those of another. But in this respect his task has been easy, for the more he has considered the needs of the various classes, the more he has come to believe that the elementary training of all should be alike. The student who is to be a lawyer, a doctor, or a man of business, needs that same careful attention to details, that same power of accurate ob¬ servation which is expected of the coming chemist ; and he who is to be the chemist needs the same high development -of his reasoning powers as he who takes chemistry only for the intellectual training it can give.

IV

PREFACE.

This book is designed especially for the use of two classes of students. First for those whose instruction is placed in the hands of a teacher who cannot devote his whole time to chemistry ; and secondly, for young men and women who are eager to study chemistry but have no teacher at all.

In regard to the first class — those instructed by teachers who are not strictly and solely teachers of chemistry — the writer believes that it is not possible for any teacher to get the best results from his students if he has to divide his attention, his energy, his love, between two or more subjects. We cannot serve two masters. Those students who are so fortunate as to have an instructor who can devote his whole time to the presentation of elementary chemistry need no book at all. The instructor will himself more than take the place of a book. But it is seldom that a school or col¬ lege has a chemist who can devote his whole time to developing the elementary course. Generally the in¬ structor in chemistry must teach some other study. Even when he can give all his attention to chemistry, his time often is chiefly devoted to the more advanced students. Though the instructor can well replace the book, no book can fully take the place of an instructor. It is hoped, however, that this book may be of some service in supplementing the work of those instructors who have not the time to do for their pupils all that they really desire.

To those students who can never have any instruc¬ tor, but want to study chemistry, the strictly inductive method here followed lends itself well. There are,

PREFACE.

y moreover, no experiments inserted that have not been well tried, and found to work successfully in the hands of beginners. Wherever there seems danger — and danger there must be, to some extent, in every course of chemistry that is worth the giving — abundant warning is inserted. Through all the development of this course at Exeter there has never been an accident at all serious.

It will be noted by him who looks through the pages of this book, first, that the method of presenting ele¬ mentary chemistry here embodied is preeminently a practical or laboratory method, and, secondly, that the method is preeminently inductive.

To-day no plea for the laboratory or practical method of presenting any study seems needed. As James Russell Lowell has said, " Practical application is the only mordant which will set things in the memory. Study without it is gymnastics, and not work, which alone will get intellectual bread.” In no branch of learning does the laboratory method seem more essen¬ tial than in chemistry, and in no branch has this method been more widely adopted than in chemistry. Everywhere laboratories are being built, and nowhere, so far as the writer has ever heard, has there been a change back to the old method after the new has once been tried. The results, however, always justify the change from the old to the new. Professor Cooke, director of the Chemical Laboratory at Harvard Uni¬ versity, where for years chemistry has been taught in no other way than by the laboratory method, writes, "How little of what we value comes to us by the way of direct teaching ! There may be such a thing

VI

PREFACE.

as too much teaching, and even — in spite of the paradox — too good teaching ; for, after all, personal experience is, at the university as elsewhere, the most efficient teacher, and he who encourages us to help ourselves is our safest guide.”

In working out the course indicated in this book it has been the writer’s aim to make this " personal ex¬ perience ” for the student as large as possible. He always tells his Exeter students that he is their com¬ panion more than their teacher ; that their own experi¬ ence, acquired little by little, through hours of work in the laboratory, must be their true teacher ; while he himself simply is their guide, showing where the path runs smoothest, warning against innumerable by-paths, pleasant to follow it is true, but that lead nowhere, pointing out the dangers to be avoided and, alas ! not infrequently having to point out the beauties that other travelers on the same way have noted, — beauties that would otherwise be passed by, all unheeded by the impetuosity of youth.

At first the student is told little or nothing. He is compelled to find out all things for himself. To assist him in finding the essential, and to make sure that he has succeeded in this, frequent questions are inserted in the text of the experimental part. [For the use to be made of these questions, see Introduction.] The author believes that questions inserted thus, just at the point when the inquiry naturally springs to the lips of a bright student, are of more value than the same ques¬ tions inserted all together at the end of a book or even in groups at the end of the chapters.

PREFACE.

Yll

There is a marked tendency among bright students who are taking up a new subject for study, to ask questions. This tendency can readily be checked by the teacher’s refusing to answer such questions and telling the pupils to confine themselves to the text of the book ; or it can be developed, by proper training, into one of the highest and most valuable powers of the human mind — logical reasoning. It was by attempting to win something of good from this asking of questions that the author of this book was led to arrange the work of his elementary class on a strictly inductive basis. A fresh young mind is very loath to take any¬ thing for granted, — it is naturally questioning. To be sure, it is always easy to destroy this natural condition, and to accustom a pupil to have implicit faith in his teacher ; implicit faith in his book ; in fact, from the very method by which we have most of us been taught, we are obliged to say, if questioned as to our reason for believing a certain statement, that we believe it because so and so has told us, or because such and such a book says so. How much more of profit and pleasure will come to a future generation if only we can teach the children of to-day — who are to be the men and women of to-morrow — to think and to reason for themselves. As President Eliot of Harvard has recently said : " The main processes or operations of the mind” which should be developed " in an individual in order to increase his general intelligence and train his reasoning power” are, first, " observation , that is to say, the alert, intent, and accurate use of his senses”; next, " the function of making a correct record of things observed”; next,

PREFACE.

viii

" the faculty of drawing correct inferences from recorded observations. ... It is often a long way from the patent fact to the just inference. For centuries the Phoenician and Roman navigators had seen the hulls of vessels disappearing below the blue horizon of the Mediterranean while their sails were visible ; but they never drew the inference that the earth was round.”

It is easier to learn [?] a thing from a book or from a teacher than by reasoning it out for ourselves. But do we get from the memorizing process the results that are needed for an education? There must come a time when almost every student will find himself in a great school where he himself is not pupil but master, where there are no books to which he can refer. Herbert Spencer, speaking of the state of education, has said : ''Nearly every subject dealt with is arranged in abnor¬ mal order ; definitions, and rules, and principles being put first, instead of being disclosed, as they are in the order of nature, through the study of cases. And then pervading the whole is the vicious system of rote learn¬ ing — a system of sacrificing the spirit to the letter. See the results.” Though there have been marked changes since these words were written, some thirty years ago, still there is at the present day much " rote learning,” even among chemical students.

As an instructor for several summers in the Harvard Summer School at Cambridge [where teachers from almost all parts of the country assemble], the writer has had an opportunity to judge of the methods of instruc¬ tion generally employed, and to " see the results.” To him the results have not seemed satisfactory. Those

PREFACE.

IX taught by the common methods, at the best, have a considerable knowledge of facts, and sometimes can make a few simple analyses, but they seldom have the power of doing any thinking for themselves . Believing, as the author does, that there is no other study which, pursued for either one, two, or three years, can give so much in return that is of an educational value, he has been grieved and ashamed to realize how little is obtained by the many, mostly faithful, students of that science. Seeking for the cause, the writer has come to the conclusion that it lies in the method of presenting the subject. It is seldom that a pupil knows much of anything about this science till he has studied it four, five, or more years. Then the real meaning of all he has been working over gradually dawns upon him. But how is it with the great majority of one, two, and three year students who, never intending to be chemists, have taken up the study only as a part of a liberal education ? Most of these have actually wasted the time spent on their chemistry. The trouble is that most text-books aim at giving a synopsis of the whole of chemistry. The writers do not seem to realize how vast an accumulation of facts now lie open to the chemist : that to try to learn all these facts is as profitless a task as for the beginner in English compo¬ sition to start by learning all the words in his diction¬ ary. Is it not better for both to confine themselves to a little that is of everyday occurrence and learn that little thoroughly? Then again, to the writer, it seems that the text-books for beginners err in being 'r arranged in abnormal order : definitions, and rules and principles

X

PREFACE.

being put first, instead of being disclosed, as they are in the order of nature, through the study of cases.” In the following pages a " study of cases ” conies first. In fact for some time the pupil does nothing but study cases ; very simple ones at first — many, though, that have been familiar to him all his life ; then less familiar and more complicated ones ; and, finally, in Ex. 32, " A Chemical Investigation,” he has before him a problem not unlike the many that are constantly pre¬ sented to the chemist who is working on the border¬ land of the science. To the end of this " Chemical Investigation,” the whole course is inductive. It is believed that not an essential question can be asked that the student cannot answer either from observation of the phenomena or from reasoning based on previous experiment. Through the whole of Part I the student becomes acquainted with the methods — both mental and practical — of the scientific chemist of to-day. He learns to experiment , to observe , to reason . He accepts nothing simply because his teacher, or the book, says it is so. Everything he verifies by himself to his own satisfaction. Then, having learned by many experi¬ ments [particularly by " A Chemical Investigation ”] how the chemist obtains the facts that are at the basis of all his reasoning, the student is prepared to trace with pleasure [in Part III] the history of chemistry, to note what observations lead to the establishment of certain theories, and the recognition of what facts lead to the overthrow of these same theories ; to recognize the gradual unfolding of chemical law ; and, finally, to inspect the foundations on which our present Atomic

PREFACE.

XI

Theory rests, and have an opinion of his own as to its stability. The author has thought best to give a more extended account of the development of the laws and theories of chemistry than is usually found in text¬ books. He has been led to this for several reasons : first, because he believes that every educated man or woman should possess a knowledge of these laws and theories ; secondly, because he feels that a consideration of their development gives the student an excellent introduction to the true spirit of scientific investigation ; and, finally, because he is well aware that advanced students of chemistry generally lack a fundamental knowledge of the history and development of their own branch of science. Text-books for beginners usually omit a thorough treatment of the laws and theories as beyond their scope, while the books for advanced students also omit the same on the ground that the student has already learned the fundamental principles. Where, then, is the student to get this knowledge ?

It may also be noted that for a long time no hint is given that there are such things as chemical symbols. Not to accustom the pupils from the first to express facts in the language of chemistry, will doubtless seem to many both silly and wrong. But to do so would not be in accord with the spirit of the inductive method here employed. When the student has mastered the facts, it is a pleasure to see how readily he ex¬ presses those facts by the proper symbols. This he then does accurately and almost without an effort. The writer several years ago adopted the plan of having his students express the facts in English till

Xll

PREFACE.

enough facts had been collected for the students to use the language of chemistry freely and accurately. He has no desire to go back to the old method. Then, too, when symbols are used before they can be fully understood, there is danger that the symbols, and not the facts they express, may be looked at as the realities. For instance, on a recent [English] examina¬ tion paper there appeared the following : " Account

for the basicity of phosphorus and hypophosphorus acids, respectively, by reference to their constitutional formulae.” At the best, formulae can only express the facts we have found out about substances ; they cannot account for any of these facts, and the student should not be taught that they can. In this connection it may be of interest to note the following taken from the intro¬ duction to the first edition of Meyer’s Moderne Theorien der Chemie.” The translation reads, " Chemical symbols and formulae, which a few years ago received such prominence, are now regarded with indifference, since what was formerly expressed symbolically and indistinctly or even without proof or clearness by their aid, can now be expressed in clear words with fixed meaning.” And again, very recently, no less an au¬ thority than Professor Remsen, of Johns Hopkins University, has written that he " sometimes thinks, and the intervals between the thoughts are getting shorter, that if the use of formulae were given up entirely in elementary instruction, better results would be ob¬ tained.”

February, 1894.

OOIsTTEIsTTS.

PAGE

Introduction . . xxiii

Measuring . 3

Weighing . 4

Making a wash-bottle . 6

Part I. Experiments

Ex. 1. Iron

B. With Air . 11

B. With Air . 13

5. Artificial Preparation of Oxygen

A. Erom Red Oxide of Mercury . 15

B. Erom Chlorate of Potassium . 16

6. Action of Undiluted Oxygen Gas

A. On Iron . 17

B. On Phosphorus . 18

C. On Carbon . 18

7. Preparation of Oxygen from Water . 19

8. Examination of that Constituent of Water which is

not Oxygen . 20

A. Preparation from Water by means of Iron . 20

B. Specific Gravity . 22

C. Action of Air on Warm Hydrogen . 22

B. Modifications . 24

C. Action of Oxygen on Hot Sulphur . 25

X1Y

Contents

PAGE

Ex. 11. Sulphurous Acid . 27

12. A Second Oxide of Sulphur . 27

Part II. Additional Experiments

Ex. 1. Bromine . 77

2. Bromides . 78

A. Properties of Hydrogen Bromide . 78

B. Sodium Bromide . . . 78

C. Replacement of Bromine . 78

B. Solubility . 79

C . Action on the Skin . 79

D. Action on Starch . 79

4. Iodides

A. Properties of Potassic Iodide . 80

B. Replacement of Iodine by Chlorine . 80

C. Will Bromine Displace Iodine ? . 81

5. Fluorine and Fluorides

A. Properties of Calcic Fluoride . 81

B. Preparation of Fluoride of Hydrogen . . . 81

C. Etching of Glass by Hydrofluoric Acid . 82

6. Arsenic and its Compounds

. A. Properties of Arsenic . 83

C. Reduction of the Oxide of Arsenic . . 84

T>. Arsenide of Hydrogen . 84

E. Detection of Arsenic . 85

<7. Chloride . 88

CONTENTS. Xvii

Ex. 7. Antimony page

B. Hydrogen Antimonide . 88

E . A Chemical Examination . . . 89

B. Nitrate of Bismuth . 89

9. Tin

C. Crystalline Structure . 90

D. Action of Strong Acids with Tin . 90

E. Replacement of Tin by Zinc . 91

10. Lead

C. Action of Water on Oxide of Lead . 91

B. Action of Acids on Lead . 91

E . Replacement of Lead by Zinc . 92

F. Lead Chloride . 92

G. Lead Sulphate . 92

H. Plumbers’ Solder . 92

J. Pusible Alloy . 93

C. Action of Acids on Silver . 93

B. Replacement of Silver by Copper . 94

E. Replacement of Silver by Calcium, Sodium

and Potassium . 94

F. Sulphide of Silver . 95

G. Oxide of Silver . 95

H. Purification of Silver . 95

12. Gold

B. Action of Acids on Gold . 96

C. Chloride of Gold . 97

B. Gold Amalgam . 97

E. Color of Gold . 97

XY111 CONTENTS.

Ex. 13. Platinum page

B. Action of Acids on Platinum . 98

C. Action of other Chemicals, besides Acids, on

D. Action of Metals with Platinum . 98

E. Platinum Sponge . 98

C. Action of Acids on Aluminum . 99

D. Sulphate of Aluminum . 99

E. Alum . 100

Chapter I. Introduction . 103 Physical and Chemical Changes . 103

Ex. 1. Two kinds of Changes . 104

2. Changes caused by Water of Crystallization 106

3. Change caused by the Action of Sulphuric

Acid on Water . 106

Analyses, Syntheses, and Metatheses . 107

Ex. 4. Synthesis of Chloride of Ammonium . 108

5. Metatheses . 110

Chapter III. The Period of Alchemy . 114

Ex. 6. A So-called Transmutation . 116

7. Death of a Metal . 117

8. Resurrection of a Metal . 117

Chapter IV. The Medical Period . 120

Chapter Y. The Period of Robert Boyle . 125

Ex. 9. The Law of Boyle . 126

10. Qualitative Tests . 132

A. Tests used by Boyle . 132

B. Tests by Physical Changes . 132.

C. Tests by Chemical Changes . 133

11. Mechanical Mixture and Chemical Com¬

pound . 135

A. Iron and Sulphur . 136

B. Zinc and Sulphur . 136

CONTENTS.

XIX

PAGE

Chapter VII. The Pneumatic Period . 140

Ex. 12. Weight and Specific Gravity of Air . 141

13. The Law of Dalton . 143

14. Weight and Specific Gravity of Carbonic

Dioxide . 145

15. Weight and Specific Gravity of Hydrogen

16. Weight and Specific Gravity of Illuminat¬

ing Gas . 149

A. The Combustion Products of a Can¬

B. The Weight of the Products is Equal

to the Weight of the Factors . 159

Chapter VIII. The Modern, or Atomic Theory, Period . 161

§1. Introductory . 161

Ex. 18. Law of Definite Proportions by Weight .... 163

§ 2. Quantitative Analysis . 164

Ex. 19. Analysis of Table Salt . 165

§ 3. Multiple Proportions . 168

Ex. 20. Multiple Proportions . 169

A. The Oxides of Sulphur . 169

B. The Oxides of Nitrogen . 169

C. The Chlorides of Iron . 170

§ 4. Dalton’s Atomic Theory . 170

§ 5. Combining Number . 172

Ex. 21. Determination of the Combining Number

for Zinc . 172

§ 6. Prout’s Hypothesis . 175

§ 7. Molecules . 176

§ 8. Relative Weight of the Atoms . 177

Ex. 22. Law of Definite Proportions by Volume.... 179

§ 9. The Molecular Theory . 180

Ex. 23. Spaces between the Molecules . 182

24. Irregular Expansion of Liquids . 184

25. Regular Expansion of Gases . 185

§ 10. Determining Atomic Weights . 192

XX

CONTENTS.

PAGE

§11. Determining Molecular Weights. . 195

Ex. 26. Determination of Molecular Weights by

the Physical Method . 196

A. Molecular Weight of Carbonic Di¬

oxide . 196

B. Molecular Weight of Oxygen Gas .... 196 27. Determination of Molecular Weights by

the Chemical Method . 197

A. Molecular Weight of Chlorate of

B. Molecular Weight of Chloride of

C. Molecular Weight of Sulphate of

§ 12. Specific heat . 202

Heat . 203

Ex. 28. Transference of Motion . 203

29. Specific Heat of Zinc . 205

30. Specific Heat of Iron . 207

31. Specific Heat . 207

Law of Dulong and Petit . 208-209

Determination of the True Atomic Weight of Zinc

from its Combining Number and its Specific Heat.. 210

§13. Isomorphism . 211

Ex. 32. Isomorphism . 211

§ 14. The Periodic Law . 213

Table of Atomic Weights . 216

Table of Atomic Symbols . 219

To Mark Glass . 226

To Cut Glass . 226

To Fire-Polish the Edges of Glassware . 228

To Bend Glass Tubes and Rods . 228

To Draw out Glass Tubes . 229

To Make a Matrass . . 230

To Render Corks Air-Tight..... . 230

CONTENTS.

XXI

Manipulations page

To Render Joints Air-Tight . 231

To Cut Rubber Neatly and Quickly . . 231

To Pass a Glass Tube through a Hole in a Rubber Stopper.... 231

To Bore a Round Hole in Glass . . . 231

To Prevent Mixing Glass Stoppers . 232

To Hold Hot Beakers, Test-Tubes, etc. . 232

To Use the Pneumatic Trough . 232

To Use Filter Papers . 233

To Dry Bottles, Flasks, etc . 234

To Remove Stoppers that have Stuck . 234

To Pour Gases . 235

To Use a Bunsen Burner . 235

To Use the Bunsen Blast-Lamp . 236

A. Apparatus for the Electrolytic Decomposition of Water.. 239

B. Hydrogen Explosions.. . 241

C. Test Papers . 242

D. Suction Pumps . 243

E. Catch-Bottles . 244

F. Generator for Gases . 246

G. Hood . 247

H. Preparation of Chlorine . 247

I. Sodium Amalgam . 248

J. Test Solutions . 249

K. Use of the Mouth Blow-Pipe . 250

L. Arsenical and Antimonial Papers for Testing . 250

M. To Dry Precipitates . 251

N. To Nurse a Crystal . 251

O. Distilled Water . 252

P. Directions for a Student Who Has no Instructor . 254

Index . 259

Introduction

The student should provide himself with a blank-book — best, one with no ruling whatever — with pages not less than six by eight inches, and containing not less than 150 leaves;1 also an apron large enough to cover chest as well as legs, or, better, overalls and a light, cheap workingman’s jacket. Before the time appointed for the first work in the laboratory he should apply to his instructor for the assignment of desk, apparatus, and chemicals, and the directions for begin¬ ning work.2

The first three exercises are preliminary to the regu¬ lar work. Their chief purpose is to enable the pupil to form the acquaintance of the system of weights and measures used in scientific work, and to accustom him¬ self to the use of apparatus.

In all scientific work it must be the student’s aim to observe , to experiment , to reason . His goal is the Truth. Let him continually ask the question “ Why? ” The

1 Experience has shown that it is best to get a blank-book with leather back and tips. Such a book should not cost over thirty-five or forty cents. Laboratory usage is apt to destroy the light cloth back of the ordinary pasteboard-covered blank-book. The common blank-book also quickly wears out at the corners, and, as the leather tips cost but little, they are recommended.

2 A student who is going to use this book without an instructor will find his directions in Appendix P.

XX1Y

INTRODUCTION.

laboratory note-book must be a store-house for the observations from the experiments. A full page should be reserved before beginning the description of any experiment [or before that of every part of an experi¬ ment when the parts themselves are long or promise to demand much arithmetical calculation]. On this page the student should put his first rough notes at the moment the observations are made . Here also should appear all figuring, the results of which only he wishes to appear in the course of his description. There must be no note-taking nor figuring of any kind on bits of paper , apparatus , etc . All the notes, and the whole figuring for mathematical problems must appear. Remember that a page is particularly reserved for this rough work, and the student must not allow himself to form the habit of entrusting his notes to papers, that are always apt to be misplaced or destroyed. Moreover, if a mis¬ take has been made in number only, it is irritating, indeed, to be obliged to repeat all the experiment when, if the original data wer$ present, the mistake could be corrected, often at a glance. Do not correct mistakes by erasure and rewriting. Cross out the old and let the new appear by its side. Do not fear that this method will spoil the appearance of the book in the eyes of the instructor. Every instructor of experience knows that, though greatly to be sought after, infallibility is not attainable by a beginner in laboratory work, or, in fact, by any other student, while erasures, even by the best of students, must be looked at with some suspicion. Try, however, to con¬ fine all correction of *nistakes to these pages just

INTRODUCTION.

XXY mentioned as reserved for rough notes and figuring. Do not attempt to write the fair account of the experiment till the experiment has been performed completely and satisfactorily in the laboratory and the necessary ob¬ servations and calculations [if any] have been made on the preliminary page. When the experiment is thus finished, and every question that has arisen in con¬ nection with it has been answered, and the whole is fully understood, then write out on the page [or pages] following the preliminary page, a good, clear statement of the experiment, making evident to any future reader the apparatus and material used ; the method followed ; what has been observed ; and the conclusion drawn, or what the experiment has shown. Ink should be used for writing this account if it is desired that the note¬ book shall have the neatest possible appearance at the end of the year. The preliminary page, however, best be kept in pencil. It has been found a good plan to reserve all left-hand pages for preliminary pages, and all right-hand pages for the account written in ink.

Although some pupils seem to profit by thinking over an experiment for a day or two, after having made their preliminary rough notes, before writing the per¬ manent account, yet there is danger of forming in this way a habit of negligence. In general, the full account should be completed not later than one week from the time the experiment was done in the laboratory.

Represent apparatus , crystalline forms , etc., as far as possible , by sketches. A drawing will often express clearly and forcibly as much as pages of writing. Do not feel discouraged -if the first drawings seem failures.

XXVI

Introduction.

Make good use of the eyes and resolve that each suc¬ ceeding figure shall be a little better than the one before, and there need be no fear for the appearance of the last.