UC-NRLF 
 
Lummor So x oo Of Ohomio 
 
 LIBRARY 
 
 OF THE 
 
 UNIVERSITY OF CALIFORNIA. 
 
 OIKT OF^ 
 
 /? f OIKT OF* 
 
 Accession No. (0* Class No. 
 
' : 
 &<i>i FRANCISCO, CAL 
 
ELEMENTARY CHEMISTRY 
 
 BY 
 
 GEORGE RANTOUL WHITE, A.M. 
 
 ii 
 
 INSTRUCTOR TN CHEMISTRY AT PHILLIPS EXETER ACADEMY 
 
 
 BOSTON, U.S.A. 
 
 PUBLISHED BY GINN & COMPANY 
 1894 
 
COPYRIGHT, 1894 
 BY GEORGE RANTOUL WHITE 
 
 ALL RIGHTS RESERVED 
 
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. V 
 
 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. 
 
tKEFACE. vii 
 
 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, 
 
Vlll PREFACE. 
 
 " 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 " 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 " comes 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 Theo- 
 rien 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. 
 
COISTTEE'TS. 
 
 PAGE 
 
 INTRODUCTION xxiii 
 
 PRELIMINARY WORK 
 
 Measuring 3 
 
 Weighing 4 
 
 Making a wash-bottle 6 
 
 PART I. EXPERIMENTS. 
 Ex. 1. Iron 
 
 A. Properties 11 
 
 B. With Air 11 
 
 2. Phosphorus 
 
 A. Properties 12 
 
 B. With Air 13 
 
 3. Mercury 14 
 
 4. Carbon 14 
 
 5. Artificial Preparation of Oxygen 
 
 A. From Red Oxide of Mercury 15 
 
 B. From 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 
 
 9. Hydrogen 
 
 A. Preparation from Water by means of Iron 20 
 
 B. Specific Gravity 22 
 
 C. Action of Air on Warm Hydrogen 22 
 
 10. Sulphur 
 
 A. Properties 23 
 
 B. Modifications 24 
 
 C. Action of Oxygen on Hot Sulphur 25 
 
XIV CONTENTS. 
 
 PAGE 
 
 Ex. 11. Sulphurous Acid 27 
 
 12. A Second Oxide of Sulphur 27 
 
 13. Sulphuric Acjd 29 
 
 14. Removal of Hydrogen from Sulphuric Acid 30 
 
 15. Action of Water on Oxide of Iron 32 
 
 16. Action of Water on Oxide of Phosphorus 33 
 
 17. Action of Water on Oxide of Carbon 33 
 
 18. Zinc 
 
 A. Properties 34 
 
 B. Oxidation of Zinc 34 
 
 C. Action of Water on Oxide of Zinc 34 
 
 19. Action of Zinc on the Non-combustible Oxide of 
 
 Carbon ; or, 
 
 Preparation of a Second Oxide of Carbon 35 
 
 20. Oxidation of the Combustible Oxide of Carbon 37 
 
 21. Action of Zinc on Sulphuric Acid 37 
 
 22. Action of Oxide of Zinc on Sulphuric Acid 38 
 
 23. Sulphides 
 
 A. Mutual Action of Iron and Sulphur 39 
 
 B. Action of Hydrogen on Warm Sulphur 39 
 
 O. Action of Sulphuric Acid on Sulphide of Iron.. 40 
 
 24. Copper 
 
 A. Properties 41 
 
 B. Oxidation 41 
 
 C. Reduction of the Black Oxide 42 
 
 25. Magnesium 
 
 A. Properties 43 
 
 B. Oxidation 43 
 
 C. Magnesium Oxide -with Water 43 
 
 JD. Magnesium and Sulphuric Acid 43 
 
 26. Calcium 
 
 A. Properties 44 
 
 B. Oxidation 44 
 
 C. Reaction of Oxide of Calcium and Water 45 
 
 D. Action of Calcium on Water 45 
 
 E. Reaction of Hydrate of Calcium and Sul- 
 
 phuric Acid 46, 
 
 F. Reaction of Hydrate of Calcium and Carbonic 
 
 Acid ........ 
 
CON 
 
 Ex. 26. Calcium PAGE 
 
 G. Analysis of Marble 50 
 
 If. Reaction of Marble and Sulphuric Acid 51 
 
 27. Sodium 
 
 A. Properties 52 
 
 B. Oxidation 52 
 
 C. Reaction of Oxide of Sodium and Water 53 
 
 D. Action of Sodium on Water 63 
 
 E. Reaction of Sodium Hydroxide and Sulphuric 
 
 Acid 54 
 
 F. Reaction of Sodium Hydroxide and Carbonic 
 
 Acid 54 
 
 G. Reaction of Hydrate of Sodium and the Non- 
 
 combustible Oxide of Carbon 55 
 
 H. Reaction of Carbonate of Sodium and Sul- 
 phuric Acid 55 
 
 /. Reaction of Sodium and Mercury 55 
 
 28. Chlorine 56 
 
 29. Chlorides 
 
 A. Chloride of hydrogen 56 
 
 B. Chloride of Sodium 57 
 
 C. Preparation of Hydrochloric Acid on a Large 
 
 Scale 57 
 
 D. Solubility of Hydrochloric Acid 58 
 
 E. Reaction of Hydrochloric Acid and Marble .... 58 
 
 F. Action of Sodium on Hydrochloric Acid 59 
 
 G. Action of Sodium Hydroxide with Hydro- 
 
 chloric Acid 60 
 
 30. Potassium 
 
 A. Properties 61 
 
 B. Oxidation 61 
 
 C. Reaction of the Oxide and Water 61 
 
 D. Reaction of Potassium and Water 61 
 
 E. Action of Potassium on the Dioxide of Carbon.. 61 
 
 F. Reaction of Potassium Hydroxide and Sul- 
 
 phuric Acid 62 
 
 31. Nitrogen 63 
 
 32. A Chemical Investigation 63 
 
 A. Preparation of Nitric Acid 64 
 
 B. Action of Magnesium on Nitric AcidU ........ Q 
 
XVI CONTENTS. 
 
 Ex. 32. A Chemical Investigation PAGE 
 
 C. Action of Copper on Nitric Acid 65 
 
 Z>. Action of Carbon on Nitric Acid 66 
 
 E. Keaction of Nitric Acid and Potassium Hy- 
 droxide 67 
 
 33. Ammonia 
 
 A. Preparation of Ammonia 68 
 
 B. Ammonia Fountain 70 
 
 C. Salts of Ammonia 71 
 
 34. Oxides of Nitrogen 72 
 
 PART II. ADDITIONAL EXPERIMENTS. 
 
 Ex. 1. Bromine 77 
 
 2. Bromides 78 
 
 A. Properties of Hydrogen Bromide 78 
 
 B. Sodium Bromide 78 
 
 (7. Emplacement of Bromine 78 
 
 3. Iodine 
 
 A. Properties 79 
 
 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 
 
 6. 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 
 
 B. Oxidation 83 
 
 C. Reduction of the Oxide of Arsenic 84 
 
 D. Arsenide of Hydrogen 84 
 
 E. Detection of Arsenic 85 
 
 7. Antimony 
 
 A. Properties ; 87 
 
 B. Oxidation 87 
 
 C. Chloride ... .88 
 
CONTENTS. Xvii 
 
 Ex. 7. Antimony PAGE 
 
 D. Hydrogen Antimonide 88 
 
 E. A Chemical Examination 89 
 
 8. Bismuth 
 
 A. Properties 89 
 
 B. Nitrate of Bismuth 89 
 
 9. Tin 
 
 A. Properties 89 
 
 B. Oxidation 90 
 
 C. Crystalline Structure 90 
 
 D. Action of Strong Acids with Tin 90 
 
 E. Replacement of Tin by Zinc 91 
 
 10. Lead 
 
 A. Properties 91 
 
 B. Oxidation * 91 
 
 C. Action of Water on Oxide of Lead 91 
 
 D. 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 
 
 7. Fusible Alloy 93 
 
 11. Silver 
 
 A. Properties 93 
 
 B. Oxidation 93 
 
 C. Action of Acids on Silver 93 
 
 D. 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 
 
 A. Properties 96 
 
 B. Action of Acids on Gold 96 
 
 C. Chloride of Gold 97 " 
 
 D. Gold Amalgam 97 
 
 E. Color of Gold 97 
 
 13. Platinum 
 
 A. Properties 98 
 
XV111 CONTENTS. 
 
 Ex. 18. Platinum PAGE 
 
 B. Action of Acids on Platinum 98 
 
 C. Action of other Chemicals, besides Acids, on 
 
 Platinum 98 
 
 D. Action of Metals with Platinum 98 
 
 E. Platinum Sponge 98 
 
 14. Aluminum 
 
 A. Properties 99 
 
 J5. Oxidation 99 
 
 (7. Action of Acids on Aluminum 99 
 
 D. Sulphate of Aluminum 99 
 
 E. Alum .' 100 
 
 PART III. HISTORY AND DEVELOPMENT OF THE LAWS AND THEO- 
 RIES or CHEMISTRY. 
 
 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 II. THE EARLIEST PERIOD Ill 
 
 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 V. 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 135 
 
 B. Zinc and Sulphup .,,... 136 
 
CONTENTS. XIX 
 
 + 
 
 PAGE 
 
 CHAPTER VI. THE PHLOGISTON PERIOD 138 
 
 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 
 
 Gas 148 
 
 16. Weight and Specific Gravity of Illuminat- 
 
 ing Gas 149 
 
 17. Conservation of Mass 157 
 
 A. The Combustion Products of a Can- 
 
 dle 157 
 
 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. Kelative 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 
 
 Potassium 198 
 
 B. Molecular Weight of Chloride of 
 
 Potassium 199 
 
 C. Molecular Weight of Sulphate of 
 
 Potassium 200 
 
 12. Specific heat 202 
 
 Heat 203 
 
 Ex. 28. Transference of Motion 203 
 
 29. Specific Heat of Zinc 206 
 
 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 
 
 LANGUAGE OP CHEMISTRY 218 
 
 Table of Atomic Symbols 219 
 
 STOICHIOMETRT 224 
 
 MANIPULATIONS 226 
 
 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 Bender Corks Air-Tight 230 
 
CONTENTS. XXI 
 
 MANIPULATIONS 
 
 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 
 
 APPENDICES ............................................................................................... 237 
 
 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 
 
 0. Distilled Water ......................................................................... 252 
 
 P. Directions for a Student Who Has no Instructor .............. 254 
 
 IXDEX ... 259 
 
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. , ->-"" "' 
 
 - 
 
XXIV LNTKODUCTION. 
 
 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 were 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 mistakes to these pages just 
 
INTRODUCTION. XXV 
 
 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 INTKODUCTION. 
 
 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. 
 
 Be sure to insert an answer in the laboratory-book 
 every time a question is asked in the text-book. Make 
 this answer in the form of a statement in such a way 
 that the answer may be understood by a person who 
 does not know the question. First formulate an 
 answer to every question, and then turn to the in- 
 structor and ascertain if the answer is correct, before 
 writing it in the note-book. It seems to the author 
 that every teacher should pay particular attention to 
 this or some similar method of questioning, as it 
 teaches the student to do his own thinking, and gives 
 the instructor a chance to watch the working of the 
 student's mind with a view to giving help to the 
 student in acquiring correct methods of reasoning. 
 
 Particular attention should also be given to express- 
 ing chemical changes by means of diagrams, as on page 
 32, but it is not advisable to use chemical symbols for 
 abbreviations in these diagrams, even if the student 
 thinks he knows the full significance of a chemical 
 symbol. 
 
 At Exeter the instructor meets the students, in class, 
 four times a week. In general, at each of the first 
 three of the four periods he assigns some new work 
 to be done in the laboratory, gives any needed direc- 
 tions or precautions, and then holds a review of the 
 work that was assigned one week before. In these 
 reviews the experiments are taken up in their order, 
 
INTRODUCTION. XXvii 
 
 the questions in the text are put to the students, and 
 the instructor endeavors to find out, and clear away, 
 any difficulties his students may have met. At the 
 fourth period, which is the last in the week, the 
 instructor has his students write out the fair accounts 
 in ink. While they are writing he passes among them, 
 examines their books, and criticises, particularly, 
 their manner of recording the work done. This 
 fourth period has come to be, at Exeter, a period 
 of instruction in English composition as well as in 
 chemistry. Between these four periods the students, 
 still under the direct oversight of the instructor, per- 
 form their experiments in the laboratory, and make 
 their rough preliminary notes. About 100 hours of 
 laboratory work have been found necessary, by the 
 most careful workers, to complete Part I. Part II re- 
 quires about fifty hours, and the experimental work of 
 Part III requires about fifty hours. 1 If a student has 
 only a limited amount of time to devote to his chem- 
 istry, the author advises him to take Part III after 
 finishing Part I. 
 
 1 It is hoped that students who take up this course in chemistry 
 will have had such laboratory practice in physics that they can omit 
 the actual performance of many experiments of Part III, e.g., "Law 
 of Boyle"; "Weight and Sp. Gv. of Air"; " Law of Dalton "; Ex- 
 periments 14, 15 and 16 on the Sp. Gv. of gases ; " Spaces between 
 the Molecules"; "Irregular Expansion of Liquids"; "Regular 
 Expansion of Gases"; and the experiments under Sp. Heat. In 
 every case of omission, however, reference should be made to the 
 data already prepared and recorded in the note-book of physics, and 
 the results should be carefully reviewed for use in the work in 
 chemistry. 
 
 The fifty hours noted above are for a student who has not had 
 previous training in Physics. 
 
XXV111 INTRODUCTION. 
 
 Part II contains work of the same nature as that of 
 Part I. This additional work, on highly interesting 
 substances, is intended for students who can devote 
 more time to their chemistry than those who are limited 
 to the minimum that is necessary for a general edu- 
 cation. It is possible to arrange the work so that the 
 brightest students in a class may do both Part I and Part 
 II while those of average ability are doing Part I, e.g., 
 bright students may be allowed to work ahead of the 
 class, putting only their rough notes in the note-book 
 till the class, in review, has caught up ; or two sections 
 of the class may be formed. But no experiment of 
 Part I should be omitted by any one. 
 
 When the student is in the laboratory he should be 
 careful always : 
 
 To read through the description of each part of 
 every experiment before commencing to do that 
 part. 
 
 To note carefully all cautions. 
 
 To leave balances clean and in proper adjustment. 
 
 To keep all weights clean. 
 
 To resist the temptation to use weights for any 
 other purpose than weighing. 
 
 To avoid putting test papers in liquids. [See 
 Appendix C.] 
 
 To use only clean apparatus. 
 
 To put on the preliminary page of the note-book 
 only brief notes, and notes right to the point. 
 
 To use the utmost care in all work with hydrogen 
 
INTRODUCTION. XXIX 
 
 And at all times : 
 
 To use his utmost good judgment, and if in 
 difficulty or in danger, to try to think his way out 
 clearly and quickly. 
 
 Chemicals and apparatus should be provided well in 
 advance of the time they will be needed, in order that 
 there may be no loss of time in waiting for suitable 
 apparatus or the necessary chemicals. 
 
 Mr. M. A. Buck, at 5 Tremont Street, Boston, is 
 prepared to furnish apparatus and chemicals suited to 
 the needs of students who pursue this course. On 
 application, he will furnish carefully prepared lists 
 of all apparatus and chemicals needed, either for the 
 whole book or for any part, for a liberal allowance, 
 or for the minimum amount required by careful stu- 
 dents, and his arrangements are such that he can 
 usually furnish the articles, whether ordered in com- 
 plete sets or individually, at prices below the dealers' 
 regular quotations. 
 
 As Mr. Buck was an assistant in the Exeter Labora- 
 tory for several years during the development of this 
 course, the author feels sure that he will prove well 
 fitted to furnish exactly the right articles to make the 
 work run with the least amount of friction from 
 "misfit" apparatus and chemicals unsuited for the 
 work in hand. 
 
PRELIMINARY WORK, 
 
PRELlMr^rART WORK. 
 
 IN THE LABORATORY. 
 I. MEASURING. 
 
 HAVE ready a metric rule, about thirty centimeters 
 long and graduated to millimeters ; a rule about one 
 foot long and graduated in inches and fractions of 
 inches, down at least to one eighth inch; 1 a glass 
 cylinder, capacity 50 or 100 cubic centimeters, and 
 graduated to cubic centimeters; a graduate holding 
 one fluid ounce ; several glass beakers, flasks, and 
 bottles of different sizes; a test-tube rack containing 
 five or six test-tubes of different sizes. 
 
 Measure, first in the metric system, then in the 
 English, the length of your laboratory desk; also its 
 width; estimate its area in square centimeters, in 
 square inches, in square millimeters, in square meters. 
 In recording measurements use the decimal point, e.g., 
 if the length of your desk is one meter, and two deci- 
 meters, and five centimeters, and seven millimeters, do 
 not record the measurement l m , 2 dm , 5 cm , and 7 mm ; but 
 express it 1.257 m , or 125.7 cm , or the like. How many 
 centimeters are there in one inch ? How many inches 
 in one meter? How many square centimeters in one 
 
 1 A convenient form of rule is one having centimeters on one side 
 and inches on the other. 
 
4 PRELIMINARY WORK. 
 
 square inch? What fraction of a square inch does 
 a square centimeter occupy ? Put the answers to these 
 questions in your note-book. Also fix the round num- 
 bers in your mind. 
 
 Take your graduated cylinder [commonly called 
 44 graduate "], fill your largest flask to the brim with 
 water, pour the water from the flask into the cylinder, 
 and find how many cubic centimeters the flask holds. 
 Find also the capacity in cc [cc stands for cubic centi- 
 meters] of your other flasks, beakers, bottles, and test- 
 tubes. 
 
 One purpose of this work in measuring is to enable 
 you to tell at a glance about how much the laboratory 
 vessels in common use contain. It is best, then, in 
 making these measurements, not to fill the beakers to 
 the brim, but conveniently full only. Try to fix the 
 various capacities in mind. 
 
 Also find the capacity of at least two bottles, your 
 smallest beaker, and a test-tube in fluid ounces, using 
 your oz. graduate as a measure. Fix the values in mind 
 as well as record them in your note-book. Bottles are 
 commonly designated, in trade, by the number of ozs. 
 they contain. 
 
 II. WEIGHING. 
 
 Have ready a platform balance, capable of holding a 
 load of 5 kilos and sensitive at least to one tenth of 
 a gram; a set of iron weights, 2000-10 g inclusive 
 [g stands for gram, sometimes written gramme]; a 
 smaller balance, sensitive at least to one one hundredth 
 of a gram; a set of weights, 50 g -10 mg inclusive [mg 
 
PRELIMINARY WORK. 5 
 
 stands for milligrams], accurate at least to one one 
 hundredth of a gram ; a pair of brass forceps for hand- 
 ling the weights. 
 
 Take the large balances, fill three of your larger 
 vessels conveniently full of water; weigh each sepa- 
 rately, then all three together. Weigh accurately to a 
 single gram. See if the sum of the three separate 
 weights equals the combined weight. Record all ob- 
 servations in your note-book. In recording use the 
 decimal point as in the case of your measurements. 
 
 Balance your graduate on one pan with any con- 
 venient article, as, for instance, a vessel partly filled 
 with water or, better, with lead shot. 1 Pour water into 
 the graduate to the amount of exactly 50 CC [100 CC if 
 you have a 100 CC graduate]. Get the weight of this 
 water and notice that one cc of water weighs exactly 
 one gram. 
 
 Take the smaller balances, and, using the smaller 
 weights [which must be handled with the forceps only], 
 weigh [accurately to centigrams 2 ] three nails, first sep- 
 arately, then all together. The sum of the separate 
 weights should not vary from the combined weight 
 more than 0.05 g . If the variation is greater, repeat all 
 the weighings. Record results showing the variation, 
 if any. 3 
 
 1 It is a good plan always to have at hand in the laboratory two or 
 three saucers or similar stout vessels filled with shot, to be used for 
 balancing vessels whose contents only are to be weighed accurately. 
 
 2 If you are not familiar with the denominations of the metric 
 system, look up this system in some arithmetic or in the dictionary. 
 
 3 Unless perfectly familiar with the English system of weights and 
 the relation between these weights and the metric, obtain a set of 
 English weights, and with these weigh all the articles you have 
 
PRELIMINARY WORK. 
 
 III. MAKING A WASH-BOTTLE. 
 
 Take a 500 CC flask and a cork to fit ; also about 1 
 meter of soft glass tube with a bore of about 6 mra 
 [mm stands for millimeters]. Put the cork on the floor 
 and with the sole of the shoe roll it to soften it and 
 make it fit the neck of the flask tightly. With a rat- 
 tail file bore two holes through the cork. Let each 
 hole be round and of such size that the glass tube will 
 fit it tightly. Take a piece of the glass tube about 
 10 cm [cm stands for centimeters] longer than the height 
 of the flask. 1 Stand the glass tube in the flask, make 
 a mark on the tube half way between its upper end 
 and the top of the flask. 2 Bend the glass tube 8 at the 
 mark until the shorter limb forms with the longer an 
 angle of about 45. The bend should form a curve, 
 not a sharp angle. Pass the longer limb through a 
 hole of the stopper, then at a point about half way 
 between the first bend and the open end of the longer 
 limb, make another but lesser bend. This latter bend 
 should bring the lower end of the tube, when the cork 
 is inserted in the flask, to the vertex of the angle made 
 by the bottom of the flask with its side. Be sure to 
 make the second bend toward the first, i.e., in making 
 the second let the open end of the longer limb approach 
 the open end of the shorter limb not recede still 
 
 weighed with your metric weights. Compare results, and note that 
 one ounce is equal to about 28.3 grams and that one pound contains 
 about 454 grams. 
 
 1 To cut glass tubes, see Manipulations [at end of book]. 
 
 2 To mark tubes, see Manipulations. 
 8 See Manipulations. 
 
PRELIMINARY WORK. 7 
 
 farther from it. Now take a piece of glass tube about 
 15 centimeters long, bend this slightly, best till the 
 two limbs form an obtuse angle of 135. Take a third 
 piece of glass tube and draw it out 1 to a diameter of 
 about 2 mm . From this drawn-out tube cut a tip for the 
 wash-bottle. At one end this tip should be of the same 
 diameter as the original tube; at the other, not over 
 2 mm ; in length, 3-5 cin . Wipe all soot from the three 
 tubes. Fire polish 2 every rough end of the tubes. 
 Insert the second bent tube through its hole in the 
 cork, letting the end be flush with the lower end of 
 the cork. This tube forms the mouth-piece. Attach, 
 by means of a rubber connector, i.e., a piece of small 
 rubber tube l-2 cm long, the tip to the shorter end of 
 the longer bent tube. This tip forms the jet, and, 
 owing to its flexible connection of rubber, can be 
 directed by the fingers in different directions when the 
 wash-bottle is used for washing precipitates. The 
 slight inner bend in the longer tube enables the whole 
 of the water to be blown from the bottle when the flask 
 is tipped up, as it usually is, in use. Fill the bottle 
 about two thirds with water. [Distilled water 3 is best, 
 though not necessary, for the following experiments. 
 When necessary, the fact will be stated.] Wet the 
 cork to fill the pores, insert the cork in the flask, and 
 blow through the mouth-piece. The tip should deliver 
 a fine, steady stream. Insert a sketch of your wash- 
 bottle in your note-book. 
 
 1 See Manipulations. 2 See Manipulations. 3 See Appendix O. 
 
PART I. 
 
 EXPERIMENTS 
 
PART I. EXPERIMENTS. 
 
 Experiment 1. 
 Iron. A solid substance. 
 A. The Properties of Iron. 
 
 TAKE an iron nail and a piece of fine iron wire. 
 Note as many of the properties of iron as you can, e.g., 
 color [make a fresh scratch with a file to get the true 
 color] ; hardness [see what it will scratch, and what 
 will scratch it, try, for instance, glass, chalk, wood, a 
 file, etc.] ; tenacity [try pulling apart the nail, the 
 wire] ; brittleness [mention some things you find, on 
 trying, to be more brittle, some less] ; fusibility [try to 
 melt the wire, first in the flame of the Bunsen burner, 1 
 then in that of the blast-lamp] ; volatility [see if any 
 heat you can produce will make it go off in vapor in 
 the way steam does from hot water]. 
 
 B. Action of Air on Hot Iron. 
 
 Fill a small porcelain crucible about half full of iron 
 filings. Weigh carefully [to centigrams]. Set the 
 crucible on a pipe-stem triangle supported on a stand. 
 Heat with a Bunsen burner for about ten minutes with 
 occasional stirring [with a glass rod], that the air may" 
 come in contact with all the filings. Cool the crucible. 
 
 1 For the use of burners, see Manipulations. 
 
12 IRON. 
 
 Why? Again weigh. What has caused the gain? 
 See if you can detect any difference of lustre between 
 filings not heated in air and those heated. Sprinkle 
 a few filings in the flame and note the phenomenon. 
 What is a phenomenon? Do not return filings once 
 used to the bottle. Let us call that which has come 
 from the air and fastened itself to the filings oxygen, 
 and the new dull-black substance formed oxide of 
 iron. Let us call oxide of iron a compound, because 
 it is obviously compounded of two other substances. 
 Let us call iron itself a simple substance, because 
 we cannot make it from two or more other substances, 
 nor can we get two or more other substances from it. 
 What is a simple substance ? What is a compound ? 
 
 Having found that there is in the air a peculiar sub- 
 stance capable of joining iron, it becomes of interest to 
 ascertain what proportion of the air this substance 
 occupies. In our investigation we shall need the aid 
 of another simple substance, phosphorus, with which 
 the oxygen unites even more readily than with iron. 
 
 Experiment 2. 
 
 Phosphorus. Another solid substance. 
 A. The Properties of Phosphorus. 
 
 Take a piece of yellow phosphorus and a little red 
 phosphorus. 
 
 Caution ! Caution ! Caution ! 
 
 Yellow phosphorus is very poisonous indeed, ex- 
 tremely inflammable, and a phosphorous burn is very 
 
PHOSPHORUS. 13 
 
 painful. This substance must be stored under water, 
 and cut only under water, best in the pneumatic 
 trough or in a large basin. Matches must not be kept 
 in closets or drawers. 
 
 Examine the phosphorus and note its most important 
 properties, as color, consistency, fusibility, inflamma- 
 bility, etc. Do not handle the yellow with bare fingers. 
 Use iron forceps. Dry it rapidly by pressing it gently 
 between filter or blotting papers. In stating the prop- 
 erties, make two tables : one for the red, the other for 
 the yellow. 
 
 B. Action of Air on Warm Phosphorus. 
 
 Have ready a dry, 1 quick-sealing pint fruit-jar, 2 and a 
 clean iron deflagrating spoon, also about half a gram 
 of phosphorus. If you use the yellow phosphorus it 
 must be cut under water, dried quickly by pressing 
 between filter papers, and at once placed in the spoon. 
 Have at hand a Bunsen burner flame, over which the 
 spoon may be held in order to light the phosphorus. 
 
 The rubber washer to the jar should be greased 
 [vaseline is good] to make it tight. Hold the spoon 
 in one hand and the cover to the jar in the other. 
 Light the phosphorus, and with a quick but deliberate 
 motion plunge the spoon in the jar, at once put on the 
 cover, fasten it and step back, as the jar may crack. 
 
 Note, as the phosphorus burns away, the white 
 powder formed. As soon as the jar cools, open it, 
 
 
 
 1 To dry flasks, jars, and other pieces of apparatus, see Manipula- 
 tions. 
 
 2 A quick-sealing fruit-jar with a rubber washer. Those called 
 "Lightning" are excellent. 
 
14 MERCURY AND CARBON. 
 
 holding the mouth under water, which, rushing in, will 
 show that a part of the air has gone. Make a rough 
 estimation of what part [by volume] has gone. This is 
 the same part that, in Ex. 1, B, left the air, joined the 
 iron, and increased the weight. Remember that we are 
 going to call this gas which has the power of joining 
 other things, oxygen. We will call the new substance 
 made from the oxygen and the phosphorus [the white 
 powder that formed in the jar] oxide of phosphorus. 
 Note that not all the air was used, part was left. 
 This part is another gaseous substance which we shall 
 study later. 
 
 Experiment 3. 
 Mercury. A liquid substance. 
 
 Caution! Be careful in the use of heat with mer- 
 cury, as the vapor of mercury is a vigorous poison. 
 Take a globule of mercury as large as a pea and note 
 its chief properties. In doing this, review Ex. 1, A, 
 and Ex. 2, A. Note those respects in which mercury 
 resembles iron or phosphorus, and those in which it 
 differs from these substances. 
 
 Experiment 4. 
 Carbpn. 
 
 Take a bit of charcoal, a bit of graphite [from a 
 44 lead" pencil], some soot, a bit of gas-retort carbon, 
 and [if obtainable] a diamond. Also burn a piece of 
 
UBITBESITTI 
 
 OXYGEN. 
 
 thin paper to get the carbonaceous residue, which often 
 keeps the original form. Study these different forms 
 of carbon and note chief properties. What is meant by 
 allotropic forms ? 
 
 Experiment 5. 
 Artificial Preparation of Oxygen. 
 
 A. From the Red Oxide of Mercury. 
 
 Take a piece of hard glass tube, and red oxide of 
 mercury. Caution ! Red oxide of mercury is a vigorous 
 poison. Note. Red oxide of mercury may be made by 
 prolonged heating of mercury in contact with air. Re- 
 call the preparation of the black oxide of iron that you 
 made in Ex. 1, B. If the red oxide of mercury itself 
 is heated vigorously, it is separated into the mercury 
 and the oxygen from which it was made. 
 
 Make a small matrass 1 from hard glass tube. Fill 
 the bulb about one half with the red oxide of mercury, 
 and heat over the Bunsen burner flame. Test for 
 oxygen by plunging down the tube a bit of glowing 
 [not flaming] carbon [best made from a splinter of 
 wood or a burned match]. What did we call the sub- 
 stance formed in Ex. 1, B, when oxygen joined the iron 
 filings? what the substance formed from the union of 
 oxygen and phosphorus when, in Ex. 2, B, the phos- 
 phorus burned? What, then, shall we call the sub- 
 stance formed when the oxygen now joins the carbon, 
 causing the intense heat and fire at the end of the 
 splinter? What becomes of this new substance which 
 1 See Matrass, under Manipulations. 
 
16 OXYGEN. 
 
 is formed? Note the globules that collect in the cool 
 part of the tube. Break open the tube and examine 
 them. What are they ? 
 
 This process, by which a compound substance is split 
 into simpler ones, is called Analysis, and is typical of a 
 vast number of chemical changes. 
 
 B. From Chlorate of Potassium. 
 
 Note. As red oxide of mercury is expensive, come 
 other method than that of part A is desirable for pre- 
 paring oxygen on the large scale. It is found that 
 chlorate of potassium, when heated to a high tempera- 
 ture, is also broken up into two substances, one of 
 which is oxygen. 
 
 Have ready a Kjeldahl flask 1 clamped to a stand at 
 such a height that the body of the flask may be heated 
 conveniently by a Bunsen burner. Fit the flask with a 
 one-hole cork, and from the cork let a glass tube, of not 
 less than 5 mm bore, pass down into a trough of water. 2 
 The end of the delivery tube 3 should be turned up a 
 little in the water. Soak the cork for a minute or two 
 to fill small holes. 
 
 Put in the flask about 15 g of chlorate of potassium. 
 Weigh the flask with its charge. Do not have the 
 cork in when you weigh. Clamp the flask in position. 
 Caution ! In this experiment never insert the cork 
 tightly, as the tube may plug up, and if the cork cannot 
 
 1 A stout, long-necked, pear-shaped flask of hard glass. 
 
 2 See Pneumatic Trough, under Manipulations. 
 
 8 The term "delivery tube" will appear frequently hereafter, and 
 is to be taken to mean a tube for the delivery of a gas from a flask, 
 bottle, or the like. 
 
OXYGEN. 17 
 
 blow out [like a safety valve], the flask may explode. 
 Have ready four pint jars filled with water and stand- 
 ing inverted on the bridge of the pneumatic trough. 
 What does pneumatic mean? Heat the chlorate of 
 potassium with a Bunsen burner. Caution! Do not 
 allow the hand .to come directly under the flask, for 
 if the flask should crack and the hot, melted chlorate 
 run out, the hand might be scalded. Move the flame 
 all around on the bottom of the flask in order that no 
 part of the glass may get too hot and soften. Catch 
 the gas evolved. Catch at least four jars full. Not 
 more than a few cc of water should be left in a jar. 
 Snap on the covers while the jars are still inverted with 
 their mouths under water. Use rubber washers, well 
 greased, when sealing the jars. Set the jars of gas 
 away for further use. Uncork your flask before you 
 stop heating it. Why? Weigh the flask with the 
 residue. Compare weight with first weight. Explain 
 the change in weight. Take your first-caught jar of 
 gas, and prove that the gas is similar to that from the 
 red oxide of mercury, ^.e.,that it is oxygen. Prove this 
 by plunging in a bit of glowing carbon. 
 
 Experiment 6. 
 A. Action of Undiluted Oxygen Gas on Iron. 
 
 Have ready a jar of oxygen gas [from Ex. 5, B], also 
 a small amount of very fine iron filings. Two minutes' 
 continuous filing of a board nail with a five or six-inch 
 file over glazed paper furnishes an ample amount of 
 
18 OXYGEN. 
 
 good filings. Those used in trade often are not fit for 
 this experiment. Place the filings in a little heap in a 
 clean and dry deflagrating spoon. 1 Heat them [spoon 
 and all] over a Buiisen burner for a moment till a dull 
 glow runs through the heap ; then plunge them at once 
 into the jar of oxygen and put on the cover. Compare 
 the action of pure oxygen gas with that of the oxygen 
 in the air [see Ex. 1, B], which is diluted with nearly 
 eighty per cent [by volume] of another gas. Save the 
 oxide of iron for Ex. 15. 
 
 B. Action of Undiluted Oxygen Gas on Phosphorus. 
 
 Proceed as in Ex. 2, B, except that the phosphorus 
 is to be burned in a jar of pure oxygen and greater 
 precautions in every way are to be taken, as the action 
 is violent and the danger of the jar exploding much 
 greater. Weigh the phosphorus exactly. In no case 
 use more than .55 g for a pint jar. It is best to throw a 
 cloth around the jar after the action and keep the cloth 
 around till the jar is opened under water. This will 
 catch pieces of glass if there is an explosion. What 
 becomes of the white oxide of phosphorus in this 
 experiment ? 
 
 C. Action of Undiluted Oxygen Gas on Carbon. 
 
 Proceed as in B, but use a lump of charcoal weigh- 
 ing about l g instead of the phosphorus. Get the char- 
 coal well on fire by heating it with a Bunsen burner 
 
 1 If the bottom of the deflagrating spoon is too thick, the filings will 
 not become heated enough by the Bunsen burner before they are 
 coated with oxide, and in this case the experiment will be a failure. 
 
OXYGEN. 19 
 
 and seal the jar as soon as possible. Why ? Do not use 
 a deflagrating spoon that has any phosphorus in it. 
 Test the spoon by holding it a minute in the Bunsen 
 flame. 
 
 A pretty effect may be obtained if a little powdered 
 charcoal is sprinkled over the lump of charcoal. 
 
 If on opening the jar under water the oxygen does 
 not appear to have been used, test the remaining gas 
 with a glowing match. Give the chief properties of 
 oxide of carbon. This addition of oxygen to another 
 substance is called oxidation. The term is also some- 
 times applied to the addition of other substances. 
 
 Experiment 7. 
 Preparation of Oxygen from Water. 
 
 Have ready some water in a suitable vessel 1 into 
 which pass two platinum electrodes s'o arranged that 
 the electric current in passing from one electrode to the 
 other must pass through the water. Pass a current of 
 electricity through the water from one electrode to the 
 other. If the resistance of the water to the passage of 
 the electric current is too great for a rapid evolution of 
 gas, add a little sulphuric acid. In some way the acid 
 greatly helps the current to get through the water. 
 Fill a small tt with water. Place your thumb over the 
 mouth of the tt, and invert the tube over the electrode 
 that is giving off the gas the slower. Catch a tt of the 
 gas. Do not let any of the other gas get in. Test the 
 
 i See Appendix A. 
 
20 HYDROGEN. 
 
 contents of the tt [glowing match test], and compare 
 with the gas got from the air [see Ex. 1, B and Ex. 
 2, B] ; also with the gas from red oxide of mercury 
 [see Ex. 5, A]. Give all the properties you can of 
 oxygen. 
 
 Experiment 8. 
 
 Examination of that Constituent of Water which is 
 not Oxygen. 
 
 Again pass the electric current through water, as in 
 Ex. 7. This time collect the gas which is given off in 
 larger quantity. Catch a tt full. Test this with a 
 glowing match, still holding the tt upside down. Why 
 upside down ? Answer this after doing Ex. 9, B. Is 
 the gas oxygen ? If not found to be oxygen, test at 
 once with a flaming match. Again catch some of the 
 gas, about two-sevenths of a tt this time. Carefully 
 let the air fill the rest of the tube. Put your thumb 
 over the end, and shake to mix the air with the gas. 
 Now apply quickly a lighted match. What takes 
 place chemically ? Let us call this new gas hydrogen. 
 
 Experiment 9. 
 
 A. The Preparation of Hydrogen from Water by Means 
 of Iron. 
 
 Note. Ex. 1, B, taught us that iron when hot has 
 attraction for oxygen. If water [best in the form 
 of steam] is passed over red-hot iron the iron will 
 decompose the water, take the oxygen to itself and 
 
HYDROGEN. 21 
 
 leave hydrogen. What must then happen to the 
 iron ? Proceed as follows, and see if your inference as 
 to the answer to this question is confirmed by experi- 
 ment. Take a piece of half -inch gas pipe about two 
 feet long with a one-hole cork in each end. Put about 
 30 g of iron filings 1 in the gas pipe, as near the middle 
 as possible, but be sure there is a passage through the 
 whole tube. Clamp the gas pipe to a stand at each 
 end. Heat the filings by means of two Bunsen burners 
 directed at the same point on the gas pipe. Fit your 
 wash-bottle flask with a one-hole cork and delivery 
 tube. Set the flask on a tripod stand on which is a 
 piece of fine iron gauze about four inches square, to 
 prevent the bottom of the flask being unevenly heated. 
 Put some water in the flask, set a Bunsen burner 
 below, generate steam and pass the steam over the hot 
 filings. Have a delivery tube passing from the filings 
 down into the pneumatic trough. Let all corks be 
 tight. Catch several tts of the gas evolved. Do not 
 try to keep it corked up, but catch the gas when you 
 need it for the following work. Reject the first two 
 tubefuls because there is apt to be air in them. 
 
 Caution ! Caution ! Caution ! 
 
 Hydrogen and air form an extremely dangerous explo- 
 sive mixture. Use the utmost care in all work with 
 hydrogen. Think what you are going to do in every case 
 before you act. 
 
 Test the third and fourth tubes, as you tested in Ex. 
 8, to prove that this is the same gas we agreed to call 
 
 1 The filings should be as free as possible from dirt and oil, other- 
 wise a troublesome smoke may appear. 
 
22 HYDROGEN. 
 
 hydrogen. Note all phenomena as you test. How do 
 you explain what happens when you apply the flame ? 
 
 What shall we call the substance that results when 
 the oxygen of the air joins the hydrogen, causing 
 the intense heat and fire ? What is the common name 
 for this substance? As in making oxygen from 
 chlorate of potassium, here uncork your wash-bottle 
 flask before you stop heating. Why ? 
 
 B. Specific Gravity of Hydrogen. 
 
 Catch a tt of hydrogen. Put your thumb over the 
 end of the tube. Remove the tube from the trough. 
 Hold the tube upside down. Remove the thumb care- 
 fully. Wait while you breathe naturally ten times, 
 i.e., wait about half a minute. At once apply a flame 
 to the tt's mouth. Again catch a tt full and proceed 
 as before, but now hold the tt, with its mouth up, 
 while you breathe ten times. Again catch a tt full. 
 Hold a second tt bottom side up and carefully pour the 
 hydrogen from the other up into the second. At once 
 test the contents of the second for hydrogen. What 
 do you say in regard to the weight of hydrogen ? 
 
 C. Action of Air on Warm Hydrogen. 
 
 Have ready an eight-ounce, wide-mouth bottle fitted 
 with a two-hole stopper. Let there be projecting 
 up straight from one hole a piece of hard glass tube 
 about six inches long with one end just reaching 
 through the cork, and with the other [upper] end 
 drawn down to an opening about like the tip to a wash- 
 bottle nozzle. Through the second hole of the cork a 
 
SULPHUR. 23 
 
 piece of common glass tube should be inserted reaching 
 well into the bottle and connecting the bottle with the 
 hydrogen gas pipe. This bottle serves as a catch-bottle 
 or trap to condense any steam that gets by the filings. 
 It best be set in a dish of cold water or, better, in 
 the pneumatic trough. Generate hydrogen as in A, but 
 apply the blast lamp for a few minutes that the filings 
 may be heated red-hot and cause a good flow of hydro- 
 gen. As there is some danger of the catch-bottle blow- 
 ing up, apply to the instructor l for a method of testing 
 the explosive quality of the contents of this bottle. 
 When all is safe, light the hydrogen as it issues from 
 the small jet, and let it burn in the air. What is the 
 burning ? What the product of combustion ? Hold a 
 dry and cold tt over the jet. Do not smother the 
 flame, however. Note the substance that forms on the 
 sides of the tt. What is it ? 
 
 Experiment 1O. 
 
 Sulphur. 
 
 A. The Properties of Sulphur. 
 
 Take some roll brimstone, and some flowers of sul- 
 phur. Note the chief properties of sulphur. Review 
 the records of iron, phosphorus, mercury, carbon, 
 oxygen, hydrogen, and all the oxides you have made. 
 Compare sulphur with the other substances you have 
 studied. 
 
 1 See Appendix B. 
 
24 SULPHUB. 
 
 B. Modifications of Sulphur. 
 
 1. Dissolve about a gram of roll brimstone in about 
 five cc of sulphide of carbon [one of the very few 
 things in which sulphur will dissolve]. Caution ! 
 /Sulphide of carbon is very volatile and inflammable. 
 Have no fire near. Best grind the sulphur to a powder 
 in a mortar to make it dissolve quickly. The flowers 
 do not dissolve as well as the roll. Pour the solution 
 out in a crystal pan, 1 and let the sulphide of carbon 
 evaporate spontaneously. Examine the form and color 
 of the crystals deposited. 
 
 2. Melt enough roll brimstone to fill a small common 
 beaker nearly full. In melting the sulphur, the beaker 
 should be set on iron gauze or asbestos- paper. If the 
 sulphur in the beaker catches fire turn off your gas and 
 smother the fire with an inverted dish or a cloth. Take 
 care that the temperature does not rise much above the 
 melting point of the sulphur. Let the sulphur cool till 
 crystals begin to shoot across the surface and just meet 
 in the middle, then promptly pour out into water what 
 remains liquid. Note the form and color of the 
 crystals left in the beaker. Compare with those of 1. 
 
 3. Melt some sulphur in a tt. Hold the tt over a 
 naked Bunsen flame. 2 Raise the temperature till the 
 substance, after it melts to a liquid, becomes thick and 
 viscous. What is meant by viscous? Then pour the 
 sulphur out in a fine stream into cold water. Note the 
 form of the sulphur in the water. Compare sulphur 
 
 1 A shallow glass dish. 
 
 2 See Manipulations for method of holding a hot tt. 
 
SULPHITE. 25 
 
 with carbon, phosphorus, etc., in regard to allotropy. 
 What is allotropy ? 
 
 C. Action of Oxygen on Hot Sulphur. 
 
 Prepare more oxygen in .the following manner. 
 Take 12 g chlorate of potassium and mix with it 3 g of 
 powdered black oxide of manganese. 1 The black oxide 
 should be mixed intimately with the chlorate. Do not 
 spill any. Heat the mixture in a Kjeldahl flask as in 
 Ex. 5, B. Do not use here a pneumatic trough filled 
 with water, for collecting the gas, but fill three or four 
 dry jars by displacement, i.e., pass the delivery tube 
 [best have one ending in about 15 cm rubber tube,] 
 directly into the jar. Hold the cover on as well as 
 possible. The oxygen gas, which is somewhat heavier 
 than air, will collect at the bottom of the jar and push 
 the air up and out. You can tell when the jar is full 
 by holding a glowing match at the crack left between 
 the cover and the edge. When the jar is full, with- 
 draw the rubber tube slowly that the oxygen may fill 
 the space occupied by the tube. Snap on the cover at 
 once. Set away, for the next experiments, at least two 
 jars that seem perfectly dry. Do not throw away the 
 contents of the Kjeldahl flask, but, when cool, add 
 about 100 CC of warm water. The white chloride of 
 potassium dissolves, while the black oxide of manganese 
 does riot. Take a funnel and a filter paper 2 to fit the 
 funnel. Pour the contents of the flask on the filter 
 
 1 The black oxide of manganese of trade is sometimes adulterated 
 with coal dust. Such adulteration might cause a serious explosion in 
 this experiment. Why? 
 
 2 For directions about filter papers, see Manipulations. 
 
26 SULPHUR. 
 
 paper. By means of the wash-bottle pass about 100 CC 
 of water through the black oxide of manganese to carry 
 through the chloride of potassium. Dry the black 
 oxide and weigh it. In order to dry the black oxide, 
 have ready a weighed porcelain evaporating dish. 
 Transfer the black oxide to this dish, using a fine 
 stream from the wash-bottle to wash the last traces of 
 the oxide into the dish while you hold the paper just 
 above the dish. Evaporate off the water, avoiding all 
 spattering, 1 and with a small flame dry the black oxide 
 in the dish to constant weight. In drying, never 
 allow the black oxide to be heated to redness. Why? 
 To dry a substance to constant weight, heat it until it 
 seems dry, then Aveigh it, again heat it, weigh again, 
 and if the weight is the same as that previously found 
 no further drying is necessary. If there has been a loss 
 after the second heating, again heat, weigh and so con- 
 tinue till no further loss in weight is found. You 
 should have the same amount of black oxide that you 
 started with, i.e., 3 g . 
 
 Note. This black substance is the oxide of the metal 
 manganese. Compare it with the oxide of iron you 
 made. We do not know its action in this experiment, 
 but it certainly makes the oxygen come off easily. 
 What do you think of its action ? Compare the use of 
 sulphuric acid when you decomposed water with the 
 electric current. 
 
 1 Spattering is best avoided by evaporating at such a low tempera- 
 ture that the liquid does not actually boil. Best set the evaporating 
 dish over a beaker containing water which is kept boiling by a 
 Bunsen burner beneath. This method of slow evaporation is called 
 " Evaporation over the water-bath." 
 
SULPHUROUS ACID. 27 
 
 Burn a small piece of sulphur on a clean deflagrating- 
 spoon in a jar of oxygen. Open under water, note the 
 condition of the jar, and at once snap on the cover 
 again. If no water has entered the jar, let in about 
 50 CC . Shake with the water that has entered. Again 
 open under water and note the condition of the jar. 
 Note the properties of the new compound formed, 
 especially its state, color, odor, and solubility in water. 
 What shall we call the new compound? Will it 
 weigh more than the original oxygen? 
 
 Experiment 11. 
 
 Sulphurous Acid. 
 
 Again burn sulphur in a jar of oxygen. Do not open 
 under water, but remove the spoon carefully, and add 
 about 20 CC of water. Shake well. Try -the effect of 
 the liquid on a bit of blue litmus paper. 1 Try the 
 effect of water itself on the same kind of test paper. 
 Taste a very small amount of the new liquid. Let us 
 call our new substance sulphurous acid. What three 
 simple substances must there be in this acid? 
 
 Experiment 12. 
 A Second Oxide of Sulphur. 
 
 Oxygen may be made to join the gaseous oxide of 
 sulphur and form a second oxide of sulphur. Have 
 
 1 For the preparation and use of litmus paper see Appendix C. 
 
28 OXIDE OF SULPHUR. 
 
 ready weighed in a clean and dry defiagra ting-spoon 
 just 0.3 g of sulphur. Burn the sulphur as in Ex. 11, 
 but do not remove the spoon. The 0.3 g of sulphur are 
 not enough to use all the oxygen. Therefore you have 
 in the jar, after the burning, oxygen and oxide of 
 sulphur. What are the properties of oxygen, of 
 oxide of sulphur ? Have ready a suction pump l and a 
 tube of hard glass containing a little platinum sponge, 
 or platinized asbestos. 2 This tube containing the plati- 
 num should be 15-20 cm long and have a bore of about 
 6 min . The platinum sponge, or asbestos, should not be 
 packed so tightly that the gases cannot easily pass 
 through. 3 Also have ready a piece of glass tube bent 
 in the form of a U, the total length of this tube to be 
 about 40 cm . One end of this tube should be connected 
 with the platinum sponge tube, and the other with the 
 suction pump each by a piece of rubber as short as 
 possible, for the oxide formed corrodes rubber. Place 
 the U-tube in a freezing mixture. 4 Suck dry air through 
 the whole apparatus, slowly, for five minutes, to remove 
 all moisture. The air may be dried by connecting the 
 platinum sponge tube with two catch-bottles 5 of sul- 
 phuric acid. Heat the platinum sponge well with a 
 Bunsen burner. The sponge tube may best be sup- 
 ported by a stand and wire gauze. As soon as the 
 
 1 For the use of the suction pump see Appendix D. 
 
 a O.IK of platinized asbestos is sufficient, but 0.2 are better. 
 
 8 It is well to insert within the hard glass tube two bits of small 
 soft glass tube one on each side of the platinum in order to pre- 
 vent the platinum being driven out by any sudden puff of gases. 
 
 4 Crushed ice or snow, salt, and enough water to make a pasty mass, 
 are good for a freezing mixture. 
 
 6 See Appendix E. 
 
SULPHURIC ACID. 29 
 
 sponge is hot, and the whole apparatus dry, disconnect 
 the catch-bottles, fit a piece of rubber tube about 15 cm 
 long to that end of the platinum sponge tube from 
 which the catch-bottles were removed, pass the end of 
 this rubber tube to the bottom of the jar containing 
 the mixture of oxygen and the gaseous oxide of sul- 
 phur, and then, using the hand to prevent, as far as 
 possible, the air mixing with the contents of the jar, 
 let the pump slowly suck the gases from the fruit jar, 
 over the hot platinum, into the cooled U-tube. Look 
 for white crystals in the U-tube, which must be kept 
 very cold. 
 
 If you should weigh the platinum sponge before the 
 experiment and after, you would find no change in 
 weight. The sponge itself does not make any part of 
 the crystals. From what must the crystals be made? 
 Remove the crystals from the cold bath and examine 
 them before they melt. Let us call this new substance 
 the second oxide of sulphur. Keep the new substance 
 for the next experiment. 
 
 Experiment 13. 
 Sulphuric Acid. 
 
 Compare the record of Ex. 11, where you made sul- 
 phuroMS acid. Now take the second oxide of sulphur 
 made in Ex. 12 [which becomes liquid if allowed to 
 stand long at ordinary temperature], and add a few 
 drops of water from the wash-bottle. Try the effect 
 
30 SULPHURIC ACID. 
 
 of the resulting liquid on blue test paper. Dilute more 
 and taste of a very little. Let us call our new acid 
 sulphuric acid. What three things, each simple, must 
 there be in sulphuric acid? In what respect does 
 sulphuric acid differ from sulphurous? 
 
 Experiment 14. 
 
 Removal of Hydrogen from Sulphuric Acid. 
 
 Take a small flask fitted with a one-hole cork and 
 a delivery tube reaching to a pneumatic trough. Pour 
 about 10 CC of water into the flask. Then add 5 CC of 
 sulphuric acid. 1 Caution! Never add water to sul- 
 phuric acid. Add the sulphuric acid to the water. 
 Sulphuric acid and water can generate great heat. If 
 the amount of acid is large and that of water small, 
 this heat may boil the water with explosive violence. 
 
 Have ready about 10 g of iron [best in the form of 
 small nails]. Add the iron to the flask before the 
 liquid has had time to cool, and insert the cork with its 
 delivery tube. Caution! Keep all fire away. Why? 
 After the gas has passed long enough to drive the air 
 from the flask, catch a tt of it and test it. What is it ? 
 Prove that iron has not the power of removing the 
 hydrogen from water, at a low temperature, by putting 
 some nails in a tt and warming till the water is at 
 
 1 When the student has once made a compound substance, it is not 
 supposed that he is to make enough for all subsequent work. He 
 should be supplied with the commercial article. 
 
SULPHATE OF IKON. 31 
 
 least as warm as was the mixture in the flask. If 
 the hydrogen did not come from the 10 CC of water, 
 whence must it have come ? What has happened to 
 that part of the sulphuric acid that was made of sulphur 
 and oxygen? Answer this question by experiment, 
 as follows : 
 
 Put the contents of the flask in an evaporating dish. 
 Add about 25 CC of water. Set the dish on tripod or 
 ring, and warm gently till no more hydrogen is given 
 off. [While warming, keep the volume of the liquid 
 as nearly constant as possible by adding water if any 
 evaporates off.] Filter and evaporate the liquid till a 
 little of it, when taken out in a tt and cooled, will 
 deposit crystals. Then at once, while still hot, again 
 filter the liquid into a beaker. Hold the beaker so that 
 cold water shall flow over the outside till the liquid 
 within is cold. Note the crystals formed. Filter, 
 spread the crystals on paper to dry. Note their prop- 
 erties. Let us call the new substance sulphate of iron. 
 The green crystals are made of sulphate of iron and 
 water of crystallization, i.e., water which is in some 
 way joined to the sulphate of iron. Many substances 
 in this way form crystals by the addition of water. 
 Put some of the green crystals in a dry tt and heat 
 over a Bunsen burner. Note the formation on the 
 sides of the tt. What forms there? Of what simple 
 substances do you say sulphate of iron is composed? 
 Of what compound substances were the green crystals 
 composed? 
 
 Iron is a simple substance, and sulphuric acid, we 
 have proved^ contains hydrogen, sulphur, and oxygen. 
 
32 OXIDE OF IRON WITH WATER. 
 
 The mutual action of iron and sulphuric acid may be 
 
 iron hydrogen . 
 
 represented by a diagram, thus: ' sulpliur 1ms 
 
 oxygen 
 
 indicates that the iron has changed place with the hydro- 
 gen of the acid, i.e., the hydrogen has become free, and 
 the iron has become combined with the sulphur and 
 oxygen that were in the acid, making a new substance 
 iron sulphate whose composition may be repre- 
 
 firon "I 
 
 sented thus : sulphur . 
 
 loxygen j 
 
 Remembering that water is oxide of hydrogen, i.e., 
 hydrogen -f oxygen, we may represent the formation of 
 the green crystals thus : 
 
 iron 
 
 sulphur 
 
 oxygen 
 
 hydrogen 
 oxygen 
 
 Note. We have already proved that sulphuric acid 
 contains more than one portion of oxygen: hence 
 
 "oxygen" in our Uuip^ur | stands for the total amount 
 
 (^oxygen J 
 
 of oxygen present in the acid. How have we proved that 
 there is more than one portion of oxygen in sulphuric acid? 
 
 asar + . g^es < r =) 
 
 Note. Having found that water added to either 
 oxide of sulphur forms an acid, it becomes of interest 
 to see if water can form an acid with any other oxide 
 except the oxides of sulphur. 
 
 Experiment 15. 
 Action of Water on Oxide of Iron. 
 
 Add a little water to the oxide of iron made in Ex. 6, A. 
 Test with litmus paper. Has an acid been formed ? 
 
OXIDES WITH WATER. 33 
 
 Experiment 16. 
 
 Action of Water on Oxide of Phosphorus. 
 
 Again prepare some oxide of phosphorus, by burning 
 a small amount of phosphorus in a dry jar of air, or, 
 better, oxygen. To the oxide add about 10 CC of water. 
 Shake. Test the properties of the resulting liquid. 
 Taste of a drop. How many and what simple sub- 
 stances have been used in the preparation of phosphoric 
 acid? 1 
 
 Experiment 17. 
 
 Action of Water on Oxide of Carbon. 
 
 Again prepare some oxide of carbon. Be sure, by 
 testing, that all vessels used in this experiment are 
 free from sulphuric acid. To the jar containing the 
 oxide of carbon add about 10 CC of water. Shake well. 
 Test the resulting liquid both by litmus and by taste. 
 Compare its acid properties with those of the other 
 acids you have made. Which acid has the most marked 
 acidity? Which the least? Let us call the acid sub- 
 stance made in this experiment carbonic acid. What 
 simple substances make up carbonic acid? Place the 
 carbonic acid in a small beaker and warm. What 
 happens? Finally bring the liquid just to a boil. 
 Test the liquid remaining in the beaker with litmus. 
 
 1 Phosphorus is capable of forming several acids : the one made here 
 is commonly called metaphosphoric acid. 
 
34 ZINC. 
 
 What is the liquid left? Are the component parts of 
 carbonic acid bound together strongly or not? What 
 are the component parts of carbonic acid? 
 
 Experiment 18. 
 
 Zinc. 
 
 A. The Properties of Zinc. 
 
 Take some zinc, sheet, granular, 1 and dust. Get 
 the chief properties of this substance. 
 
 B. Oxidation of Zinc. 
 
 Put a few grams of zinc in a small Hessian crucible. 
 Heat over the blast-lamp till the zinc melts. Continue 
 the heating, with an occasional stir by means of an 
 iron rod, till the zinc burns. What is the burning 
 chemically? Examine the product of the combustion, 
 which sometimes forms what is called Philosophers' 
 Wool. Get the properties of oxide of zinc, especially 
 its color when hot when cold. Save some zinc oxide 
 [free from zinc] for C. Having found that many oxides 
 with water form acids, it becomes interesting to add 
 water to every new oxide we make. 
 
 C. Action of Water on Oxide of Zinc. 
 
 Take a little of the zinc oxide made in B, put it in a tt 
 and add water. Note effect. Test the liquid with litmus, 
 
 1 Granular ainc [the most convenient form for general chemical 
 use] may be made by melting any form of zinc in a ladle, Hessian 
 crucible, or other suitable vessel, and pouring the molten metal from 
 a height into a vessel of water. 
 
A SECOND OXIDE OF CARBON. 35 
 
 particularly with litmus that has been turned slightly red 
 by a weak acid, as carbonic. Compare [and state the 
 result of comparison] the action of water on oxide of 
 zinc with action of water on other oxides you have tried. 
 
 Experiment 19. 
 
 Action of Zinc on the Non-combustible Oxide of 
 Carbon; or, 
 
 Preparation of a Second Oxide of Carbon. 
 
 Have ready a piece of large, hard glass tube about 
 20 cm long. Put in the midst of this tube four or five 
 grams of zinc in the form of zinc dust. 1 Also have 
 ready a rubber bag nearly filled with the non-combustible 
 oxide of carbon. 2 Clamp the glass tube with its charge 
 of zinc at a convenient height for heating the zinc with 
 a Bunsen burner. Fit an empty gas bag to one end of 
 the tube and the bag containing the oxide of carbon to 
 the other. Heat the zinc and slowly pass the gas from 
 bag to bag for a few minutes. Note the formation of 
 oxide of zinc yellow when hot, white when cold. 
 Whence came the oxygen to form oxide of zinc? Does 
 the resulting gas occupy as much space as the original 
 gas? Remove the bag from the tube without letting 
 any of the gas escape. Fit a cork, through which 
 passes a short piece of glass tube, ending in about 15 cm 
 
 1 The zinc dust should be in the form of a very fine powder. 
 
 2 This gas should be prepared by the instructor and given to the 
 student whenever needed up to the time of doing the experiment in 
 which the student learns the action of an acid on marble. For a 
 method for preparing this gas on a large scale, see Appendix F. 
 
36 REDUCTION. 
 
 rubber tube, to the mouth of the rubber bag. Catch a 
 small bottle, e.g., a two-ounce salt-mouth bottle, full of 
 the gas over the pneumatic trough. Do not use more 
 than one half of all, as some must be saved for Ex. 20. 
 Set fire to the new gas in the bottle. Have a dark back- 
 ground, as the new gas will burn with only a pale flame, 
 Note the color of the flame. Caution ! Do not breathe 
 any of this gas, as it is a vigorous poison. What are 
 the chief properties of this new gas ? Compare it espe- 
 cially with the gas from which it was made. What do 
 you consider the new gas to be ? How formed ? How 
 distinguished from the first gas you made from carbon ? 
 This taking away of oxygen [or any similar substance] 
 from another substance is called reduction. Reduction 
 is the opposite of oxidation. Mention several cases of 
 oxidation we have already had. Mention several of 
 reduction, and tell in each of the latter by what means 
 the reduction was accomplished. 
 
 Note. If the non-combustible oxide of carbon did not 
 contain at least two parts of oxygen what would be left 
 in the bags when the zinc had taken to itself one part 
 of oxygen to form the zinc oxide that you saw in the 
 tube ? What was left in the bags ? Are we not justi- 
 fied, then, in writing the non-combustible oxide as if it 
 contained a double portion of oxygen? Let us here- 
 after call this oxide the dioxide of carbon. 1 
 
 The chemical change brought about in this experi- 
 ment may be represented by a diagram, thus : 
 
 1 The old-fashioned name for this oxide is carbonic acid. It is not, 
 however, an acid. 
 
OXIDATION. B7 
 
 Experiment 2O. 
 Oxidation of the Combustible Oxide of Carbon. 
 
 Have ready in a short, e.g., 25 cm , piece of combustion 
 tube 1 a small amount of the red oxide of mercury. 
 Attach an empty rubber bag to one end of the tube and 
 a bag containing the combustible oxide of carbon, made 
 in Ex. 19, to the other end. Heat the oxide of mercury 
 gently with a single Bunsen burner, and slowly pass the 
 gas from end to end. Note the effect on the oxide of 
 mercury. When no further effect is visible, cease passing 
 the gas and test for the combustible oxide of carbon, then 
 for the non-combustible. Use the flame test. How do 
 you explain the change that has taken place ? Draw a 
 diagram that will show the change. Let us hereafter 
 call this combustible oxide the monoxide of carbon. 2 
 
 Note. When charcoal instead of zinc is used in 
 Ex. 19, there result from the one bag of the carbon 
 dioxide two bags of the carbon monoxide. Explain 
 this doubling of volume. If these two volumes of 
 carbon monoxide should be passed over hot oxide of 
 mercury how many volumes of carbon dioxide would 
 result ? 
 
 Experiment 21. 
 
 Action of Zinc on Sulphuric Acid. 
 
 Make an experiment parallel to Ex. 14, but use zinc, 
 best in the granular form, where you there used iron. 
 
 1 Hard glass tube, with a bore of 10-20 mm . 
 
 2 Carbon monoxide is also called, correctly, carbonous oxide. Com- 
 pare the names of sulphurous and sulphuric oxides and acids. 
 
38 
 
 FACTORS AND PRODUCTS. 
 
 Be sure you omit no part of the experiment. Of what 
 simple substances are the crystals composed? Note. 
 This experiment teaches you one of the best ways 
 known for making large quantities of a certain gas. 
 What gas ? Draw diagrams to show the changes. 
 Compare the diagram of Ex. 14. 
 
 Experiment 22. 
 Action of Oxide of Zinc on Sulphuric Acid. 
 
 Proceed as in Ex. 21, but here use oxide of zinc. 
 Be sure you note how the oxide behaves when put into 
 pure water as well as when put into water and sul- 
 phuric acid. Why is hydrogen not given off in this 
 experiment as in Ex. 21 ? State what has happened 
 chemically in this [22d] experiment. Also state the 
 products of the chemical change. What were the 
 factors of the chemical change? What simple sub- 
 stances combined made each factor ? What simple sub- 
 stances combined make each product? What is a 
 chemical factor, what a product ? 
 
 Note that a diagram like the following will not only 
 show the simple substances in both factors and prod- 
 ucts, but will express the chemical change that has 
 taken place. 
 
 zinc 
 
 oxy. 
 
 A 
 
 hyd. < 
 
 oxy. 
 sul. 
 
SULPHIDE OF IRON. 89 
 
 Experiment 23. 
 Sulphides. 
 
 A. Mutual Action of Iron and Sulphur, when warmed ; or, 
 Formation of Sulphide of Iron. 
 
 Take about one-half a cc of iron filings and an 
 equal volume of flowers of sulphur. Mix well, then 
 heat well in a large bulb tube * or in a tt. Break the 
 tube and examine the substance formed. Let us call 
 this sulphide of iron. Get its chief properties. 
 Express the change thus : iron + sulphur = sulphide 
 of iron ; or thus : iron + sulphur = [g^ 11 ]. 
 
 B. Action of Hydrogen on Warm Sulphur ; or, 
 Formation of Sulphide of Hydrogen. 
 
 Generate hydrogen as follows : Place in a 250 CC flask 
 about 100 CC of water and about 20 CC of sulphuric acid. 
 Add about 30 g granular zinc. Have ready a tt, with 
 about 10 g sulphur [best in the form of roll brimstone] 
 in it ; also a tube to connect the hydrogen flask with 
 the tt, so that hydrogen can be conducted two thirds 
 of the way down into the tt of sulphur. The sulphur 
 tt should be fitted with a two-hole cork. Through one 
 hole of this cork enters the hydrogen tube, which 
 passes two thirds of the way down into the tt ; through 
 the second hole of the cork passes out an exit tube. 
 The exit tube, made of hard glass, should start even 
 with the lower surface of the cork, pass up through 
 the cork, then be bent at a right angle. Toward its 
 1 Same as Matrass of Ex. 5, A. 
 
40 StTLMlbti OF 
 
 outer end the exit tube should be drawn down to a 
 capillary tube and turned up at a right angle in the 
 midst of this capillary part. The capillary part should 
 have a total length of not less than 10 cm . Caution ! 
 Pass tne hydrogen till safe to light it at the tip of the 
 capillary tube. Prove that all is safe by the explosion 
 tube^ as in Ex. 9, C. Then boil the sulphur till the 
 vapor of the sulphur nearly fills the tt. If the hydro- 
 gen is still burning, blow out the flame. Note the odor 
 of the new gas coming. Let us call this new substance 
 sulphide of hydrogen. Of what must sulphide of 
 hydrogen be composed ? Place a Bunsen burner flame 
 under the exit tube just before it is narrowed to the 
 capillary part. What is the deposit in the capillary 
 part ? What, then, must be going off ? Light the jet 
 and see if your answer to the last question is correct. 
 Express all the chemical actions in the form of equa- 
 tions in a manner similar to that indicated for Part A 
 of this experiment. 
 
 C. Action of Sulphuric Acid on Sulphide of Iron. 
 
 State the simple substances that have gone to make 
 up each of these compounds. Put in a 250 CC flask 50 CC 
 water and 15 CC sulphuric acid. Warm somewhat. 
 Then put in 25 g sulphide of iron. When the action 
 begins catch in a dry fruit jar some of the gas formed. 
 Catch by displacement. How do you catch by dis- 
 placement? Do not warm after the sulphide of iron 
 has been added. What is the gas formed? Test a 
 jarful by the flame test. What are deposited on the 
 sides of the jar? What is left in the jar after the 
 
41 
 
 fire? Tell by the odor. How must this have been 
 formed? Get the properties of sulphide of hydrogen, 
 particularly odor and solubility. This gas is often 
 called sulphuretted hydrogen. In this experiment 
 what has happened to the sulphide of iron and to the 
 sulphuric acid? Answer this question after doing as 
 follows : Transfer the contents of the flask to a porce- 
 lain evaporating dish. Evaporate with a very gentle 
 heat till a little of the liquid taken out and cooled will 
 deposit crystals. Immediately filter the contents of 
 the dish. Cool the liquid which runs through and 
 examine the crystals deposited. What are these 
 crystals ? 
 
 Draw a diagram which will show the simple sub- 
 stances in both the factors and the products, and will 
 indicate the chief chemical change. 
 
 Experiment 24. 
 
 Copper. 
 A. The Properties of Copper. 
 
 Take some sheet copper and some copper wire. Get 
 the chief properties of copper, as color, lustre, hard- 
 ness, tenacity, etc. 
 
 B. Oxidation of Copper. 
 
 Take small pieces of copper wire. Proceed just as 
 in Ex. 1, B, but use copper instead of iron. What 
 shall we call the black coating formed on the bits of 
 wire ? Get the chief properties of this new substance. 
 
42 COPPER. 
 
 Save some for C. How much oxygen gas was taken 
 from the air in this experiment? 
 
 C. Reduction of the Black Oxide of Copper to Copper. 
 
 Take the black oxide of copper made in B. Place 
 this in a piece of hard glass tube. The tube best be 
 drawn out and turned up, as in the hydrogen sulphide 
 experiment. Generate hydrogen as in Ex. 23. When 
 it is desirable to generate a constant stream of hydro- 
 gen, it is well to have a thistle tube as well as a delivery 
 tube passing through the cork of the generating flask. 
 The lower end of the thistle tube should pass nearly to 
 the bottom of the flask. Why? Through the thistle 
 tube portions of a mixture of one volume of sulphuric 
 acid to five of water can be poured from time to time 
 as the action lessens. In this way no air is admitted, 
 as there would be if the stopper should be taken out 
 and the acid solution poured in. Caution ! Keep all 
 fire away. Why? Dry the hydrogen by passing it 
 through a catch-bottle of sulphuric acid. Then pass 
 the hydrogen through the hard glass tube and over the 
 oxide of copper. Test with explosion tube. When 
 safe, light the jet of hydrogen, and as the gas passes, 
 gently heat the oxide of copper. Note the phenomenon. 
 Explain. What becomes of the oxygen that was united 
 with the copper forming the oxide of copper ? Examine 
 your apparatus and see if your answer to the last ques- 
 tion is proved correct. What is left where copper 
 oxide was ? What is a reduction ? What is oxidation ? 
 Contrast reduction and oxidation. 
 
 Draw a diagram to show the chief chemical change 
 in this part of the experiment. 
 
MAGNESIUM. 43 
 
 Experiment 25. 
 Magnesium. 
 
 A. Properties of Magnesium. 
 
 Take some magnesium in the form of ribbon and 
 powder. Get the chief properties of magnesium. 
 Note particularly the color, lustre, tenacity, brittleness, 
 and weight. 
 
 B. Oxide of Magnesium. 
 
 Make this substance. Describe your method of prep- 
 aration. Get the chief properties of oxide of mag- 
 nesium. Save some of the oxide for C. 
 
 C. Action of Magnesium Oxide with Water. 
 
 Place some of the oxide from B on a piece of litmus 
 paper that has been turned slightly red with an acid. 
 Add a drop of water and note effect on the litmus. 
 Treat, in a tt, some more of the oxide with water. 
 Filter the contents of the tt. Evaporate the nitrate to 
 see if any considerable amount of magnesium oxide dis- 
 solved or formed a soluble compound. In filtering, the 
 liquid which filters through is called the nitrate, while 
 the substance left on the paper is called the precipitate. 
 
 D. Reaction of Magnesium and Sulphuric Acid. 
 
 Note. When two substances mutually act, i.e., act 
 each on the other, a reaction is said to take place. 
 Follow through the chemical change that takes place 
 when magnesium and sulphuric acid are allowed to 
 react with each other. What do you mean by reaction 
 
44 CALCIUM. 
 
 chemically? Describe this experiment in full. Make 
 use of your notes on all work with zinc and with sul- 
 phuric acid. What do you call the substances that are 
 the products in this case ? What would have been the 
 products if you had taken oxide of magnesium instead 
 of magnesium ? Draw diagrams to show the changes. 
 Note the tendency of magnesium, a metal, to push 
 the hydrogen from the acid, and to take the place of 
 the hydrogen it has driven out. Mention all other 
 cases you have dealt with in which a metal has pushed 
 the hydrogen from an acid. Mention two cases of this 
 kind in which the metal, when it began to act with the 
 acid, was itself already joined to another substance. 
 Watch for the manifestation of this power of a metal 
 in all your following work, and whenever you note it 
 make a record of it in your note-book. 
 
 Experiment 26. 
 
 Calcium. 
 A. The Properties of Calcium. 
 
 Examine a small bit of this interesting simple sub- 
 stance, and note its chief properties, as color, lustre,, 
 hardness, and ease with which the air acts upon it. 
 
 /'. Oxidation of Calcium. 
 
 Burn a small bit of calcium in a clean porcelain 
 crucible and identify the oxide as the same substance 
 as quick lime. Get the chief properties of oxide of 
 calcium. 
 
HYDROXIDE OF CALCIUM. 45 
 
 C. Reaction of Oxide of Calcium and Water. 
 
 Take a lump of quick lime weighing about 20 g . 
 Put it in a porcelain evaporating dish. Blow on it, 
 from the wash-bottle, water as long as the water is 
 absorbed. Do not add any more water than this. 
 Wait a few minutes for the change to take place. 
 Note phenomena. Remember that several times we 
 have made acids from oxides and water. With moist 
 litmus paper, both blue and red, test the properties 
 of the new substance here formed. Also test with 
 turmeric l paper. Test the solubility of the new sub- 
 stance by shaking some in a tt with water, filter- 
 ing, and evaporating the nitrate. Compare with the 
 solubility of the similar compound made from oxide 
 of magnesium and water. Let us call this new com- 
 pound hydroxide of calcium or hydrate of calcium. 
 Save about 10 g of it for E. What simple substances 
 are in hydroxide of calcium? What is slaked lime? 
 
 D. Action of Calcium on Water. 
 
 Have ready a short narrow tt, say, two or three 
 inches long and half an inch wide. Fit this tt with 
 a one-hole rubber stopper and delivery tube. The 
 delivery tube should be bent like an S, and its total 
 length should not be more than 4 or 5 inches. Also 
 have ready, instead of the pneumatic trough, a beaker 
 nearly full of water. Let there be standing in the 
 beaker an ordinary tt, inverted, and full of water. 
 Fill the short tt to its stopper with water, and put a 
 1 See Appendix C. 
 
46 SULPHATE OF CALCIUM. 
 
 small bit of calcium in this water. At once insert 
 the stopper and hang the apparatus, by means of the 
 S tube, over the edge of the beaker so that the gas 
 evolved shall go up and displace the water in the 
 long tt. With a flaming match test the gas evolved. 
 What is it ? Whence came it ? Evaporate the residue 
 in the short tt and note that hydroxide of calcium has 
 been formed. Explain its formation. 
 
 E. Reaction of Hydrate of Calcium and Sulphuric Acid. 
 
 What is another name for hydrate of calcium ? Take 
 about 10 g of powdered hydrate of calcium. Add about 
 30 CC of water. Stir till the hydrate of calcium is well 
 mixed with the water. Note consistency. Caution! 
 Protect the eyes from spattering, and add slowly, with 
 constant stirring, about 5 CC of sulphuric acid. Stir for 
 about two minutes. The sulphate of calcium forms 
 at once, and " sets up " pasty or even hard. Compare 
 its solubility with that of the sulphates of iron, zinc, 
 and magnesium. Draw a diagram to show the change. 
 
 Sulphate of calcium occurs in nature both with and 
 without water of crystallization. Gypsum is the kind 
 that has the water. If gypsum be heated [110-120 C.] 
 the water passes off. The residue is called plaster of 
 Paris. Put a bit of gypsum in a bulb-tube and heat. 
 Record observation. Plaster of Paris has the power 
 of again taking up water, and in so doing solidifies. 
 Make a paste of plaster of Paris and water and watch 
 it solidify. 1 Record observations. 
 
 1 A cast may be made by pressing into the soft plaster a coin whose 
 surface has been slightly greased and allowing the coin to remain till 
 the plaster has "set." 
 
CARBONATE OF CALCIUM. 47 
 
 F. Reaction of Hydrate of Calcium and Carbonic Acid. 
 
 Note. Recall the reactions of sulphuric acid and the 
 various substances you have tried with that acid. 
 
 Here use an aqueous solution of hydrate of calcium, 
 called lime-water, best made as follows. Take finely 
 powdered hydrate of calcium and mix with cold water. 
 Let settle for a few minutes. Pour off, and reject as 
 much of the liquid as possible, as it contains a con- 
 siderable amount of alkaline impurities dissolved by 
 the water from the lime. Mix this washed hydrate of 
 calcium with more cold water. Filter. Keep the 
 nitrate in a well-corked bottle. Take about 10 CC of 
 the hydrate of calcium solution and 20 CC of carbonic 
 acid water. 1 Mix, and heat in a beaker until the new 
 substance appears. Let settle, and decant, or filter. 
 Decant means to pour off carefully, without filtering, 
 a clear liquid from a precipitate that has settled from 
 the liquid. Examine the new substance and recognize 
 it as the same substance as powdered marble or chalk. 
 Let us call it carbonate of calcium. Test its solubility 
 in water. Why did it not appear [when the carbonic 
 acid and hydrate of calcium were mixed] until you 
 heated ? In order to answer the last question proceed 
 as follows. Put about 10 CC of lime-water in a tt. Add 
 
 1 The instructor should prepare the carbonic acid water by passing 
 carbon dioxide gas into a bottle half filled with cold water, and shak- 
 ing till the water has absorbed all the gas it can, or, better, buy the 
 water [soda water] from any soda-fountain keeper. Keep the carbonic 
 acid water in a tightly-stoppered bottle in a cool place. A beer bottle 
 with a rubber stopper that can be snapped down is good for keeping 
 this water. 
 
48 HARD WATER. 
 
 l cc , only, of carbonic acid water. Note result, then add 
 the other 19 CC of carbonic acid water and shake to mix. 
 Water which has dissolved sulphate of calcium is called 
 permanently hard water. Water [containing carbonic 
 acid, e.g., water which has made its way through swamps 
 where there is decomposing vegetable matter], which 
 has dissolved carbonate of calcium is called temporarily 
 hard water. Why is one called permanently hard and 
 the other temporarily? How may temporarily hard 
 water be made soft? Hard water is said to "kill" 
 soap. Prepare a solution of soap thus. Put about 
 one gram of shavings from soap in about 10 CC of water 
 in a tt. Shake till most of the soap has dissolved. 
 Have ready two tts, in one of which are 10 CC of 
 distilled water, and in the other an equal volume of 
 hard water, e.g., water that has been filtered from 
 sulphate of calcium, or water that, by means of car- 
 bonic acid, has been made to take up carbonate of 
 calcium. By means of a pipette, or long tube drawn 
 out at the end to a wash-bottle tip, take up some of 
 the clear soap solution and drop this, drop by drop, 
 alternately in the tt of pure water and in the tt of 
 hard water. Shake each tt after every two drops, 
 and note in which tt frothing is produced the sooner. 
 Note how many drops are required to produce frothing 
 in each case. What inference do you draw in regard to 
 the relative values of pure and hard waters for washing 
 purposes? Define stalactite. Define stalagmite. 
 
 When oxide of zinc acted with sulphuric acid, and 
 sulphate of zinc was formed, we concluded that the 
 reason no hydrogen was given off [as there was when 
 
LIME WATEK. 49 
 
 zinc and sulphuric acid were put together] was because 
 the hydrogen joined the oxygen of the zinc oxide and 
 formed water. Remember that hydrate of calcium is 
 made of oxide of calcium and water. If a similar 
 thing happens when sulphate of calcium is formed, 
 what simple things must there be in sulphate of cal- 
 cium? And if a similar thing happens when hydrate 
 of calcium and carbonic acid react to form the carbonate 
 of calcium, what simple things must there be in car- 
 bonate of calcium? As confirmation of your answer 
 to the last question, pass the non-combustible oxide of 
 carbon through a tt of hydrate of calcium in aqueous 
 solution [lime-water], and note that the same carbonate 
 of calcium is formed. Explain the formation, making 
 use of a diagram. 
 
 Note. Lime-water is a good test for the presence of 
 the non-combustible oxide of carbon because the two so 
 readily react and form carbonate of calcium. 
 
 [1] Hold a tt inverted over the flame of a candle. 
 Then add about 2 CC of lime-water. Shake, and note 
 effect. 
 
 [2] Try the products of combustion from the flame 
 of common house gas with lime-water. Also test the 
 gas itself for oxide of carbon. 
 
 [3] Take a tt half full of lime-water and, by means 
 of a glass tube reaching well into the lime-water, blow 
 your breath several times through the liquid. Note 
 effect, and explain. The non-combustible oxide of car- 
 bon, or carbon dioxide, is also called carbonic anhydride. 
 What is the meaning of the term anhydride? Why 
 applied to this oxide? 
 
50 ANALYSIS OF MARBLE. 
 
 G. Analysis of Marble [calcic carbonate]. 
 
 Note. We have already made a synthesis of marble. 
 What is a synthesis ? Mention several syntheses you 
 have made. Explain in full the synthesis of marble. 
 
 Take a piece of large hard glass combustion tube 
 about 15 cm long and closed at one end. [Best get a 
 piece of tube about 30 cm long and make two 15 cm 
 tubes by melting and pulling apart in the middle.] 
 Be sure the end is good and stout, not cooled too 
 quickly, and not ending in a lump of thick glass that 
 is likely to crack off when the tube is again heated. 
 Fit a cork and delivery tube to the open end. Put 
 in the tube about 10 g of coarsely powdered marble. 
 Caution ! Let the delivery tube dip only the least 
 possible distance below the surface of the pneumatic 
 trough, as deep dipping causes back pressure which is 
 apt to blow out the softened glass. Heat the marble 
 with a blast>-lamp. Apply the blast gently at first. 
 Collect in tts the gas evolved. Test it. What is 
 it? Prove that your inference is correct. [See note 
 at end of I 1 .] State how you have already proved of 
 what this constituent of marble is composed. As it 
 is impossible to make all the gas come off in a closed 
 tube, i.e., without a current to carry it away, take a 
 small lump of marble, hold it with forceps, and heat 
 in the blast-lamp flame till it glows brightly. Note 
 the lime [or calcium] light. Examine the residue, and 
 recognize it as quick lime, i.e., oxide of calcium. How 
 did you form oxide of calcium ? [See B.} 
 
 Mix well one gram of powdered oxide of calcium 
 with half a gram of powdered magnesium. Put the 
 
MARBLE AND ACID. 51 
 
 mixture in a small dipper. Caution! Keep the eyes 
 away. Heat over a Bunsen burner flame. The mag- 
 nesium takes the oxygen away from the calcium with 
 great eagerness. Note phenomena. Have ready the 
 short tt and fittings used in D. Put the contents of 
 the dipper in the tt. Nearly fill the tt with water. 
 Put in the stopper quickly. Catch the gas given off. 
 What is it ? Use the flame test. What does the evolu- 
 tion of this gas prove in regard to the chemical change? 
 What happened to the magnesium? Arrange your 
 analysis in the form of a table. What is an analysis ? 
 
 H. Reaction of Marble and Sulphuric Acid. 
 
 State the simple substances that make marble. State 
 the simple substances that make sulphuric acid. Take 
 10 g of powdered marble. Put them in a flask, add 30 CC 
 of water and then 6 CC of sulphuric acid. Catch the gas 
 evolved, and test it. What is it ? How do you prove 
 your answer correct ? 
 
 Note how the new white substance formed collects 
 around the marble, prevents the acid from coming in 
 contact with the marble, and thus hinders the action. 
 If the new white substance was readily soluble in the 
 water, there would be no such hindrance. Many sub- 
 stances which are soluble in water are not soluble in 
 sulphuric acid, hece in many cases, e.g., in the prep- 
 aration of hydrogen by means of zinc and sulphuric 
 acid, and in the preparation of sulphide of hydrogen 
 from sulphide of iron and sulphuric acid, it is necessary 
 to use water to dissolve some product which otherwise 
 would retard, if not actually prevent, the action. 
 
52 SODIUM. 
 
 Evaporate the residue from the flask and recognize 
 it as sulphate of calcium. If there are bad fumes on 
 evaporating, put the residue under the hood, 1 and evap- 
 orate there. Prove that the residue is not carbonate 
 of calcium. How do you prove this? Explain the 
 chemical change that has taken place. How can you 
 detect a carbonate ? 
 
 Experiment 27. 
 
 Sodium. [Latin name, Natrium.] 
 A. The Properties of Sodium. 
 
 Examine a small bit of sodium, 2 and get the chief 
 properties, particularly color, lustre, hardness, and 
 attraction for oxygen. Caution! The attraction of 
 sodium for oxygen makes sodium a dangerous sub- 
 stance to handle. When experimenting with sodium 
 keep it away from every substance that has oxygen, 
 e.g., water, and the moisture of your hand, even. 
 
 B. Oxidation of Sodium. 
 
 Let a bit of freshly cut sodium be exposed to the 
 air for five seconds. What happens? What is the 
 coating formed? Place a bit of sodium in a porce- 
 lain crucible and, protecting the eyes by a glass plate, 
 warm. Note phenomenon. Save some of the result- 
 ing substance for C. 
 
 1 See Appendix G. 
 
 2 Sodium is a dangerous substance if handled carelessly, or allowed 
 to get into water. It should be kept under kerosene, or some similar 
 liquid, whenever not in use, 
 
SODIUM WITH WATER. 53 
 
 C. Reaction of Oxide of Sodium and Water. 
 
 Treat the oxide of sodium made in B with a few 
 drops of water. Protect the eyes as in B. Test the 
 solution with test papers. Is it acid or the opposite? 
 Compare with the action of other oxides and water. 
 Filter, if dirty, and evaporate to dryness. Examine 
 the new substance, and let us call it hydrate [or better, 
 hydroxide] of sodium. Why call it hydroxide ? Why 
 hydrate ? Rub a little sodium hydroxide between the 
 fingers and note the greasy feeling. Put a little 
 hydroxide of sodium on the bottom of a beaker and 
 leave it exposed to the air for an hour. The peculiar 
 property thus manifested is called deliquescence. 
 What is deliquescence? 
 
 Note. Substances that have the opposite effect from 
 acids on test papers are said to be alkaline. 
 
 D. Action of Sodium on Water. 
 
 Have ready, in a beaker, about 100 CC of cold water 
 and a tt, upside down, filled with water. Make a little 
 wire gauze net on the end of a wire. Wrap a bit of 
 sodium, not larger than a small pea, in the gauze and 
 plunge it below the water. Catch, in the invested tt, 
 the gas evolved. Caution! Keep the eyes well pro- 
 tected, for if the sodium gets out of the gauze an 
 explosion is likely to follow. Why? Examine the 
 gas caught. What is it? Filter the liquid left in 
 the beaker, if any impurities from the gauze have got 
 in. Evaporate to dryness in a porcelain dish. Test 
 a bit of the substance with moist test papers, and by 
 feeling. What is it ? Explain its formation. 
 
54 NEUTRALIZATION. 
 
 E. Reaction of Sodium Hydroxide and Sulphuric Acid. 
 
 Make two aqueous solutions as follows : [1] Take 
 100 CC of water and 5 CC of sulphuric acid. [2] Take 
 100 CC of water and 8 g of hydroxide of sodium. Have 
 ready a porcelain evaporating dish. Fill about one 
 fourth of the dish with the sulphuric acid solution, and 
 add about as much hydroxide solution. Stir. Then 
 add first one and then the other till drops taken out 
 on a rod and touched to test papers show the contents 
 of the dish to be neutral, i.e., neither acid nor alkaline. 
 Note, this process is called neutralization. Evaporate 
 the liquid in the dish to crystallization. Examine the 
 crystals, and get their properties. What are they? 
 Compare Ex. 26, JE. Compare also the formation of 
 the products in Exs. 21, 22, 23, 0, and 25, D. Explain 
 the formation of the compound in this case. What 
 simple things in this compound? Is any water of 
 crystallization present? Test the answer to the last 
 question by experiment. 
 
 F. Reaction of Sodium Hydroxide and Carbonic Acid. 
 
 Make an aqueous solution of sodium hydrate of the 
 proportions l g hydrate and 20 CC water. Take about 
 10 CC of carbonic acid solution, and add the solution of 
 hydroxide of sodium till the liquid is no longer acid. 
 Evaporate to dryness. Examine the residue. What 
 is it? It is composed of what simple substances? 
 What is sal soda? Test sal soda for a carbonate. 
 Leave a good clear crystal of sal soda exposed to the 
 air for an hour or more. Note the phenomenon. The 
 property that here manifests itself is called efflores- 
 
SODIUM AMALGAM. 55 
 
 cence. What is efflorescence? Compare with deli- 
 quescence. 
 
 G. Reaction of Hydrate of Sodium and the Non- 
 Combustible Oxide of Carbon. 
 
 Take 0.5 s of hydrate of sodium. Dissolve it in a tt 
 half full of water. Pass the dioxide of carbon through 
 the liquid for about two minutes. Evaporate to dryness. 
 Examine the residue. Dissolve the residue in 5 CC of 
 water, and test for a carbonate. Explain the formation 
 of a carbonate in this case. 
 
 H. Reaction of Carbonate of Sodium and Sulphuric Acid. 
 
 Parallel to E. State factors and products. Give 
 results in full, explaining, particularly, the chemical 
 change. 
 
 I. Reaction of Sodium and Mercury. 
 Caution ! Caution ! Caution ! 
 
 Use extreme care and do not let particles fly in your 
 eyes when the two substances join. 
 
 Take a bit of sodium and a globule of mercury. 
 Support the cover to a porcelain crucible on a ring 
 of the ring stand. Warm the cover. Pour on a 
 globule of mercury about 2 mm in diameter. Then put 
 a bit of sodium of about the same size near the mer- 
 cury. Set the stand on the floor. Stand at a distance, 
 and poke, with a long rod, the sodium into the mercury. 
 Note phenomena. Examine the resulting product. A 
 substance formed from mercury and another metal is 
 called an amalgam. This then is sodium amalgam. 
 
56 CHLOUItfE. 
 
 Throw the amalgam into a small dish of water. Note 
 that the sodium acts as pure sodium, but less rapidly, 
 and that [after a few hours], when the sodium is all 
 gone [into what?], the original mercury remains. Give 
 chief properties of sodium amalgam. 
 
 Review your work with sodium and its compounds, 
 and make diagrams to express the chemical changes 
 that you have brought about. 
 
 Experiment 28. 
 Chlorine. 
 
 Take a jar of chlorine. 1 Get the chief properties of 
 chlorine, particularly its color and odor. Also note its 
 action on moist litmus. Caution! Chlorine is very 
 irritating to the mucous membranes. In getting the 
 odor, breathe only the least possible amount. In large 
 quantities chlorine is a violent poison. 
 
 Experiment 29. 
 
 Chlorides. 
 
 A. Chloride of Hydrogen. 
 Caution ! Caution ! Caution ! 
 
 Chlorine and hydrogen unite with frightful violence. 
 Always think what you are going to do with chlorine 
 before you act. Never let hydrogen and chlorine mix 
 
 1 Chlorine gas should be provided by the instructor and given, in tts 
 and fruit jars, to the students as needed. For a method for preparing 
 chlorine, see Appendix H. 
 
CHLOKIDE OF SODIUM. 57 
 
 accidentally. Never let a mixture of chlorine and 
 hydrogen remain standing in the light or near a fire. 
 A mixture of chlorine and hydrogen explodes sponta- 
 neously if left in the sunlight. Finally, use your 
 utmost good judgment. 
 
 Have ready a jar of chlorine gas and a flask that is 
 delivering hydrogen gas through a rubber tube ending 
 with a "hard glass wash-bottle tip. When safe, light 
 the stream of hydrogen gas, carefully raise the cover a 
 little from the jar of chlorine, and slowly pass the hydro- 
 gen flame down into the chlorine. Note the change 
 in the flame as chlorine, instead of oxygen, joins the 
 hydrogen. Note the properties of the product of the 
 union, particularly state and acidity. Chloride of 
 hydrogen is commonly called hydrochloric acid. 
 
 B. Chloride of Sodium. 
 
 Have ready a tt of dry chlorine, and a piece of freshly- 
 cut sodium. The piece of sodium should be a slice cut 
 very thin, and large enough to cover about one quarter 
 of the nail of your little finger. Keep the tt well away 
 from the eyes. Drop the sodium in the tt. Cork, and let 
 stand over night. Spread out the new substance to air. 
 Get the properties. Try, by taste, to recognize it as 
 common table salt. Do not taste if any unchanged 
 sodium remains. Why? What simple substances form 
 table salt ? Let us call it chloride of sodium. 
 
 C. Preparation of Hydrochloric Acid on a Large Scale. 
 
 Take sulphuric acid and table salt. State the simple 
 substances that make up each of these compounds. 
 
58 HYDROCHLORIC ACID. 
 
 Have ready a small flask with cork and delivery tube. 
 Put about 10 g of the chloride of sodium in the flask. 
 Add about 15 CC of sulphuric acid. Warm if necessary 
 to start the action. Catch the gas by displacement. 
 It will be found to be a heavy gas. Why not here use 
 the water trough for catching ? Fill at least three jars. 
 Be sure the jars are/^ZZ. Tell when full by the smell. 
 What is this gas? How have you made it before? 
 Now get the properties of this gas. Explain its for- 
 mation from table salt and sulphuric acid. Make a 
 diagram to show the simple substances, and their 
 change of place. Compare the action of sulphuric 
 acid in this case with its action on sulphide of iron. 
 State the factors and the products in both cases. Save 
 two jars of hydrochloric acid gas for subsequent use. 
 
 D. Solubility of Hydrochloric Acid. 
 
 
 Take a jar of hydrochloric acid gas [made in C]. Put 
 
 in about 20 CC of water. Snap on the cover. Shake. 
 Open under water. Is the gas soluble ? Test, with 
 litmus, for the acid property of the liquid. For con- 
 venience in handling, hydrochloric acid is usually sold 
 in aqueous solution. The crude hydrochloric acid of 
 trade is called muriatic acid. It is yellow from 
 impurities. 
 
 E. Reaction of Hydrochloric Acid and Marble. 
 
 Have ready a small flask fitted with a one-hole cork 
 and delivery tube. Put a few lumps of marble in the 
 flask, and cover them with aqueous hydrochloric acid. 
 Catch the gas evolved and test it. What is it? After 
 
HYDEOCHLOKIC ACID. 59 
 
 the acid has ceased acting, remove any marble that may 
 be left, and evaporate the liquid to dry ness. Of what 
 is marble composed? What then must be the residue 
 from evaporation? Note the chief properties of chlo- 
 ride of calcium. Leave a little exposed for an hour 
 or two to the air of the laboratory. What property do 
 you note ? Why is chloride of calcium a good chemical 
 with which to dry gases and other substances ? 
 
 Had sal soda been used in this experiment instead of 
 marble, what gas would have been given off, and what 
 would the residue on evaporation have been ? 
 
 Draw diagrams to show the reactions, both when marble 
 was used and in a case in which sal soda is substituted. 
 
 Note. This experiment teaches the best way to pre- 
 pare a certain gas on a large scale. What gas? 
 
 F. Action of Sodium on Hydrochloric Acid. 
 
 Have ready a jar of hydrochloric acid gas and some 
 sodium amalgam. To insure success the jar must be 
 full of the gas, and the sodium amalgam must have 
 been recently made, and freshly broken into very small 
 pieces. 1 The hydrochloric acid gas must have been 
 dried by passing it through a catch-bottle of sulphuric 
 acid, or there will be danger of an explosion. Why? 
 Nor must there be any moisture in the jar at all. Be 
 sure the washer to the jar is well greased. 
 
 Sodium amalgam is here used, instead of pure sodium, 
 because the mercury modifies the action of the sodium 
 and makes it controllable. That the mercury itself 
 does not act, to any appreciable extent, on the acid, may 
 
 1 For the preparation, on the large scale, of sodium amalgam see 
 Appendix I. 
 
60 POTASSIUM. 
 
 be shown, after the experiment, by noting that the 
 mercury, in liquid form, may be found in the trough. 
 
 To the jar of hydrochloric acid gas add about 25* 
 of sodium amalgam. Shake well. Note phenomenon. 
 Open under water. At once note how much vacuum 
 there was, at the same time letting the unused amalgam 
 drop into the trough. [A zinc trough must not be 
 used here because mercury amalgamates with zinc and 
 makes it brittle.] Put the cover on at once, but do 
 not seal, for, if any amalgam is left in the jar, there 
 may be an explosion. Why ? At once apply a flame 
 to the gas remaining in the jar. What gas is this? 
 Of what is hydrochloric acid made? What becomes 
 of the chlorine in this experiment? 
 
 O. Action of Sodium Hydroxide with Hydrochloric Acid. 
 Dissolve about 5 g of sodium hydroxide in about 50 CC 
 of water. Neutralize this solution with one of some- 
 what diluted hydrochloric acid. Evaporate till crystals 
 'begin to form. Examine the crystals and recognize 
 them by their color, form, and taste as table salt. 
 Explain their formation. What was the other product 
 of the chemical change ? Draw a diagram. 
 
 Experiment 3O. 
 Potassium. [Latin name, Kalium.] 
 
 Note, as you work with potassium, how closely it 
 resembles sodium, and how much like sodium com- 
 pounds are the corresponding potassium compounds. 
 Caution ! Same as in the use of sodium. 
 
POTASSIUM COMPOUNDS. 61 
 
 A. The Properties of Potassium. 
 
 Examine a small bit of potassium and get its chief 
 properties ; particularly, color, lustre, hardness, and 
 affinity for oxygen. Note that it has metallic prop- 
 erties. Is it a metal? 
 
 11 Oxidation of Potassium. 
 
 Take a bit of potassium and place it on a crucible 
 cover exposed to the air. Cut the potassium to expose 
 more surface to the oxygen of the air. Note the 
 rapidity of the oxidation. 
 
 C. Reaction of Oxide of Potassium and Water. 
 Parallel to Ex. 27, O. 
 
 D. Reaction of Potassium and Water. 
 
 Have ready a fruit jar with enough water in it to 
 cover the bottom. Drop in a bit of potassium as 
 large as a small pea. Instantly step back two yards 
 or more. Note phenomena. Explain the action com- 
 pletely. Evaporate the liquid to dryness. Test a 
 bit of the residue with moist test papers and by feeling. 
 What is it? Explain its formation. 
 
 E. Action of Potassium on the Dioxide of Carbon. 
 
 Have ready a piece of hard glass tube about 10 inches 
 long. Also a generator which is delivering dry car- 
 bonic dioxide. [See note at end of Experiment 29, E.'] 
 Put in the tube a piece of potassium as large as a small 
 pea. Attach the tube to the generator, and clamp 
 
62 POTASSIUM COMPOUNDS. 
 
 it at a convenient height for heating with a Bunsen 
 burner. Pass the oxide of carbon until it will put out 
 a match at the open end of the tube. Then warm the 
 potassium. Note that it burns at the expense of the 
 oxygen of the carbonic dioxide. Note the black particles 
 of carbon that have lost their oxygen: note also the 
 white powder. What is the latter? Answer this as 
 follows: After the action has ceased and the tube is 
 cool, wash out the tube into a beaker, using as little 
 water as possible. Filter from the carbon. Test the 
 nitrate for a carbonate. How test? Explain com- 
 pletely the formation of a carbonate. 
 
 F. Reaction of Potassium Hydroxide and Sulphuric Acid. 
 
 Parallel to Ex. 27, E. Examine the sulphate of 
 potassium carefully, as you will be referred to this 
 again. Note particularly the color, form, and taste 
 of the crystals. Hold some in a Bunsen flame and 
 note flame coloration. Heat some of the crystals in 
 a porcelain dish and note that no water of crystalliza- 
 tion is present. Be sure you can recognize this substance 
 again. 
 
 Draw a diagram to show the chemical reaction. 
 Also note the invariable tendency, again manifested 
 in this change, of a metal to push the hydrogen from 
 an acid. Mention all the other cases you can recall 
 in which this tendency has been manifested. 
 
 Test the flame coloration of all the potassium com- 
 pounds you can find. Note the flame coloration pro- 
 duced by table salt. Test the flame coloration of all 
 the sodium compounds you can find. 
 
NITROGEN. 63 
 
 Experiment 31. 
 Nitrogen. 
 
 We early learned that about one fifth the volume of 
 the air is oxygen. Let us now examine the other 
 constituent. Have ready a large cork with a little 
 hollow dug out of its smaller end. Put about 0.3 g 
 of phosphorus in the hollow of the cork. Float the 
 cork on water in the pneumatic trough. Set fire to 
 the phosphorus, and invert a jar of air over the burning 
 phosphorus. What becomes of the oxygen of the air? 
 What becomes of the oxide of phosphorus ? Examine 
 the remaining gas. Compare it with all the gases you 
 have made. Let us call it nitrogen. Give the prop- 
 erties of nitrogen. 
 
 Experiment 32. 
 
 A Chemical Investigation. 
 
 There is often found as an efflorescence from the soil 
 in hot countries, especially in Bengal, Egypt, Persia, 
 and a few places in America, a white substance of a 
 salt-like nature called nitre or saltpeter. This sub- 
 stance is used largely for making gunpowder, and often 
 for making one of the most powerful acids known, 
 nitric acid. Let us direct an investigation to finding 
 what simple substances are in nitre, and what ones are 
 in nitric acid which is made from nitre. First let us 
 prepare nitric acid. 
 
64 A CHEMICAL INVESTIGATION. 
 
 A. Preparation of Nitric Acid. 
 
 Take nitre and sulphuric acid. Put in a small, 
 tubulated, glass-stoppered glass retort, 30 g of nitre 
 and 10 CC of sulphuric acid. Heat, gently at first, 
 using a tripod and gauze. Caution ! Do not put 
 the hand where the molten mass or the acid could harm 
 it, should there be an accident. Distil 10 or 15 CC of 
 liquid, letting it drop so slowly that little or none 
 of the vapor fails to condense. Get the properties of 
 the liquid. It is so powerful that before testing it 
 with test papers for acid properties, some of it should 
 be diluted with several times its volume of water or 
 it will destroy the paper itself. Let us call the liquid 
 nitric acid. Have ready about 100 CC of water heated 
 to 80 or 90 C. When the liquid in the retort has 
 cooled somewhat, insert a funnel in the tubulature of 
 the retort, and cautiously pour the hot water directly 
 into the midst of the liquid. Caution! If the con- 
 tents of the retort are too hot, there is danger that the 
 hot water will be converted into steam so rapidly that 
 an explosion may result, and if too cold, crystals may 
 fix themselves so firmly to the sides of the retort that 
 they cannot be removed without danger of breaking 
 the glass. When the water is all added, stir the con- 
 tents of the retort till the crystals are either dissolved 
 or broken enough to be removed. Fill an evaporating 
 dish with the liquid from the retort. Evaporate to 
 crystallization. Examine the crystals. Test the flame 
 coloration produced by these crystals and satisfy your- 
 self by color, taste, form, etc., that you now have the 
 same substance made in Ex, 30, F. [It may be neces- 
 
A CHEMICAL INVESTIGATION. 65 
 
 sary, before you can get good crystals, to wash out the 
 sulphuric and nitric acids that remain. Do this wash- 
 ing by putting the crystals oh a filter, in a funnel, and 
 letting a very small amount of cold water run through. 
 Why not let much water run through? It would be 
 well to recrystallize the substance from hot water to 
 purify it.] What is the substance in hand ? Of what 
 simple substances is it formed? Remembering the 
 effect of metals on the hydrogen of acids, what do you 
 say here came from the sulphuric acid? What from the 
 nitre ? What then did the sulphuric acid lose, and what 
 became of this that left the sulphuric acid? Review 
 all the acids that you have made, i.e., sulphurous, 
 sulphuric, phosphoric, carbonic, hydrochloric, and note 
 that all have hydrogen in them. What, then, do you 
 say is one simple substance in nitre? What is one 
 simple substance in nitric acid? As confirmation of 
 your belief that there is hydrogen in nitric acid allow 
 magnesium to act on some of the acid, as follows. 
 
 B. Action of Magnesium on Nitric Acid. 
 
 Have ready a tt fitted with a one-hole cork and 
 delivery tube reaching to a pneumatic water trough. 
 Put about 5 CC of nitric acid in the tt, and add about 
 10 CC of water. Put in a small strip of magnesium 
 ribbon, and at once insert the cork and catch the 
 gas in a tt at the trough. Apply a flame. What 
 gas is present? 
 
 C. Action of Copper on Nitric Acid. 
 
 Take copper and nitric acid. Put about 50 g of 
 copper clippings in a small flask. The flask should 
 
66 CHEMICAL INVESTIGATION. 
 
 have a two-hole cork through which passes a funnel 
 tube as well as a delivery tube. Add enough water 
 to seal the funnel tube. Then add a mixture of 1 vol. 
 of nitric acid to 1 vol. of water. Add this mixture 
 a little at a time. Collect the gas over water. Catch 
 three jars of it. Reject the first. Why? Get the 
 properties of the gas from the second. Is it hydrogen ? 
 Note that on exposure to the air it oxidizes spontane- 
 ously, and the oxide formed is brown. In the third 
 jar of gas burn about 0.3 g of phosphorus. Have the 
 phosphorus well on fire before plunging into the jar. 
 Take all the usual precautions. Note the formation of 
 the white oxide of phosphorus. Therefore the sub- 
 stance under examination had oxygen in it. How 
 much oxygen ? Answer this by opening under water. 
 From what sources may the oxygen have come ? Test 
 the residual gas. Use the flame test. Is it carbonic 
 dioxide or nitrogen? Whence came this gas? What 
 simple substances have we now proved to be in nitric 
 acid? 
 
 D. Action of Carbon on Nitric Acid. 
 
 Take nitric acid and charcoal. Put in a Kjeldahl 
 flask about 50 CC of nitric acid. Add three or four 
 sticks of charcoal, each about as large as your little 
 finger. Have a delivery tube leading to a catch-bottle 
 containing water to catch any nitric acid that may pass 
 over. Why must the acid be caught? Answer this 
 question after the experiment is finished. Warm the 
 nitric acid till gas passes off freely. After the gas has 
 passed long enough to remove all air from the flask, 
 catch-bottle, and tubes, collect some in Us and examine 
 
A CHEMICAL INVESTIGATION. 67 
 
 it. What is it? Pass some into a tt containing an 
 aqueous solution of calcic hydroxide. What happens ? 
 Explain the formation of the gas in the Kjeldahl flask. 
 What third simple substance must there be in nitric 
 acid? 
 
 Note the vigor of nitric acid as follows. Put about 
 30 CC of nitric acid in a porcelain evaporating dish. 
 Add a piece of cloth. Warm. Stir with a glass rod. 
 Note effect on cloth. Stir the hot solution with a 
 piece of wood. Note effect on wood. How do you 
 explain the action on cloth, and on wood? 
 
 E. Reaction of Nitric Acid and Potassium Hydroxide. 
 
 Parallel to Ex. 30, F, except that you use nitric acid 
 instead of sulphuric. Examine the resulting substance. 
 Remembering the effect of metals on the hydrogen of 
 acids, state what you think has been the change in 
 this case, also what new substances have resulted, and 
 of what simple substances each is composed. Let us 
 call the white substance resulting nitrate of potassium. 
 
 Note. The substance resulting from the replacement 
 of hydrogen in an acid by a metal is called a salt, e.g., 
 sulphates of calcium, magnesium, zinc, iron, etc., car- 
 bonates of calcium, potassium, etc., nitrates of sodium, 
 potassium, etc., are all salts to the chemist, as well as 
 chloride of sodium. The last we have made by neutral- 
 izing hydrochloric acid with sodium hydroxide, as well 
 as by the union of chlorine and sodium. 
 
 Identify, by color, form, taste, flame coloration, etc., 
 the nitrate of potassium formed in this experiment as 
 nitre or saltpeter. 
 
68 AMMONIA. 
 
 Finally answer our original questions. What is 
 nitre, and of what simple substances composed ? 
 What is nitric acid, and of what simple substances 
 composed ? 
 
 To the Student. Up to this point you have worked 
 out everything by yourself. You have yourself proved 
 everything asked. However pleasant it may have been 
 to discover all the truth for yourself, it is obviously 
 unadvisable to proceed in this manner throughout your 
 work in chemistry. Life is too short for you to prove 
 to your own satisfaction all that has been discovered 
 by all the workers in the field of chemistry in all the 
 years. Now that you have completed a somewhat 
 elaborate chemical investigation, and have learned how 
 the pioneers of chemistry attack their problems, you 
 are going to be asked to take much on faith, that is, 
 you are going to be asked to believe many statements 
 of facts without stopping to verify all. 
 
 Experiment 33. 
 
 Ammonia. 
 
 A. Preparation of Ammonia. 
 
 Take the colorless oxide of nitrogen of Ex. 32, (7, 
 and hydrogen. Prepare two jars of this colorless oxide 
 of nitrogen as in Ex. 32, C. Also prepare five jars of 
 hydrogen gas, free from air but not, necessarily, dry. 
 Have ready in, a pail, or tub, of water a bottle [large 
 
AMMONIA. 69 
 
 enough to hold all the gases J ], inverted, and full of 
 water. Insert a large funnel in the neck of the bottle 
 and pour the oxide of nitrogen and the hydrogen up 
 into the large hottle. 2 Be careful, and do not spill any 
 of the gases. The large bottle should be fitted with a 
 two-hole rubber stopper. Through one hole let a piece 
 of straight glass tube about 15 cm long pass, and through 
 the other let a piece of glass tube bent at right angles 
 pass just through the stopper. The straight piece 
 should pass well into the bottle, and each should have 
 a few cm of rubber tube attached to its outer end. 
 Let each rubber tube have a pinch-cock. 
 
 Remove the funnel from the large bottle, insert the 
 stopper with its tubes closed, and take the bottle from 
 the pail. Connect the straight glass tube, by means 
 of its rubber tube, to the water tap. Connect the 
 bent glass tube to another tube containing platinum 
 sponge or platinized asbestos. Let there be a catch- 
 bottle containing water put just before the tube con- 
 taining the platinum. Turn on the water, and force 
 the gases through the water of the catch-bottle, and 
 note the bubbles, in order to tell how fast the gases 
 
 1 If you have not a bottle large enough, you can halve the amounts 
 of the gases used, i.e., take one jar of oxide of nitrogen, and two and 
 one half jars of hydrogen. 
 
 2 If you have not the pail and large funnel, you can proceed as 
 follows. Take the large bottle and pour into it two jarfuls of water. 
 Make a mark at the height to which the water reaches. Then pour in 
 five more jarfuls, and make another mark at the height of the seven 
 jarfuls of water. Next fill the remainder of the bottle with water, 
 invert it on the bridge of the pneumatic trough, and pass the two gases, 
 first the oxide of nitrogen, then the hydrogen, directly from the 
 generating flasks into the bottle, stopping the flow of each when the 
 water has fallen to the proper mark. 
 
70 AMMONIA FOUNTAIN. 
 
 are passing. Gradually force the mixed gases out 
 over the platinum. When the gases have driven all the 
 air from the catch-bottle, and not before, heat the 
 platinum. If the heat is applied before the air has 
 gone, there is danger of an explosion in the catch- 
 bottle. Why? Note the formation of water. From 
 what is it made? Note the formation of a new gas. 
 Note its odor and action on moist test papers. Of 
 what is it composed ? Let us call it ammonia. Pass 
 some of the new gas into a tt containing a little water, 
 and note that the water dissolves the gas. Try the 
 action of the water solution on test papers. A water 
 solution of the gas is sold in trade as " aqua ammonia." 
 
 1>. Ammonia Fountain. 
 
 In order to show the great solubility of ammonia 
 and the alkaline properties of aqua ammonia, make an 
 ammonia fountain as follows. Have ready two 250 CC 
 flasks, 1 each fitted with a good tight cork. Arrange a 
 stand with a ring so that one flask can be supported, 
 inverted, just above the other. Pass a glass tube 
 through a hole in the cork of the lower flask so that 
 it reaches to the bottom of the flask and projects about 
 an inch above the cork. Through the cork in the 
 upper flask pass a piece of tube drawn out to a fine 
 point like the wash-bottle tip. The opening of the tip 
 should have a diameter not less than l mm and not more 
 than 2 mm . The tip should end at about the middle of 
 the upper flask. Connect the glass tubes by a rubber 
 connector. Bore a second hole in the cork of the lower 
 
 1 Kjeldahl are best because they can stand more pressure without 
 breaking than can ordinary flasks. 
 
SALTS OF AMMONIUM. 71 
 
 flask and pass a bit of glass tube bent at a right angle 
 through it to admit air. Fill the lower flask one half 
 or two thirds full of water. Add enough red [acid] 
 solution of litmus to color the water distinctly red. 
 Take the upper flask from its support, and fill it full 
 of ammonia. Best prepare the ammonia by putting 
 about 50 CC of commercial aqua ammonia in a flask and 
 heating to drive off the gas. Conduct the gas into the 
 flask by a rubber tube. Ammonia is a light gas com- 
 pared with air. Get the flask full of ammonia gas. 
 At once insert the cork and put the flask in position. 
 Then connect with the lower flask. Blow, a little, in 
 the air vent of the lower flask to start the fountain. 
 Step back, as the flask may burst from the violence of 
 the action. Note phenomena [physical and chemical]. 
 Explain. 
 
 C. Salts of Ammonium. 
 
 What is a salt, chemically? How have we made 
 salts? 
 
 An aqueous solution of ammonia behaves much like 
 an aqueous solution of sodium [or potassium] hydroxide. 
 It is alkaline to test papers, and will react with acids 
 and form white salt-like substances ; in fact, it seems 
 as though hydrogen and nitrogen together act like a 
 metal. When thus acting together they are given the 
 name of ammonium. Thus aqua ammonia is con- 
 sidered a solution of ammonium hydroxide. 
 
 1. CHLORIDE OF AMMONIUM. 
 
 Neutralize about 10 CC of aqua ammonia [diluted with 
 30 CC of water] with hydrochloric acid, also diluted. 
 
72 OXIDES OF NITROGEN. 
 
 Evaporate to crystallization. Examine the product. 
 What shall we call it? Put a little of this product 
 in the bottom of a dry tt. Heat gently. Note subli- 
 mate on the sides of the tt. What is sublimation ? 
 
 2. SULPHATE OF AMMONIUM. 
 
 Make this substance, and describe it. Will it 
 
 sublime ? 
 
 3. NITRATE OF AMMONIUM. 
 
 Make this substance, and describe it. 
 
 Experiment 34. 
 Oxides of Nitrogen. 
 
 Note that we have already made two oxides of 
 nitrogen : one a colorless gas, the other a brown gas. 
 Review "A Chemical Investigation," Part (7, and now 
 state the proportion of oxygen to nitrogen [by volume] 
 in the first, or colorless, oxide of nitrogen. What can 
 you say in regard to the amount of oxygen in the 
 second, or brown, oxide, compared with the amount 
 in the first? 
 
 There are other compounds known which contain 
 nitrogen and oxygen only. Of these perhaps the most 
 interesting is the so-called nitrons oxide or laughing- 
 gas. Nitrous oxide is best prepared by decomposing 
 ammonium nitrate by heat. Water and laughing gas 
 are the products of this decomposition. 
 
 Take about 10 g of ammonium nitrate. Heat this 
 gently in a large tt fitted with a one-hole cork and a 
 
OXIDES OF NITROGEN. 73 
 
 delivery tube. Conduct the gases through three catch- 
 bottles. Let the first catch-bottle contain no liquid, 
 but be kept cold to condense the water formed in the 
 decomposition of the nitrate. Let the second catch- 
 bottle contain a little aqueous solution of hydroxide 
 of sodium, to catch any acid-forming fumes. Let the 
 third catch-bottle contain a little aqueous solution of 
 sulphate of iron, to catch any of the [harmful] color- 
 less nitric oxide that may be formed as a by-product. 
 These by-products are most apt to be formed if the 
 heat is applied too suddenly to the nitrate, or if the 
 temperature is allowed to rise much above 170 C. 
 
 As nitrous oxide is soluble in cold water, the end 
 of the delivery tube from the last catch-bottle should 
 dip beneath the surface of some warm water, in a beaker 
 or other vessel, and not into the cold water of a pneu- 
 matic trough. Catch the nitrous oxide in large tts. 
 Get its properties. Particularly test it with a large 
 glowing splinter of wood. Does it oxidize to a brown 
 second oxide on exposure to the air, as did the first oxide 
 of nitrogen you made ? Inhale a little nitrous oxide. 
 
 Nitrous oxide has a greater proportion of nitrogen 
 than does the first oxide of nitrogen you made. What 
 proportion did you prove the first oxide has? That 
 oxide is called nitric oxide. Compare the names 
 sulphurous and sulphurzV, as applied to oxides and 
 acids of sulphur. 
 
Note. At this point, before going on with Part II, the student 
 should re-read carefully the Introduction to this book, and take 
 note whether or not he has been following the suggestions there 
 made. 
 
PART II. 
 
 ADDITIONAL EXPERIMENTS. 
 
PART II. ADDITIONAL EXPERIMENTS. 
 
 Experiment 1. 
 
 Bromine. 
 
 EXAMINE a small amount of bromine and get its 
 chief properties. Do not breathe in more than the 
 least bit of bromine, for this substance is very bad 
 for the mucous membranes. 
 
 Note particularly state, color, odor, volatility, and 
 effect on moist test papers. To observe the properties 
 it is best to take the bromine bottle to the hood, and 
 with the window pulled so as to admit the arms only, 
 pour a single drop of bromine into a tt and examine 
 at leisure. On no account let a drop of bromine touch 
 the flesh, as it makes a corrosive sore. Add about 5 CC 
 of water to a tt full of bromine vapors. Shake. Note 
 solubility. Warm, and note effect. Do this last 
 experiment under a hood. Again prepare, in a tt, 
 about 5 CC of bromine water. Add about 2 CC of ether. 
 [Caution! Ether is dangerously inflammable. Have 
 no fire near.] Shake. Note the solubility of bromine 
 in ether as compared with its solubility in water. Note 
 color of bromine solution in ether. Note also how 
 slightly ether mixes with water. Is ether heavier or 
 lighter than water? Try, in a similar way, the solu- 
 bility of bromine in sulphide of carbon. [Caution ! 
 
78 BROMIDES. 
 
 Sulphide of carbon also is dangerously inflammable. 
 Have no fire near.] Note the color of the solution 
 of bromine in sulphide of carbon. 
 
 Experiment 2. 
 Bromides. 
 
 Hydrogen unites with bromine, but not so vigorously 
 as with chlorine. By passing the vapors of bromine 
 and hydrogen gas over hot platinum sponge the union 
 may be made. The resulting hydrogen bromide is 
 much like hydrochloric acid. It is also very soluble 
 in water, and is commonly used in aqueous solution. 
 
 A. Properties of Hydrogen Bromide. 
 Take about l cc of aqueous hydrobromic acid in a tt, 
 and get the properties both of the liquid and of the 
 gaseous bromide of hydrogen that may be evolved by 
 warming the liquid. Compare especially with hydro- 
 chloric acid. 
 
 B. Sodium Bromide. 
 
 Neutralize about l cc of hydrobromic acid solution with 
 sodium hydroxide or sodium carbonate solution. 
 Evaporate to dryness. Examine the product. Get the 
 chief properties of the sodium bromide. Compare it 
 with table salt, e.g., in color, form, and taste. 
 
 C. Replacement of Bromine, in a Bromide, by Chlorine. 
 Make, in a tt, a solution of 10 CC of water and O.l g 
 of bromide of potassium. Add about 5 CC of chlorine 
 
IODIN 
 
 water, i.e., water which has dissol 
 Add about l cc of sulphide of carbon. Why add the 
 sulphide of carbon? Shake. Note effect. What has 
 happened ? 
 
 Experiment 3. 
 Iodine. 
 
 A. Properties of Iodine. 
 
 Examine a crystal of iodine and get its chief proper- 
 ties. Note particularly state, color, solubility, and color 
 of vapor. To note the last, have ready a tt Jfefot at the 
 lower end. Drop in a crystal of iodine and examine 
 the vapor. 
 
 B. Solubility of Iodine. 
 
 Get the relative solubility of iodine in the following 
 solvents : water, alcohol, ether, and sulphide of car- 
 bon. Caution ! Remember that alcohol and ether, as 
 well as sulphide of carbon, are dangerously inflammable. 
 Have no fire near. Save, for (7, the alcohol solution, 
 which is called tincture of iodine. 
 
 C. Action of Iodine on the Skin. 
 
 Drop a small drop of iodine solution, saved from B, 
 on the skin. Note effect. 
 
 D. Action of Iodine on Starch. 
 
 Prepare some starch paste as follows : Have ready 
 in a porcelain evaporating dish 50 CC of boiling water. 
 
 1 Chlorine water may be made by allowing chlorine gas to bubble up 
 through cold water contained in a catch-bottle, flask, or other vessel. 
 
80 IODIDES. 
 
 Rub in a mortar l g of starch and a few drops of water 
 to the consistency of cream. Stir the starch into the 
 boiling water and set aside. 
 
 Put in a tt about l cc of water, add two or three drops 
 of starch paste, then add [after shaking till the paste is 
 well mixed with the water] a single drop of an aqueous 
 solution, or a minute crystal, of iodine. Heat the solu- 
 tion and note the effect. Cool, and note again. Dip a 
 strip of filter paper in the starch paste and suspend it 
 across the mouth of a tt containing a small crystal of 
 iodine in the bottom. Note effect. What does this show ? 
 
 Experiment 4. 
 Iodides. 
 
 Hydrogen unites with iodine, but not readily. By 
 using platinum sponge and iodine vapors the union 
 may, with difficulty, be made. Hydrogen iodide, or 
 hydriodic acid, as it is usually called, resembles hydro- 
 chloric and hydrobromic acids. It forms iodides similar 
 to bromides and chlorides. 
 
 A. The Properties of Potassic Iodide. 
 
 Examine this substance. Note its chief properties. 
 State what relation it has to hydriodic acid, to bromide 
 of potassium, to chloride of potassium. 
 
 B. Replacement of Iodine by Chlorine. 
 Make a solution, in a tt, of 10 CC of water and O.l g of 
 iodide of potassium. Add about 5 CC of chlorine water. 
 Then about l cc of sulphide of carbon. Shake. Note effect. 
 
FLUORINE AND FLUORIDES. 81 
 
 Stir a crystal of potassic iodide into a starch solution. 
 Note effect. Add a few drops of chlorine water. Note 
 effect. Explain. 
 
 C. Will Bromine Displace Iodine? 
 
 Perform an experiment to prove which has the 
 stronger attraction for potassium -- iodine or bro- 
 mine. Record details of the experiment, and the 
 conclusion reached. 
 
 Experiment 5. 
 
 Fluorine and Fluorides. 
 
 We have studied iodine, bromine, chlorine, and the 
 corresponding iodides, bromides, and chlorides. It has 
 long been known that there must be a fourth member 
 of this halogen 1 group, because salts were known 
 called fluorides similar to the bromides, chlorides, 
 and iodides. The simple substance itself has recently 
 been prepared and is called fluorine. Fluorine is 
 much like chlorine, but acts more energetically. 
 
 A. The Properties of Calcic Fluoride. 
 
 Examine some fluoride of calcium and get its chief 
 properties. 
 
 B. Preparation of Fluoride of Hydrogen. 
 
 Compare the " preparation of hydrochloric acid on a 
 large scale," Ex. 29, C. Put about l g calcic fluoride 
 
 1 Halogen means salt-making. Note that chlorine makes common 
 gait, and bromine and iodine similar salts, 
 
82 HYDROFLUORIC ACID. 
 
 in a tt. Add enough sulphuric acid to make a paste. 
 Warm gently. Smell cautiously. A small amount of 
 this gas can seriously injure the lungs. Hold a glass 
 rod wet with water in the mouth of the tt. Get the 
 chief properties of hydrofluoric acid. 
 
 C. Etching of Glass by Hydrofluoric Acid. 
 
 Hydrogen fluoride is an extremely corrosive sub- 
 stance. All metals, except lead, gold, and platinum, 
 act with it to form metallic fluorides. Even glass is 
 eaten away by hydrogen fluoride, with the formation 
 of silicon fluoride, the silicon coming from the sand 
 which was used to make the glass. Hence hydrofluoric 
 acid cannot be kept in a glass bottle. It can be kept 
 in lead, platinum, or rubber. 
 
 Warm a bit of glass, e.g., the bottom of a beaker or 
 of a crystal pan, and drop on it a little wax or candle 
 grease. Spread the grease thin, and let it harden by 
 cooling. Then trace some figure or name in the grease, 
 cutting through to the glass. Generate hydrogen fluo- 
 ride again, as in .5, using for a generating vessel a 
 small beaker, a large tt, or, still better, a lead dish. 
 Expose the prepared glass to the action of the vapors 
 of hydrogen fluoride for a few minutes. Do not melt 
 the grease while the vapors are acting. Then warm 
 the glass, to melt the grease, and wipe off the grease 
 with filter paper. Examine the surface of the glass. 
 Breathe on it. What do you note ? Explain. 
 
ARSENIC AND ITS COMPOUNDS. 83 
 
 Experiment 6. 
 
 Arsenic and its Compounds. 
 
 Caution ! In all your work with arsenic and its 
 compounds use extreme care, and do not get poisoned. 
 
 A. The Properties of the Simple Substance Arsenic. 
 
 Examine a small bit of arsenic and note its chief 
 properties. Keep it well away from the mouth. Do 
 not test its chemical properties without the advice of 
 the instructor. Put a piece, not larger than a common 
 pin's head, in a hard glass bulb tube, clean and dry, 
 with a long stem. Heat gently. Note effect. Be sure 
 you put the tube when used [and all remnants of 
 arsenic and arsenic compounds] in a small waste-box 
 provided for the purpose. 1 
 
 B. Oxidation of Arsenic. 
 
 Do this under a hood with window pulled down. 
 Burn, on the cover of a porcelain crucible, a bit of 
 arsenic, not larger than a pin's head. Note the oxide 
 formed. This white oxide is the "white arsenic," 
 or, more commonly, "arsenic," of the apothecaries. 
 Describe it. 
 
 Again burn arsenic [the smallest possible amount] 
 in order to get the peculiar odor of the oxide. Note 
 that it has a garlic odor, and reminds one of onions. 
 
 1 These arsenic residues should not be thrown with the other labora- 
 tory waste, but should be guarded from contact with chemicals. 
 
84 OXIDE OF ARSENIC. 
 
 C. Reduction of the Oxide of Arsenic. 
 
 Carbon has the power of removing the oxygen from 
 this oxide. Compare the removal of oxygen from the 
 non-combustible oxide of carbon by means of zinc. 
 Fill the bulb of a hard glass matrass half full of a 
 mixture of equal parts of powdered charcoal and oxide 
 of arsenic. Warm gently. Note arsenic mirror. Is 
 all the oxygen taken irom the arsenic, or is a lower 
 oxide left as in the case of the reduction of the dioxide 
 of carbon? 
 
 />. Arsenide of Hydrogen. 
 
 Caution ! Arsenide of hydrogen is one of the most 
 poisonous substances known. Use every care. 
 
 Arsenic, like sulphur, forms a gaseous compound 
 with hydrogen, similar to the sulphide of hydrogen. 
 The arsenic compound is called arsenide of hydro- 
 g-en, or arsine, 1 and is characterized by its frightfully 
 poisonous nature. Take a small, e.g., a 2 oz. or a 4 oz. 
 salt-mouth bottle. Fit with a two-hole rubber stopper. 
 Pass a funnel-tube through one hole and nearly to the 
 bottom of the bottle. Through the other hole pass a 
 short right-angled piece of glass tube. The inner end 
 of this glass tube should be flush with the smaller end 
 of the rubber stopper. With the right-angled tube, 
 connect a tube containing chloride of calcium in small 
 lumps. What is a chief property of chloride of cal- 
 cium? Connect with the chloride of calcium tube a 
 piece of hard glass tube drawn to a pin-hole bore and 
 turned up at a right-angle, similar to the tube used 
 
 1 Also called arseniuretted hydrogen. 
 
DETECTION OF ABSENIC. 85 
 
 for the production of hydrogen sulphide, Ex. 23, B. 
 Put in the bottle about 5 g of c.p. 1 zinc, and a few 
 cc of c.p. sulphuric acid, diluted, e.g., 1 vol. acid to 
 5 vols. of water. Let the hydrogen evolved pass 
 through the tubes till all the air is removed and till 
 the gas can be lighted [by the explosion tube] when 
 it issues from the turned-up small glass tube. When 
 the hydrogen is burning well, place the flame of a 
 Bunsen burner under the hard glass tube just before 
 the point where it narrows to a pin-hole size. Do 
 not remove this flame till the experiment is finished. 
 Then add, through the funnel-tube, to the bottle five 
 drops, and no more, of an arsenical solution. Use the 
 arsenical solution especially prepared by the instructor 
 for this purpose and no other solution. 2 Wash the 
 whole of the solution used down the funnel tube into 
 the bottle by means of pure water from the wash-bottle. 
 Continue the heating for 30 minutes at least. The 
 hydrogen of the sulphuric acid joins the arsenic and the 
 arsenide of hydrogen passes off. Compare the forma- 
 tion of sulphide of hydrogen. The gas is decomposed 
 as it passes through the hot tube, and the hydrogen 
 passes on and burns, while the arsenic is left, as a 
 mirror, in the contracted tube. Compare the action 
 of heat on sulphide of hydrogen. Keep the arsenic 
 mirror for future work. 
 
 E. Detection of Arsenic. 
 
 D gives us a method for detecting arsenic. It is 
 always necessary first to make sure that the arsenic 
 
 1 In chemistry, c.p. stands for chemically pure. 
 
 2 See Appendix J. 
 
86 DETECTION OF ARSENIC. 
 
 is in such a form that the hydrogen can join it and 
 form the arsenide of hydrogen. Therefore the sub- 
 stance which you suspect contains arsenic should first 
 be treated with sulphuric acid [or, in the case of a 
 piece of cloth, carpet, or other substance likely to 
 contain wool, with nitric and sulphuric acids]. 
 
 Arrange the apparatus as in D. Start the hydrogen, 
 and when safe to light the jet do so, and put the Bunsen 
 burner in place. Allow the hydrogen alone to pass for 
 15 minutes with the tube at a dull red. This prelim- 
 inary test is to make sure that there is no arsenic in the 
 zinc or the acid used, and none left from a previous 
 experiment. 
 
 Cut from a piece of wall paper, or any similar sus- 
 pected material supposed to contain arsenic, one square 
 decimeter. Be sure you include all the colors of the 
 figures, if the material is figured. Tear the substance 
 in small bits and put these in a clean and dry porcelain 
 evaporating dish. Add a little c.p. sulphuric acid. 
 Warm gently, and stir with a glass rod till solution 
 takes place. The solution will not be transparent, 
 and is generally black. Do not use enough acid to 
 make the solution really liquid it should be some- 
 what pasty. 1 Add about 20 CC of cold water, or an equal 
 weight of ice or snow, to dilute the strong acid. When 
 cool, filter. The arsenical solution runs through. If 
 there is any precipitate, wash this a little and add the 
 washings to the filtrate. If the apparatus has shown 
 
 1 If the substance contains wool its sulphur must now be oxidized. 
 Add to the sulphuric acid solution about 5 CC of c.p. nitric acid. Evap- 
 orate till white fumes appear. Repeat this treatment. Then dilute 
 with water, again evaporate till white fumes appear, and go on as above. 
 
ANTIMONY. 87 
 
 no arsenic after the preliminary test of 15 minutes, 
 add the solution to be tested through the funnel. Be 
 careful and do not let many bubbles of air go down the 
 funnel-tube with the solution. If arsenic now appears 
 the experiment should be continued for 30 minutes in 
 order to catch all the arsenic as a mirror. Caution! 
 If arsenic appears, do not break any joints of the appa- 
 ratus, nor remove the Bunsen burner, for 30 minutes, 
 or there will be danger of being poisoned by the escap- 
 ing arsenide of hydrogen. It is also well to keep the 
 little jet of hydrogen burning all the time to decompose 
 any hydrogen arsenide that may escape the decompo- 
 sition above the Bunsen burner. If the wind blows the 
 flame of the Bunsen burner, protect it with a book, or 
 something else, or the arsine may escape undecomposed. 
 
 Experiment 7. 
 Antimony, [Stibium.] 
 
 In doing this experiment note the similarity between 
 antimony and arsenic. 
 
 A. The Properties of Antimony. 
 
 Get the chief properties of antimony. Try sublim- 
 ing some in a small matrass. 
 
 B. Oxidation of Antimony. 
 
 To oxidize it well, heat it on a crucible cover before 
 a small mouth blow-pipe. Place on the cover a piece 
 
88 HYDRIDE OF ANTIMONY. 
 
 of antimony as large as a pin's head. Using a 
 Bunsen burner, direct the blow-pipe flame 1 against 
 the antimony. Note the fumes of oxide that rise. 
 Suddenly stop the blast, and note the globule of 
 molten antimony as it becomes coated with oxide. 
 Drop a small molten globule of antimony from some 
 height down on a piece of paper whose edges are 
 turned up [to prevent the antimony running off], 
 and note effect. 
 
 C. Chloride of Antimony. 
 
 Take a jar of chlorine. Sift in a little antimony, 
 which has been ground, in a mortar, to the finest 
 possible powder. 1 Note the phenomena, and examine 
 the compound formed. Review the formation of table 
 salt. 
 
 D. Hydrogen Antimonide. 
 
 Treat a solution of some antimony compound 2 in 
 the apparatus used in Ex. 6, D. Hydrogen joins the 
 antimony, and gaseous antimoiiide of hydrogen results. 
 Examine the antimony mirror, and compare it with 
 the arsenic mirror, particularly as to position in the 
 tube, color, and lustre. Heat each gently, and see 
 which sublimes easier. Prepare a solution of bleach- 
 ing lime [about 1 part lime to 10 of water] and 
 dip, alternately, the mirrors in this solution. Which 
 dissolves the easier ? 
 
 1 For use of blow-pipe, see Appendix K. 
 
 2 See Appendix J, 2. 
 
BISMUTH. 89 
 
 E. A Chemical Examination. 
 
 Examine two pieces of paper, 1 one containing arsenic, 
 the other antimony. Compare the two mirrors which 
 you get, and determine which is arsenic and which is 
 antimony. 
 
 Experiment 8. 
 
 Bismuth. 
 
 A. The Properties of Bismuth. 
 
 Examine a small piece of the metal and get its chief 
 properties. 
 
 B. Nitrate of Bismuth. 
 
 Prepare nitrate of bismuth by putting a lump of 
 bismuth in a small amount of nitric acid. Heat 
 somewhat. Add to this nitrate about l cc of water. 
 Note solubility. Then add the solution to 100 CC of 
 water and note the formation of a basic nitrate, insol- 
 uble in water, which settles out as a light milky 
 precipitate. 
 
 Experiment 9. 
 
 Tin. [Stannum.] 
 A. The Properties of Tin. 
 
 Examine tin in various forms, e.g., bar, granular, foil, 
 and on iron as "tin plate." Get the chief properties 
 of tin, noting particularly its color, lustre, hardness, 
 1 See Appendix L. 
 
90 TIN COMPOUNDS. 
 
 "cry," and whether it is much or little affected by 
 water and the air. To note its cry, bend a bar or 
 pinch it between the teeth. 
 
 B. Oxidation of Tin. 
 
 Oxidize granular tin in a small Hessian crucible 
 over a blast-lamp, or in a Fletcher furnace. Stir often. 
 Examine the oxide and get its chief properties. 
 
 C. Crystalline Structure. 
 
 Take a piece of "scrap tin plate," i.e., a bit of tinned 
 iron that has been cut off in the making of tin ware. 
 Heat this over the Bunsen burner flame till the tin 
 begins to run. Plunge into cold water suddenly. 
 Remove the superficial oxidation by rubbing the sur- 
 face with a bit of filter paper wet in nitric and hydro- 
 chloric acids. Remove the acids by rubbing with a 
 weak solution of sodium hydroxide. Wash off the 
 sodium hydroxide with water. Examine the crystal- 
 line structure presented by the tin. 
 
 D. Action of Strong Acids on Tin. 
 
 1. Treat tin, in a tt, with hydrochloric acid cold 
 and hot. 
 
 2. . Treat tin, in a tt, with sulphuric acid cold and 
 hot. 
 
 3. Treat tin, in a tt, with nitric acid cold and hot. 
 
 Note effect in each case. Save substances formed. 
 
LEAD. 91 
 
 E. Replacement of Tin by Zinc. 
 
 Use the chloride of tin made in D. Make a strong 
 solution of chloride of tin. Put this in a large tt. 
 Clean a narrow strip of zinc and insert it in the 
 solution. Note effect. Explain. 
 
 Experiment 1O. 
 
 Lead. [Plumbum.] 
 
 A. The Properties of Lead. 
 
 Examine a piece of lead and note the chief properties. 
 B. Oxidation of Lead. 
 
 Put some lead in a Hessian crucible and heat it over 
 the blast^lamp. Stir to admit air. Note that the lead 
 forms several oxides of different colors. Do not let the 
 heat become very great. Save some oxide. 
 
 C. Action of Water on Oxide of Lead. 
 
 In a mortar grind a little of the oxide of lead, from 
 B, with about 5 CC of water. Filter and see if anything 
 has gone into solution. Test the liquid also with test 
 papers. State what you can about this experiment 
 from a chemical point of view, from a sanitary point 
 of view, e.g., in reference to the use of lead pipes for 
 conveying drinking water, inasmuch as soluble com- 
 pounds of lead are poisons. 
 
 D. Action of Acids on Lead. 
 Similar to 9, D. Record results in tabular form. 
 
92 LEAD COMPOUNDS. 
 
 E. Replacement of Lead by Zinc. 
 
 Similar to 9, jK, except a solution of lead nitrate 
 best be used. Note the formation of a " lead tree." 
 Explain. 
 
 F. Lead Chloride. 
 
 Treat a strong solution of 5 g of lead nitrate with an 
 excess of hydrochloric acid. Explain the replacement 
 that takes place. Dilute a little and filter. While the 
 precipitate of lead chloride is still on the filter, wash it 
 a little with a stream from the wash-bottle. Get its 
 chief properties. Put the precipitate of lead chloride 
 in a tt. Add three times its volume of cold water. 
 Warm. Note solubility in hot water. Let the solution 
 cool, and note the formation of crystals. 
 
 G. Lead Sulphate. 
 
 Compare the results of D for the action of sulphuric 
 acid on lead itself. Now prepare lead sulphate by 
 adding sulphuric acid to a solution of lead nitrate. 
 Wash the precipitate, as in F, and get its chief prop- 
 erties. Note that this is a roundabout way for prepar- 
 ing a salt when we cannot readily get it by treating 
 the metal with the acid. Such roundabout methods 
 are often used by the chemist. 
 
 H. Plumbers' Solder. 
 
 Melt, in a Hessian crucible, equal parts of tin and 
 lead. The resulting alloy is common solder. Note 
 how much more easily solder may be melted than either 
 
SILVER. 93 
 
 lead or tin. Two or more metals thus fused together 
 form what is called an alloy. 
 
 I. Fusible Alloy. 
 
 Take 15 g of bismuth, 8 g of tin, and 8 g of lead. Put 
 each under boiling water, and note that no one of them 
 melts. Dry the metals, and fuse the three together in 
 an iron spoon or a crucible ; cool, and place the alloy 
 thus produced in boiling water. Note effect. While 
 still melted, pour the alloy into a narrow, thin-walled 
 tt. Let cool. Note effect. Explain. 
 
 Experiment 11. 
 
 Silver. [Argentum.] 
 
 A. The Properties of Silver. 
 
 Examine a small piece of silver and note its chief 
 properties, particularly the effect of air and water on it. 
 
 B. Oxidation of Silver. 
 
 Attempt to form an oxide of silver in all the ways 
 you know for oxidation. 
 
 C. Action of Acids on Silver. 
 
 Try your strongest acids sulphuric, hydrochloric, 
 and nitric "in the cold " l and when hot. Evaporate 
 some of the acid after each attempt, and compare the 
 
 I This expression means at ordinary temperature, 
 
94 SILVER. 
 
 amounts of residue. Try dilute and strong acids. 
 Save any salts found. Make a carefully prepared 
 table of results. 
 
 D. Replacement of Silver by Copper. 
 
 Take 0.5 g of silver nitrate, dissolve it in 10 CC of 
 water. Add a freshly cleaned strip of copper. Note 
 effect. Spread the silver on a hard surface and rub 
 it with some hard instrument, as a knife blade, to 
 restore its lustre. 
 
 K. Replacement of Silver by Calcium, Sodium, and 
 Potassium. 
 
 1. Replacement of silver by calcium, and the forma- 
 tion of silver chloride. 
 
 Put a small crystal of nitrate of silver in about 10 CC 
 of water. Shake till solution takes place. Have ready 
 a solution of a small lump of calcic chloride in about 
 10 CC of water. Mix the solutions. Filter. Examine 
 the precipitate of silver chloride. Expose some to light 
 sunlight is best. Note effect. Explain the changes. 
 Name the factors and the products. 1 
 
 2. Replacement of silver by sodium, and the forma- 
 tion of silver bromide. 
 
 Proceed as in 1, but use sodic bromide for calcic 
 chloride. 
 
 3. Replacement of silver by potassium, and the for- 
 mation of silver iodide. 
 
 1 After every experiment in which silver or silver nitrate is used, 
 any residues (solid or liquid) containing silver should be saved. When 
 a considerable quantity of these residues has been obtained, the 
 instructor should regain the silver from them. See II, Method II. 
 
PURIFICATION OF SILVER. 95 
 
 Proceed as in 1, but use potassic iodide for calcic 
 chloride. 
 
 F. Sulphide of Silver. 
 
 Dissolve a small crystal of nitrate of silver in a tt 
 half full of water. Generate sulphide of hydrogen 
 [from sulphide of iron and dilute sulphuric acid in a 
 flask or in a tt], and pass the gas through the nitrate 
 solution in the tt. Examine the sulphide of silver 
 formed. Explain the replacement that has caused the 
 formation of silver sulphide. What is left in solution ? 
 Hold a silver coin for a moment in a stream of sul- 
 phuretted hydrogen. Note effect. 
 
 G. Oxide of Silver. 
 
 Add about 0.5 g of nitrate of silver to half a tt of 
 water. Then add a few drops of a strong solution of 
 sodium hydroxide. Examine the silver oxide formed. 
 Explain the chemical changes. 
 
 H. Purification of Silver. 
 METHOD I. BY REPLACEMENT WITH COPPER. 
 
 Dissolve a silver coin, e.g., a dime, by heat, in dilute 
 nitric acid. There is copper in silver coins. What two 
 salts then are in the nitric acid solution? If there 
 seems much nitric acid left it should be mostly evapo- 
 rated off. Insert a clean strip of copper and set aside 
 for some time. Explain the change. Collect the silver 
 deposited. Throw it on a filter, and wash thoroughly 
 with water from the wash-bottle. Why wash ? Evap- 
 orate the filtrate and washings to dryness. Examine 
 the substance left. What is it ? 
 
yo GOLD. 
 
 METHOD II. BY REDUCING A CHLORIDE. 
 
 Dissolve a coin, as above, in nitric acid. Add hydro- 
 chloric acid [or a solution of table salt] as long as a 
 precipitate is formed. Explain the chemical changes. 
 Filter. Wash the precipitate thoroughly. Why ? 
 Dry the precipitate. 1 Remove the chloride of silver 
 from the paper, and put the chloride in the midst of 
 a piece of combustion tube. Generate hydrogen gas. 
 Take every precaution. Fit two corks to the combustion 
 tube, and pass hydrogen gas over the chloride and out 
 through an exit tube. Light the hydrogen by the 
 explosion tube and in no other way. When the hydro- 
 gen is burning, and not before, heat the chloride well. 
 Note the effect on the hydrogen flame. Explain. 
 When all the chloride is reduced, examine the silver 
 left. What is reduction? 
 
 Experiment 12. 
 
 Gold. [Aurum.] 
 
 A. The Properties of Gold. 
 
 Examine a small piece of gold [leaf or foil will do] 
 and note its chief properties, particularly its color, 
 hardness, and malleability. 
 
 B. Action of Acids on Gold. 
 
 Try your strongest acids on gold. Gold is called 
 the " king of metals " because of its resistance to the 
 Action of acids. 
 
 ? See Appendix M, 
 
CHLOKIDE OF GOLD. 9T 
 
 C. Chloride of Gold. 
 
 By treating hydrochloric acid with nitric acid, chlorine 
 may be set free. Explain this. At the moment chlorine 
 is set free, or, as it is called, at the moment of its birth 
 [commonly " in statu nascendi "], chlorine has unusual 
 power of uniting with other things. Explain this great 
 power of nascent chlorine. Nascent chlorine can, with 
 success, attack gold and produce gold chloride. 
 
 Put in a watch-glass a drop or two of hydrochloric 
 acid and a drop of nitric acid. Warm, and drop in 
 about 1 sq. cm. of gold foil. Note effect. Carefully 
 evaporate the solution and examine the gold chloride 
 formed. The mixture of hydrochloric and nitric acids 
 is called aqua regia, or royal water, as it attacks gold, 
 the king of metals. Silver and gold are called the 
 noble metals because they do not tarnish in ordinary 
 air. 
 
 D. Gold Amalgam. 
 
 Put a small drop of mercury on a watch-glass. 
 Spread over it a piece of gold leaf as large as a 
 sq. cm. Note effect. Why should a gold ring be 
 kept out of mercury? 
 
 E. Color of Gold. 
 
 Examine a piece of gold leaf, or foil, as it lies with 
 the light reflected from it. Hold a piece of gold leaf 
 up to the light and note the color as the light is 
 transmitted through it. Best lay the leaf on a plate 
 of glass for convenience in handling. 
 
98 PLATINUM. 
 
 Experiment 13. 
 
 Platinum. 
 A. The Properties of Platinum. 
 
 Examine a small bit of platinum and get the chief 
 properties, particularly color and fusibility. Why is 
 platinum an excellent substance from which to make 
 crucibles ? 
 
 B. Action of Acids on Platinum. 
 
 Try your strongest acids on platinum. Also aqua 
 regia. Save any salts formed. 
 
 C. Action of Other Chemicals, besides Acids, on Platinum. 
 
 Try other chemicals [than those of B], e.g., alkalies, 
 salts, etc. Why is platinum an excellent substance for 
 chemical utensils ? 
 
 1). Action of Metals with Platinum. 
 
 Heat, in a clean crucible, a bit of platinum with a bit 
 of lead. Note the formation of a fusible alloy. Why 
 should not metals be heated in platinum dishes ? 
 
 E. Platinum Sponge. 
 
 Put about 2 CC of a solution of chloride of ammonium 
 in a tt. Render acid with hydrogen chloride solution. 
 Add, drop by drop, the chloride of platinum solution 
 made in B. Note the formation of a yellow precipitate. 
 Collect about l cc of this having made sure that the 
 
ALUMINUM. 99 
 
 ammonium chloride is in excess, and not the platinic 
 chloride. Separate the precipitate, by decantation, 
 from its liquor. Dry the precipitate a little by very 
 gentle heat. When it is only slightly moist, put it 
 in a bit of platinum foil, made into a little cup, and 
 heat to redness in a small Bunsen flame as long as 
 fumes are given off. All the simple substances, except 
 the platinum, will go off. What then go off? Examine 
 the platinum sponge formed. It is metallic. Direct 
 a small jet of house gas [better, hydrogen] against a 
 surface of freshly-made platinum sponge. Note effect. 
 
 Experiment 14. 
 Aluminum. 
 
 A. The Properties of Aluminum. 
 
 Examine the metal ingot, sheet, or wire form - 
 and note the chief properties, as color, lustre, hardness, 
 and, approximately, the specific gravity. 
 
 B. Oxidation of Aluminum. 
 Try to oxidize aluminum. 
 
 C. Action of Acids on Aluminum. 
 
 Try all the acids you can diluted and strong 
 hot and cold. Results in a table. 
 
 1). Sulphate of Aluminum. 
 Prepare the sulphate and crystallize it. 
 
100 ALUM. 
 
 E. Alum. 
 
 Make, in a tt, a saturated solution of sulphate of 
 aluminum. In a second tt make a saturated solution 
 of sulphate of potassium. Take 10 CC of each of these 
 solutions. Mix. Shake. Evaporate about one third 
 the water. Let crystallize. Examine the crystals 
 under a microscope, comparing them with the original 
 crystals of sulphate of aluminum and sulphate of potas- 
 sium. Recrystallize the alum from hot water. Nurse l 
 a good crystal. Compare the solubility of the alum 
 with that of the original sulphates. What is an alum ? 
 
 1 See Appendix N. 
 
PART III. 
 
 HISTOEY AND DEVELOPMENT 
 
 LAWS AND THEORIES OF CHEMISTRY. 
 
PART III. 
 LAWS AND THEORIES OF CHEMISTRY. 
 
 CHAPTER I. 
 
 INTRODUCTION. 
 
 CHEMISTRY may be defined as that department of 
 human knowledge which has to do with those phe- 
 nomena that result from changes of substance. 
 
 An examination of the many changes to which 
 matter is subject shows that these changes fall into 
 two groups there are changes in which the compo- 
 sition of the substance is not altered, and others in 
 which there is a change of substance. The first are 
 called physical changes, the second chemical. As 
 examples of physical changes may be given : the 
 formation of the solid, ice, from the liquid, water ; 
 the glowing of platinum wire when the electric cur- 
 rent is passed through it ; the dissolving of sugar 
 when stirred into water. In no one of these cases 
 is it thought there is any change of substance, i.e., 
 the ice is oxide of hydrogen just as much as is the 
 water, the platinum is still platinum, and the sugar 
 remains sugar. But when the electric current was 
 passed through water we found that the water dis- 
 appeared, and two gases of unlike properties were 
 
104 CHEMICAL CHANGES. 
 
 evolved ; when platinum was treated with aqua regia, 
 in Ex. 13, B, Part II, a chloride not at all like the 
 metal platinum resulted ; when sugar is dropped on 
 a hot stove a black charcoal is left, while water vapor 
 passes off into the air. These last are chemical 
 changes because in every one there has been a change 
 of substance. 
 
 When a rod of iron becomes heated and glows with 
 a red color, is the change a physical one, or is it 
 chemical ? When iron becomes magnetized, and is 
 capable of attracting to itself other pieces of iron, to 
 which class does the change belong? When iron 
 burns and the black oxide is left, when it is acted 
 on by moist air and the red rust is left, or when it is 
 acted upon by sulphuric acid and the green sulphate 
 is left, what are the changes, chemical or physical ? 
 Give the reasons for your answers. When glass is 
 softened by heat is the change chemical or physical ? 
 When the iron filings were heated in contact with 
 air was the blackening of their surface caused by a 
 physical or a chemical change ? When salt stirred into 
 water disappears is the change physical or chemical? 
 Answer this last question after doing the following 
 experiment. 
 
 Experiment 1. 
 Two Kinds of Changes. 
 
 1. Dissolve about one gram of table salt in about 
 10 CC of water. Evaporate the water, and examine the 
 residue as to color, taste, etc. Note that it is the same 
 
SOLUTION. 105 
 
 salt that was taken, i.e., there has been no change of the 
 substance, therefore the solution is called a physical 
 change. 
 
 2. Warm, in a tt, with a little sulphuric acid and 
 about 10 CC of water, some iron filings till solution takes 
 place. Evaporate the liquid, and examine the residue. 
 What kind of a change has taken place ? How do you 
 know ? Which dissolved the iron, or the sulphate 
 of iron which resulted from the chemical change ? 
 Would it be right, as is frequently done, to call this 
 a chemical solution of the iron? 
 
 3. Have ready a porcelain evaporating dish contain- 
 ing 15-20 CC of water. Take about 5 g of dry powdered 
 carbonate of sodium and stir this into the water till a 
 clear solution results. Evaporate to dry ness. Examine 
 the residue. Compare it with carbonate of sodium in 
 color, form, 1 and taste. What is it ? 
 
 Next put 15-20 CC of hydrochloric acid solution in a 
 porcelain dish. Add about 5 g of carbonate of sodium 
 and stir till a clear solution results. Evaporate to 
 dry ness. Examine the residue. Compare it with the 
 original carbonate of sodium in color, form, 1 and taste. 
 What is it ? What kind of a change took place when 
 water alone was used? When hydrochloric acid was 
 used ? What went into the solution in the first place ? 
 What in the second ? How do you distinguish between 
 a simple physical solution and a chemical solution ? 
 
 The loss or gain of water sometimes causes a change. 
 Recall the change that followed when, in Ex. 14, 
 
 1 The form can best be observed under a microscope of medium 
 power. 
 
106 HYDRATION. 
 
 Part I, the water of crystallization was driven out 
 by heat from the green crystals of sulphate of iron ; 
 also the changes when, in Ex. 27, Part I, sal soda 
 effloresced, and when [in the same experiment] sodium 
 hydrate deliquesced. 
 
 Experiment 2. 
 Changes caused by Water of Crystallization. 
 
 Put a small lump of blue crystallized sulphate of 
 copper in a porcelain crucible, and warm gently till 
 the water of crystallization has gone. Note change 
 in color. Add a little water. Again note change in 
 color. 
 
 Experiment 3. 
 
 Change caused by the Action of Sulphuric Acid on 
 
 Water. 
 
 Put about 20 CC of cold water in a tt. Add, cau- 
 tiously, about 5 CC of sulphuric acid. Stir with a glass 
 rod. Note the change in temperature. 
 
 Note. These changes, caused by the removal or addi- 
 tion of water, seem to lie in the borderland between 
 the true physical changes and the true chemical ones. 
 Some chemists think that simple solution [e.g., when 
 salt disappears by dissolving in water, or when sul- 
 phuric acid dissolves in water] is always accompanied 
 by a reaction of the substance with the solvent. 
 
ANALYTICAL CHEMISTRY. 107 
 
 Analyses. Syntheses. Metatheses. 
 
 Changes of substance, that is, chemical changes, may 
 be divided into three classes, analyses, syntheses, and 
 metatheses. 
 
 Changes of Substance by Analyses. 
 
 ANALYTICAL CHEMISTRY. 
 
 The word analysis is derived from the Greek, and 
 means an unloosing. It is applied in chemistry to 
 unloosing the bonds which bind together the con- 
 stituents of a compound. Those changes in which 
 compound substances are separated into simpler con- 
 stituents are called analytical. 
 
 Analysis may be either proximate or ultimate. A 
 proximate analysis is one in which a compound is 
 separated into simple constituents, but not necessarily 
 into the simplest; e.g., when we found, by heating, 
 that marble was separated into two oxides oxide of 
 carbon and oxide of calcium we made a proximate 
 analysis. Both constituents, however, were capable of 
 further separation. An ultimate analysis is one in 
 which the simplest constituents of a compound are 
 determined; e.g., when, by heating red oxide of mer- 
 cury, we found that it was separated into two sub- 
 stances mercury and oxygen neither of which has 
 been separated, we made an ultimate analysis. 
 
 Note that already we have made analytical changes 
 in several cases. Review your laboratory work, and 
 now note the analyses made of 
 
108 SYNTHETICAL CHEMISTRY. 
 
 Red oxide of mercury, v- 
 
 Water [hydrogen oxide], ^ 
 
 Sulphuretted hydrogen [hydrogen sulphide], p 
 
 Carbonic dioxide, *- 
 
 Hydrochloric acid, -" 
 
 Marble. 
 f 
 
 State in every case into what factors each substance 
 was analyzed. 
 
 Changes of Substance by Syntheses. 
 
 SYNTHETICAL CHEMISTRY. 
 
 The word synthesis is derived from the Greek, and 
 means putting together. It is applied in chemistry to 
 the formation of compounds. Synthetical chemistry is- 
 the opposite of analytical. We have already made 
 syntheses many times. Refer to the proper experi- 
 ments, and explain the syntheses of 
 
 Iron oxide, Sulphuretted hydrogen, 
 
 Water, Slaked lime, 
 
 Sulphurous acid, Hydrochloric acid, 
 
 Sulphuric acid, Table salt. 
 
 State the factors in each case. 
 
 Experiment 4. 
 Synthesis of Chloride of Ammonium. 
 
 Make a synthesis of chloride of ammonium from 
 ammonia gas and hydrochloric acid gas. Put a little 
 aqua ammonia in a tt, and a little hydrochloric acid 
 
METATHETICAL CHEMISTRY. 109 
 
 solution in a second tt. Bring the mouths of the 
 two tubes near each other. The gases will join in 
 the air, and white fumes of the chloride of ammonium 
 appear. If the action is not rapid enough, heat each 
 tt to drive the gases from their solutions. 
 
 Changes of Substance by Metatheses. 
 
 METATHETICAL CHEMISTRY. 
 
 The word metathesis is derived from the Greek, and 
 means an exchanging. It is applied in chemistry to 
 those changes in which two or more substances change 
 places; e.g., when hydrogen is made by the action of 
 zinc on sulphuric acid, the change is metathetical, for 
 'the zinc takes the place of the hydrogen, and the 
 hydrogen is left in a free condition as was the zinc 
 at first. We have already made a great many metath- 
 eses. Cite references, and explain the metathetical 
 changes when you made 
 
 Hydrogen from sulphuric acid, 
 
 Hydrogen from water by means of hot iron, 
 
 Zinc sulphate from zinc oxide and sulphuric acid, 
 
 Combustible oxide of carbon, 
 
 Sulphuretted hydrogen from sulphide of iron and an acid, 
 
 Sulphate of magnesium, 
 
 Marble powder, 
 
 Sulphate of sodium, 
 
 Hydrochloric acid from table salt, 
 
 Carbonate of potassium from potassium and dioxide of carbon, 
 
 Nitric acid. 
 
110 METATHESES. 
 
 Experiment 5. 
 Metatheses. 
 
 1. Dissolve about 5 g of nitrate of lead in about 100 CC 
 of water. Put the solution in a beaker. Insert a small 
 strip of clean zinc. Note the changing places by the 
 zinc and the lead the lead lets go its hold of the 
 nitrogen and oxygen part of the nitrate and appears 
 as metallic lead, while the zinc joins that which the 
 lead has left. 
 
 2. In a tt dissolve about one tenth of a gram of 
 silver nitrate in about 5 CC of water. In a second tt 
 dissolve about one third as much table salt in about 
 5 CC of water. Pour, drop by drop, one solution into, 
 the other. Here there is an interchange the silver 
 leaving its nitrogen and oxygen to join the chlorine 
 which leaves its sodium, while the sodium joins the 
 nitrogen and oxygen left by the silver. The chloride 
 of silver, not being soluble in water, appears as a heavy 
 precipitate. 
 
 3. Dissolve about l g of potassic sulphocyanate in 
 about 200 CC of water in a beaker. Potassic sulpho- 
 cyanate, on analysis, is found to contain potassium, 
 sulphur, carbon, and nitrogen the potassium having 
 taken the place of the hydrogen in an acid consisting 
 of hydrogen -f sulphur + carbon -}- nitrogen. Into 
 this solution drop a single drop of ferric chloride. 
 Look for the metathesis as the chloride of iron falls 
 through the solution. What simple substances are 
 there in ferric chloride? Explain the metathesis 
 here. 
 
THE EARLIEST PERIOD. Ill 
 
 CHAPTER II. 
 THE EARLIEST PERIOD. 
 
 examination of the records of very ancient 
 nations, as the Chinese, Jews, Egyptians, and Phoe- 
 nicians, shows that these people possessed some knowl- 
 edge of chemical processes. The Chinese early learned 
 the arts of glass and porcelain making. The Phoe- 
 nicians are noted for their skill in dyeing. The Jews, 
 as shown by the Old Testament, were acquainted with 
 certainly four, and probably six, metals, some of which 
 could be obtained only from ores, by chemical means. 
 And the Egyptians are famous not only for their 
 knowledge of a large number of chemical processes, 
 but for the skill with which they applied these in their 
 arts. Independently of the Chinese, the Egyptians 
 discovered a method for making glass. It is probable 
 that this discovery was accidental, soda having been 
 added to sand as a flux to aid in separating gold from 
 the sand. It was chiefly from the Phoenicians and 
 Egyptians that the Greeks, and later, the Romans, 
 obtained considerable knowledge of chemical pro- 
 cesses. 
 
 But all the chemical knowledge of these ancient 
 nations was disjointed, unclassified, and never do we 
 find an attempt at a scientific explanation of chemical 
 phenomena. It is strange that a critical examination 
 of chemical changes could have escaped the keen 
 minds of the Greeks. Their whole attention seems 
 to have been given to the deductive method of 
 
112 THE EABLIEST PERIOD. 
 
 reasoning. Seldom did they study Nature inductively, 1 
 and never do they seem to have tested their deduc- 
 tions by experiments. Though the Ancients never 
 deliberately planned experiments to give an insight 
 into the constitution of bodies, they made numerous 
 speculations as to the nature of the world, and the 
 matter of which it consists. The most celebrated 
 of these is Aristotle's theory of the elements. By 
 elements are here meant the foundation substances 
 of which all the world is made. 
 
 Aristotle assumed that there were four of these 
 elements earth, water, air, and fire. But to Aris- 
 totle these words did not convey the same meaning 
 that they do to us. To him they represented different 
 properties that matter itself possesses : earth stood for 
 that which is cold and dry; water for the cold and 
 wet; air, hot and wet; fire, hot and dry. But these 
 four were not entirely sufficient to Aristotle for explain- 
 ing all phenomena. Hence he added -a fifth, 2 called 
 
 1 The distinction between the deductive and inductive methods of 
 reasoning should be well fixed in mind. The inductive method is 
 preeminently the method by which the far-reaching developments in 
 all branches of natural science during the last centuries have been 
 attained. The facts have first been observed, collected, and arranged. 
 Then from the special cases general principles have been discovered. 
 The deductive method is the method of speculative philosophy. It is 
 the method employed so largely by the Greek and most other philoso- 
 phers. From general principles deductions are made to fit special 
 cases. 
 
 2 This fifth element of Aristotle became later the quinta essentia 
 [whence our word quintessence] of the Alchemists, among whom it 
 caused much trouble. They made many vain endeavors to obtain 
 this, not understanding that Aristotle considered it of the nature ol 
 spirit and not matter, and therefore intangible. 
 
THE EARLIEST PEKIOD. 113 
 
 aether. This last was all-pervading and of a spiritual 
 nature. Although this theory of the elements is called 
 the Aristotelian it is said to have originated with 
 Empedocles, who flourished about a hundred years 
 before Aristotle, 1 and it is possible that Empedocles 
 himself obtained it from some earlier source, as it is 
 claimed that ancient writings in India declare the 
 world is made of five elements, earth, water, air, fire, 
 and aether; while Buddha considered it made of these 
 five together with a sixth consciousness. 
 
 For Review? Of what nature was the chemical 
 knowledge possessed by the ancient nations ? Mention 
 a chemical process known to the Chinese, to the Jews, 
 to the Phoenicians, to the Egyptians. Where did the 
 Greeks and Romans get their knowledge of chemical 
 processes ? How did the Ancients' treatment of chem- 
 ical phenomena differ from our own ? What is meant 
 by the deductive method? What by the inductive? 
 Give an illustration of the use of the inductive method. 
 [This illustration may well be taken from " A Chemical 
 Investigation," Part I, of this book.] 
 
 1 Aristotle lived 384-322 B.C. 
 
 2 To the Student. After you have read each section of Part III you 
 should at once try to formulate answers to the questions asked. If 
 you cannot make satisfactory answers to all, re-read the whole section, 
 looking particularly for answers to the questions that have troubled 
 you. Again formulate answers to all the questions, and, if any are 
 still unanswered, search for the proper answers without re-reading the 
 whole section. 
 
114 THE PERIOD OF ALCHEMY. 
 
 CHAPTER III. 
 THE PERIOD OF ALCHEMY. 
 
 ACCORDING to Aristotle's theory, water is cold and 
 wet, while air is hot and wet. Each, then, has a 
 common property wetness. It was thought that 
 when the substance water is heated and boils away 
 it becomes air. This was considered a transmutation, 
 that is, a changing of one substance into another. 
 During the years that immediately preceded the Chris- 
 tian era, and during the first years of this era, many 
 men came to think that if a change of the nature just 
 indicated was possible, it must be possible also to 
 change a base metal into a noble, e.g., to transmute 
 lead into gold. It was at this time, it may be said, 
 that chemistry began to have a being. Not that 
 chemistry as a science began to exist so early, but 
 chemistry as a distinct department of knowledge. Up 
 to this time, as has been shown in Chapter II, many 
 nations possessed a knowledge of a number of chemical 
 processes, but it does not appear that any attempt had 
 been made to collect a knowledge of these processes 
 into a distinct class, or to direct a number of them to 
 the attainment of a given end. But when the atten- 
 tion of men became centered on the problem of the 
 transmutation of metals, then it was that chemical 
 processes began to be grouped together and used for 
 the solution of the problem. Even then, however, 
 no attempt was made to group the processes in any 
 natural series or to explain the phenomena. As late 
 
THE EGYPTIAN AKT. 115 
 
 as the eleventh century, chemistry has been defined [in 
 an encyclopedia by Suidas] as " the artificial preparation 
 of silver and gold." 
 
 The word chemeia, from which comes our word chem- 
 istry, has been traced back to the fourth century, but 
 was probably used even before that. Its derivation is 
 uncertain. There is a word chemi, an ancient name for 
 Egypt. This word also meant dark, and may have been 
 applied to Egypt on account of the dark color of its soil. 
 The word was also applied to the dark or mysterious 
 portion of the eye, and also, it is said, to a black prepa- 
 ration used in alchemy. Hence it is somewhat doubtful 
 whether chemeia meant the Egyptian art, the black or 
 mysterious art, or the art which made use of this prepa- 
 ration. The term alchemy comes from the Greek word 
 chemeia, and the Arabic article al used as a prefix. 
 
 The period of alchemy began with the first attempt 
 at the transmutation of base metals into silver and 
 gold, and extended into the sixteenth century, when 
 chemistry gradually passed into its medical period. 
 No exact date can be set for the origin of alchemy. 
 In searching for its rise, tradition carries us far back 
 among the myths of the past, but historical proof of 
 the practice of alchemy is wanting before the fourth 
 century. It was in Egypt, and toward the close of 
 the fourth century and during the first years of the 
 fifth, that alchemy first attained distinction. In the 
 seventh century, the Arabs overran Egypt and absorbed 
 the chemical knowledge together with many other 
 things possessed by the Egyptians. Early in the eighth 
 century the Arabs advanced and captured Spain. Here 
 
116 THE PERIOD OF ALCHEMY. 
 
 they founded universities, and for years fostered learn- 
 ing and the arts. To the Arabian universities in Spain 
 there came many students from the western nations, 
 particularly from France, Italy, and Germany. Here 
 alchemy was studied, and these students, on their 
 return, spread alchemistic ideas among many nations. 
 It may be said that alchemy reached its height in the 
 thirteenth century, and, although in the sixteenth it 
 began to be supplanted by medical chemistry, it did 
 not entirely die out till many years later. In the 
 seventeenth century, Van Helmont says that he changed 
 mercury into gold, claiming to have a substance one 
 part of which could transmute two thousand parts of 
 mercury. In the eighteenth century, too, pieces of 
 metal [usually bronze covered with gilt] were often 
 shown as proofs of alchemistic changes, and even as 
 late as the present century 1 it has been claimed that 
 metals have really been transmuted. In order to see 
 on what kind of observations the alchemists based their 
 hope of transforming metals, let us for the time being 
 put aside all the knowledge of chemical changes which 
 we have gained from our work in the laboratory, and 
 try the following experiments which the old alchemists 
 used to perform. 
 
 Experiment 6. 
 A So-Called Transmutation. 
 
 In a small beaker put about 50 CC of strong copper 
 sulphate solution. In this immerse a piece of sheet 
 1 See Schmieder's History of Alchemy, 1832. 
 
ALCHEMISTIC EXPERIMENTS. 117 
 
 iron. 1 When a deposit has formed on the iron, remove 
 this deposit, press it into a ball, lay it on the desk and 
 rub it with some hard instrument in order to polish it. 
 Note that it is copper. To the alchemists this seemed 
 a change of iron into copper. Copper sulphate solu- 
 tion was obtained, as it may be to-day, from the pools 
 that form in certain mines. 
 
 Experiment 7. 
 Death of a Metal. 
 
 Heat in a small Hessian crucible, over a blast-lamp, 
 a small piece of lead. Stir well, to give good air 
 contact, till there is left only a dirty powder. Tp 
 the alchemists the metal had been destroyed, and the 
 ashes left were the remains from its death. 
 
 Experiment 8. 
 Kesurrection of a Metal. 
 
 In a small Hessian crucible heat about a gram of 
 oxide of lead, and add several grains of wheat. 2 Stir 
 the wheat, as it chars, into the oxide. Continue heat- 
 ing and adding wheat till globules of molten lead 
 appear. To the alchemists this was the resurrection 
 of the metal. How do you explain the transformation? 
 
 1 Nails, stout wire, or other forms of iron will do nearly as well. 
 
 2 It is best first to put the wheat in a covered crucible, or other dish, 
 and heat before use. Otherwise the grains may "pop" and cause 
 annoyance. 
 
118 THE PERIOD OF ALCHEMY. 
 
 Although the transmutation of metals was the most 
 prominent feature of alchemy, there early crept in a 
 second pursuit which soon claimed a large share of 
 attention. This latter was a search for the Philoso- 
 pher's Stone, a substance of miraculous powers. Not 
 only was it to be the means by which the transmuta- 
 tions themselves were to be effected, but it was to be 
 a cureall for disease, and a bestower of long life and 
 perpetual youth upon its possessor. Many are the 
 claims for the discovery and virtues of this stone 
 some of them most preposterous. Thus, Roger Bacon 
 claims that it could transform more than a million times 
 its weight of a base metal into gold. Many alchemists 
 who claimed to possess it declared that they had pro- 
 longed their lives three hundred, four hundred, and 
 even more years. Even the production of living beings 
 by its means was believed possible. 
 
 It is interesting to note that in the period of alchemy 
 we find theories proposed for the composition of sub- 
 stances. Geber, 1 the most famous of the Arabian 
 alchemists, held that there were two elementary sub- 
 stances, mercury and sulphur. As Aristotle's elements 
 do not correspond with our substances of the same 
 names, so Geber's mercury and sulphur must not be 
 mistaken for the substances to which we give these 
 names. Mercury to him was that which produced 
 lustre, malleability, and other metallic properties, while 
 sulphur was that which caused combustibility. Geber 
 believed the metals were compounds, that the noble 
 metals were very rich in mercury while the base ones 
 
 1 He was a physician who flourished in the eighth century. 
 
ALCHEMISTIC THEORIES. 119 
 
 contained an excess of sulphur. By this theory it did 
 not seem unreasonable to suppose that sulphur might 
 be withdrawn from a base metal, and in this way trans- 
 formation accomplished. Valentine, the most eminent 
 man of the last years of the period of alchemy, added 
 a third element, salt, to Geber's mercury and sulphur. 
 Salt to .him, 'however, was not what we mean by salt. 
 It was the principle which enabled a body to resist fire 
 and maintain a solid condition. Valentine proposed 
 the use of chemical preparations in medicine, and a 
 little later chemistry and medicine became so much 
 allied that it is customary to speak of the following 
 years as the iatro, or medical, period of chemistry. 
 
 For Review. When was the period of alchemy ? Give 
 the derivation of the words chemistry and alchemy. 
 What was the original pursuit of the alchemists ? What 
 a second -pursuit ? Where did alchemy probably have 
 its birth ? What part did the Arabs play in the devel- 
 opment of alchemy ? In what way did alchemy spread 
 over the western world? Mention two famous alche- 
 mists. What was Geber's theory of the composition of 
 substances? What did Valentine add to Geber's ele- 
 ments ? What important step did Valentine propose ? 
 
120 THE MEDICAL PERIOD. 
 
 CHAPTER IV. 
 
 THE MEDICAL PERIOD. 
 
 ALTHOUGH chemical preparations had now and then 
 during the period of alchemy been used in medicine, 
 it was Paracelsus 1 who, during the first half of the 
 sixteenth century, united chemistry and medicine. 
 He boldly maintained that the "object of chemistry 
 is not to make gold, but to prepare medicines." He 
 considered the human body made up of chemical sub- 
 stances, and believed that changes in these substances 
 caused diseases which could be cured by the adminis- 
 tration of chemical preparations. Following the lead 
 of Paracelsus, the chief aim of chemists for more than 
 a century was the establishment of medicine upon a 
 chemical basis. The result of this new development 
 in chemistry was of great good to both chemistry and 
 medicine. On the one hand, the properties of chem- 
 icals were carefully observed, methods for preparation 
 elaborated, and many new substances found ; while, 
 on the other hand, corrosive sublimate, sugar of lead, 
 compounds of antimony, and many other substances 
 previously considered too poisonous to use in medicine, 
 became valuable agents for the physician. It was during 
 this period that the German, Libavius, in 1595, published 
 the first chemical text-book of note his Alchymia. 
 
 Perhaps the most eminent chemist of this period 
 was Van Helmont, of Brussels. 2 He did not accept 
 
 1 Paracelsus lived 1493-1541. He was born in Switzerland, but 
 traveled and worked in many lands. 
 
 2 Van Helmont lived 1577-1644. 
 
VAN HELMONT. 121 
 
 Aristotle's theory of the elements, nor was he satisfied 
 with that of Geber or of Valentine. He denied that 
 fire had any material existence, and announced that 
 when a metal is treated with an acid and disappears 
 it is not destroyed, proving, as he did by experiment, 
 that a substance continues to exist in its compounds. 
 Of equal importance with his other researches are his 
 observations on gases. 1 Up to this time no distinction 
 had been made between the various gases, such as 
 hydrogen, carbonic dioxide, sulphurous oxide, etc., all 
 being considered air. Van Helmont not only made a 
 distinction between gases and vapors calling aeriform 
 substances which, when cooled, became liquids, vapors ; 
 and those which did not, gases but also noted the 
 properties of a number of aeriform substances, and dis- 
 tinguished one from another. He studied particularly 
 carbonic dioxide, which he called gas sylvestre. This 
 gas he found could be obtained when coal is burned, 
 when beer ferments, by treating limestone or potash 
 with acids, from mineral waters, and in certain caves. 
 That Van Helmont did much to promote the union of 
 chemistry and medicine is shown by the experiments 
 that he carried on with the juices and secretions of the 
 animal body, als*o by the explanations he gave for the 
 changes which take place within the body. He believed 
 the acid of the gastric juice is the agent which causes 
 digestion, but that if this juice exists in too large a 
 quantity sickness results. To cure this kind of sick- 
 ness he used as medicine alkaline preparations, while, 
 to cure sickness caused by a lack of gastric juice, he 
 
 1 It was Van Helmont who invented the word gas. 
 
122 THE MEDICAL PERIOD. 
 
 administered acid substances. That Van Helmont, 
 though preeminently a medical chemist, still held 
 alchemistic beliefs is shown by an elaborate descrip- 
 tion he has left of a method for changing mercury into 
 gold and silver. And it may also be said that his work 
 on gases should give him a place in a period which is 
 usually put a little later the pneumatic period. 
 
 During these years of medical chemistry there lived 
 three men who, though they did but little themselves 
 toward bringing about a union between medicine and 
 chemistry, yet deserve to be remembered for their 
 work in practical chemistry Agricola, a German 
 metallurgist, Palissy, a French potter, and Glauber, 
 a Bavarian chemist. 
 
 Agricola was a physician, but while he practiced 
 medicine he found time to study mineralogy and metal- 
 lurgy in the mines and smelting works of Saxony, many 
 of whose technical products he has described in a book 
 he wrote. 
 
 Palissy devoted himself to improving the art of mak- 
 ing pottery. He cared little for speculations, and did 
 not believe in the theories of alchemists nor in those of 
 Paracelsus himself. He based his work upon experi- 
 ments, and although at first he met many disappoint- 
 ments and failures he finally carried his art to a high 
 degree of perfection. Especially well did he succeed 
 in making enamels and in enameling earthen ware, par- 
 ticularly that ware called Faience. The records 1 he 
 has left are characterized by clearness and simplicity. 
 
 1 E.g., L'Art de Terre, in which he speaks of clays, firings, etc., 
 shows how much superior is experiment to theory alone, and gives a 
 most entertaining account of his early struggles and mistakes. 
 
GLATTBEK. 123 
 
 Glauber, 1 who has been called the Paracelsus of the 
 seventeenth century, really devoted much less attention 
 to medical chemistry than to applied chemistry. He 
 enriched pharmaceutical chemistry with many prepara- 
 tions. It is believed that he first obtained hydrochloric 
 acid by treating table salt with sulphuric acid, and first 
 obtained nitric acid by treating nitre with sulphuric 
 acid. It was in the residue from making hydrochloric 
 acid that he found sulphate of sodium, which was called 
 sal mirabile Grlauberi, and to this day bears the name of 
 Glauber's salt. Glauber was also a writer on economic 
 subjects, frequently urging Germany to make use of its 
 own raw materials and not sell so much of these to other 
 countries only to buy them back when manufactured 
 into various finished products. 
 
 In the course of this medical period we see here and 
 there a use made of the inductive method. Experi- 
 menting itself was already largely employed, but seldom 
 were theories founded on the results of the experiments. 
 Paracelsus himself spent many of his early years in 
 travel, claiming that the true way for a physician to 
 gain knowledge of real value was not to read books 
 and argue over the precepts of the Ancients, but to 
 examine cases found in his own day and discuss these. 2 
 
 1 Glauber lived 1604-1668. 
 
 2 It is sad to note that this sensible method gained for him nothing 
 but contempt and ridicule from his fellow physicians who clung most 
 tenaciously to the "Authority of the Ancients." At one time Para- 
 celsus was town physician at Basel and here talked so plainly against 
 the impositions practiced by the pharmacists that the latter found 
 means for having him driven from the city, and it is even said that 
 at a later period these same enemies caused his death by throwing 
 him over a precipice. 
 
124 THE MEDICAL PERIOD. 
 
 Palissy, we find, made experiment the sole basis for 
 his work in pottery; while Van Helmont based many 
 of his assumptions on experiment, unfortunately, how- 
 ever, not interpreting his experiments correctly, as, for 
 instance, when he assumed that water was the basis of 
 all organic substances because water appeared whenever 
 he burned these ; and, again, when he assumed that 
 only water was necessary for the growth of some plants, 
 because, as it seemed to him, he had been able to make 
 certain plants grow on the surface of pure water. 
 
 For Review. Who united chemistry and medicine ? 
 When ? What advantage came to chemistry from this 
 union ? What to medicine ? When was the first text- 
 book on chemistry published? What did Van Hel- 
 mont reject ? What deny ? What prove ? What did 
 he observe in regard to gases ? Who invented the word 
 gas? For what is Agricola noted? For what Palissy? 
 For what Glauber? What proof have we that the 
 inductive method was used as early as the medical 
 period ? 
 
ROBERT BOYLE. 125 
 
 CHAPTER V. 
 
 PERIOD OF ROBERT BOYLE. 
 
 To modest, unpretending Robert Boyle, chemistry is 
 so much indebted that we are justified in designating 
 the active years of his life as a distinct period in chem- 
 ical history. He was born in Ireland in 1627, but 
 spent most of his life in England where he died at 
 London in 1691. It was Boyle who first saw clearly 
 that the inductive method is the only safe method to 
 follow in the pursuit of knowledge. He it was who 
 first gave a proper definition for the term element. 
 And to Boyle is due the establishment of chemistry 
 as a true science. But these three important results 
 are by no means all that came from his labors. The 
 discoveries of Boyle were of particular value in applied 
 chemistry, e.g., his preparation of ruby glass, his dis- 
 covery of phosphorus, 1 phosphoric acid, etc. 
 
 Boyle also devoted his attention to the study of 
 gases, as is shown in his work on " The Spring of the 
 Air" and in other publications. His keen observation 
 led him to the discovery of the law [in regard to the 
 effect of pressure on a gas] which bears his name. 
 
 1 Phosphorus had already been discovered by Brand of Hamburg, 
 but its preparation was kept a secret and Boyle had to rediscover it. 
 
126 PERIOD OF ROBERT BOYLE. 
 
 Experiment 9. 
 
 The Law of Boyle. 1 
 
 Take a piece of glass tube 8-10 mm bore, of uniform 
 caliber, about 1.5 meter long, closed at one end and 
 bent to form two parallel arms, one of which is at least 
 three times as long as the other. The longer arm must 
 have the open end of the tube. Have ready about 500 g 
 of mercury that is clean and dry. 
 
 Note. Dirty or wet mercury will not give a good 
 result, and will render the tube unfit for a second 
 determination. 2 The closest attention to details is 
 necessary in this experiment if a satisfactory result 
 is looked for. 
 
 Pour a little mercury into the tube to "seal the 
 bend." Shake the mercury around till it stands as 
 high in one arm as in the other, when the two arms 
 are upright, thus making sure that the confined air 
 is not under any abnormal pressure from an excess 
 of mercury in the long arm. For convenience in 
 adding mercury, it is well to set the tube on the 
 floor. With a piece of string fasten the tube upright 
 to some convenient support, as a knob to a drawer 
 of your desk. From this time on avoid as much 
 as possible any heating of the confined air from 
 contact with the hands or other parts of the body. 
 Why avoid heating? Measure the length of the 
 column of air to be experimented on, i.e., the column 
 
 1 See foot-note, page xxvii of the Introduction. 
 
 2 Dirty mercury can often be cleaned by treatment with a few drops 
 of strong nitric acid. 
 
THE BAROMETER. 127 
 
 in the short tube. If the tube tapers at all it should 
 be rejected. Why? Allowance should be made if 
 the end of the tube is not closed square across but is 
 rounded, as is usual. Note that there is already a 
 considerable pressure on the confined air, because the 
 whole pressure of the atmosphere [equal to the weight 
 of a column of air directly over the surface of the 
 mercury in the long arm, and extending up as far as 
 the air itself reaches] is exerted on the surface of the 
 mercury in the open arm, and this pressure is trans- 
 mitted by the mercury around the bend to the lower 
 surface of the confined air. Determine, 1 as follows, 
 the amount of this pressure of the atmosphere : Take 
 a piece of glass tube at least a meter long and 4 or 
 5 mm bore. Heat the tube about 5 cm from the end, 
 and draw off a piece in order to leave one end of the 
 long tube closed. Fill the long tube within about 
 two finger-widths of the top with mercury. Put your 
 thumb over the end and slowly invert the tube, letting 
 the big bubble of air pass up, sweeping along the little 
 bubbles. Repeat the inversions till the big bubble has 
 collected all the air it can ; then fill the tube completely 
 with mercury, and, without letting any air enter, plunge 
 its open end beneath the surface of mercury held in 
 some stout dish, as a porcelain mortar. Support the 
 tube upright, and note the formation of a " Torricelli's 
 vacuum" at the top. The instrument you have now 
 
 1 If you have a barometer this pressure can be determined readily 
 and more accurately from this than from the crude apparatus made 
 in this experiment. However, no part of this experiment should be 
 omitted, but in the last part it would be . better to substitute the 
 reading of a good barometer for the reading made from your own. 
 
128 PERIOD OF ROBERT BOYLE. 
 
 made will serve you very well as a barometer, i.e., an 
 instrument for measuring the varying pressure of the 
 atmosphere. The better you have removed the air from 
 the mercury, and the purer your mercury, the more 
 nearly will the readings of your instrument approach 
 those of a high-grade barometer. Measure the height 
 of the column of mercury which the air pressure is 
 able to support. Mercury is 13.6 times as heavy as 
 water. Estimate the pressure of air against one square 
 centimeter of surface. One square centimeter occupies 
 0.155 square inch. Estimate, then, the pressure in 
 pounds against one square inch. 
 
 Air pressure is usually expressed simply by the 
 measurement of the length of the column of mercury 
 [in the barometer] which the air supports. 
 
 Return to your bent glass tube with its volume of 
 confined air. Add mercury to the long arm till the 
 surface of the mercury in this arm is as many centi- 
 meters above the surface of the mercury in the short 
 arm as the surface of the mercury in the tube of 
 the barometer stands above the surface of the mer- 
 cury in the cistern of the barometer, i.e., double 
 the pressure on the confined air in the short arm. 
 Measure the length of the short column now, and 
 note the effect that doubling the pressure has had 
 on the size of the volume. Why would it not have 
 doubled the pressure if you had simply increased 
 the height of the mercury in the long arm by 76 cm 
 [more or less] above its own original height, and not 
 above the new height of the mercury in the other 
 arm? 
 
ELEMENTS. 129 
 
 The. Law of Boyle may be stated thus. The volume 
 of a gas is inversely proportional to the pressure to which 
 it is subjected, i.e., if the pressure is doubled the volume 
 is halved; three times the original pressure gives one 
 third the original volume, etc. 
 
 As to the value of the inductive method, Boyle 
 clearly stated that if men really cared to get at the 
 truth there was no way by which they could benefit 
 the world more than by going to work and performing 
 experiments, collecting observations, but not attempt- 
 ing to propose theories till all the phenomena involved 
 had been noticed. From this statement, and Boyle's 
 consistent practice of what it teaches, we see that he 
 was the first to pursue chemistry in a truly scientific 
 spirit. That Boyle wished to establish chemistry as a 
 science independent of medicine, physics or any other, 
 and that up to this time chemistry had not been 
 regarded as a separate science, is shown by his state- 
 ment that he found most of the disciples, of chemistry 
 had hardly any object in view except the preparation 
 of medicines, or the ennobling of metals ; that he him- 
 self was tempted to enter the art not as a physician or 
 an alchemist, and that with this in view he drew up a 
 scheme of chemical philosophy. 
 
 Boyle saw that neither Aristotle's theory of elements 
 nor the theories of the alchemists were sound. He 
 maintained that only substances that cannot be decom- 
 posed into simpler constituents should be regarded as 
 elements ; that many of the substances held in his day 
 to be simple would sometime be decomposed ; and that 
 
130 PEEIOD OF ROBERT BOYLE. 
 
 one should not attempt to fix any definite number for the 
 elements. A belief like this shows what a long step in 
 advance of all previous chemists the clear-sighted Boyle 
 was able to take. His views in regard to the nature of 
 elements have not been essentially modified to the 
 present day. 1 
 
 In his attempts to separate compounds Boyle did so 
 much analytical work, and devised so many processes 
 for separation and for the recognition of the presence 
 of substances in compounds, that he may be said to 
 have founded the department of chemistry called Qual- 
 itative Analysis. It is true that, during the periods 
 of alchemy and medical chemistry, attempts had been 
 made to get at the constitution of bodies, but little 
 advance had been made toward any systematic scheme 
 for separation. It is seldom that separation can be 
 made in so simple a manner as when red oxide of 
 mercury is converted by heat into mercury and oxygen, 
 or as we have done in any of those analyses noted on 
 pages 107-108. 
 
 Boyle saw that it is not necessary to separate a 
 metal, a gas, an oxide, from its compound in order 
 to prove that it is present, but was able to tell the 
 presence of substances by certain changes. He found 
 
 1 It may be said that at the present date there seems some slight 
 reason to believe that elements chemically similar may sometime be 
 found mutually convertible, and that finally a dream of the alchemists 
 may, in a measure, be realized. Speculation is rife, and speculation 
 based on some semblance of facts, as to the possible separation of all 
 so-called elements. That hydrogen may be found to be the basis of 
 all, or that an unknown element of unexpected simplicity may be 
 found a component of all, hydrogen included, has even been suggested 
 by chemists of repute. 
 
QUALITATIVE TESTS. 131 
 
 that when a solution of a calcium salt is added to a 
 solution containing sulphuric - acid, or a solution of a 
 silver salt added to one containing hydrochloric acid, 
 a white precipitate is caused. By means, then, of 
 calcium and silver salts, he was able to test for sul- 
 phuric and hydrochloric acids, respectively ; and by 
 means of these two acids, conversely, he tested for 
 calcium and silver salts. He tested for ammonia with 
 the vapors of hydrochloric acid, the production of a 
 white cloud proving its presence. He also made use of 
 plant extracts, as those from litmus, violet, cornflower, 
 etc., in testing for acids and alkalies. He used his 
 plant juices both in solution and on papers as we do 
 still. To this use of "tests" Boyle first applied the 
 name, ever since kept, Analysis. 1 
 
 In the practice of Qualitative Analysis at the present 
 day the chemist does not generally isolate substances 
 in order to prove them present, but, like Boyle, uses 
 certain "tests," i.e., he brings about a series of chem- 
 ical changes, from an inspection of which he is able to 
 judge what substances are present without ever having 
 seen them. During the last hundred years observa- 
 tions have been greatly multiplied and systems of pro- 
 cedure devised so that Qualitative Analysis to-day 
 requires, on the part of the analyst, a familiarity with 
 a vast number of changes, a knowledge of when, and 
 in what order these should be brought about, and an 
 ability to interpret their results. 
 
 1 Assaying would be a better term to use for this testing, because 
 this testing is seldom strictly analyzing. 
 
132 PERIOD OF ROBERT BOYLE. 
 
 Experiment 1O. 
 
 Qualitative Tests. 
 A. Tests used by Boyle. 
 
 First prepare re-agents, or test solutions, as follows: 
 [Each solution should be kept in a clean, stoppered 
 bottle, or flask.] 
 
 I. Sulphuric acid. To 20 CC of water add l cc of 
 sulphuric acid. . 
 
 II. Hydrochloric acid. To 15 CC of water add l cc 
 of the strongest laboratory hydrochloric acid solution. 
 
 III. Silver salt. To 20 CC of water add half a gram 
 of nitrate of silver. Shake till the nitrate dissolves. 
 
 IV. Calcium salt. To 20 CC of water add 6 grams 
 of chloride of calcium. Shake till solution takes place. 
 If the solution is not clear, filter into a narrow-necked 
 bottle. 
 
 In a tt containing a few cc of I drop a little of IV. 
 Note formation of a white precipitate. Try a similar 
 experiment, mixing some of II with some of III. 
 
 H. Tests by Physical Changes. 
 
 Take a piece of glass rod, heat one end till it softens, 
 fasten in a piece of platinum wire about 5 cm long, and 
 make a loop in the end of the wire. Moisten the loop, 
 and take up a little chloride of potassium. Using the 
 glass rod as a handle, hold the chloride in the flame 
 of the Bunsen burner and note the flame coloration. 
 Remove all chloride from the wire, testing it in the 
 flame to make sure no trace is left; and in the same 
 way note the flame coloration produced by chloride of 
 
CHEMICAL TESTS. 133 
 
 lithium, by chloride of sodium, by chloride of barium. 
 The colors here seen are "characteristic," i.e.^ they 
 indicate to the chemist the presence of the metals, 
 potassium, lithium, sodium, barium, respectively, in the 
 substances tested. 1 
 
 C. Tests by Chemical Changes. 
 
 Have ready four tts labeled , 5, c, d. Put a bit 
 of silver in a, a bit of lead in 5, a bit of copper in e, a 
 bit of white arsenic in d. In each case the amount 
 of the substance should not be larger than a small pea. 
 Add to every tt about l cc of nitric acid, and warm till 
 solution takes place. Add about 10 CC of water to every 
 tube. Divide every one of the four solutions into two 
 portions, putting part in other tubes labeled a\ b\ c\ d\ 
 corresponding to a, 5, c, d, respectively. To every one 
 of the solutions, #, 5, <?, d, add a few drops of hydro- 
 chloric acid solution. Note effect. Heat the solutions 
 in which hydrochloric acid causes a precipitate. Note 
 effect. Cool. Note effect. To the solutions not pre- 
 cipitated by hydrochloric acid add aqua ammonia till 
 alkaline to test papers. Note effect. Into the solu- 
 tion still unchanged pass sulphide of hydrogen gas. 
 Note effect. Record all observations in the form of a 
 table in the note-book. Note that hydrochloric acid 
 was a characteristic test for both silver and lead, giving 
 with silver an insoluble white precipitate, with lead a 
 white precipitate soluble when heated; that, after the 
 
 1 If the laboratory possesses a spectroscope, examine the four flames 
 through this instrument, and map in your note-book the lines seen in 
 each case. 
 
134 PERIOD OF ROBERT BOYLE. 
 
 addition of hydrochloric acid had proved there was 
 neither silver nor lead in c, the blue color produced 
 by ammonia was a test for copper ; and that, when 
 the absence of silver, lead, and copper had been proved 
 in d, the production of a lemon-colored precipitate, by 
 sulphide of hydrogen, was a test for arsenic. 
 
 But for the successful practice of qualitative analysis, 
 the chemist must know not only what tests to use, but in 
 what order the proper tests are to be used. In order 
 to see that this is so, to the solutions numbered a\ b\ 
 c\ d\ at once pass in sulphide of hydrogen, i.e., use the 
 last re-agent first. Note that here you get three black 
 precipitates about alike in color, solubility, etc., and no 
 distinction is possible. 
 
 At the present day there are about seventy sub- 
 stances which resist every effort of the chemist at 
 separation. These are called the elements, but it is 
 by no means certain that some, if not all, may not be 
 separated when we have better means of analysis, or 
 more knowledge to apply the means we do have. 
 
 The most commonly occurring elementary substances 
 are the following : 
 
 Aluminum, Gold, Oxygen, 
 
 Antimony, Hydrogen, Phosphorus, 
 
 Arsenic, Iodine, Platinum, 
 
 Barium, Iron, Potassium, 
 
 Bismuth, Lead, Silver, 
 
 Bromine, Magnesium, . Sodium, 
 
 Calcium, Manganese, Sulphur, 
 
 Carbon, Mercury, Tin, 
 
 Chlorine, Nickel, Zinc. 
 
 Copper, Nitrogen, 
 
MIXTURES AND COMPOUNDS. 135 
 
 For a complete list of the elements at present recog- 
 nized, see page 216. 
 
 Boyle even proposed a theory that was far in advance 
 of any previous chemical theory. His theory was that 
 matter is made up of small particles corpuscles ; that 
 a chemical compound results from a mutual attraction 
 of the particles when particles of certain kinds of matter 
 come together. Moreover, no one before had stated 
 clearly, as he now did, that a chemical compound is 
 formed by the union of two or more factors, and that 
 the compound itself has properties entirely different 
 from either factor. He distinguished correctly between 
 a mere mixture and a chemical compound. 
 
 Experiment 11. 
 Mechanical Mixture and Chemical Compound. 
 
 Not every mixing of substances results in the forma- 
 tion of a true chemical compound. 
 
 A. Iron and Sulphur. 
 
 Weigh out, of very fine iron filings, 56 decigrams ; 
 of flowers of sulphur, 32 decigrams. Grind the two 
 well together in a mortar till the eye can no longer 
 distinguish the separate particles of either substance, 
 and the mass looks homogeneous. Apply a magnet, 
 and note that the iron may be separated from the 
 sulphur. Again grind together, and put the mixture 
 in a large tt. Heat well over a Bunsen flame. Break 
 the tt, and examine the product. Grind in a mortar, and 
 
136 PERIOD OF ROBERT BOYLE. 
 
 again apply the magnet. Note that no separation can 
 now be made, for one particle seems attracted as much, 
 or as little, as every other. The substance formed is a 
 compound, and one particle has the same properties as 
 every other. What is this compound? What were 
 the factors ? 
 
 B. Zinc and Sulphur. 
 
 Caution ! In mixing the zinc and the sulphur for 
 this experiment do not grind them in a mortar, as 
 pressure alone is capable of producing the chemical 
 union with explosive suddenness. 
 
 With a spatula, mix, as intimately as possible, 65 
 decigrams of zinc dust and 32 decigrams of flowers 
 of sulphur. Put some of this powder under a micro- 
 scope and note that combination has not taken place, 
 as the gleaming, dark-colored pieces of zinc may be 
 distinguished from the irregular, somewhat smutted 
 [by the zinc powder] granules of sulphur. Heap the 
 greater part of the mixture on a brick, stone, or some 
 other substance not harmed by heat, and set fire to it. 
 Note phenomena. Examine with a microscope some 
 of the product where the change has been complete. 
 Can you see either zinc or sulphur? What kind of 
 a change has taken place ? What caused the change ? 
 What did the chemical change itself cause? What 
 did the heat cause? 
 
 The simplicity and clearness of Boyle's writings 
 form a pleasing contrast to the self-laudatory works 
 of Paracelsus, the contradictory ones of Van Helmont, 
 and the generally obscure writings of most of the other 
 
CHEMISTRY A TBUE SCIENCE. 137 
 
 medical chemists and the alchemists. Robert Boyle 
 was a seeker after the truth. Where he did not him- 
 self see clearly he never attempted to deceive by involv- 
 ing his reader in doubt and obscurity. Animated by 
 the spirit of pure investigation, he placed scientific 
 speculation on that sure foundation experimentation 
 
 - upon which it has ever since so securely rested. 
 
 From the time of Boyle, chemistry has been dependent 
 upon neither medicine, physics, nor any other science, 
 but has of itself been a true science with the solution 
 of a definite problem the composition of substances 
 
 as its goal, and a method the inductive both 
 systematic and logical, its means for attaining the 
 wished-for goal. Boyle, too, gave chemistry its highest 
 aim the pursuit of absolute Truth. 
 
 For Review. When did Boyle live ? State the law 
 of Boyle. What three important services did he render 
 chemistry ? How did he define an element ? To what 
 did he apply the term analysis ? State one of Boyle's 
 analytical tests. Describe some chemical tests by means 
 of physical changes. Describe a series of tests by means 
 of chemical changes. How many elements are now 
 recognized? Mention the most commonly occurring 
 elementary substances. What theory did Boyle pro- 
 pose to explain chemical changes? Distinguish between 
 a mere mixture and a chemical compound. Upon what 
 foundation did Boyle rest his speculations ? What high 
 aim did he give chemistry ? 
 
138 THE PHLOGISTON PERIOD. 
 
 CHAPTER VI. 
 
 THE PHLOGISTON PERIOD. 
 
 This period, in which the attention of chemists was 
 directed mainly to the explanation of combustion, may 
 be said to cover the eighteenth century. It began, 
 however, even before Boyle's death, in Becher's theory, 
 that when substances were burned, a terra pinguis, as 
 he called it, passed off. Stahl, 1 who worked chiefly 
 at Berlin during the early part of the eighteenth 
 century, was the chief developer of the phlogiston 
 theory. Stahl believed that all combustible bodies, 
 metals rightly included, contained within them a sub- 
 stance which he called phlogiston, and that this 
 substance passed off when combustion took place, 
 and returned when such substances as we call oxides, 
 e.g., red oxide of mercury, black oxide of iron, etc., 
 were, as we say, reduced. Substances which burned 
 vigorously he thought contained much phlogiston, 
 while those which leave little residue after combus- 
 tion, as coal and soot, he thought to be made of nearly 
 pure phlogiston. According to this theory metals were 
 compounds, while their oxides were of simpler form 
 one factor, phlogiston, having departed. 
 
 It is hard to see how the fact that the residues from 
 burning the metals are heavier than the metals, and 
 consequently, addition, and not subtraction, takes place 
 in combustion, escaped the notice of Stahl. To be 
 sure, his mind was chiefly intent on such cases as the 
 
 1 Stahl lived 1660-1734. 
 
END OF THE PHLOGISTON THEORY. 189 
 
 burning of wood, coal, etc., in which the fact that there 
 is great weight to the gases that pass off was then all 
 unknown. A little later attention was called to the 
 fact that residues from the combustion of metals do 
 weigh more than the metals themselves. This diffi- 
 culty in the way of the phlogiston theory was met by 
 some who assumed that phlogiston was the principle 
 of absolute lightness, i.e., that phlogiston had a neg- 
 ative weight, and so when it was removed from a 
 substance, the substance naturally gained in weight ; 
 and by others who simply ignored it. But after the 
 fact that the products of combustion do weigh more 
 than the combustibles had repeatedly thrust itself on 
 the attention of chemists, and after gases had been 
 more carefully studied [in the pneumatic period], it 
 became evident that the theory of phlogiston had fatal 
 weaknesses. Its death blow came in 1783, when, the 
 true nature of both oxygen and hydrogen gases having 
 been pointed out, also the fact that water consists of 
 these two substances united, the part that oxygen 
 plays in combustion was proved. To be sure, some 
 chemists notably Priestly 1 and Cavendish, whose very 
 works did much to destroy the phlogiston theory 
 vehemently denied, even till the end of the century, 
 and beyond, that this cherished theory was dead. 
 
 For Review. State the phlogiston theory. Who 
 developed this theory ? When ? How was combustion 
 explained by the phlogiston theory? How reduc- 
 tion? What important fact did the phlogistonists 
 either neglect or explain in an absurd manner? 
 
 1 Priestly has been called one of the fathers of modern chemistry, 
 but it has also been said that he was " un pere qui ne voulut jamais 
 reconnoitre sa fille." 
 
140 PNEUMATIC PERIOD. 
 
 CHAPTEE VII. 
 
 PNEUMATIC PERIOD. 
 
 We may apply the name pneumatic to an important 
 period which immediately preceded the last or modern 
 period of chemistry. The name pneumatic is derived 
 from a Greek word meaning air or wind. It is applied 
 to that period of chemistry in which the attention of 
 chemists was devoted chiefly to a study of gaseous sub- 
 stances. The pneumatic period is over-lapped by that 
 of phlogiston, and even by the medical, for we found 
 that Van Helmont worked with aeriform matter, and, 
 in fact, he is sometimes spoken of as the founder of 
 pneumatic chemistry. He first pointed out the dis- 
 tinction between various kinds of gases, as carbonic 
 dioxide, sulphurous oxide, etc., and it was he who gave 
 us the name " gas " for aeriform matter which does not, 
 on cooling to the ordinary temperature, take the liquid 
 state. Boyle was preeminently noted for his investiga- 
 tion of gases, but neither he nor his contemporaries 
 were able to distinguish between hydrogen and car- 
 bonic dioxide, both of which they thought were modified 
 forms of air. 
 
 It was Black, 1 who lived one hundred years later 
 than Boyle, who proved the difference between air and 
 carbonic dioxide. He noticed that when carbonates of 
 magnesium or of lime are heated, a gas, identical with 
 Van Helmont's gas sylvestre, goes off, and the carbonate 
 
 1 Joseph Black, born in 1728, died in 1799, was professor of chem- 
 istry at Glasgow and Edinburgh. 
 
SPECIFIC GRAVITY OF AIR. 141 
 
 loses in weight. He found that what were then called 
 caustic alkalies [our caustic hydroxides], are capable of 
 taking up this gas and becoming what were then called 
 mild alkalies [our carbonates]. Owing to this fixation 
 of the gas he gave it the name of fixed air. 
 
 Cavendish 1 came soon after Black, and contributed 
 so much to our knowledge of gases that he has been 
 called the father of pneumatic chemistry. To him we 
 owe the pneumatic trough, and he pointed out the 
 necessity for making accurate determinations of the 
 relative weights, or specific gravities, of different gases, 
 in order to distinguish one gas from another. 
 
 Let us determine the specific gravities of some 
 
 Experiment 12. 
 Weight and Specific Gravity of Air. 2 
 
 Take a large [2-4 liter] " prescription bottle." 3 Make 
 sure it is perfectly dry and clean. Fit it with a one- 
 hole rubier stopper through which passes a short piece 
 of tightly-fitting glass tube carrying a bit of rubber tube 
 fitted with a pinch-cock. Insert the stopper, 4 with its 
 tube, close the pinch-cock, and weigh the bottle, tubes 
 
 1 Henry Cavendish, born 1731, died 1810, was an English chemist 
 and physicist, very wealthy and very bashful. 
 
 2 See foot-note, page xxvii of the Introduction. 
 
 3 A cheap, stout, narrow-necked bottle. 
 
 4 In this experiment to make the joints air-tight, it is well to smear 
 the stopper and all rubber connectors with glycerine or vaseline. Be 
 sure, however, that all greasing is done before the first weighing. 
 
142 PNEUMATIC PERIOD. 
 
 and all, full of air. With a small air-pump * draw from 
 the bottle as much air as you can. Close the rubber 
 tube with the pinch-cock, again weigh the bottle with 
 its fittings, and note the loss in weight. What has 
 caused the loss? Now get the volume of air removed 
 as follows : Have ready a pail, or tub, of water. Open 
 the pinch-cock with the end of the rubber tube well 
 under water. What causes the water to rush in? 
 Lower the bottle in the water till the w r ater inside and 
 outside is on the same level. Why on the same level ? 
 Close the pinch-cock, wipe the bottle dry, and weigh 
 on the platform balances [accurately to 1 gram only]. 
 Remembering that 1 gram of water equals l cc , get the 
 volume of the water which has entered, i.e., the volume 
 of the air which was pumped out. 
 
 Find the weight of l cc of air in the room, at the time 
 of doing the experiment. This, then, is the density of 
 air, the density of any substance being the weight of 
 a unit volume of that substance. The specific gravity 
 of a substance is the number of times heavier a given 
 volume of that substance is than an equal volume of 
 some substance taken as a standard. Water is often 
 taken as the standard substance. If l cc of water weighs 
 1 gram, calculate the specific gravity of air referred to 
 water. Calculate the weight of air in a room 15 meters 
 long, 13 meters wide, and 7 meters high. After you 
 get the weight in grams get it in pounds, assuming that 
 1 pound is equivalent to 453.6 grams. 
 
 1 Small pumps like those often used for inflating the tires of bicycles, 
 serve well for this purpose, provided they have check-valves for exhaus- 
 tions. 
 
THE LAW OF D ALTON. 143 
 
 Note that air, as well as every other gas, is an elastic 
 body, which can be compressed into smaller space by 
 pressure [see Ex. 9, the Law of Boyle]. The greater 
 the pressure, the greater the amount of air in a given 
 volume, hence the greater the density. If, then, other 
 things being equal, you filled your bottle with air when 
 the barometer stood high, i.e., when, owing to atmos- 
 pheric conditions, the pressure on the air at the surface 
 of the earth was great, you would get a greater density 
 for the air than you would had the barometer stood 
 low. 
 
 The density of a gas is also affected by the tempera- 
 ture. As is well known, the higher the temperature 
 the greater the volume of a given weight of gas, and the 
 lower the temperature the less the volume. The expres- 
 sion of the exact rate at which a gas volume decreases 
 when the temperature is lowered [or increases when 
 it is raised], is called the Law of Dalton, from John 
 Dalton, who seems to have been the first to state this 
 law clearly. 1 
 
 Experiment 13. 
 The Law of Dalton. 2 
 
 Have ready a 250 CC flask fitted with a one-hole rubber 
 stopper. Also have ready about 25 cm of glass tube to 
 fit the hole in the stopper, also about 25 cm of rubber- 
 tube to fit the glass tube, also a pinch-cock to close the 
 
 1 This law is also called the Law of Charles, from a Parisian investi- 
 gator, who is said to have discovered it. 
 
 2 See foot-note, page xxvii of the Introduction. 
 
144 PNEUMATIC PERIOD. 
 
 end of the rubber tube. It is necessary to have ice or 
 snow for this experiment. 
 
 Make sure the flask and all tubes are dry. Insert 
 the glass tube through the stopper. Let the glass tube 
 reach nearly to the bottom of the flask and protrude only 
 about 1 inch from the stopper. Connect the rubber 
 tube with the glass tube. Let the pinch-cock be placed 
 at the extreme end of the rubber tube farthest from the 
 stopper. Why? Have ready a vessel of warm water. 
 Insert the stopper in the flask. Open the pinch-cock 
 and plunge the flask beneath the water, but do not let 
 any water get into the flask or tubes. Why? Bring 
 the water to the boiling point, 100 centigrade. 
 When the flask is wholly immersed in boiling water 
 close the pinch-cock and remove the flask from the water 
 bath. Keep your eyes away as the flask may burst. 
 When cool, open the pinch-cock with the end of the 
 tube under iced water. When as much water as pos- 
 sible has entered, close the cock. Make an ice-water 
 bath [with much floating ice] of your hot-water bath, 
 and return the flask. Have at hand a beaker contain- 
 ing ice-water, in which much melting ice is floating. 
 Again open the cock, with the end of the tube under 
 the surface of the ice-water in the beaker. Keeping 
 the flask well under the cold water, make the level 
 of the water in the flask and that of the water in 
 the beaker the same [by raising or lowering the 
 beaker], and close the cock. Remove the flask from 
 the ice bath. Loosen the stopper, open the cock, 
 and let the water in the tubes run into the flask. 
 Why? Get the volume of the water in the flask. 
 
OJ TOT 
 
 
 SP. GV. OF CARBONIC DIOXIDE. 
 
 * : . 
 
 Also get the total contents of the flask [when the 
 tube is in it]. From the data thus prepared, calcu- 
 late [a] the volume of the air experimented on at ; 
 [b] its volume at 100 ; [c] the amount the volume at 
 would expand in going to 100; [d] the amount it 
 would expand in going 1 ; and, finally, [e] the amount 
 that unit volume would expand in going 1. This 
 last numerical value is called the coefficient of expan- 
 sion. It should come out about 0.00366 or ^fa. If 
 l cc of gas, measured at 0, loses or gains -%\-% of its 
 volume for every degree cooled or heated, respectively, 
 at what temperature does it become 2 CC ? What would 
 be the volume of l cc of gas, measured at 0, if cooled 
 to - 273 ? What is the point - 273 called ? 
 
 The Law of Dalton may be stated thus. The volume 
 of a gas varies directly as the temperature on the abso- 
 lute scale, i.e., a scale having its point 273 below 
 C., its 273 mark at C., its 373 mark at 100 C., 
 etc. Or the law may be stated thus. TJie volume of a 
 gas measured at C. increases [or decreases], by ^\-% of 
 itself for every degree 0. that the temperature increases 
 [or decreases]. 
 
 Experiment 14. 
 Weight and Specific Gravity of Carbonic Dioxide. 1 
 
 Note. In comparing the weights of gases, air, more 
 frequently than water, is taken as a standard substance. 
 The comparison, also, is usually made at what are 
 called standard conditions, i.e., when the temperature 
 
 1 See foot-note, page xxvii of the Introduction. 
 
146 PNEUMATIC PERIOD. 
 
 is C. and the barometer is 760 mm . The expression 
 "standard conditions" is often expressed by N. T. P., 
 i.e.. Normal Temperature and Pressure. The weight 
 of l cc of air at N. T. P. is O.OO1293 g . In deter- 
 mining the specific gravity of a gas, the weight of a 
 known volume is determined, then, by the laws of 
 Boyle and of Dalton, the volume which this weight 
 would occupy under standard conditions calculated, 
 and from these figures the density is determined. 
 
 Have ready as large a flask as will ride on your 
 small balance. The flask should be fitted with a one- 
 hole rubber stopper, through the hole of which passes 
 a tightly-fitting piece of glass tube long enough to 
 reach to the bottom of the flask and to project an inch 
 or so from the top of the stopper. The outer end of 
 the glass tube should carry an inch or so of rubber 
 tube with a pinch-cock. All joints should be made 
 air-tight with vaseline or glycerine, but there should 
 be no superfluous grease. Fit the stopper to the 
 flask, fill completely to the pinch-cock with water and 
 measure the contents in cc. Clean and dry the flask, 
 making sure no water lurks in the tubes or at the 
 joints. Loosen the stopper so that air can pass in or 
 out freely, but do not remove the stopper from the 
 flask. Set the flask thus fitted on the pan of the 
 delicate balance. On the other pan set a second flask 
 of the same size closed by a solid stopper. Why? Add 
 any additional weight necessary, to one side or the other, 
 for a perfect equilibrium. Note the temperature close 
 to the flask and take the barometer reading. From 
 
SP. GV. OF CARBONIC DIOXIDE. 147 
 
 the known volume of the flask, calculate, bearing in 
 mind the laws of Boyle and of Dalton, the weight 
 of air which the open flask holds, thus : 
 
 Let W = weight of the air. Let H height of barometer. 
 V = volume as measured. x = volume at760 mm [and t~\. 
 
 t = temperature. y = volume at 760 mm and 0. 
 
 V :-x : : 760 : H. x : y : : 273 + t : 273. 
 
 Therefore x = ^^ Therefore y = |^-|^ 
 
 As the weight of l cc of air at N. T. P., or and 760 mm , 
 is 0.001293s, W - y times 0.001293. 
 
 Note. If weights to the amount of the weight of 
 air that fills the flask are placed on the scale with the 
 flask and all the air pumped out of the flask, the flask 
 and its counterpoise will still balance. 
 
 Prepare carbonic dioxide from marble and hydrochloric 
 acid. Pass it first through water and then through sul- 
 phuric acid to purify it. [Use catch-bottles.] Pass the 
 gas through the rubber and the glass tubes into the flask 
 till a match, held where the stopper is loosened, is extin- 
 guished. Insert the stopper, close the pinch-cock, and 
 remove the oxide generator. Open the pinch-cock for 
 an instant to let out any excess of gas. Close it again. 
 Note the temperature close to the flask, take height of 
 barometer, and find the gain in weight of the flask. 
 To make sure the flask is full of carbonic dioxide, 
 again pass in the gas, for five minutes, and proceed as 
 before. If there is any further gain in weight the 
 flask was not full the first time, and you must again 
 pass in the gas for five minutes, and so continue till 
 
148 PNEUMATIC PERIOD. 
 
 there is no further gain. This weighing, and pass- 
 ing, and weighing again, is called weighing to constant 
 weight. When you have got the weight constant, 
 again take temperature and pressure. The gain in 
 weight, plus the weight of the air the flask held, is the 
 weight of the carbonic dioxide at the observed tempera- 
 ture and pressure. From the weight of the carbonic 
 dioxide calculate what would be the weight of the same 
 volume if the temperature were zero and the pressure 
 760 mm , remembering that the weight of a given volume 
 of gas varies directly as the pressure and inversely as 
 the temperature on the absolute scale. The density, 
 then, of carbonic dioxide i.e., the weight of l cc 
 under standard conditions, is found by dividing the 
 weight of the gas, at N. T. P., by the volume of the 
 flask. Then the density of carbonic dioxide at N. T. P. 
 divided by the density of air at N. T. P. [0.001293] 
 gives the specific gravity of carbonic dioxide referred 
 to air. 
 
 Experiment 15. 
 Weight and Specific Gravity of Hydrogen Gas. 1 
 
 In a similar manner to that of the last experiment, 
 determine the specific gravity of hydrogen gas. 
 
 Caution ! Have no fire near when doing this experi- 
 ment. Be sure the hydrogen is pure and dry. It is 
 best to pass the hydrogen through at least three catch- 
 bottles, the first containing a solution of sodium 
 
 * See foot-note, page xxvii of the Introduction. 
 
SP. GV. OF ILLUMINATING GAS. 149 
 
 hydroxide, the others sulphuric acid. Pass in a large 
 and rapid stream of hydrogen in order to fill the flask 
 completely. 
 
 Note that hydrogen is 14.37 times lighter than 
 air. As hydrogen is the lightest gas known, it is 
 most often taken as the standard substance for specific 
 gravity determinations in the case of gases and vapors. 
 Calling the sp. gv. of hydrogen unity, calculate [from 
 the data of Experiment 14] the sp. gv. of carbonic 
 dioxide referred to hydrogen. 
 
 Experiment 16. 
 Weight and Specific Gravity of Illuminating- Gas. 1 
 
 Take the gas from the gas-burner tap. Do not have 
 an explosion. Proceed as in the previous experiment. 
 Get the sp. gv. referred to water, to air, to hydrogen. 
 
 The above method can be used for vapor density 
 determinations, i.e., for determining the specific gravity 
 of substances that are commonly solids or liquids, but 
 which, by heat, can be converted into vapors. For 
 such determinations, of course, the flask must be im- 
 mersed in a suitable bath [as one of air, paraffine or 
 oil], which can be heated ; and instead of filling by 
 passing in vapor, it is better to put a little of the 
 substance in the liquid [or solid] form in the bottom 
 of the flask where the heat of the bath will convert it 
 into vapor, the excess of which must be allowed to 
 
 1 See foot-note, page xxvii of the Introduction. 
 
150 PNEUMATIC PERIOD. 
 
 escape, leaving the flask exactly full of vapor at the 
 moment the tube is sealed and the temperature of the 
 bath and the air pressure determined. 
 
 As every gas has its own particular specific gravity, 
 a determination of specific gravity is an excellent 
 method for distinguishing one gas from another, and 
 for telling whether a given body of a known gas con- 
 tains an admixture of another gas or not. 
 
 One of the most important problems presented to 
 the chemists in the pneumatic period was the compo- 
 sition of our atmosphere was it to be considered a 
 simple substance, a compound, or a mixture of two or 
 more ingredients? The problem was solved, inde- 
 pendently, by two of the most eminent workers of the 
 time, Priestly, 1 an English clergyman, and Scheele, 2 a 
 poor Swedish apothecary. The brilliant researches of 
 Priestly added much to chemical knowledge, but, above 
 all, he will ever be remembered for his discovery, in 
 1774, of oxygen gas. Nitrogen had already, in 1772, 
 been obtained by Rutherford, and immediately after 
 his own discovery of oxygen, Priestly arrived at the 
 right conclusion in regard to the nature of air, i.e., that 
 it is a mixture of two gases. 
 
 Priestly failed, however, to find a true explanation 
 for combustion, doubtless, because he clung so tena- 
 ciously to the theory of phlogiston. He, too, as well 
 as Cavendish, never, to his dying day, was convinced 
 of the absurdity of a belief in phlogiston. 
 
 1 Joseph Priestly lived 1733-1804. 
 
 3 Karl Wilhelm Scheele lived 1742-1786. 
 
SCHEELE. 151 
 
 It is interesting to note Priestly's ideas of original 
 investigations, differing, as they do, so much from 
 those now held. It has been said that "he believed 
 that all discoveries are made by chance and he com- 
 pares the investigation of nature to a hound, wildly 
 running after, and here and there chancmg on game 
 [or as James Watt called it, his random haphazarding], 
 whilst we would rather be disposed to compare the 
 man of science to the sportsman, who having, after 
 persistent effort laid out a distinct plan of operations, 
 makes reasonably sure of his quarry." l 
 
 Scheele, however, formed a striking contrast to 
 Priestly in his methods of investigation, for of Scheele 
 it has been said truly, " his discoveries were not made 
 at haphazard but were the outcome of experiment care- 
 fully planned." Though living in- a country where he 
 had little scientific companionship and where it was hard 
 to obtain apparatus and materials for his researches, and 
 though he himself was often hard-pressed by poverty, 
 Scheele contributed an immense amount to the rapidly 
 increasing store of chemical knowledge. As examples, 
 from the long list of his works, may be selected : his 
 devising new ways for preparing medical chemicals ; 
 his qualitative analyses of many new minerals, from one 
 of which he got molybdic acid ; his proof that plumbago 
 is chiefly carbon ; his discovery of an acid [now called 
 lactic] in sour milk ; his preparation of mucic acid from 
 milk sugar ; his discovery of glycerine and many acids 
 in the vegetable kingdom, e.g., tartaric, citric, malic, 
 oxalic, and gallic; his discovery, in an investigation 
 
 1 Koscoe and Schorlemmer, Treatise on Chemistry, vol. I. 
 
152 PNEUMATIC PERIOD. 
 
 of Prussian blue, of hydrocyanic acid, whose properties 
 he described, speaking of its smell and taste, but totally 
 ignorant of its frightfully poisonous nature ; his prep- 
 aration of a beautiful bright green coloring matter, 
 ever since called Scheele's green l ; and, above all, his 
 extended w*ork on the black oxide of manganese. 
 Scheele died at the early age of forty-four, but the 
 number of discoveries in that short life is, perhaps, 
 unprecedented. A remarkable power of observation, 
 an extreme diligence, and an ability to plan experi- 
 ments which should bear directly on the question in 
 hand and give decisive results in the quickest and 
 simplest way, have given Scheele a high rank among 
 chemists of all lands and all times. He constantly 
 sought the truth by all the means at his command ; 
 he was never content to leave anything in doubt which 
 could possibly be proved by experiment; nor was he 
 ever satisfied to let his investigation of any compound 
 rest until he could both take it to pieces and put it 
 together again. To attain his ends, he begrudged no 
 amount of labor on his own part. 2 In his investiga- 
 tion of the black oxide of manganese, then called 
 magnesia nigra, he discovered no less than four sub- 
 stances, baryta, manganese, chlorine, and oxygen. It 
 was a strange coincidence that Scheele in Sweden, 
 
 1 Prepared by adding sodium arsenite to a copper solution, copper 
 arsenite being thrown down as a grass green precipitate. This sub- 
 stance has been used largely for a paint, but as its poisonous character 
 is now well known it is being superseded by other, e.g., aniline, 
 greens. 
 
 2 It is supposed that Scheele's constant application to his work, 
 particularly at night, brought on a sickness which, aggravated per- 
 haps by actual want, caused his early death, 
 
LAVOISIER. 158 
 
 independently of Priestly in England, should dis- 
 cover such an important substance as oxygen in the 
 very same year, 1774, and also arrive at the same 
 conclusion in regard to the composition of the air. 
 They concluded, as Priestly stated it, that "the air 
 must be made up of elastic fluids of two kinds." 
 Both Scheele and Priestly first prepared oxygen from 
 red oxide of mercury. 
 
 But neither Scheele nor Priestly applied his knowl- 
 edge of the nature of air to an interpretation of the 
 phenomena of combustion, a true explanation of which 
 was reserved for the French physicist and chemist, 
 Lavoisier. 1 Though the discovery was not long delayed, 
 an important intermediate step had to be taken. Cav- 
 endish isolated hydrogen and called it "inflammable 
 air." Soon after the discovery of oxygen, he found 
 that a mixture of hydrogen and oxygen when exploded 
 produce water. This was a very important discovery, 
 for hitherto water had been considered a simple sub- 
 stance* As early as 1770, Lavoisier had conducted an 
 elaborate experiment which disproved the theory that 
 by long boiling water could be converted into earth. 
 He boiled water for many days in a closed vessel, 
 having first weighed the vessel and the water. At 
 the end of the boiling he did find a considerable 
 amount of earthy matter in the water, but, as the 
 gain in weight of the water corresponded to the loss 
 in weight of the vessel, he rightly concluded that the 
 water had dissolved some of the earthy matter of the 
 vessel. 
 
 1 Born in 1743, impeached under the Reign of Terror at the time of 
 the French Revolution, Lavoisier was executed in May, 1794. 
 
154 PNEUMATIC PERIOD. 
 
 Lavoisier was a physicist, and as such had an extreme 
 love for the nicety of physical measurements. It was 
 his application of the balance to a study of chemical 
 changes that enabled him to use the discoveries of 
 Priestly, Scheele, Cavendish, and others in arriving 
 at the true explanation of the process of combustion, 
 and thus changing completely the prevailing ideas in 
 regard to the nature of combustion, as well as those 
 about the respiration of animals. 
 
 It was in 1770 that Lavoisier published an account 
 of his celebrated experiment on the change of water 
 into earth. Soon after this, he turned his attention 
 to the study of combustion phenomena, particularly 
 those in which a metal on being heated in contact 
 with the air forms a non-metallic substance. For this 
 work he made use of a delicate balance, weighing the 
 substances to be burned and weighing the products 
 of combustion. At first, Lavoisier was a believer in 
 phlogiston, but he soon threw over this belief. Though 
 the phlogistonists eagerly grasped at the newly-dis- 
 covered hydrogen and attempted to identify this as 
 their long sought for phlogiston, and though it did 
 seem as though hydrogen might be phlogiston, inas- 
 much as when hydrogen is added to the oxide of a 
 metal, the metal appears again; still there was one 
 important fact which no theory of phlogiston had 
 been able to explain, i.e., the production of quick- 
 silver when the red oxide of mercury is heated apart 
 from hydrogen, charcoal, or any other substance. 
 
 As early as 1772, Lavoisier felt so sure that he was 
 on the track of something new in regard to combus- 
 
THEORY OF COMBUSTION. 155 
 
 tion, that he sent to the French Academy a sealed 
 note containing a description of his work up to that 
 time. In this note he stated that when sulphur, 
 phosphorus, and some of the metals are burned, the 
 increase in weight is caused by the absorption of air. 
 A hundred years before this, Mayow 1 had arrived at 
 the conclusion that our atmosphere [and nitre also] 
 contains a substance which is able to unite with metals 
 when they are heated, and is also used by the lungs 
 when we breathe, changing the spent blood into the 
 fresh arterial. This substance, contained in the air 
 and in nitre, he called spiritus igno-aereus or nitro 
 aereus. Had Mayow lived, it is possible that he, 
 instead of Lavoisier, might have made the great gen- 
 eralization which fell to the lot of the latter. 
 
 In his note to the French Academy, Lavoisier stated 
 that when litharge [an oxide of lead] is heated with 
 coal in a closed vessel a great volume of air is pro- 
 duced. It was not long, however, before he himself 
 saw that it was not air, but another gas which was 
 produced in this reduction of litharge. As we have 
 seen, the discovery of oxygen came in 1774. Lavoisier, 
 unhampered by any desire to perpetuate the phlogiston 
 theory, saw at once that the discovery of oxygen gave 
 the key to the explanation of the most important chem- 
 ical question of the times. He saw that, if you assume 
 that in combustion this gas combines with the metals, 
 charcoal, sulphur, etc., you can explain the increase in 
 weight as well as all other changes without having to 
 resort to any such absurdity as a substance with a 
 
 1 John Mayow, born 1645, died in 1679 at the early age of 34. 
 
156 PNETTMATIC PERIOD. 
 
 negative weight. In 1775 he published his opinions 
 in regard to the action of oxygen; in 1776 he showed 
 that when the diamond is burned oxide of carbon is 
 produced ; and in 1777 he proved the amount of 
 oxygen, by volume, in the air by burning phosphorus 
 in a closed vessel, and noting that one fifth of the air 
 had disappeared after the burning. 
 
 Briefly stated, Lavoisier's oxidation theory was that 
 substances burn only in extremely pure air ; that when 
 a substance is burned, for the increase in weight there 
 is a corresponding decrease in the weight of the air; 
 also, that the substance burned is changed into a sub- 
 stance which is generally an acid, though the metals 
 yield substances which are not acid. From this it will 
 be seen that Lavoisier thought the acids contained 
 oxygen. He tried to prove that oxygen itself was an 
 acidifying principle, believing, for instance, that sul- 
 phuric aeid consisted of sulphur and oxygen, and phos- 
 phoric acid of phosphorus and oxygen. Even hydrochlo- 
 ric acid he thought must contain oxygen, and, assuming 
 that when hydrogen is burned an acid must result, he 
 attempted to find the acid. In 1783, however, Caven- 
 dish discovered that water is the product of the com- 
 bustion of hydrogen. Then Lavoisier made use of this 
 discovery of Cavendish's in explaining correctly the 
 manner in which hydrogen is produced from water by 
 red-hot iron ; the cause for the appearance of water 
 when oxides are reduced by hydrogen ; and the produc- 
 tion of hydrogen from acids by adding them to metals. 
 
 These important explanations led to such great 
 reforms in chemistry that the admirers of Lavoisier 
 
CONSERVATION OF MASS. 157 
 
 have sometimes claimed that he was the founder of 
 scientific chemistry. That chemistry was a science 
 long before this, however, we have already seen. 
 
 To Lavoisier we must give the credit of first dis- 
 covering a law of general application in chemistry. 
 Never before his time do we find a man thoroughly 
 impressed with the idea that no matter is lost how- 
 ever great the change in which it is involved. He, 
 however, seems to have had this belief constantly fixed 
 in mind, and as constantly to have directed his ex- 
 periments toward proving that the sum of the weights 
 of the factors, in a chemical change, is exactly equal to 
 the sum of the weights of the products. This great 
 generalization is called The L.aAv of Conservation of 
 Mass, or of the Indestructibility of Matter. 
 
 Experiment 17. 
 Conservation of Mass. 
 
 The Law. The sum of the weights of the products 
 of a chemical change is exactly equal to the sum of the 
 weights of the factors. 
 
 A. The Combustion Products of a Candle. 
 
 Take a piece of fine iron gauze. Cut from it a 
 circular piece about three and one half inches in 
 diameter. Take a square foot of the same gauze. 1 
 With the square foot make a cylinder around the 
 
 i One piece of gauze will do for a large class of students, 
 
158 PNEUMATIC PERIOD. 
 
 circular piece, so that the circular piece shall form 
 a shelf half way down the cylinder and divide the 
 volume of the cylinder in two equal portions. The 
 cylinder may be kept in place around the disk by 
 being wound with wire. 
 
 Place a five-inch piece of paraffine candle on one 
 pan of a platform balance. Set the cylinder over the 
 candle. In the upper compartment put 150-200 g of 
 hydroxide of sodium 1 in stick form. Balance the 
 apparatus with any convenient tare. Light the candle 
 and let its flame pass up among the sticks of hydroxide. 
 At the end of five minutes note the gain in weight. 
 Put out the flame and wait five minutes more. Note 
 that during the second five minutes there is a slight 
 gain in weight, due to the absorption of moisture from 
 the air by the deliquescent hydroxide of sodium. This 
 gain, however, is only a small fraction of the amount 
 gained when the candle was burning. Therefore, 
 though the candle was gradually disappearing, the 
 substance of the candle was not annihilated. What 
 have we already found, by means of lime water, to 
 be one of the products when a candle burns in air? 
 Hold a clean, cold, and dry tt directly over the flame of 
 a candle, but not near enough to the flame to touch it. 
 What is a second product of the burning? Analysis 
 would show that the candle is composed of a substance 
 paraffine which is itself composed of carbon and 
 hydrogen only. What happens to hydroxide of sodium 
 
 1 As soon as one student has used this hydroxide of sodium it should 
 be put in a bottle, for, if kept away from the air, it will serve for eight 
 or ten students. The circular shelf of gauze, however, should be 
 washed after every trial. 
 
CONSERVATION OF MASS. 159 
 
 when in contact with dioxide of carbon, when in contact 
 with water? Why was there an actual gain in weight 
 in this experiment? 
 
 B. The Weight of the Products is Equal to the Weight of 
 the Factors. 
 
 Take, of thoroughly dry nitrate of barium, exactly 
 10 g and, of thoroughly dry sulphate of potassium, 
 exactly 7 g . Dissolve each substance in a separate 
 beaker containing about 100 CC of water. Bring both 
 solutions just to a boil. Add one to the other, washing 
 the last drops from the beaker by means of the wash- 
 bottle. Note the metathesis. The barium changes 
 place with the potassium, and there results sulphate 
 of barium and nitrate of potassium. Let the sulphate 
 settle. Have ready a weighed filter paper in a 3-inch 
 funnel. Decant the clear liquid, through the filter, 
 into a good-sized weighed beaker, or evaporating dish. 
 Transfer the precipitate to the filter, washing out every 
 bit by means of the wash-bottle. Do not lose any pre- 
 cipitate, and save all the wash water. Collect all the 
 filtrate, and evaporate, cautiously, to dryness. Get 
 the weight of the residue. Also dry the precipitate 
 and get its weight. Compare the sum of the weights 
 of the two products with the sum of the weights of 
 the two factors. 
 
 For Review. What is the meaning of pneumatic? 
 To what period of chemistry is it applied ? What did 
 Van Helmont contribute to this period? What did 
 Boyle contribute to our knowledge of gases? What 
 
160 PNEUMATIC PERIOD. 
 
 did Black contribute? State the law of Dalton [or 
 Charles]. What is the absolute scale of temperature? 
 When did Cavendish live ? What do we owe to him ? 
 What is the distinction between density and specific 
 gravity? How may gases be distinguished from one 
 another ? Who determined the composition of the 
 atmosphere ? When was nitrogen discovered ? When 
 was oxygen discovered, and by whom? What is 
 Scheele's green? What enabled Scheele to accom- 
 plish so much in so few years ? When, and by whom, 
 was the composition of water proved? Who was 
 Lavoisier? What did Lavoisier apply in chemistry? 
 State Lavoisier's theory of combustion. What was 
 Lavoisier's theory in regard to acids ? State the first 
 great law of chemistry. What is this law called? 
 Give an illustration of this law. 
 
THE ATOMIC THEORY PERIOD. 161 
 
 CHAPTER VIII. 
 
 THE MODERN, OR ATOMIC THEORY, PERIOD. 
 
 1. John Dalton 1 proposed the most celebrated 
 theory chemistry has ever had a theory which has 
 been a safe guide for its followers ever since. Soon 
 after Lavoisier established the law of conservation of 
 mass, two other fundamental laws of chemistry were 
 discovered, and it was while pondering over these last 
 two laws that Dalton formed an hypothesis in regard 
 to the constitution of matter which soon developed 
 into his famous Atomic Theory. 
 
 During the last decade of the eighteenth century, 
 Richter, 2 a German chemist, investigated the neutral- 
 ization of acids with alkalies, and stated that when 
 several portions, all equal in weight, of an acid are 
 taken and neutralized, each with a different alkali, 
 the amounts of the alkalies are equivalent. He also 
 believed that the composition of a substance is con- 
 stant, e.g., that whenever nitre is made by neutralizing 
 nitric acid with hydroxide of potassium the amount 
 of potassium in a given weight of the nitre is always 
 the same, and that when zinc sulphate is formed by 
 the action of zinc on sulphuric acid the percentage of 
 zinc in the resulting sulphate does not vary whether 
 a large or a small amount of acid has been used., 
 
 There was an eminent French chemist, however, 
 
 1 Lived, 1766-1844, in England. 
 
 2 Jeremias Benjamin Richter, born in 1762, died in 1807, worked in 
 Breslau and at Berlin. 
 
162 THE MODERN PERIOD. 
 
 Berthollet, 1 who, in the first decade of the nineteenth 
 century, advanced ideas very much opposed to those 
 of Richter. Berthollet did not believe that compounds 
 possess a fixed composition. He maintained that when 
 a compound is formed from two simple substances, the 
 amount of either constituent in the resulting compound 
 varies according to the quantity of that factor at hand, 
 e.g., that if an acid be treated with a large amount of a 
 metallic hydroxide, the resulting salt will contain more 
 metal than it would had a smaller proportion of the 
 hydroxide been used, and vice versa. 
 
 On account of the above assumption, Berthollet 
 soon became involved in a dispute, which lasted for 
 eight years, with another chemist, Proust. 2 Proust 
 had already shown that a number of substances never 
 vary in composition. He now undertook to prove 
 the falsity of Berthollet's assumption, and in the end 
 succeeded in showing that his opponent had often 
 analyzed mixtures, instead of true chemical com- 
 pounds. Very likely Berthollet himself had been led 
 astray by the now well-known fact that some sub- 
 stances form with others a series of compounds, e.g., 
 sulphur, we have found, forms with oxygen sulphurous 
 oxide and sulphuric oxide, carbon also, we saw, forms 
 two oxides, and nitrogen forms not less than five. 
 While Berthollet believed that metals form oxides 
 with gradually and indefinitely increasing amounts of 
 oxygen, Proust proved that the formation goes on in 
 jumps, i.e., that a given substance, capable of forming 
 two oxides, after it has taken up a given amount of 
 
 1 Claude Louis Berthollet, born in 1748, died 1822, 
 
 2 Born 1755, died 1826. 
 
DEFINITE PROPORTIONS BY WEIGHT. 163 
 
 oxygen and formed the first oxide, will not, as the 
 conditions are varied, take up a little more and then 
 a little more oxygen till complete saturation is reached, 
 but will jump at once from the first proportion to the 
 last. As the result of this famous controversy a second 
 great law of chemistry became established. This law 
 may be stated thus. Every distinct chemical compound 
 has a fixed and unalterable composition. This is called 
 The Law of Definite Proportions by Weight. 
 
 Experiment 18. 
 
 Law of Definite Proportions by Weight. 
 
 Weigh out exactly 10 grams of sal soda. The sal 
 soda should be in good clear crystals, not effloresced. 
 Put the sal soda in a beaker tall enough to avoid sub- 
 sequent spattering out. Dissolve in 40-50 CC of water. 
 Add hydrochloric acid solution till no more effervescence 
 takes place. Transfer the liquid to a weighed evapo- 
 rating dish, washing the last traces from the beaker 
 into the dish with pure water from the wash-bottle. 
 Evaporate to dryness, avoiding all spattering. Get 
 the weight of the residue. 
 
 Again take exactly 10 grams of sal soda, treat with 
 hydrochloric acid as before, but when the effervescence 
 has ceased add a considerable excess of hydrochloric 
 acid. Evaporate, and weigh. Compare the weight 
 with the first. Has there been, in the second case, 
 a taking up of an excess of the acid principle? 
 
164 THE MODEBN PERIOD. 
 
 2. QUANTITATIVE ANALYSIS. 
 
 The branch of chemistry called Quantitative Analysis 
 is based upon the law of definite proportions by weight. 
 In Qualitative Analysis, the chemist has to determine 
 what substances are present in the body to be analyzed. 
 In Quantitative Analysis, he determines how much of 
 a substance, known to be present, is present. As in 
 Qualitative Analysis, so in Quantitative, the substance 
 looked for can sometimes be isolated, e.g., when we 
 desire to know the amount of mercury in a given 
 weight of the red oxide of mercury, we can heat the 
 substance and weigh the resulting mercury; or if we 
 wish to know the amount of iron in iron oxide we 
 can pass hydrogen over the hot oxide, and after the 
 hydrogen has carried off all the oxygen we can weigh 
 the remaining iron ; or when we have passed the electric 
 current through a compound in solution, often one of 
 the constituents is deposited, or driven off as a gas, 
 and this we can collect and weigh. But in a vast 
 number of cases, when quantitative analyses are called 
 for, no such isolation can be made. In these cases cer- 
 tain chemical changes are brought about which convert 
 the whole of the substance looked for into some sub- 
 stance whose percentage composition is known, or can be 
 found, and whose weight can be determined accurately. 
 For instance, we desire to know the amount of chlorine 
 in a gram of the salt just made in Ex. 18. It would be 
 very hard to isolate this chlorine from its sodium, and 
 next to impossible to weigh it accurately if isolated. 
 But we can easily combine the chlorine with silver [while 
 
QUANTITATIVE ANALYSIS. 165 
 
 at the same time we combine the sodium with nitrogen 
 and oxygen to form nitrate of sodium] and thus convert 
 the chlorine all into silver chloride, which we can 
 weigh. If, now, we determine the percentage of chlo- 
 rine in silver chloride, as we can do in a simple manner, 
 we can, by arithmetic, calculate the weight of chlorine 
 in the silver chloride that was formed from our original 
 gram of salt, for the law of definite proportions by 
 weight declares that every compound has a fixed and 
 unalterable composition, hence the percentage composi- 
 tion of silver chloride made in one way must be the 
 same as that of silver chloride made in any other way. 
 Knowing the weight of chlorine in the silver chloride 
 made from our salt, we know the weight of chlorine in 
 the salt because all the chlorine of the salt went into 
 this silver chloride. 
 
 Experiment 19. 
 
 Analysis of Table Salt. 
 
 What simple substances have we already proved to 
 be in table salt ? How did we prove this ? 
 
 Have ready about 5 g of c.p. sodium chloride. To 
 make sure that the salt is thoroughly dry, pulverize it, 
 put it in a porcelain evaporating dish and heat for about 
 five minutes over the Bunsen burner flame. When cool, 
 weigh out, on the small balances, exactly l g of the salt. 
 Put the salt in a medium-sized beaker, add about 30 CC of 
 distilled water, and warm till solution takes place. Then 
 weigh out, and place in a similar beaker, 5.0 g of nitrate 
 
166 THE MODERN PERIOD. 
 
 of silver. Dissolve the nitrate of silver also in about 
 30 CC of distilled water. Heat both solutions till you 
 just cannot bear your hand on the sides of the beakers, 
 then, using a glass rod to direct the stream, pour, care- 
 fully, with constant stirring, the salt solution into the 
 nitrate solution. With a stream of water from the 
 wash-bottle, wash out into the main liquid the last 
 traces of the salt solution. Protect the contents of 
 the beaker from the action of sunlight. Continue to 
 heat, gently, till the precipitate has settled. Have 
 ready, in a funnel, a well dried and weighed filter. 
 Decant the clear liquid, down a rod, through the filter. 
 Transfer all the precipitate to the filter. In order to 
 get out the last particles make use of the glass rod 1 and 
 a stream from the wash-bottle. Wash the precipitate 
 well with distilled water, and dry 2 it on the paper. 
 Dry to constant weight, but do not burn the paper. 
 Get the weight of the silver chloride formed. 
 
 In order to find the amount of chlorine, we must 
 know what per cent of chlorine there is in silver chlo- 
 ride itself. Determine this as follows: 
 
 Weigh out, on the small balances, exactly l g of pure 
 silver. Place the silver in a small beaker, and add 
 about 2 CC of nitric acid diluted with two or three times 
 its volume of water. Heat, gently, to produce rapid 
 solution. When the silver is all changed to the soluble 
 nitrate, add about 25 CC of distilled water. In a second 
 beaker dissolve in about 30 CC of distilled water, at least 
 2 g of c.p. chloride of sodium. Heat each solution; mix; 
 
 1 For this work it is well to have on the end of the glass rod a piece 
 of tightly fitting rubber tube about l cm long. 
 
 2 See Appendix M, 
 
ANALYSIS OF TABLE SALT. 167 
 
 let settle ; filter ; wash, dry, and weigh the precipitate, 
 exactly as in the previous part of the experiment. 
 The silver has taken to itself chlorine from the chlo- 
 ride of sodium. The precipitate consists of silver 
 chloride. 
 
 The amount that this chloride of silver weighs in 
 excess of the l g of silver represents the amount of 
 chlorine the silver has taken, and from these figures 
 the per cent of chlorine in chloride of silver may be 
 found. 
 
 Now calculate the amount of chlorine in the l g of 
 chloride of sodium, and also the amount of sodium. 
 Let the final results be stated in parts per 100, i.e., 
 in percentages. A good worker should come within 
 \jo of the true amount of chlorine. 1 
 
 For Review. 1 and 2. Who proposed the cele- 
 brated atomic theory ? What was it that Kichter noted 
 in the last decade of the eighteenth century? What 
 did Richter believe in regard to the composition of 
 substances? What did Berthollet maintain? What 
 did Proust prove ? How, probably, did it happen that 
 Berthollet was led astray ? State the second great law 
 of chemistry. What is this law called? State the 
 results of an experiment that illustrate this law. What 
 is the object of Quantitative Analysis ? How does 
 Quantitative Analysis depend on the second great law 
 of chemistry? Describe, briefly, an experiment that 
 shows how quantitative determinations are usually 
 made in chemistry. 
 
 1 With the best of balances a good worker should come within 0.1% 
 of the true amount. 
 
168 THE MODERN PERIOD. 
 
 3. MULTIPLE PROPORTIONS. 
 
 Had Proust, in his examination of those cases in 
 which a given substance forms two or more oxides, 
 thought to start with some definite amount of the one 
 substance and calculate ratios between the varying 
 amounts of the second which unite with the first, he 
 would probably have been g the discoverer of the third 
 great law of chemistry. For instance, 10 g of carbon 
 produce either 23. 3 g of the combustible oxide or 36. 6 g 
 of the non-combustible. Now deducting, in each case, 
 the 10 g of carbon, we find that in the first case there has 
 been a taking on of 13.3 g of oxygen and in the second 
 26. 6 g or just twice as much, i.e., the ratio between the 
 two amounts of oxygen, when the amount of carbon 
 remains fixed, is a very simple one 1:2. But it does 
 not seem ever to have occurred to Proust to make such 
 a comparison. Dalton, however, saw that it might be 
 done. It was when examining two gaseous hydrogen 
 compounds of carbon olefiant gas and marsh gas 1 - 
 that Dalton did this. In 100 g of olefiant gas there are 
 85. 7 g of carbon and 14. 3 g of hydrogen, while in 100 g 
 of marsh gas there are 75. O g of carbon and 25. O g of hy- 
 drogen. Now, calling the amount of hydrogen, in each 
 case, any fixed number, as 10, and making proportions, 
 
 14.3 : 85.7 : : 10 : x 25 : 75 : : 10 : x 
 
 x = GO x = 30 
 
 30 : 60 : : 1 : x 
 
 1 The "fire-damp" of the mines. The oxide of carbon which 
 results from the explosion of this gas mixed with air is called the 
 " choke-damp." 
 
MULTIPLE PROPORTIONS. 169 
 
 we find that the amount of carbon in the first case is 
 to the amount of carbon in the second case as 2:1. 
 Dalton also examined the two oxides of carbon, and 
 found, as we have seen, that the amount of oxygen 
 in the one is to the amount in the other as 1:2. 
 For Dalton, this simplicity of numbers seemed to have 
 a deep meaning. In order to find the underlying law, 
 he set out to make an examination of other cases, par- 
 ticularly the formation of various oxides of nitrogen. 
 He soon made the discovery of the law of multiple 
 proportions. 
 
 Experiment 2O. 
 Multiple Proportions. 
 
 A. The Oxides of Sulphur. 
 
 We have studied two oxides of sulphur. In 100 
 parts, by weight, of one there are 50 parts of sulphur 
 and 50 parts of oxygen. In the second, there are 40 
 parts of sulphur and 60 parts of oxygen. Calculate 
 the amount of oxygen there is, in each case, if the 
 amount of sulphur, in each case, is called unity. Then 
 calculate the ratio between the amounts of oxygen 
 found. Note that the ratio is 2 : 3 exactly. 
 
 B. The Oxides of Nitrogen. 
 
 There are five oxides of nitrogen. 
 In the first the nitrogen rr 63.6% and the oxygen rr 36.4% 
 
 " " Second rr 46.6% " " " rr 53.4% 
 
 " " third " = 36.8% " " = 63.2% 
 " " fourth " " = 30.4% " " = 69.6% 
 
 " " fifth rr 25.9% " " rr 74.1% 
 
 Find the simple ratio for these compounds. 
 
170 THE MODERN PERIOD. 
 
 C. The Chlorides of Iron. 
 There are two chlorides of iron. 
 
 The first has 44.1% iron and 55.9% chlorine 
 " second 34.4% " " 65.6% " 
 
 Find the simple ratio. 
 
 The Law of Multiple Proportions may be stated 
 thus : When varying quantities of one substance join a 
 fixed amount of some other, the varying amounts of the 
 first bear to each other a ratio expressed in simple numbers, 
 as 1:2, 1 : 3, 2 : 3, or the like. 
 
 4. D ALTON'S ATOMIC THEORY. 
 
 Dalton did not rest on the discovery of his law of 
 multiple proportions. He was eager for an explana- 
 tion of the law as well as for one of the law of definite 
 proportions by weight. As an explanation of the facts 
 embodied in these two laws, he soon proposed one of 
 the most remarkable hypotheses that any branch of 
 science has ever known remarkable not only for the 
 manner in which it explained the facts known at its 
 inception, but also for the position which it has ever 
 since held as the very foundation of our modern chem- 
 ical science. The essence of this hypothesis was this : 
 that every simple substance is made up of minute 
 atoms, all alike and all of the same weight; that every 
 compound substance is made up of minute particles, 
 all alike, and each a collection of atoms of different 
 simple substances grouped in simple and unalterable 
 
ATOMS. 171 
 
 numerical ratio and chemically united. The atoms, as 
 the name implies, were considered indivisible. 
 
 It has long been a favorite discussion among specula- 
 tive philosophers whether there can be such a thing as 
 an indivisible particle of matter, some claiming that 
 such a substance is not only conceivable, but likely to 
 exist ; while others have said that every body we know 
 is capable of division, that each part from the division 
 is capable of subdivision and again these parts are 
 divisible, and so the division may be carried on forever 
 without arriving at a true atom, that is, a particle ab- 
 solutely indivisible. Herbert Spencer, 1 a philosopher 
 still living, after discussing this question, has concluded 
 that true atoms are inconceivable. But the chemist of 
 to-day finds it convenient to assume that there are such 
 particles and, what is more, he has some very clear 
 ideas in regard to them. 
 
 However, let us not consider the present conception 
 of atoms till we have traced Dalton's work a little 
 farther. Dalton was even bold enough to believe that 
 he could get at the [relative] weights of these atoms, or 
 minute particles, which make up all matter. He 
 thought that this end could be attained by noting the 
 amount of one substance which combines with a given 
 weight of another in the formation of a compound. 
 For instance, he made an experiment and concluded 
 that 6.5 g of oxygen united with l g of hydrogen, 2 in the 
 formation of water, and, assuming that the hydrogen 
 and oxygen united atom and atom, he gave to oxygen 
 
 1 "First Principles." 
 
 2 Dalton's determination here was not accurate, as the best modern 
 determinations give almost 8s of oxygen to Is of hydrogen. 
 
172 THE MODERN PERIOD. 
 
 the atomic weight of 6.5, calling hydrogen unity. But 
 this assumption, that one atom of oxygen joined one 
 atom of hydrogen, was not based on a knowledge of the 
 fact, and was therefore a mere speculation. We shall 
 return to this point. 
 
 Dalton prepared a table giving numbers for the atomic 
 weights of several different atoms. These numbers he 
 frequently altered, and himself recognized the necessity 
 for a most careful determination in the case of every 
 elementary substance, of its " combining number," that 
 is, the number expressing the proportion by weight in 
 which the substance joins other substances. Even to 
 the present day these combining numbers have not been 
 definitely fixed, and experiments are constantly being 
 carried on directed to the accurate determination of the 
 combining number for some one or other of the ele- 
 mentary substances. 
 
 5. COMBINING NUMBER. 
 
 Let us determine the combining number for an 
 elementary substance. 
 
 Experiment 21. 
 Determination of the Combining- Number for Zinc. 
 
 We know that zinc will displace hydrogen in acids, 
 the zinc entering into combination where hydrogen was. 
 If, then, we should take a large weighed piece of zinc 
 and let an acid act on it till just one gram of hydrogen 
 had passed off, the loss in weight of the zinc would show 
 
COMBINING NUMBER FOB ZINC. 173 
 
 the amount of the latter which had entered into com- 
 bination in the hydrogen's place. The number express- 
 ing the number of grams of zinc here used would be 
 the combining number for zinc, if that for hydrogen is 
 assumed to be unity. Hydrogen is such a light gas 
 that it would require an experiment on a large scale to 
 obtain a whole gram, therefore the experiment can be 
 made better as follows. 
 
 Take a 100 CC flask. Fit it with a good one-hole cork, 
 or, better, a rubber stopper. Have a delivery tube 
 reaching to the pneumatic trough. Put in the flask 
 10 CC of hydrochloric acid solution, and 20 CC of water. 
 Take some freshly cleaned c.p. zinc, and, using the 
 delicate balances, weigh out [accurately to centigrams] 
 1.30 g . This amount will produce a convenient quantity 
 of hydrogen. Have ready, inverted and full of water, 
 in the pneumatic trough, a 500 CC flask for catching the 
 gas. When all is ready drop the zinc in the flask and 
 insert the stopper. Let the action run to completeness. 
 Keep all undue heat away. Why ? Note whether any 
 water has been sucked back toward the flask. If any 
 has, make the proper allowance in measuring the gas 
 caught. Note the temperature of the air surrounding 
 the flask ; also read the barometer. Make the level of 
 the water inside and outside the flask the same. Place 
 the palm of the hand over the mouth of the flask and 
 quickly invert the flask. From the graduate add water 
 to the brim. Note how many cc of gas the flask had 
 collected. One cc of hydrogen at standard conditions 
 weighs O.OOOO9 g . Calculate the iveight of hydrogen 
 displaced. [Note.] If the lest possible result is desired, 
 
174 THE MODERN PERIOD. 
 
 it is necessary to consider the effect of the moisture 
 that the hydrogen has taken up as it passed through 
 the water of the pneumatic trough. We shall soon 
 learn that two gases can occupy the same vessel at the 
 same time, and that the more gases there are in a given 
 flask the more the pressure, each gas exerting its own 
 pressure against the confining walls. Although the 
 amount of water vapor that any gas, as hydrogen, takes 
 up on its passage through water, is small and conse- 
 quently the amount of pressure due to this aqueous 
 vapor is small, still it affects the accuracy of the result 
 of an experiment like this. When the hydrogen was 
 collected it was not subjected to the full pressure of 
 the atmosphere because the water vapor bore part of 
 the pressure. 
 
 It has been found by accurate experimenters that the 
 part borne by the water vapor is represented 
 
 At 10 by 0.9 cm. of mercury. At 21 by 1.8 cm. of mercury. 
 
 11 " 1.0 " " " 22 " 2.0 " " " 
 
 12 " 1.0 " " 23 " 2.1 " " 
 
 13 " 1.1 " " " 24 " 2.2 " " " 
 
 14 " 1.2 " " " 2o " 2.3 " " 
 
 15 " 1.3 " " " 26 " 2.5 
 
 16 " 1.3 " " " 27 " 2.7 " " " 
 
 17 " 1.4 " " " 28 " 2.8 " 
 
 18 " 1.5 " " " 29 3.0 
 
 19 " 1.6 " " " 30 " 3.2 " 
 
 20 " 1.7 " " " 31 3.3 " 
 
 Before reducing your observed volume of hydrogen 
 to volume at standard conditions, calculate the true 
 pressure under which the hydrogen itself was when 
 collected. Taking the weight of the hydrogen and the 
 
PKOUT'S HYPOTHESIS. .' 175 
 
 weight of the zinc, and calling the combining number 
 for hydrogen unity, make a proportion and get the 
 combining number for zinc, i.e., the number which 
 represents the number of grams of zinc that take the 
 place of 1 s of hydrogen. 
 
 6. PBOUT'S HYPOTHESIS. 
 
 While Dalton's theory was in its infancy an anony- 
 mous writer l proposed an hypothesis, that all the 
 combining numbers are whole numbers. He assumed 
 that there was one fundamental substance, hydro- 
 gen ; that the other elements themselves were com- 
 posed of various proportions of hydrogen condensed, 
 and, hence, the weights of all other elements must be 
 simple multiples of that of hydrogen. Though the 
 hypothesis that all the weights of the heavier elements 
 are multiples of those of the lightest is a very pleasing 
 speculation, we can to-day regard it only as such. The 
 most trustworthy determination of the combining 
 weights of hydrogen and oxygen, in the formation of 
 water, 2 does not give the simple ratio 1:8 but 1:7.93. 
 [Dalton's was 1:6.5; later, 1:7.] 
 
 For Review. 3, 4, 5, and 6. A consideration of 
 what facts led Dalton to the discovery of the third 
 great law of chemistry? State the law of multiple 
 
 1 The writer was found afterward to be Prout. 
 
 2 Probably no quantitative determinations in chemistry have been 
 carried on with greater care and ingenuity than those directed to 
 finding the combining numbers for oxygen and hydrogen. 
 
176 THE MODERN PERIOD. 
 
 proportions. State the essence of Dalton's atomic 
 hypothesis. What is an hypothesis? What is meant 
 by the term atom? State, briefly, the opinions that 
 have been held in regard to the divisibility of matter. 
 How did Dal ton think he could find the relative 
 weights of his atoms? What was the weak point of 
 his method ? What is meant by the " combining 
 number"? Describe, briefly, an experiment which 
 illustrates a method for determining a combining 
 number. What was Front's hypothesis? 
 
 7. MOLECULES. 
 
 Dalton's atomic hypothesis explained perfectly the 
 law of definite proportions by weight and the law 
 of multiple proportions. For if the atoms of every 
 simple substance have all the same weight, and if the 
 particles of compound substances are made up of the 
 atoms of different simple substances grouped in unalter- 
 able ratio, then it must follow that every particle of 
 every compound will have a fixed and invariable com- 
 position; while in the formation of two or more com- 
 pounds, as oxides, from a fixed quantity of one 
 substance and varying quantities of a second, the 
 varying quantities of the second must all be multiples 
 of the weight of the atom of this second substance. 
 
 That every particle of a compound is made up of a 
 group of chemically-joined atoms of different kinds, and 
 that the weight of every particle of a compound is the 
 sum of the weights of the atoms of which it is composed, 
 are very important points. Although, tlve statement 
 
DALTON'S SYMBOLS. 177 
 
 that the total weight of every particle of a compound is 
 exactly equal to the sum of the weights of its constit- 
 uent atoms may seem self-evident to us, it was not so in 
 Dalton's time, for it must be remembered that heat was 
 then considered a material substance. Let us also bear 
 well in mind the distinction here made between the 
 particle of a substance and an atom. The smallest par- 
 ticle into which a substance can be divided by physical 
 means, i.e., by any means except a chemical change 
 which destroys the substance itself, is generally called 
 a molecule. Simple substances, as well as compounds, 
 have their molecules. A molecule of a simple substance 
 generally has more than one atom in it, but never con- 
 tains atoms of more than one kind, whereas a molecule 
 of a compound substance always contains more than 
 one kind of atoms. 
 
 To express his ideas more clearly, Dalton adopted 
 a set of symbols. 
 
 O represented an atom of oxygen. 
 O " " " " hydrogen. 
 
 " " " carbon. 
 
 O O " a particle [molecule] of water. 
 
 " " " " olefiant gas. 
 
 O " " " " " carbonous oxide. 
 
 O O represented a particle [molecule] of carbonic oxide. 
 
 8. RELATIVE WEIGHT OF THE ATOMS. 
 
 We have already said that Dalton assumed that 
 hydrogen and oxygen, in the formation of water, unite 
 atom and atom, and therefore he concluded that the 
 
178 THE MODERN PERIOD. 
 
 weight of the atom of oxygen is 6.5 if the weight of 
 the atom of hydrogen is assumed to be 1, and, in gen- 
 eral, that the numbers expressing the atomic weights 
 are identical with those for the combining numbers of 
 the elements. There are, however, no grounds for such 
 an assumption. If 8 grams of oxygen [let us take the 
 more recently determined (round) number, rather than 
 Dalton's incorrect 6.5] join one gram of hydrogen, 
 either 8, or some multiple or submultiple of 8, repre- 
 sents the true weight of the atom of oxygen. If the 
 two gases join atom and atom, the weight of the oxygen 
 atom must be eight microcriths 1 ; but if two atoms of 
 hydrogen join one of oxygen to form the molecule of 
 water, then, if the oxygen atom is eight times as heavy 
 as the two of hydrogen, it must be sixteen times as 
 heavy as one. If there are three of hydrogen to one 
 of oxygen, the oxygen atom must weigh twenty-four 
 microcriths, if the hydrogen atom weighs one. And, 
 on the other hand, if there are two atoms of oxygen 
 and only one of hydrogen, as the two of oxygen out- 
 weigh one of hydrogen eight to one, then the atomic 
 weight of oxygen is only four. 
 
 In Dalton's time there were no means for determining 
 which multiple of the simplest combining number for 
 an element should be taken as its true atomic weight. 
 And up to the present day no method has been dis- 
 covered which will prove conclusively which multiple 
 of a combining number must be selected. But from 
 time to time laws have been discovered which assist us 
 
 1 The unit at present used in speaking of atomic weights is the 
 weight of an atom of hydrogen, and is called a microcrith, the word 
 with standing for the weight of a liter of hydrogen gas. 
 
DEFINITE PROPORTIONS BY VOLUME. 179 
 
 much in our inquiry. In 1808 Gay-Lussac, 1 a French 
 chemist, published an account of some work that he 
 and Von Humboldt had been carrying on with gases. 
 Gay-Lussac's attention had been arrested by the fact 
 that, when water is formed from hydrogen and oxygen, 
 exactly two volumes of hydrogen to one of oxygen are 
 always required. Examining a large number of chem- 
 ical changes in which gases are involved, he discovered 
 another important law of chemistry. He found that 
 a simple numerical ratio holds between the volumes 
 of two gases that unite to form a compound, and 
 also between the sum of the volumes of the uncom- 
 bined gases and the volume of the product [when the 
 product is in the gaseous form]. In Part I we made 
 a number of changes in which gases were involved. 
 Note that one jar of oxygen gas yielded one jar of sul- 
 phurous oxide ; that one bag of carbon dioxide yielded 
 one bag of carbon monoxide ; that one bag of carbon 
 monoxide then yielded one bag of carbon dioxide ; and 
 that, in the formation of ammonia, five volumes of hydro- 
 gen and two volumes of nitric oxide were required as 
 factors, while the products, steam and ammonia, had 
 they been measured, would have occupied two volumes 
 each. In each of these cases the ratio between corre- 
 sponding gaseous volumes may be expressed by very 
 simple whole numbers, thus: 1:1, 1:1, 1:1, 5:2, 
 2 : 2, and 5 + 2 = 7 : 2 + 2 = 4. The Law of Definite 
 Proportions by Volume may be stated thus : In any 
 chemical change the relative volumes of the gaseous factors 
 and products bear to each other a simple numerical ratio. 
 
 1 Born in 1778 j died in 1850. 
 
180 THE MODERN PERIOD. 
 
 Experiment 22. 
 Law of Definite Proportions by Volume. 
 
 By means of the electric current decompose water 
 held in any suitable vessel. Have ready two small tts. 
 Mark 1 on one a volume of l cc , and on the other a 
 volume of 2 CC . Fill both tubes with water. Invert 
 the l cc tube over the pole that is giving off oxygen, 
 and at once invert the other over the hydrogen pole. 
 Note the ratio of the volumes of the two gases evolved 
 in any given time. 
 
 9. THE MOLECULAR THEORY. 
 
 Soon after the discovery of the law in regard to 
 volumes, an Italian physicist proposed an hypothesis 
 which is now the basis of the celebrated Molecular 
 Theory. In the year 1811, Avogadro made the sugges- 
 tion that " equal volumes of all substances, when in the 
 state of gas, and under like conditions, contain the same 
 number of molecules." Three years later the French 
 electrician, Ampere, came to the same conclusion, and 
 this hypothesis is now known either as that of Avogadr6 
 or of Ampere. Let us see on what facts this supposi- 
 tion in regard to the structure of gases is based. 
 
 Consider for a moment the case of water, which so 
 easily passes from its common state of a liquid to that 
 
 1 This may be done by pouring the proper amount of water from 
 a graduate into the tt and marking its height on the outside of the 
 glass. 
 
THE MOLECULAR THEORY. 181 
 
 of a gas, steam. A cubic inch of water forms about 
 a cubic foot of steam. Now three suppositions can be 
 made in regard to the manner in which the cubic inch 
 of water is able to occupy the cubic foot of space when 
 the water has been converted into steam. First, it may 
 be supposed that the cubic inch of water on being heated 
 simply swells out until it occupies the whole cubic foot 
 as completely in the gaseous state as in the liquid. In 
 the next place, it may be supposed that the water is 
 not itself an absolutely homogeneous mass of matter, 
 but that it is made up of minute particles, each exactly 
 like every other, and that when the change of state 
 takes place these particles do not change their size at 
 all, but are simply driven much farther apart. In the 
 third place, it may be supposed that, as in the second, 
 the water is made up of minute particles, but that 
 when the water is converted into steam these particles 
 themselves swell out till they occupy many times 
 more space than before, and in this way the cubic 
 foot becomes completely occupied. In both the first 
 and the last cases there will be no vacant space what- 
 ever in the cubic foot of steam, but every part will 
 have its portion of matter, whereas in the second case, 
 if the particles do not change their original size, there 
 will be vacant spaces, in fact, the vacant spaces 
 will be vastly larger than those occupied by the 
 particles of matter. Before we discuss the relative 
 probability of these three assumptions, let us make an 
 experiment. 
 
182 THE MODERN PERIOD. 
 
 Experiment 23. 1 
 Spaces between the Molecules. 
 
 Have ready a dry Kjeldahl flask fitted with a two- 
 hole rubber stopper. Through one hole pass a piece of 
 glass tube. About a cm of this tube should project 
 inside the flask, and about a cm outside, when the 
 stopper is in position. To the outer end of this tube 
 fix 5 or 6 cm of rubber tube carrying two pinch-cocks, 
 one near each end of the rubber tube. Let a piece of 
 glass tube rise from near the bottom of the flask, pass 
 through the second hole in the stopper, and then be 
 bent at a right angle. By means of a bit of small 
 rubber tube connect to this bent glass tube the short 
 arm of another piece of glass tube bent thus : -, |. Let 
 the short arm of the latter tube, which is to serve for 
 a pressure gauge, be about 30 cm long, and the long arm 
 at least 50 cm . Have ready a bath of boiling water, 
 which contains some common salt [to raise the tem- 
 perature above 100]. Immerse the Kjeldahl flask in 
 the bath, but take care not to plunge the flask in the 
 hot liquid so suddenly that the glass may crack. Clamp 
 the flask upright, and also fasten the gauge tube firmly. 
 Look at the flask and make sure that it is dry. Pass 
 dry air into the flask. A good way to pass in the air 
 is by means of the blast-lamp bellows. Force a slow 
 stream of air, first through a catch-bottle of sulphuric 
 acid, then through the short rubber tube into the flask, 
 while the excess of air escapes through the gauge tube. 
 After the dry air has been passing into the flask for 
 
 1 See foot-note, page xxvii of the Introduction. 
 
SPACES BETWEEN THE MOLECULES. 183 
 
 five minutes, close the lower pinch-cock and disconnect 
 the catch-bottle. Pour mercury into the gauge tube 
 till the short arm is about one third filled. Open the 
 pinch-cock [for a moment only] to relieve any undue 
 pressure, and mark the height on the short arm to 
 which the mercury rises. Note that the flask is now 
 exactly full of air [gas No. 1]. Put two or three 
 drops [only] of water in the rubber tube, and close the 
 upper pinch-cock. Then open the lower pinch-cock, 
 and squeeze the water down into the flask. Again 
 close the lower pinch-cock. Note that the water evapo- 
 rates and forms steam [gas No. 2], Note the effect 
 on the pressure gauge. Add mercury to the gauge till 
 the mercury in the short arm stands again at the mark, 
 i.e., till the volume occupied by the two gases within the 
 flask is the same as that previously occupied by the air 
 alone. Next introduce two or three drops of alcohol or 
 of ether [or both, one after the other], and note how 
 several gases may occupy the same vessel at the same time. 
 Caution ! In working with alcohol and ether take great 
 pains to avoid fire, as both are readily inflammable. 
 
 Let us now consider our suppositions in regard to the 
 manner in which a cubic inch of water, after passing 
 into the condition of steam, occupies a cubic foot of 
 space. By experiment we have just found that when 
 a vessel is full of one gas, another, and still another, 
 can be added. Hence it cannot be that the whole 
 space is occupied by the steam, or by any other gas. 
 It is true that it may be thought that the whole mass 
 of the steam may form an elastic body, and that, when 
 
184 THE MODERN PERIOD. 
 
 another gas is added, this elastic body of steam con- 
 tracts, and the other gas, another elastic body, occupies 
 half the space. But if any given portion of the con- 
 tents of the flask be drawn off and examined, it will 
 be found that this portion contains not one gas alone 
 but some of all that have been added to the flask. In 
 order to see that gases mingle and do not push one 
 another aside, proceed as follows : Take a Kjeldahl 
 flask. Heat its bulb well over a free Bunsen flame. 
 Remove the flask from the flame. Drop in a few 
 small crystals of iodine. Cork tightly. Hold the 
 flask to the light. Shake, and note that the colored 
 iodine vapor mingles with the air. 
 
 We have, therefore, proved that our first supposition, 
 namely, that the cubic inch of water simply swells out 
 and occupies completely the whole of the cubic foot, 
 cannot be an expression of the truth. We are then 
 forced to the conclusion that the water is made up of 
 particles the molecules of Avogadro. 
 
 Let us try two other experiments that will help us 
 in deciding whether the particles are large, elastic, and 
 side by side in the gaseous condition or are some dis- 
 tance apart, i.e., whether the particles themselves swell 
 up or keep their original size even when in the state of 
 steam. 
 
 Experiment 24. 
 Irregular Expansion of Liquids. 1 
 
 Have ready three small [2 oz. is a good size] bottles, 
 all of the same size, and each fitted with a good one- 
 1 See foot-note, page xxvii of the Introduction. 
 
IRKEGTJLAR EXPANSION OF LIQUIDS. 185 
 
 hole cork, or, better, a one-hole rubber stopper. Fit to 
 each stopper a piece of glass tube about 50 cm long with 
 its lower end flush with the under side of the stopper. 
 Fill the first bottle with water, the second with alcohol, 
 and the third with ether. 
 
 Caution ! Keep all fire away from ether and from 
 alcohol. 
 
 Fill each bottle to the brim, and insert its stopper, 
 cautiously, in such a way that the liquid may be driven 
 part way up the glass tube, and that no air may be left 
 in the bottle. Have at hand a vessel of water large 
 enough to hold all three bottles at the same time, and 
 so placed that it may be heated, forming a water-bath. 
 Set the three bottles with their contents side by side in 
 the water-bath. Make a mark on each stem, at the 
 point where the liquid stands. Heat the water-bath, 
 and note the expansion of the three liquids. Note that 
 the ether expands by far the most rapidly. When the 
 ether shows signs of boiling remove it from the bath, 
 and set it away, safe from fire. Note that the alcohol 
 expands the next in amount. When the alcohol shows 
 signs of boiling, remove it, and stop heating the bath. 
 Record the results. 
 
 Experiment 25. 
 Regular Expansion of Gases. 1 
 
 Caution! In order to insure success in this experi- 
 ment it is necessary to have the gases experimented on 
 perfectly dry, to have all joints carefully greased and 
 1 See foot-note, page xxvii of the Introduction. 
 
186 THE MODERN PERIOD. 
 
 tight, to have the ice-bath thoroughly cooled to C., 
 and to make sure that each determination is carried 
 on with the apparatus in precisely the same position ; 
 that each time the delivery tube dips the same distance 
 under the water in the pneumatic trough ; that the level 
 of the water in the measuring cylinder is, each time, 
 kept the same distance above the water in the trough 
 at the time the volume of the displaced gas is read; 
 and, in short, that all conditions are the same for each 
 gas tried. 
 
 Have ready a 2 oz. bottle fitted with a two-hole rubber 
 stopper. Through one hole of the stopper pass a piece 
 of glass tube which shall reach nearly to the bottom of the 
 bottle, and project above the stopper a cm or two when 
 the stopper is inserted in the bottle. Fit to the upper 
 end of this tube a bit of rubber tube carrying a pinch- 
 cock. Through the second hole insert the end of a 
 delivery tube arranged so that when the bottle is placed 
 in the water-bath the delivery tube will reach to the 
 pneumatic trough. Make sure that the bottle is per- 
 fectly dry. Carefully grease all rubbers to make all 
 joints air-tight. Have ready, in the water-bath, a 
 mixture of crushed ice and water, or snow and water 
 [but no salt]. Use much ice, as a pasty mass is best. 
 This mixture gives a uniform temperature. What tem- 
 perature? Insert the stopper with its fittings, open 
 the pinch-cock, and set the bottle in the bath. Make 
 sure that the bath wholly covers the bottle and reaches 
 the stopper. Fill the bottle with dry air in the same 
 way that you filled the flask in Ex. 23. When dry air 
 has passed in for five minutes, close the pinch-cock, 
 
KEGULAR EXPANSION OF GASES. 187 
 
 and disconnect the catch-bottle. Make sure that the 
 bottle is still well surrounded with a pasty mass of ice 
 and water. Open the pinch-cock [for a moment only] 
 to relieve any undue pressure. Place your graduate, 
 inverted and full of water, over the end of the delivery 
 tube in the pneumatic trough. Heat the water-bath 
 till the water boils. If the blast-lamp flame is used 
 the water will boil in a few minutes. Catch, in the 
 graduate, the air driven out by the expansion of the 
 contents of the bottle while the temperature rises from 
 the freezing point to the boiling. Note the number 
 of cc caught. 
 
 Again make an iced water-bath. Now pass dry 
 hydrogen down into the bottle till the gas which 
 bubbles up from the pneumatic trough will, when 
 caught in a tt, burn well. Proceed exactly as before, 
 and note the amount of hydrogen driven over by the 
 expansion. How does the expansion of hydrogen 
 compare with that of air? 
 
 Again make an iced water-bath, and try the expan- 
 sion of an equal volume of illuminating gas. Take 
 the gas from the gas tap at your desk. Dry the gas 
 by passing it through sulphuric acid. 
 
 Finally, what do you say in regard to the expansion 
 of gases ? 
 
 Had the vapors of water, of alcohol, and of ether 
 been tried for the same number of degrees [100] of 
 temperature, the result would have been the same, 
 but, of course, the initial temperature must have been 
 higher, e.g., 100 instead of 0, and the vapors could 
 not be caught above water. Why not? Nor could 
 
188 THE MODERN PERIOD. 
 
 the dioxide of carbon be tested in this way, for it is 
 enough soluble in water to prevent an accurate deter- 
 mination, if measured above water. 
 
 Let us consider the meaning of the results of Exs. 24 
 and 25. We find that every substance in the liquid 
 form has its own special rate of expansion. But if 
 the temperature is so high that the liquids have been 
 changed to gases, the expansion of the substances in 
 the gaseous state is for each about the same. Now it 
 must be the effect of the particles acting each on the 
 other that causes the different rates of expansion for 
 liquids, but, if we assume that these same particles, 
 without change of size, are driven so far apart, in 
 the conversion of the liquids into gases, that they 
 have little or no effect upon each other, it seems natural 
 that heat should have the same effect on one gas 
 that it does on another, i.e., that all gases should 
 have the same rate of expansion, particularly, if we 
 assume, with Avogadro, that there are, in equal vol- 
 umes, equal numbers of the particles. From a con- 
 sideration of these facts and many others, physicists 
 have come to the conclusion that matter is made up 
 of minute particles, that, in the state of gas, these 
 particles are not closely packed, but, in fact, that the 
 spaces between them are very large in comparison 
 with the size of the particles themselves ; that, in the 
 liquid state, the particles are near together, and influ- 
 ence one another ; and that, in the solid state, the 
 particles are still nearer together, and cannot move 
 from their relative positions. 
 
 It is, moreover, believed that all molecules are in 
 
SIZE OF THE MOLECULES. 189 
 
 constant motion, that, in the case of gases, they are 
 moving about among themselves, with great velocity; 
 that, in the case of liquids, the motion is much more 
 restricted; and that, in the case of solids, the motion 
 is one of vibration or of rotation, and not a changing 
 of place. 
 
 There seems no hope that the best of microscopes 
 will ever be able to show the molecules. The phy- 
 sicists estimate that the diameters of the molecules 
 of some substances, as alum and albumen, that 
 have remarkably large molecules, range from the one 
 10,776,000th of an inch to the one 5,000,000th of 
 an inch. But "the best microscopes made to-day 
 will enable one to see as barely visible a point the 
 one hundred-thousandth of an inch, so that such a 
 microscope would need to be as much more powerful 
 than it now is as one hundred thousand is contained 
 in five millions, that is, fifty times, in order to see 
 the albumen molecule, and for the alum molecule as 
 many times as one hundred thousand is contained in 
 ten million seven hundred thousand, that is, one 
 hundred and seven times. Now, one who is familiar 
 with the microscope would probably admit that one 
 might be made through improved methods of making 
 and working glass hereafter to be discovered, two 
 or three, or even ten times better than the best we 
 have now ; but the idea of one being made fifty or a 
 hundred times more powerful than we have to-day, 
 I do not think would be allowed to have any degree 
 of probability. The powers of the microscope have not 
 been doubled within the last fifty years, and I suppose 
 
190 THE MODERN PERIOD. 
 
 more time and ingenuity have been given to the problem 
 of improving it than will ever be given to it in the 
 same interval again." l 
 
 To give some idea of the actual size of the molecules 
 of water, it may be added that it has been estimated 
 that if a drop of water should be magnified to the size 
 of the earth, the molecules would appear not larger 
 than cricket-balls, and not smaller than small lead shot. 
 
 The great molecular theory, which has sprung from 
 the hypothesis made by Avogadro, serves to explain 
 phenomena, and by its application undiscovered facts 
 have been predicted and verified time and again. Still 
 we must remember that it is only a theory, that we 
 never have seen the molecules, and, after all, there 
 may not be such things as molecules, but this theory 
 is based on facts of a very substantial nature, and 
 we cannot help thinking that in it lie the elements, 
 at least, of some absolute truth. We must, however, 
 in all our work, bear in mind the distinction there is, 
 and always must be, between facts and the hypotheses 
 and theories that are put forth to explain the facts. 
 "When, however," to quote from Professor Cooke, 2 
 44 we come to study the history of science, the dis- 
 tinction between fact and theory obtrudes itself at 
 once upon our attention. We see that, while the 
 prominent facts of science have remained the same, its 
 history has been marked by very frequent revolutions 
 in its theories or systems. The courses of the planets 
 
 1 A. E. Dolbear. " Matter, Ether and Motion." 
 
 2 "The New Chemistry." Let every student who wishes to know 
 more about the molecular theory get this book, and study the first 
 chapters. 
 
PACT AND THEORY. 191 
 
 have not changed since they were watched by the 
 Chaldean astronomers, three thousand years ago ; but 
 how differently have their motions been explained 
 first by Hipparchus and Ptolemy, then by Copernicus 
 and Kepler, and lastly by Newton and Laplace ! 
 and, however great our faith in the law of universal 
 gravitation, it is difficult to believe that even this 
 grand generalization is the final result of astronomical 
 science. 
 
 "Let me not, however, be understood to imply a 
 belief that man cannot attain to any absolute scientific 
 truth ; for I believe that he can, and I feel that every 
 great generalization brings him a step nearer to the 
 promised goal. Moreover, I sympathize with that 
 beautiful idea of Oersted, which he expressed in the 
 now familiar phrase, 'The laws of Nature are the 
 thoughts of God' . . . Through the great revolu- 
 tions which have taken place in the forms of thought, 
 the elements of truth in the successive systems have 
 been preserved, while the error has been constantly 
 eliminated ; and so, as I believe, it always will be, 
 until the last generalization of all brings us into the 
 presence of that law which is indeed the thought of 
 God." 
 
 For Review. 7, 8, and 9. Show how Dalton's 
 atomic hypothesis explained two of the fundamental 
 laws of chemistry. What is meant by the term mole- 
 cule? How does a molecule usually differ from an 
 atom? Do simple substances have molecules? Give 
 some of Dalton's symbols, and tell what he wished 
 
192 THE MODERN PERIOD. 
 
 each to represent. State why Dalton's value for the 
 relative weight of the oxygen atom may have been 
 far from correct. Describe, briefly, the work of Gay- 
 Lussac, which led to the discovery of a fourth great law 
 of chemistry. State the law of definite proportions 
 by volume. Who was Avogadro ? When did he make 
 his famous suggestion? Who, soon after, made the 
 same suggestion ? What was this famous suggestion ? 
 What three suppositions can be made in regard to the 
 change of volume that takes place when a cubic inch of 
 water passes into steam? Show why two of these 
 suppositions cannot be expressions of the truth. Give 
 reasons for thinking that the third supposition is an 
 expression of the truth. What is believed in regard to 
 the movements of the molecules ? What is believed 
 in regard to the actual sizes of the molecules ? 
 
 10. DETERMINING ATOMIC WEIGHTS. 
 
 The law of Gay-Lussac, together with the hy- 
 pothesis of Avogadro, proved of great assistance in 
 seeking to establish the true weights of atoms and of 
 molecules. For instance, we can now prove that the 
 molecule of hydrogen gas contains two atoms of hydro- 
 gen. If one volume of hydrogen gas is mixed with one 
 volume of chlorine gas and exploded, it is found that 
 the resulting hydrochloric acid gas occupies just as 
 much space as the two factors before the explosion, 
 i.e., one volume of hydrogen plus one volume of chlo- 
 
TRUE ATOMIC WEIGHTS. 193 
 
 rine gives two volumes of hydrochloric acid. This 
 may be represented thus : 
 
 hydro- 
 chloric acid 
 gas 
 
 hydro- 
 chloric acid 
 
 Let us assume that our unit volume here contained 
 just 1,000000 molecules. Then, by the hypothesis of 
 Avogadro, if there are 1,000000 molecules in the one 
 volume of hydrogen, there must be 1,000000 mole- 
 cules of chlorine in the one volume of chlorine, and 
 2,000000 molecules of hydrochloric acid in the result- 
 ing two volumes of hydrochloric acid gas. Analysis 
 shows that every molecule of hydrochloric acid con- 
 tains both hydrogen and chlorine, therefore, in the 
 2,000000 molecules of hydrochloric acid there must 
 be at least 2,000000 atoms of hydrogen, but these 
 2,000000 atoms of hydrogen came from only 1,000000 
 molecules of hydrogen gas, hence we are forced to 
 believe that every molecule of hydrogen has two atoms 
 of hydrogen in it. 
 
 If, then, a single atom of hydrogen weighs one micro- 
 crith, and we have proved that there are at least two 
 atoms of hydrogen in the molecule of hydrogen gas, 
 the molecular weight, i.e., the weight of a molecule 
 of hydrogen, must be at least two microcriths. As 
 no proof has ever been presented to show that there 
 are more than two atoms in the molecule of hydrogen, 
 the accepted molecular weight of hydrogen is two 
 microcriths. 
 
 Experiment shows, moreover, that two volumes of 
 hydrogen and one volume of oxygen join and form 
 
194 
 
 THE MODERN PERIOD. 
 
 two volumes of steam. This may be represented 
 thus : 
 
 hydrogen 
 
 hydrogen 
 
 steam 
 
 steam 
 
 Let us assume, as before, that each single volume con- 
 tains 1,000000 molecules. Then, as the three volumes 
 are condensed to two volumes, the 3,000000 molecules 
 must, by the hypothesis of Avogadro, be condensed to 
 2,000000 molecules. Analysis shows that each mole- 
 cule of steam has in it at least one atom of oxygen. As 
 there are 2,000000 of the steam molecules, there must 
 be 2,000000 oxygen atoms. These 2,000000 oxygen 
 atoms came from 1,000000 oxygen molecules. Hence 
 each molecule of oxygen must have at least two atoms 
 of oxygen. Finally, as there were 2,000000 molecules 
 of hydrogen used, and each molecule, as proved, on page 
 193, had two atoms of hydrogen, 4,000000 atoms of 
 hydrogen must have gone into the 2,000000 molecules 
 of steam. Hence each molecule of steam must have two 
 atoms of hydrogen. And as there is at least one oxygen 
 atom in each molecule of steam, we conclude that the 
 eomposition of water [steam] is two atoms of hydrogen 
 and one atom of oxygen. If, then, the oxygen out- 
 weighs the hydrogen 8:1, the single atom of oxygen, 
 being eight times as heavy as two atoms of hydrogen, 
 must be sixteen times as heavy as one atom of hydro- 
 gen. And sixteen is the atomic weight we assign to 
 oxygen. If it is true that there are two and only two 
 atoms of oxygen in the molecule of oxygen gas, what 
 is the molecular weight of oxygen? What is the 
 molecular weight of water? 
 
MOLECULAR WEIGHT DETERMINATIONS. 195 
 
 11. DETERMINING MOLECULAR WEIGHTS. 
 
 If we accept the hypothesis of Avogadro as an 
 expression of the truth, we can calculate the molecular 
 weights of all substances which are naturally in the gas- 
 eous state or can be converted into this state, e.g., water 
 can have its molecular weight taken when it is in the 
 form of steam, and some solid substances, as paraffines, 
 can be heated till vaporized in order to have their molec- 
 ular weights taken. The determination of molecular 
 weights by means of Avogadro's hypothesis is called 
 the Physical Method for Molecular Weight Deter- 
 minations. It is a very simple method. 
 
 If equal volumes of all aeriform substances contain 
 the same number of molecules, the weight of any one 
 molecule must bear the same ratio to that of any other 
 molecule that the weight of a given volume of the first 
 gas bears to the weight of the same volume of the 
 second gas. Having proved that a molecule of hydro- 
 gen weighs 2 mc [two microcriths], if we get the weight 
 in grams of a given volume of hydrogen gas and the 
 weight in grams of the same volume of some other gas, 
 and reckon how many times heavier the given volume 
 of the latter is than the same volume of hydrogen, or, 
 in other words, if we determine the specific gravity of 
 the second gas in reference to hydrogen [instead of to 
 air or to water] as a standard, and multiply by 2, we 
 shall have the molecular weight of the second gas. 
 The reason it is necessary to multiply by 2 is because, 
 although each molecule of the second gas is just as 
 many times as heavy as a molecule of hydrogen, as is 
 
196 THE MODEEN PERIOD. 
 
 the whole volume of the second gas than an equal vol- 
 ume of hydrogen gas, yet the molecule of hydrogen 
 itself weighs 2 mc , being composed of two atoms, each of 
 which contains unit quantity, that is l mc , of hydrogen. 
 
 Let us determine some molecular weights by the 
 physical method. 
 
 Experiment 26. 
 
 Determination of Molecular Weights by the Physical 
 Method. 
 
 A. Molecular Weight of Carbonic Dioxide. 
 
 We have already got the sp. gv. of carbonic dioxide 
 referred to air and to hydrogen. See Ex. 14, page 145, 
 and Ex. 15, page 148. Now get the molecular weight 
 of .carbonic dioxide. 
 
 As coal gas and air, two other substances whose sp. 
 gv. we have determined, are mixtures and not chemical 
 compounds, they have no such things as molecular 
 weights, for they contain molecules of different sub- 
 stances. 
 
 B. Molecular Weight of Oxygen Gas. 
 
 Determine the sp. gv. of oxygen gas by the method 
 of Ex. 14, page 145. From this result get the molec- 
 ular weight of oxygen gas. 
 
 Although the physical method for determining mo- 
 lecular weights is a very simple and useful one, it is 
 limited in its application to substances which are gases 
 or can be converted into vapors. The molecular weights 
 
MOLECULAR WEIGHT DETERMINATIONS. 197 
 
 of other substances are determined by what is called the 
 chemical method. In using the chemical method it is 
 always necessary to get a start by the physical method, 
 i.e., the determination of the molecular weight of some 
 gas is first made from its sp. gv. referred to hydrogen. 
 Then a chemical change is brought about, in which 
 both the substance whose molecular weight it is desired 
 to find and the gas whose molecular weight is known 
 are involved. 
 
 If one molecule of the substance whose molecular 
 weight is known always produced one molecule of the 
 substance whose molecular weight is required, or vice 
 versa, the "application of the chemical method would be 
 extremely simple, for the gram weight of the first 
 would be to the gram weight of the second as is the 
 molecular weight of the first to the molecular weight 
 of the second. But as one molecule of the known 
 often furnishes either more than enough atoms to form 
 just one molecule of the unknown or less than enough 
 [and vice versa] the application is difficult and usually 
 requires a study of many chemical changes into which 
 the unknown enters before the number of atoms in the 
 molecule and the correct molecular weight can be fixed. 
 
 Experiment 27. 
 
 Determination of Molecular Weights by the Chem- 
 ical Method. 
 
 We have already determined, by the physical method, 
 the molecular weight of oxygen. Let us assume that 
 
198 THE MODERN PEEIOD. 
 
 we have found this weight to be 32 mc . Now if we 
 bring about some chemical change in which oxygen is 
 involved, we can get the molecular weight of some 
 other substances. 
 
 A. Molecular "Weight of Chlorate of Potassium. 
 
 If your chlorate of potassium is not known to be 
 pure, dissolve 10-20 g. of it in hot water and recrystal- 
 lize. Powder the crystals and dry at a temperature 
 between 100 and 200 C. 
 
 In a weighed porcelain crucible put about two grams 
 of pure dry chlorate of potassium. Get the exact weight 
 of the chlorate. Put the cover on the crucible. This 
 cover should be weighed also, that its weight may be 
 added in case there is any spattering. Heat the chlo- 
 rate, gently, with a Bunsen burner, but take care that 
 the contents of the crucible do not foam up and pour over 
 the sides. After the chlorate has melted continue heat- 
 ing till the mass again becomes solid. Then apply the 
 blast-lamp, gently, till the mass again melts. Just as 
 soon as the second melting has taken place, remove 
 the flame, let cool, and weigh. Again just melt the 
 substance, let cool, and weigh. Continue till the 
 weight is constant. Note the loss in weight caused 
 by the escape of the oxygen. 
 
 We can now calculate the molecular weight of 
 chlorate of potassium. In making our calculations, 
 however, we meet with one difficulty. We do not 
 know how many atoms of oxygen each molecule of 
 chlorate has furnished for making the molecules of the 
 oxygen gas. If one molecule of the chlorate has lost 
 
MOLECULAR WEIGHT DETERMINATIONS. 199 
 
 one atom, only, of oxygen, the ratio of the weight of 
 the chlorate to the weight of the oxygen gas gone off 
 is x : half 32, or 16, because we have proved that there 
 are two atoms of oxygen in the molecule of oxygen gas, 
 also that its total molecular weight is 32. If every 
 molecule of the chlorate has lost two atoms of oxygen, 
 the ratio is x : 32, because the two atoms of oxygen are 
 just enough to form a single molecule of oxygen gas. 
 If, however, every molecule of chlorate has lost three 
 atoms of oxygen, the ratio is x : one and a half times 
 32, or32 + 16 = 48. A study of the chemical changes 
 into which chlorate of potassium enters shows that it 
 has three atoms of oxygen, and all are given up in this 
 experiment. Hence in making our calculations we must 
 consider that one molecule of the chlorate has furnished 
 enough oxygen to form a molecule and a half of oxygen 
 gas. Therefore the molecular weight of one molecule and 
 a half of oxygen [32 + 16 = 48] is to the molecular weight 
 of one molecule of the chlorate [#], as is the weight in 
 grams of the oxygen given off, to the weight in grams 
 of the chlorate taken. Make the proper proportion, and 
 get the molecular weight of chlorate of potassium. 
 
 B. Molecular "Weight of Chloride of Potassium. 
 
 From the data of A get the molecular weight for the 
 chloride of potassium which was left in the crucible 
 after heating. 
 
 Note. It is obvious that if we can find any chemical 
 changes in which either the chlorate of potassium or 
 the chloride enters, and if we can weigh the factors 
 
200 THE MODERN PERIOD. 
 
 and the products, we can make proportions and calcu- 
 late the molecular weights for the other substances 
 involved in the changes. We are, of course, sometimes 
 limited, because we cannot always tell just how many 
 atoms leave one molecule, or how many go to some 
 other. But it is seldom that we are left with nothing to 
 help us in our choice between several multiples. 
 
 C. Molecular Weight of Sulphate of Potassium. 
 
 In getting the molecular weight of sulphate of 
 potassium we shall take advantage of the fact that we 
 have just determined the molecular weight of chloride 
 of potassium, and of the fact that the sulphate can be 
 made from the chloride by the action of sulphuric acid. 
 
 Put in a weighed porcelain crucible a small amount 
 [from l g to 1.5 g ] of finely powdered, dry, c. p. chloride of 
 potassium. Get the exact weight of the chloride used. 
 Add a little sulphuric acid [c.p. is best], drop by drop, 
 while you pass the Bunsen burner flame, now and then, 
 below the crucible. Heat, gently at first, with the 
 Bunsen burner as long as fumes come readily, but avoid 
 all spattering out. Finally, apply the blast-lamp flame 
 till the molten mass becomes a spongy solid. Cool and 
 weigh. Heat to constant weight. As it takes two 
 molecules of the chloride to make one of the sulphate, 
 it is necessary, in making our proportion in this case, 
 to take double the molecular weight of the chloride to 
 compare with the molecular weight of the resulting 
 sulphate. 
 
 Find, also, the molecular weight of sulphuric acid, 
 assuming that it takes one molecule of the acid to 
 
MOLECULAR WEIGHT DETERMINATIONS. 201 
 
 produce one molecule of the sulphate from the two 
 molecules of the chloride, and that the amount of the 
 sulphuric acid needed to act on l g of chloride was 0.65 g . 
 Finally, get the molecular weight of hydrochloric acid, 
 assuming that during the change of the chloride into 
 the sulphate there escaped two molecules of hydro- 
 chloric acid gas, and that the weight of this gas pro- 
 duced by l g of the chloride was 0.49 g . 
 
 Knowing the molecular weights of sulphuric and 
 hydrochloric acids, we could, in a similar manner, get 
 molecular weights for substances with which these 
 acids react. 
 
 Neither the physical nor the chemical method for 
 determining molecular weights can be applied univer- 
 sally. The physical method is confined to substances 
 which are naturally gases, or can be converted into 
 vapors at a comparatively low temperature ; while the 
 chemical is limited, inasmuch as a start has to be made 
 from some determination obtained by the physical. 
 
 For Review. 10 and 11. Prove [using the law 
 of Gay-Lussac and the hypothesis of Avogadro] that 
 the molecule of hydrogen gas contains two atoms of 
 hydrogen; that a molecule of water [steam] has two 
 atoms of hydrogen; that the weight of an atom of 
 oxygen is 16 microcriths. What is a microcrith? 
 What is a crith ? What is the weight [in microcriths] 
 of a molecule of hydrogen ? Of a molecule of oxygen ? 
 Of a molecule of water? Define the physical method 
 for determining molecular weights. Describe an experi- 
 ment that illustrates this method. Define the chemical 
 
202 THE MODERN PERIOD. 
 
 method for determining molecular weights. Describe 
 
 an experiment that illustrates this method. In what 
 
 respect is the physical method limited? In what 
 respect is the chemical method limited ? 
 
 12. SPECIFIC HEAT. 
 
 Another aid in determining which multiple of the 
 combining number should be taken for the atomic 
 weight, was found in the relation discovered to exist 
 between the specific heats of elementary substances and 
 their atomic weights. 
 
 In the year 1819 this discovery was announced by 
 two French chemists, Dulong and Petit. 
 
 The specific heat of any substance may be defined as 
 the amount of heat required to raise the temperature of 
 one gram of that substance one degree, compared with 
 the amount of heat required to raise the temperature of 
 the same amount [one gram] of a standard substance 
 [water] the same distance [one degree]. 
 
 Be sure you see clearly the distinction between 
 temperature and heat itself. The temperature of a 
 body is simply its state in respect to heat or cold. 
 What the heat itself is we do not know. The most 
 reasonable explanation of heat is that it is motion of 
 some kind. If, for instance, a piece of iron, as a nail, 
 is pounded vigorously with a hammer, it soon becomes 
 too hot to be held. 
 
HEAT. 203 
 
 Experiment 28. 
 Transference of Motion. 
 
 Take a nail, and having placed it on some hard sub- 
 stance that will not be harmed, pound it vigorously 
 with a hammer till it becomes too hot to be held. 
 
 It is believed that at the moment the motion of the 
 hammer is arrested, the particles of the iron receive a 
 kind of motion, 1 which is manifested, as we say, by an 
 increase of temperature. It is not thought that the 
 particles of a solid move around among one another, but 
 that the motion is a vibratory or a rotary one ; the 
 greater the vibration or the rotation, the greater the 
 heat. The particles of gases, however, are supposed to 
 change places very rapidly. 
 
 It might be thought that the amount of motion, i.e., 
 the amount of heat, imparted to a gram of one sub- 
 stance in order to raise its temperature one degree, 
 would, if imparted to a gram of any other substance, 
 cause a rise of just the same extent, but experiment 
 shows that this is not so. When exposed to the same 
 source of heat, some substances reach a given tempera- 
 ture quicker than others. Of all substances, water is 
 the slowest to reach the given temperature; e.g., the 
 amount of heat that will raise a given number of grams 
 of water from C. to 10 C. would raise the same 
 amount of iron from C. to 88 C.; the same amount 
 of mercury to 300 C.; the same amount of silver to 
 175 C.; and so on. 
 
 1 It is supposed that, even before struck with the hammer, the parti- 
 cles had a considerable amount of this same kind of motion. 
 
204 THE MODERN PERIOD. 
 
 The amount of heat that is required to raise one 
 gram of water one degree is called a calorie, 1 and is the 
 unit taken for determinations of quantities of heat, just 
 as the degree is the unit taken for temperatures. The 
 specific heat of a substance may also "be defined as the 
 number of calories required to raise a given weight of 
 the substance a given number of degrees compared with 
 the number of calories required to raise the same weight 
 of water the same number of degrees. If the weight 
 selected is a gram for both the water and the other 
 substance, and the distance the temperature is to be 
 raised is one Centigrade degree, then the number ex- 
 pressing the specific heat of the other substance is 
 always a fraction, and less than 1 ; for it takes but one 
 unit of heat to raise one gram of water 1 C., and it 
 takes less heat for a gram of every other substance. 
 
 Let us determine the specific heats of a few sub- 
 stances. 
 
 First, prepare a calorimeter, i.e., a piece of appara- 
 tus for measuring heat quantities. Take a beaker that 
 holds about 200 CC , and a second beaker somewhat 
 larger. The second beaker should be of such a size 
 that when the 200 CC one is set in it there will be a 
 space of l-2 cm between the walls. Place a layer of 
 cotton-wool on the bottom of the larger beaker ; on 
 this cotton set the smaller beaker, and pack loosely 
 the space between the walls with cotton. This packing 
 will serve to prevent a considerable loss of heat in 
 subsequent work. 
 
 1 This small amount of heat is sometimes called the millicalorie, in 
 distinction from the large calorie more frequently used, which is the 
 amount of heat it takes to raise one kilogram of water one degree. 
 
SPECIFIC HEAT OF ZINC. 205 
 
 Experiment 29. 
 Specific Heat of Zinc. 1 
 
 Have ready the calorimeter just made, a thermome- 
 ter, and a long, wide tt. 2 Also have ready some water, 
 boiling, in a large beaker, iron pot, or any other suit- 
 able vessel. Twist around the neck of the large tt a 
 piece of wire stiff enough to serve as a handle. Pour 
 exactly 100 CC of cold water 3 into the inner beaker of 
 the calorimeter, and exactly 50 g of zinc [dust or fine 
 granular] into the large tt. Warm the thermometer 
 somewhat in the steam of the boiling water, and then 
 take the temperature of the boiling water. Cool the 
 thermometer somewhat, and set it in the water in the 
 calorimeter. Heat the zinc to the temperature of the 
 boiling water by plunging the large tt and its charge 
 well down into the boiling water, and keeping them 
 there at least five minutes. Be sure the water con- 
 tinues to boil well. A bit of cotton should be stuffed 
 in the mouth of the tt to prevent spray going in. 
 
 With the thermometer stir the water in the calorim- 
 eter, and note its temperature accurately to a tenth of 
 a degree. Remove the thermometer ; also the plug of 
 cotton from the mouth of the tt. Then at once pour 
 the zinc into the cool water, again insert the thermom- 
 eter, stir as long as the temperature continues to rise, 
 
 1 See foot-note, page xxvii of the Introduction. 
 
 2 This tt should be about 15 cm long, and, if possible, 2 cm wide. 
 
 3 When ice or snow or even very cold water is at hand, it is 
 well to cool this water [before measuring out the 100 CC ] a few degrees 
 below the temperature of the laboratory. Why ? 
 
206 THE MODERN PERIOD. 
 
 and note the total rise of the temperature, accurately 
 to a tenth of a degree. 
 
 In spite of the cotton packing there will be some loss 
 of heat, and the temperature will not rise quite as far 
 as it should. If at the start the water in the calorim- 
 eter was cooled about as much below the temperature 
 of the room as it is heated above that temperature at 
 the end of the experiment, it is fair to suppose that the 
 cold water at the start gains, abnormally, about as much 
 heat as the warm water at the finish loses, and that the 
 result of an experiment performed in this way is more 
 accurate than the result of one in which no such pre- 
 caution is taken. Then, too, some of the heat from the 
 zinc is lost in heating the thermometer, and some in 
 heating the beaker itself. Owing to such errors as 
 these, the result of this experiment will not compare 
 very well with results obtained where the utmost pre- 
 cautions are taken, and allowance is ma'de for the heat 
 absorbed by thermometer and calorimeter. However, it 
 is easy, with this apparatus, to get results near enough 
 to the truth to form good data for subsequent work. 
 
 Knowing the amount of water that was heated, and 
 the amount of zinc that gave the heat, and having noted 
 the number of degrees that the temperature of the 
 water rose, and the number that the temperature of the 
 zinc fell, we can calculate the specific heat of zinc. 
 Bear in mind that a calorie is the amount of heat it 
 takes to raise one gram of water one degree, and state : 
 
 [1] The number of units of heat that the whole of 
 the water gained. 
 
. ras 
 
 TSlVBKSr 
 
 SPECIFIC HEATS. xS 
 
 [2] The number of units of heat that the 50 g of 
 zinc lost. 
 
 [3] The number of units of heat that the 50 g 
 would have lost if they had fallen only one degree of 
 temperature. 
 
 [4] The number of units of heat that one gram of 
 zinc would have lost in falling one degree. 
 
 As it would take just as much heat to raise one gram 
 of zinc one degree as it lost in falling one degree, the 
 number obtained for [4] must represent the specific 
 heat of zinc. 
 
 Experiment 3O. 
 Specific Heat of Iron. 1 
 
 In a manner similar to that of Experiment 29, get 
 the specific heat of iron. Use iron in the form of filings 
 or small nails. 
 
 Experiment 31. 
 Specific Heat. 1 
 
 Get the specific heat of either copper [use bits of 
 wire]; lead [use 100 g of shot]; or mercury [use 100 g of 
 mercury, and have only 50 g of water in the calorim- 
 eter]. 
 
 The discovery made by Dulong and Petit was that, 
 in the case of simple substances, the greater the atomic 
 
 1 See foot-note, page xxvii of the Introduction. 
 
208 THE MODEEN PERIOD. 
 
 weight, the less the specific heat ; and after examining 
 a number of cases they concluded that it could be stated 
 as a law, that, if the specific heat of a simple substance 
 is multiplied by the weight assigned to the atom of that 
 substance, in every case the product is the same num- 
 ber 6 . This may be seen by inspecting the fol- 
 lowing table : 
 
 SUBSTAXCE. 
 
 Le&d. . . 
 
 SPECIFIC 
 HEAT. 
 
 , . 0.0314 
 
 ATOMIC 
 WEIGHT. 
 
 207 
 
 PRODUCT. 
 6 5 
 
 Mercury 
 
 0.0333 
 
 200 
 
 6.7 
 
 Antimony . 
 
 0.0508 
 
 120 
 
 6.1 
 
 Silver 
 
 . . 0.0560 
 
 108 
 
 6.0 
 
 Zinc . . 
 
 , . 0.0955 
 
 65.3 
 
 6.2 
 
 Iron 
 
 . . 0.1138 
 
 56 
 
 6.4 
 
 Phosphorus . . , 
 
 , . 0.1887 
 
 31 
 
 5.8 
 
 The explanation by Dulong and Petit for these facts 
 was that every atom has the same capacity for heat that 
 every other atom has. The atom of lead weighs 207 mc , 
 while that of phosphorus weighs only 31 mc ; and the 
 capacity of each atom for heat being the same, the 
 amount of heat that will raise 31 mc [or grams] of 
 phosphorus one degree, will raise 207 mc [or granis] 
 of lead one degree ; hence we find a less amount of 
 heat required to raise one microcrith [or gram] of lead 
 one degree than to raise one microcrith [or gram] of 
 phosphorus one degree. And this is what the above 
 table shows, i.e., that 0.0314 calorie will raise a gram 
 of lead one degree, while it requires 0.1887 calorie to 
 raise a gram of phosphorus one degree. 
 
 In other words, as each atom of lead weighs more 
 than each atom of phosphorus, there would foe> in equal 
 
LAW OF SPECIFIC HEATS. 209 
 
 amounts, say, ten grams, of the two substances a 
 less number of lead atoms than of phosphorus atoms, 
 and therefore, as each atom requires the same amount 
 of heat to heat it up to a given point, a less amount of 
 heat would be required to heat up the ten grams of 
 lead than the ten grams of phosphorus ; or, as we say, 
 the specific heat of lead is less than the specific heat 
 of phosphorus. Examine the table and note that, as 
 the specific heats increase, the atomic weights decrease, 
 and the product of the two is in every case not far 
 from six. In fact, as neither the specific heats nor 
 the atomic weights have been determined with perfect 
 accuracy, it may be supposed that when these determi- 
 nations shall have been made correctly all the products 
 will be the same. 
 
 The discovery of this relation has been of value in this 
 way. Suppose you have found the combining number 
 for copper to be 31.8, and you wish to know whether 
 to take this number 31.8, or 2 times 31.8 = 63.6, or 3 
 times 31.8 = 95.4, or some other multiple of the combin- 
 ing number, for the true weight of the atom. Determine 
 the specific heat of copper, and you will get about 0.09. 
 
 31.8 times 0.09 = 2.862 
 63.6 0.09 = 5.724 
 95.4 0.09 rr 8.586 
 
 As 5.724 is so much nearer six than either of the other 
 numbers, the true atomic weight of copper [if the law 
 of Dulong and Petit is to be trusted] is 63.6. After 
 this discovery by Dulong and Petit, it was found advis- 
 able to halve the values of several atomic weights used 
 up to that time. 
 
210 THE MODERN PERIOD. 
 
 Determine the true atomic weight for zinc from 
 its combining- number and its specific heat. In this 
 determination use the combining number and the 
 specific heat number that you found yourself. 
 
 If no other method is available, even the atomic 
 weight itself may be determined from the specific heat 
 of an elementary substance; for if 6.4, which is a 
 number very near the average of the products of all 
 reliable atomic weights multiplied by the corresponding 
 specific heats, be divided by the known specific heat, 
 the required atomic weight, or a number very near to 
 it, will be obtained 
 
 Though a help in determining the correct atomic 
 weights, perfect reliance must not be placed on this 
 discovery of Dulong and Petit, for there are a few 
 substances, e.g., carbon, boron, and silicon, the pro- 
 ducts of whose atomic weights multiplied by their 
 specific heats [taken at ordinary temperatures] do not 
 equal 6 . 
 
 For Review. 12. State the second great aid that 
 came to chemists in determining which multiple of the 
 combining number to take for the true atomic weight. 
 Who discovered this aid ? When ? What is heat sup- 
 posed to be? Distinguish between temperature and 
 heat. What is the unit amount of heat? What is 
 this unit called? What is a calorimeter? Define 
 specific heat. Describe, briefly, a method for finding 
 the specific heat of a metal. When tables are prepared 
 showing the specific heats and the atomic weights of 
 simple substances what is noticeable ? How did Dulong 
 
ISOMORPHISM. 211 
 
 and Petit explain this peculiarity? In what way is use 
 made of the relationship between specific heat and 
 atomic weight ? Show how you can tell, by means of 
 the specific heat, the best multiple of the combining 
 number for zinc to choose as the true atomic weight 
 for zinc. 
 
 13. ISOMORPHISM. 
 
 Still another help in determining atomic weights was 
 found in the discovery of a relation between crystalline 
 form and chemical composition. This discovery was 
 made by a German, Mitscherlich, who announced, just 
 about the same time that Dulong and Petit made their 
 famous discovery, that when two different substances 
 have the same crystalline form their isomorphism 1 is 
 due to the fact that the molecules of the two substances 
 have the same number of atoms, and that these atoms 
 are joined in the same way. The nature of the atoms 
 was not supposed to make any difference whatever, 
 i.e., one substance might have a chlorine atom where 
 another had a bromine atom, but there must be the 
 same number of atoms. 
 
 Experiment 32. 
 Isomorphism. 
 
 [a] Take a small amount of chloride of sodium ; also 
 a little iodide of sodium. Recrystallize each from a 
 very strong and very hot solution, and when crystalliza- 
 
 Isomorphism means a similarity of form. 
 
212 THE MODERN PERIOD. 
 
 tion has taken place, examine [best under a microscope 
 of low power] the crystals deposited. What is the 
 general form of each? 
 
 [b] Repeat the experiment, using chloride of sodium 
 and chloride of potassium. 
 
 Let us assume that we know chloride of sodium is 
 made of one atom of chlorine and one atom of sodium ; 
 also that we know the total molecular weight of the 
 substance to be 58.5 mc 23 mc belonging to the sodium 
 and 35.5 mc belonging to the chlorine. Let us also 
 assume that we have found the total molecular weight 
 of the iodide of sodium to be 149. 9 mc . As these two 
 substances are isomorphous, they must, according to the 
 law of Mitscherlich, have the same number of atoms, 
 i.e., the iodide must have one atom of iodine and one 
 of sodium. As the total weight of the two atoms is 
 149.9, and the sodium weighs 23, iodine must have 
 an atomic weight of 149.9 23. = 126.9. 
 
 Assuming that we have found the molecular weight 
 of chloride of 'potassium to be 74.6, find, by the prin- 
 ciple of isomorphism, the atomic weight of potassium. 
 
 Though this discovery by Mitscherlich has been a 
 valuable aid, later investigations have shown that it 
 cannot be relied upon, for there are some substances, 
 e.g., sodium sulphate and barium manganate, which 
 crystallize in the same form, but do not have a similar 
 composition. 
 
 For Review. 13. What was the third great aid 
 that came to chemists in determining which multiple 
 of the combining number for an element should be 
 taken as its true atomic weight? Who discovered 
 
THE PERIODIC LAW. 213 
 
 this aid? What is isomorphism? Give an illustration. 
 Why can not this method be relied upon ? 
 
 14. PERIODIC LAW. 
 
 The last discovery of importance which helps us in 
 determining atomic weights is the law of periodicity. 
 In 1864, Newlands, an English chemist, made an ar- 
 rangement of the elements according to their atomic 
 weights. He called attention to the fact that, when 
 thus arranged in form of a table, the elements fall into 
 natural groups, each group distinguished by its members 
 having similar properties. Not much serious attention 
 was paid to this table of Newlands. He was even asked, 
 jokingly, if he would not next prepare a table of 
 elements arranged according to the first letters of their 
 names, and see if he could not get similar groups. But, 
 nevertheless, this classification by Newlands contained 
 the germ of an important discovery. 
 
 In 1869, 1 Lothar Meyer, a German chemist, published 
 a classification of the elements far more extended and 
 better arranged than Newlands'. He found that if the 
 elements are written in lines from left to right accord- 
 ing to their increasing atomic weights, that [excluding 
 hydrogen, the lowest in weight, and beginning with 
 lithium], when the eighth, sodium, is reached, it much 
 resembles lithium, the first; and the ninth resembles 
 the second ; and, again, the fifteenth, potassium, re- 
 sembles lithium, the first ; and the sixteenth resembles 
 
 1 About the same time Mendele'eff:, a Russian chemist, called atten- 
 tion to the fact that he also had come to the conclusion that there was 
 a great law underlying these same facts. 
 
214 THE MODEKN PERIOD. 
 
 the ninth. Meyer arranged a table showing clearly 
 this periodic recurrence of similar properties. There 
 were a number of vacant places in the table, but it was 
 suggested that these might be filled by elements not 
 discovered. 
 
 A study of this table shows that elements whose prop- 
 erties are similar may be grouped in natural families, 
 among the members of which there is a regular increase 
 in the atomic weights, and a corresponding progressive 
 change in both physical and chemical properties. 
 
 Since 1870 much attention has been given to the 
 development of this table, and, in general, all observa- 
 tions have gone to prove that the properties of any ele- 
 ment are periodic functions of its atomic weight; or, in 
 other words, the properties of elements vary as their 
 atomic weights change. This is called The Periodic 
 Law, with which the name of Mendele'eff is so often 
 associated. 
 
 To understand the grounds on which the law is based 
 one must have an intimate knowledge of both physical 
 and chemical properties, as well as of the atomic weights, 
 of all the elements a knowledge that can scarcely be 
 obtained in a year [or perhaps years] of chemical study. 1 
 Hence we shall make no attempt at doing any experi- 
 ments to illustrate the periodic law. 
 
 The use made of the periodic law in determining 
 atomic weights is as follows : If the properties of an 
 elementary substance are known, the substance can be 
 
 1 The author advises a student who can spend a second year on 
 chemistry to devote his second year to Descriptive Chemistry, i.e., 
 largely to a study of properties of substances, rather than to Qualita- 
 tive Analysis. 
 
THE PERIODIC LAW. 
 
 215 
 
 fitted into the periodic table among elements of similar 
 properties, and, from its position, its probable atomic 
 weight can be inferred. 
 
 It is of interest to note how one of the gaps in 
 the periodic table has been filled. Mendele'eff himself 
 predicted that there was an element [missing] whose 
 atomic weight was 72. From the properties of its 
 neighbors in the table he ventured to predict the proper- 
 ties of this missing element. In 1886 Clemens Winkler 
 discovered a new element whose atomic weight has been 
 determined as 72.3. Let us look at the properties as 
 predicted by Mendele'eff: and those found by Winkler. 
 
 FOUND. 
 
 Atomic weight, 72.3. 
 Specific gravity, 5.49. 
 Forms an oxide when heated 
 in the air. 
 
 PREDICTED. 
 
 Atomic weight, 72. 
 
 Specific gravity, 5.5. 
 
 Will form an oxide when heated 
 in the air. 
 
 Oxide will have two atoms of 
 oxygen. 
 
 Easily obtained from its ore 
 by reduction with carbon or 
 sodium. 
 
 A metal. 
 
 Dirty grey. 
 
 Will melt with difficulty. 
 
 Will form a chloride with four 
 atoms of chlorine. 
 
 Chloride will boil near 100, 
 probably lower. 
 
 Will form a sulphide. 
 
 Sulphide will not be soluble in 
 water, but probably will dis- 
 solve in sulphide of ammo- 
 nium. 
 
 Scarcely acted on by acids. 
 
 Two atoms of oxygen in the 
 
 oxide. 
 Easily obtained from its ore 
 
 by reduction with carbon or 
 
 hydrogen. 
 A metal. 
 Grey-white. 
 Melts at 900 C. 
 Forms a chloride which has 
 
 foui* atoms of chlorine. 
 Chloride boils at 86. 
 
 Forms a sulphide. 
 
 Sulphide is moderately soluble 
 in water, more readily in sul- 
 phide of ammonium. 
 
 Not acted on by acids. 
 
216 
 
 THE MODEBN PEEIOD. 
 
 There are at present seventy-two elements recognized. 
 All the aids we have for the determination of their 
 atomic weights have been brought to bear, and many 
 skilful workers have devoted years of time and thought, 
 and are still devoting time and thought, to the accu- 
 rate determination of the relative weights of the atoms. 
 Still the work is by no means satisfactorily completed. 
 Below is given a list l of the seventy-two elements, and 
 the weights now assigned to them. The figures are 
 not given [though in many cases determined] beyond 
 the first place of decimals. 
 
 Aluminum, 
 
 27.1 
 
 Germanium, 72.3 
 
 Phosphorus, 
 
 31. 
 
 Antimony, 
 
 120. 
 
 Glucinum, 9.1 
 
 Platinum, 
 
 195. 
 
 Arsenic, 
 
 75. 
 
 Gold, 1*97.3 
 
 Potassium, 
 
 39.1 
 
 Barium, 
 
 137.4 
 
 Hydrogen, 1. 
 
 Praseodimium, 
 
 144.5 
 
 Bismuth, 
 
 208. 
 
 Indium, 113.7 
 
 Rhodium, 
 
 103. 
 
 Boron, 
 
 11. 
 
 Iodine, 126.9 
 
 Rhubidium, 
 
 85.4 
 
 Bromine, 
 
 79.9 
 
 Iridium, 193. 
 
 Ruthenium, 
 
 101.6 
 
 Cadmium, 
 
 112.2 
 
 Iron, 56. 
 
 Samarium, 
 
 150.? 
 
 Caesium, 
 
 132.9 
 
 Lanthanum, 13.8.2 
 
 Scandium, 
 
 44. 
 
 Calcium, 
 
 40. 
 
 Lead, 206.9 
 
 Selenium, 
 
 79. 
 
 Carbon, 
 
 12. 
 
 Lithium, 7. 
 
 Silicon, 
 
 28.4 
 
 Cerium, 
 
 140.2 
 
 Magnesium, 24.4 
 
 Silver, 
 
 107.9 
 
 Chlorine, 
 
 35.5 
 
 Manganese, 55.1 
 
 Sodium, 
 
 23. 
 
 Chromium, 
 
 52.1 
 
 Mercury, 200. 
 
 Strontium, 
 
 87.6 
 
 Cobalt, 
 
 59. 
 
 Molybdenum, 96. 
 
 Sulphur, 
 
 32.1 
 
 Columbium, 
 
 94. 
 
 Neodymium, 141. 
 
 Tantalum, 
 
 182.5 
 
 Copper, 
 
 63.6 
 
 Nickel, 58.6 
 
 Tellurium, 
 
 125. 
 
 Erbium, 
 
 166.? 
 
 Nitrogen, 14. 
 
 Terbium, 
 
 160.? 
 
 Fluorine, 
 
 19. 
 
 Osmium, 190.8 
 
 Thallium, 
 
 204.2 
 
 Gadolinium, 
 
 156.1 
 
 Oxygen, 16. 
 
 Thorium, 
 
 233.1 
 
 Gallium, 
 
 70. 
 
 Palladium, 106.6 
 
 Thulium, 
 
 171.? 
 
 1 Taken from a recent revision by Dr. Richards of Harvard Uni- 
 versity. 
 
MODERN ATOMIC WEIGHTS. 217 
 
 Tin, 119. Uranium, 240. Yttrium, 89.? 
 
 Titanium, 48.1. Vanadium, 51.3 Zinc, 65.3 
 
 Tungsten, 184. Ytterbium, 173. Zirconium, 90.6 
 
 For Review. 14. What is the fourth and last 
 great aid that has come to help in the determination 
 of atomic weights? State briefly the history of the 
 discovery of this aid. What is meant by the periodic 
 law ? How has this law been used with success ? 
 
 How many elements are now recognized? Fix in 
 mind the atomic weights now assigned to those atoms 
 in which you feel the most interest. 
 
218 LANGUAGE OF CHEMISTRY. 
 
 LANGUAGE OF CHEMISTRY. 
 
 The language of chemistry is largely symbolical. It 
 is a kind of shorthand, combinations of letters and 
 figures being used to represent the names of substances, 
 and signs to express processes. 
 
 The first letter [or the first and some other prominent 
 letter] of the Latin name of an element is used as the 
 symbol for that element. Thus, H represents an atom 
 of hydrogen ; O, an atom of oxygen ; S, an atom of sul- 
 phur ; C, an atom of carbon ; Ca, an atom of calcium ; 
 Cl, an atom of chlorine. Of course if C has been taken 
 to represent the atom of carbon it cannot also stand for 
 the atom of calcium, hence Ca, the first letter and 
 another prominent letter, are taken for the symbol. In 
 the same way, to represent chlorine, Cl is used. 
 
 In most cases the English and the Latin names 
 begin with the same letters. The following are the 
 exceptions : 
 
 ENGLISH. LATIN. SYMBOL. 
 
 Antimony .... Stibium Sb 
 
 Gold Aurum Au 
 
 Iron Ferrum Fe 
 
 Lead Plumbum Pb 
 
 Mercury Hydrargyrum .... Hg 
 
 Potassium .... Kalium K 
 
 Silver Argentum Ag 
 
 Sodium Natrium Na, 
 
 Tin Stannum Sn 
 
 Tungsten .... Wolframium W 
 
LANGUAGE OF CHEMISTRY. 
 
 219 
 
 The following is a complete list of the symbols of 
 the seventy-two elements : 
 
 SYMBOL. NAME. SYMBOL. 
 
 NAME. 
 
 SYMBOL. 
 
 . Al 
 
 Hydrogen . . H 
 
 Ruthenium. 
 
 . Ru 
 
 . Sb 
 
 Indium ... In 
 
 Samarium . 
 
 . Sm 
 
 . As 
 
 Iodine ... I 
 
 Scandium . 
 
 . Sc 
 
 . Ba 
 
 Iridium . . . Ir 
 
 Selenium . 
 
 . Se 
 
 . Bi 
 
 Iron . . . . Fe 
 
 Silicon . . 
 
 . Si 
 
 . B 
 
 Lanthanum . La 
 
 Silver . . 
 
 Ag 
 
 . Br 
 
 Lead . . . . Pb 
 
 Sodium . . 
 
 . Na 
 
 . Cd 
 
 Lithium ... Li 
 
 Strontium . 
 
 . Sr 
 
 . Cs 
 
 Magnesium. . Mg 
 
 Sulphur. . 
 
 . S 
 
 . Ca 
 
 Manganese . . Mn 
 
 Tantalum . 
 
 . Ta 
 
 . C 
 
 Mercury . . . Hg 
 
 Tellurium . 
 
 . Te 
 
 . Ce 
 
 Molybdenum . Mo 
 
 Terbium . 
 
 . Tb 
 
 . Cl 
 
 Neodymium . Nd 
 
 Thallium . 
 
 . Tl 
 
 . Cr 
 
 Nickel . . . Ni 
 
 Thorium . 
 
 . Th 
 
 . Co 
 
 Nitrogen . . N 
 
 Thulium . 
 
 . Tu 
 
 . Cb 
 
 Osmium. . . Os 
 
 Tin . .. V 
 
 . Sn 
 
 . Cu 
 
 Oxygen . . . O 
 
 Titanium . 
 
 . Ti 
 
 . Er 
 
 Palladium . . Pd 
 
 Tungsten . 
 
 . W 
 
 . F 
 
 Phosphorus. . P 
 
 Uranium . 
 
 . U 
 
 . Gd 
 
 Platinum . . Pt 
 
 Vanadium. 
 
 . V 
 
 . Ga 
 
 Potassium . . K 
 
 Ytterbium. 
 
 . Yb 
 
 . Ge 
 
 Praseodymium, Pr 
 
 Yttrium . 
 
 . Yt 
 
 . Gl 
 
 Rhodium . . Rh 
 
 Zinc . 
 
 . Zn 
 
 . Au 
 
 Rhubidium. . Rb 
 
 Zirconium . 
 
 . Zr 
 
 NAME. 
 Aluminum 
 Antimony 
 Arsenic . 
 Barium . 
 Bismuth . 
 Boron . . 
 Bromine . 
 Cadmium . 
 Caesium . 
 Calcium . 
 Carbon 
 Cerium 
 Chlorine . 
 Chromium 
 Cobalt . . 
 Columbium 
 Copper . . 
 Erbium . 
 Fluorine . 
 Gadolinium 
 Gallium . 
 Germanium 
 Glucinum . 
 Gold 
 
 The atomic weight of an element should always be 
 associated with its symbol, thus, H should represent to 
 your mind l mc of hydrogen ; C, 12 mc of carbon ; Fe, 56 mc 
 of iron ; Zn, 65.3 mc of zinc, and so on. 
 
 To express compounds there are used symbols called 
 formulae, made by writing together the symbols of the 
 atoms that are in the molecule of the compound, thus, 
 
220 LANGUAGE OF CHEMISTRY. 
 
 HC1 is 'the formula for a molecule of hydrochloric acid; 
 NaOH represents a molecule of hydroxide of sodium. 
 When there are several atoms of the same kind in the 
 molecule subnumerals are used, thus, H 2 O stands for a 
 molecule of water; HNO 3 , for one of nitric acid; H 2 , 
 for a molecule of hydrogen gas ; O 2 , for a molecule of 
 oxygen gas ; CaCO 3 , for one of carbonate of calcium ; 
 NH 3 , for one of .ammonia; and H 2 SO 4 , for one of 
 sulphuric acid. 
 
 If the symbol for every atom has the correct atomic 
 weight associated with it, there is no difficulty in tell- 
 ing the molecular weight of a substance if its formula 
 is known, for the molecular weight must be the sum of 
 the weights of all the atoms that go to make up the 
 molecule. What, then, is the molecular weight of 
 hydrochloric acid? Of carbonate of calcium? Of 
 sulphuric acid? 
 
 The formula of a molecule always tells three things: 
 first, what the substance is ; second, of what atoms it is 
 composed ; third, what the molecular weight is. 
 
 To express two or more molecules, or atoms, coeffi- 
 cients are used. Thus, 2 H 2 O represents two molecules 
 of water; 5 H 2 SO 4 stands for five molecules of sul- 
 phuric acid; 10 K 2 SO 4 , for ten molecules of sulphate of 
 potassium ; 2 H, for two atoms of hydrogen ; 2 H 2 , for 
 two molecules of hydrogen ; 7 NaCl, for seven molecules 
 of common salt ; 3 O, for three atoms of oxygen ; 3 O 2 , 
 for three molecules of oxygen; and 3 O 3 , for three 
 molecules of ozone a substance we have not studied. 
 
 Note. Be sure that you see the distinction between 
 atomic and molecular expressions. State which of the 
 
LANGUAGE OF CHEMISTRY. 221 
 
 following are atomic and which molecular : H, H 2 , 7 H, 
 2 H, 5 C1 2 , HC1, H 2 O, H 2 O 2 , 3 O. 
 
 In chemistry the action of one substance on another 
 is represented by the sign +, and equations are used to 
 express chemical changes, the factors of the change 
 being put before the sign , and the products after. 
 Thus, ZnO + H 2 SO 4 = ZnSO 4 + H 2 O, represents the 
 change that takes place when the oxide of zinc acts on 
 sulphuric acid. When water is used simply to produce 
 solution, the symbol Aq, standing for the Latin word 
 aqua, is used. Thus the reaction of ZnO and H 2 SO 4 , 
 as we conducted it, would be represented as follows: 
 ZnO + [H 2 S0 4 + Aq] = [ZnS0 4 + H 2 O + Aq]. The 
 brackets are used to indicate the solutions. As the Aq 
 seems to play no part chemically in the changes, this 
 symbol is frequently omitted altogether. The neutral- 
 ization of hydrochloric acid with hydroxide of potassium 
 is represented thus : HC1 + KOH = KC1 + H 2 O ; and 
 the neutralization of sulphuric acid with hydroxide of 
 sodium thus : H 2 SO 4 + 2 NaOH = Na 2 SO 4 + 2 H 2 O. 
 
 Write in equation form the changes that were 
 brought about : 
 
 [a] When an atom of zinc acted on a molecule of 
 sulphuric acid in water solution ; 
 
 [6] When oxygen and hydrogen gases were pro- 
 duced from water by the electric current. It will 
 not do to write this H 2 O = H 2 + O, because molecules 
 of oxygen gas came bubbling up. The equation 
 should be written, 2 H 2 O = 2 H 2 + O 2 ; 
 
 [<?] When oxygen, was made by heating the chlorate 
 
222 LANGUAGE OF CHEMISTRY. 
 
 of potassium. Here assume, as in the last case, that 
 the gas came off in molecules. The formula for a 
 molecule of chlorate of potassium is KC1O 3 , and that 
 for the chloride which results is KC1; 
 
 [d] When oxygen gas acted on phosphorus. The 
 formula for a molecule of phosphorus is P 4 , and that 
 for the resulting white oxide is P 2 O 5 ; 
 
 [e] When an atom of carbon burned in oxygen, 
 producing the dioxide of carbon, CO 2 ; 
 
 [/] When an atom of sulphur burned in oxygen, 
 producing the dioxide of sulphur, SO 2 ; 
 
 \_g~\ When a molecule of water was added to a 
 molecule of dioxide of sulphur, and there resulted a 
 molecule of sulphurous acid, H 2 SO 3 ; 
 
 [h] When O 2 and SO 2 were passed over hot plati- 
 num sponge, and SO 3 the second oxide of sulphur 
 resulted ; 
 
 [i] When sulphuric acid H 2 SO 4 was produced 
 by the addition of water to the second oxide of sulphur ; 
 
 [j] When two molecules of HC1, in water solution, 
 reacted with one molecule of carbonate of calcium, 
 CaC0 3 ; 
 
 [Jc] When five volumes of H 2 acted with two vol- 
 umes of NO, and there resulted two volumes of ammo- 
 nia NH 3 and two volumes of steam. 
 
 Note that these chemical equations are nothing more 
 than a short way of expressing chemical facts. They 
 resemble algebraic equations, inasmuch as there are the 
 same atoms on one side of the sign of equality that 
 there are on the other side ; and, consequently, the sum 
 
LANGUAGE OF CHEMISTRY. 223 
 
 of the atomic weights on one side equals the sum of 
 those on the other. But it is not true that any trans- 
 position that can be made in algebra can be made in a 
 chemical equation. Chemical equations are far less 
 flexible than algebraic ones, the chemical being limited 
 to the expression of observed facts. This is an impor- 
 tant point, and should not be forgotten. 
 
 A chemical equation always expresses two of the 
 great laws of chemistry, and, when gaseous substances 
 are involved, it expresses a third. It always expresses 
 the law of conservation of mass, as is shown by the use 
 of the equality sign. It also always expresses the law 
 of definite proportions by weight, because the symbols 
 used stand for definite weights of matter. And, when 
 any of the substances are gases, the simple ratio between 
 their coefficients expresses the law of definite propor- 
 tions by volume. 
 
 Note, that, in addition to the three facts [see page 220] 
 that the formula for a molecule always expresses, there 
 is a fourth shown when the formula is that of a gaseous 
 substance. The simple molecular formulae of gases all 
 represent the same volume. O 2 , H 2 , C1 2 , N 2 , H 2 O 
 [steam], NH 3 , NO, NO 2 , CO 2 , SO^ CO, and HC1 all 
 represent the same volume ; for, according to the 
 hypothesis of Avogadro that in equal volumes of all 
 gases there are the same number of molecules, it 
 follows that every molecule occupies just as much 
 space as every other molecule. Hence the formula 
 for the molecule of any gaseous substance represents 
 a definite volume of that substance. * 
 
224 STOICHIOMETEY. 
 
 STOICHIOMETRY. 
 
 If we know the equation that expresses any chemical 
 change and know the weight in grams of a single sub- 
 stance that enters into the change we can calculate the 
 weight of every other substance involved. This power 
 to calculate unknown weights of substances is one of 
 great value to the chemist. If, for instance, he is called 
 upon to produce 100 grams of silver chloride, it is not 
 necessary for him, as it was in the old days, to guess at 
 the amounts of nitrate of silver and of common salt to 
 use, with a good chance of making just a little less than 
 the ten grams or a considerable amount more, nor need 
 he go " by rule of thumb." By the aid of a chemical 
 equation and his knowledge of the atomic weights he 
 can calculate the exact amounts of the factors required 
 to yield the required weight of product. Let us make 
 the calculation. First write the equation expressing the 
 change. It is this : AgNO 3 + NaCl = AgCl + NaNO 3 . 
 Now write above the formula for each molecule its mo- 
 lecular weight, i.e., the sum of the weights of all the 
 atoms in the molecule. As the weights, in grams [or 
 in pounds, or in terms of any other unit], bear to each 
 other the same ratio as do the molecular weights, pro- 
 portions can be made enabling us to find the unknown 
 amounts, e.g., the molecular weight of the AgCl is to 
 the molecular Weight of the AgNO 3 , as is the gram 
 weight of AgCl [known to be 10] to the gram weight 
 ofAgNO 3 , or 143.5: 170:: 10 :z. x=UM -. There- 
 fore. ll.$5 g of nitrate of silver will be required to 
 
STOICHIOMETRY.. 225 
 
 produce 10 g of chloride of silver. Now calculate how 
 much NaCl is needed. Also calculate the weight of 
 the nitrate of sodium that will also result from the 
 change. See if the sum of the weights of the products 
 equals the sum of the weights of the factors. This 
 finding of unknown amounts is called stoichiometry. 
 
 The chief rule of stoichiometry is as follows : When 
 the gram weight of one substance which is involved in 
 a chemical change is known, in order to find the gram 
 weight of any other substance involved, make a pro- 
 portion thus : the molecular weight of the known is to the 
 molecular weight of the unknown as the gram weight of the 
 known is to x. x will be the required gram weight. 
 
 If it is desired to find the volume of a gas that will 
 be produced in a given case, first find the weight of 
 gas produced : then calculate [making use of the known 
 density of the given gas] the volume this weight would 
 occupy at N. T. P. : and, finally, calculate [using the 
 laws of Boyle and of Daltoii] the volume which this 
 volume at N. T. P. will occupy under the given con- 
 ditions, 
 
226 MANIPULATIONS. 
 
 MANIPULATIONS. 
 
 The following directions may be of service in per- 
 forming the mechanical operations that so often occur 
 in laboratory practice : 
 
 To Mark Glass. 
 
 This can best be done with a pencil that has recently 
 been invented for the purpose. Each student should 
 keep one of these pencils constantly at hand in his 
 desk. By its frequent use, particularly in marking 
 the point at which tubes are to be cut, and in labelling 
 vessels that have to be set away at the end of labora- 
 tory periods, much time and annoyance will be saved. 
 These pencils may be obtained from the publishers of 
 this book Ginn and Company. 
 
 To Cut Glass. 
 
 Small and medium tubes, and rods, are best cut as 
 follows : With a sharp triangular file make a short 
 scratch at the point where the tube is to be cut. Take 
 the tube in your hands with the two thumbs on the 
 tube under the scratch, and the fingers of each hand 
 spread out on the tube to the right and the left of 
 the scratch. The nails of the two thumbs should be 
 close together and touching the glass exactly under the 
 scratch. By means of the two little fingers bring a 
 gradually increasing downward pressure to bear, letting 
 the thumb nails act as a fulcrum. 
 
MANIPULATIONS. 227 
 
 Larger tubes, e.g., combustion tubes one or more 
 cm in diameter, may be cut in a similar manner by 
 substituting the edge of a triangular file, resting on 
 the desk, for the fulcrum, and pressing downward with 
 the palms of the two hands. If, however, the tube to 
 be cut is very short, proceed thus : Make the scratch 
 with the file, then either touch this scratch suddenly 
 with a hot iron, e.g., the end of an old file heated red- 
 hot in the Bunsen flame ; or drop upon it a bead of 
 red-hot molten glass ; or, best of all, apply to it a small 
 gas-flame, which may be made by disconnecting the 
 Bunsen burner from its tube and inserting in the end 
 of the tube a tip of hard glass drawn out like the wash- 
 bottle tip. The best flame is a vigorous, clear-cut, 
 smokeless one, about l cm long, produced by a small 
 opening and a full pressure of gas. When such a 
 flame is applied to the scratch the tube usually snaps 
 square off. If it does not snap within half a minute, 
 the change of temperature has not been sudden enough. 
 Cool the tube, and apply the flame again. If a crack 
 starts but does not run entirely around, or does not run 
 straight, turn off the gas till the flame is only about 
 2 mm long, and apply this flame to the glass just beyond 
 the end of the crack. The crack will advance to the 
 flame. Move the flame ahead, and in this way lead 
 the crack around wherever you wish. 
 
 To cut off the necks of bottles, beakers, and test- 
 tubes, make a scratch with a file, and start a crack as 
 directed above. Lead this crack, best with the 2 mm 
 flame, around the neck of the vessel. In this way 
 chipped or cracked beakers and test-tubes may often 
 
228 MANIPULATIONS. 
 
 be made into serviceable articles, by cutting off their 
 tops and fire-polishing the sharp edges. 
 
 To Fire-polish the Edges of Glassware. 
 
 All sharp glass edges, e.g., ends of tubes and rods, 
 freshly cut necks of bottles, broken edges of beakers 
 and test-tubes, should be melted in the Bunsen flame 
 till they are smooth and rounded. The flame of the 
 Bunsen burner is usually sufficient, but the work can 
 be done quicker in the flame of the blast-lamp. Great 
 care must be taken, particularly with the latter flame, 
 not to crack the glass by too sudden application of the 
 heat. Begin with a small flame, which must be in- 
 creased slowly. When heating glass there is less 
 danger of its snapping if it is immersed first in the 
 less vigorous, luminous, sooty flame, and heated as hot 
 as possible there before it is put in the Bunsen flame. 
 In the case of thick glass the article should not at first 
 be held continuously, even in the luminous flame, but 
 should be immersed for a moment, then withdrawn 
 for a moment, again immersed, and so on, till it is 
 thoroughly heated. Thick glass is more apt than thin 
 to crack by a sudden application of heat, because the 
 side where the heat is applied expands before the heat 
 has passed to the other side and expanded that, 
 hence a rupture. 
 
 To Bend Glass Tubes and Rods. 
 
 This must be done in a wide flame, and not in the 
 common Bunsen burner flame, and, except in the case 
 of very short tubes, not in the blast-lamp flame. A 
 
MANIPULATIONS. 229 
 
 common bat-wing gas jet [used for illuminating pur- 
 poses] is good, but leaves the tube sooty. Better 
 than this is the broad tip furnished for this purpose 
 with some Bunsen burners. 
 
 Hold the tube, at the point where it is to be bent, in 
 the hottest part of the broad flame. In the case of an 
 ordinary tube, a length of at least 6 cm should be im- 
 mersed in the flame. Turn the tube slowly, so that all 
 sides shall be equally heated. When the tube has 
 softened, and you feel it to be flexible, remove it from 
 the flame, and quickly, but deliberately, bend it to the 
 exact angle wanted. If the right angle is not obtained 
 at the first attempt, it is hardly worth while to heat 
 again and try to bend it into shape. Better take a 
 new piece of glass and start again. 
 
 To Draw Out Glass Tubes. 
 
 Begin as directed for bending tubes, but heat more. 
 When the glass has softened so much that it begins to 
 sag, remove it from the flame and draw it to the shape 
 wished. Wash-bottle tips, and the like, may be made 
 either with the bat-wing flame or in the Bunsen burner 
 flame. Large or very hard tubes best be drawn with 
 the aid of the blast-lamp. In using the blasi^lamp for 
 this purpose care should be taken to apply the heat 
 gradually, as directed under fire-polishing. When it is 
 desired to draw out a long length of capillary tube, 
 the glass should be made very soft, removed from the 
 flame, drawn to the right diameter, allowed to cool a few 
 seconds in order to take a " set" and then rapidly drawn 
 to obtain length. 
 
230 MANIPULATIONS. 
 
 To Make a Matrass. 
 
 A matrass is a hard glass vessel with a long slim neck 
 and a bulb-like body. For a large matrass a Kjeldahl 
 flask serves excellently. Small matrasses, often called 
 "bulb-tubes," are frequently used when a substance has 
 to be heated in a flame so hot that it would soften an 
 ordinary test-tube. 
 
 To make a small matrass : Take a piece of hard glass 
 tube of 5-1 O mm bore. Hold one end in the blast-lamp 
 flame till the glass is soft. With the forceps pinch the 
 softened walls together, and quickly draw off, and reject, 
 about l cm of the end of the tube. Immerse the closed 
 end of the tube in the blast-lamp flame ; hold it there 
 till a lump of softened glass has collected ; then put 
 the open end in your mouth and blow gently till the 
 lump of glass forms a bulb. 
 
 To Render Corks Air-tight. 1 
 
 Melt some solid paraffine a candle will do in a 
 dipper. Roll the cork a little under the foot, and 
 then soak it for a few minutes in the melted paraffine. 
 Never attempt to tighten leaky joints by applying par- 
 affine, sealing-wax, etc. This application is not worth 
 the trouble, seldom stops the leak, and looks shiftless, 
 as apparatus properly constructed never needs any such 
 doctoring. 
 
 1 Good corks need no treatment, but in a gross of corks it is seldom 
 that there are not a number which are not air-tight. 
 
MANIPULATIONS. 231 
 
 To Render Joints Air-tight. 
 
 Before putting stoppers in the necks of bottles, 
 rubber bands on jars, rubber hose on tubes, etc., the 
 surfaces of contact should be greased, if an air-tight 
 joint is wanted. Vaseline makes an excellent grease. 
 
 To Cut Rubber Neatly and Quickly. 
 
 Use a sharp knife, and keep the cut wet. A small 
 oil-stone should be kept at hand in the laboratory for 
 sharpening knives. 
 
 To Pass a Glass Tube Through a Hole in a 
 Rubber Stopper. 
 
 Apply vaseline or glycerine to the glass. In this 
 way a tube that seems too big for the hole may be 
 slipped through easily, particularly if its end has been 
 fire-polished. 
 
 To Bore a Round Hole in Glass. 
 
 It is often desirable to make a hole in the side of a 
 bottle, test-tube or beaker, without cracking the sur- 
 rounding glass. Take a triangular file [an old one will 
 do], break off its tip so that a jagged point is made. 
 Keep this point constantly wet with vaseline or some other 
 greasy substance, and with a circular grinding motion 
 of the arm and hand, bore into the glass. As the file 
 point gets blunted break off farther down. Do not 
 apply much pressure in the case of beakers and thin 
 glass, but considerable in the case of stout bottles. 
 
232 MANIPULATIONS. 
 
 When once the file has gone through, take a rat-tail 
 file and, at first cautiously, file the hole to the desired 
 size. Do not hold the glass in such a position that the 
 hand would be cut in case there should be a sudden 
 collapse of the article on which you are operating. 
 
 *To Prevent Mixing Glass Stoppers. 
 
 Never take the stopper from a laboratory bottle and 
 lay it on the desk. Always take it out by means of 
 the middle finger and the forefinger with the palm 
 of the hand held upward. This way enables you to 
 hold the stopper [inverted] between the fingers while 
 the hand is free to lift the bottle and pour its con- 
 tents. Stoppers left on the desk get contaminated and 
 mixed. 
 
 To Hold Hot Beakers, Test-Tubes, etc. 
 
 A beaker of boiling water may be lifted from the 
 fire if the fingers grasp it by the rim only. A piece of 
 paper, folded into a band 15-20 cm long and about l cm 
 wide, passed around the neck of the test-tube so that 
 the fingers may grasp the two ends of the paper, forms 
 as convenient a holder for a test-tube in which you are 
 boiling a liquid as any of the fancy ones you can buy. 
 
 To Use the Pneumatic Trough. 
 
 Note. A small iron sink can well be converted into 
 a pneumatic trough in the manner described in Appendix 
 P. Every pneumatic trough should have a " bridge." 
 The bridge recommended for the sink [Appendix P] 
 will do for any trough. 
 
MANIPULATIONS. 233 
 
 For most purposes the trough should be filled with 
 cold water. For collecting gases that are soluble in 
 cold water, e.g., laughing gas, hot water serves well. 
 In those cases in which it is desired to collect gases 
 free from water vapor, mercury is generally the best 
 liquid to use in the trough. In fact mercury is an 
 excellent substance to use at almost all times, and it is 
 unfortunate that its cost prevents its more general use. 
 As mercury amalgamates with zinc an iron [or porce- 
 lain] trough is to be preferred to one of zinc. 
 
 When a gas is to be collected by means of the 
 pneumatic trough, the liquid in the trough should 
 reach well above the bridge ; the end of the delivery 
 tube should be directly under the hole in the bridge ; 
 and the receiving vessel, inverted and filled with the 
 liquid of the trough, should stand on the bridge directly 
 over the hole. 
 
 To Use Filter Papers. 
 
 The filter paper should be cut in circular form. For 
 most purposes the paper should be folded together so 
 as to halve its surface; then it should again be folded 
 together, thus quartering it; finally, it should be opened 
 in such a manner that three of the quarters are together 
 and form one half of the sides of a cone, while the 
 fourth quarter forms the other half. In fitting the 
 filter to the funnel, the tip of the cone should be 
 inserted in the point of the funnel, and the paper 
 slightly wet by means of the wash-bottle [unless water 
 would harm the substance to be filtered]. In general, 
 the filter paper should be of such diameter that it does 
 
234 MANIPULATIONS. 
 
 not reach, when in place, quite as high as the edge of 
 the funnel. 
 
 For substances that filter slowly a plaited filter is 
 useful. To make a plaited filter : fold to quarters, as 
 in the case of the common filter; then open to a half 
 filter; the half will show a fold dividing it in halves; 
 divide each of these halves in halves by a similar fold. 
 Again open out to a half filter. Be sure that the three 
 creases which divide the half filter into quarters are all 
 alike, i.e., all have their ridges on one side and hollows 
 on the opposite. Next make a series of creases down 
 the middle of each slice, taking care to have these 
 latter creases point exactly opposite from the first. In 
 making the creases be careful and do not tear the tip of 
 the cone. Now open the paper completely, and insert 
 it in the funnel in such a way that nowhere shall there 
 be two thicknesses together. The plaits of this funnel 
 furnish a large amount of surface for filtration. 
 
 To Dry Bottles, Flasks, etc. 
 
 Fit a long, hard glass tube to the rubber tube from 
 the bellows. Hold the glass tube in the flame of a 
 Bunsen burner and force a stream of hot air into the 
 article that is to be dried. Direct the stream of hot air 
 against any drops of moisture that you may see. 
 
 To Remove Stoppers that have Stuck. 
 
 First gently tap the stopper against some rigid body 
 as a brick wall or iron beam. If this treatment fails 
 to start the stopper, immerse the bottle, top down, in a 
 
MANIPULATIONS. 235 
 
 vessel of water. Allow the stopper to remain immersed 
 for several hours. If this fails to start the stopper, wipe 
 the bottle dry and apply to its neck the heat from the 
 small gas flame mentioned under " To Cut Glass," page 
 227. Turn the neck as you apply the flame. 
 
 To Pour Oases. 
 
 With a little care gases may be poured in a manner 
 similar to that in which you pour liquids. Of course a 
 gas lighter than air must be poured up into an inverted 
 vessel. In pouring a gas from one tt to another it is 
 well to hold the fingers and hand around the mouths 
 of the two tt's in a way to protect the stream of 
 gas from any current of air that might blow it to one 
 side. 
 
 To Use a Bunsen Burner. 
 
 For almost all work the Bunsen burner should be 
 used with its air- vent open. When this vent is open 
 the air enters and mingles with the gas. Then when 
 the gas issues from the top of the burner it burns 
 rapidly, with a very hot and almost colorless flame. 
 
 If for any reason you are not using the full supply 
 of gas, the supply of air should be reduced to a corre- 
 sponding amount by partly closing the vent. 
 
 Sometimes a sudden gust of wind will drive the 
 flame down the tube of the Bunsen burner and ignite 
 the gas as it issues below. In this case the burner is 
 said to " snap," or " strike back." A " snapped " burner 
 can usually be detected by the peculiar color of the 
 flame it shoots up; also by a peculiar odor which fills 
 
236 MANIPULATIONS. 
 
 the atmosphere all around the burner. The danger 
 from a "snapped" burner is that the base gets intensely 
 hot and is apt to burn the fingers. A "snapped" 
 burner should have its supply of gas wholly turned off 
 and be re-lighted. 
 
 To Use the Bunsen Blast-Lamp. 
 
 Allow the gas to circulate in the outer chamber, and 
 force a current of air in through the small tube in the 
 center. 
 
APPENDICES. 
 
APPENDICES. 
 
 APPENDIX A. 
 
 Apparatus for the Electrolytic Decomposition of 
 
 Water. 
 
 Prepare a vessel for holding water as follows : Take 
 any common bottle of about one quart capacity. At a 
 point about one-third down from the neck to the 
 bottom cut l off the top part parallel to the bottom, so 
 that the top part, inverted and with a cork in its neck, 
 will form a stout, shallow dish. If the neck is a long 
 one, cut it off so that not more than one inch is left. 
 Fit a cork to the neck. Pass two platinum wires, each 
 about 15 cm long, between the cork and the glass, well 
 up into the body of the vessel. About one inch of wire 
 should project out from the neck. The wires should 
 be as far apart from one another as possible,' and the 
 parts [about 10 cm long] that protrude into the vessel 
 should be twisted into spirals. At their lower ends the 
 platinum wires should be connected, by being tightly 
 twisted, or, better, soldered, with copper wires leading to 
 two or more Bunsen cells or other source of electricity. 
 Support the vessel, with the neck down, on a ring of 
 the ring stand. Light a candle, and, holding the candle 
 
 1 For cutting thick glass, see Manipulations. 
 
240 APPENDICES. 
 
 inverted, let the candle grease drop down and fill the 
 neck of the bottle above the cork while you hold the 
 wires apart and keep their spirals well above the grease. 
 The grease makes the joints water-tight. 
 
 For the Bunsen cell have ready a two-quart glass 
 battery jar, a porous cup as tall as the battery jar, a 
 battery zinc to go around the porous cup, a battery 
 carbon to go in the porous cup, two [one foot long] 
 pieces of copper wire, and two binding screws to con- 
 nect wires with the zinc and with the carbon. Fill the 
 jar nearly half full of water. Add about one-tenth as 
 much strong sulphuric acid as you have added water. 
 Add the acid slowly, with constant stirring with a glass 
 rod. Caution : Sulphuric acid is very corrosive. Do 
 not get any on skin or clothes. Put the zinc in the jar 
 of acidified water, and let the acid work for about a 
 minute. Invert the zinc, and let the acid again act, 
 now on the upper part, for about a minute. Then 
 remove the zinc, and, at the sink, with a rag and a 
 little mercury, rub mercury into the zinc, both inside 
 and outside the cylinder, till the surface is bright and 
 well amalgamated. Amalgamation prevents the zinc 
 from being unduly eaten away by the acid. Put the 
 zinc back, right side up, in the acid. Put the porous 
 cup within the zinc. If too much acid has been put in 
 the outer glass vessel, now remove some. Fill the 
 porous cup about half with nitric acid, and the other 
 half with sulphuric acid, taking care that the level of 
 the acid in the porous cup is the same as that of the 
 liquid in the glass vessel without the porous cup. Put 
 the carbon in the porous cup. By means of tto binding 
 
APPENDICES. 241 
 
 screws and a short piece of copper wire, connect the car- 
 bon of the cell with one of the platinum wires, and con- 
 nect the zinc with the carbon of another cell. Be sure 
 that all points of contact between the wires and binding 
 screws have been freshly scraped clean and bright. 
 
 Note. Two cells are necessary. More than two will 
 cause the decomposition of the water to be more rapid, 
 and, consequently, more satisfactory. 
 
 Connect the zinc of the second [or last] cell with the 
 other platinum wire of the decomposition apparatus. 
 
 APPENDIX B. 
 
 Hydrogen Explosions. 
 
 One of the most frequent of accidents in a laboratory 
 for elementary chemistry is the explosion of a mixture 
 of hydrogen and air. When generating hydrogen which 
 is to be lighted or near which any kind of fire is to 
 come, always test its explosive qualities, i.e., test to 
 see whether air is still mixed with the hydrogen. 
 
 The test is best made by catching a small tt full of 
 the gas, and [having removed the tt, while still in- 
 verted, quickly, several feet from the supply of hydro- 
 gen] touching a match to the open inverted mouth of 
 the tube. A sharp ringing report shows danger, i.e., 
 that there is an explosive mixture of air and hydrogen 
 present. Continue testing till, when the flame is ap- 
 plied, there is only a gentle pop, and the hydrogen 
 burns quietly with a faint flame up into the tt. 
 
242 APPENDICES. 
 
 A tt of about l cm bore, and not more than 6 or 
 8 cm long, is the best for this test. Such a tube may be 
 made from ordinary large soft glass tube or by cutting 
 a common small tt in halves. Hydrogen explosions 
 are dangerous from the flying glass that is usually sent 
 in all directions. This method of testing is called "by 
 the explosion tube." 
 
 APPENDIX C. 
 
 Test Papers. 
 
 Note. The only test papers that are needed in ele- 
 mentary chemistry are : one to indicate an acid solution, 
 and one to indicate an alkaline solution. In preparing 
 such test papers use is made of the changes of color pro- 
 duced by acids and alkalies on certain vegetable sub- 
 stances. Litmus in acid solution is red, and in alkaline, 
 blue. 
 
 Take 1 part [e.g., 10 g ] of the litmus of trade. Mix 
 it in a porcelain evaporating dish with 6 parts [e.g., 60 g ] 
 of water. Warm gently, and stir for about ten minutes. 
 Filter. Take half the nitrate, and, with a glass rod, 
 stir in a drop or so of very dilute sulphuric acid [e.g., 
 l cc of acid to 50 CC of water]. Stir in acid till the solu- 
 tion is just turned red. Immerse strips of filter paper 
 in the red solution, keep the solution warm for a little 
 while, remove the strips and hang them on a line [in 
 a room free from ammonia] to dry. They should be of 
 a good pink color. 
 
APPENDICES. 243 
 
 Take the remainder of the red solution and add some 
 of the blue [previously saved apart], till the color is 
 again turned blue. Immerse strips of paper in this 
 liquid and hang them to dry in a room free from acid 
 fumes. To detect an acid use the blue paper ; to detect 
 an alkali use the red. Never put a test paper in any 
 solution, but always take out a drop on a glass rod, 
 and touch this drop to the test paper held between the 
 fingers. Should the paper be put in the solution, the 
 coloring matter would contaminate the solution itself. 
 It is never safe to lay a test paper on a desk, for the 
 desk itself may contaminate the test paper. 
 
 For detecting alkaline substances papers treated with 
 turmeric are in some respects preferable to those treated 
 with red litmus. To prepare turmeric papers, take 2 
 parts of water and 4 of alcohol to 1 of turmeric. Warm 
 gently, and stir for about ten minutes. Best warm the 
 alcohol solution over hot water, not over a flame, for 
 fear of fire. Filter. Immerse strips of filter paper in 
 the liquid. Keep the papers in the solution [which 
 should be kept warm] for a few minutes, and hang on 
 a line to dry as in the preparation of litmus paper. 
 
 APPENDIX D. 
 Suction Pumps. 
 
 Every laboratory should possess some form of suction 
 pump, both for general use and, in particular, for rapid 
 nitrations. The Bunsen filter pump, though expensive 
 [|7-$10] , is excellent where there is no water pressure 
 
244 APPENDICES. 
 
 available. This pump is made on the principle of the 
 Sprengel mercury pump. Where water under pressure 
 can be had any one of the satisfactory cheaper pumps, 
 as the Richards, or the Fischer [cost $l-$3], may be 
 used. 
 
 For rapid filtrations use a stout glass bottle as a receiver 
 for the filtrate. This bottle should be fitted with a two- 
 hole rubber stopper. Through one hole of the stopper 
 pass the stem of the funnel ; through the second hole 
 pass a piece of glass tubing, which can be connected 
 by a stout rubber hose with the filter pump. Make 
 [from a round piece of platinum foil about one inch in 
 diameter] a little platinum cone to fit the glass funnel. 
 Use this cone to protect the tip of the filter paper 
 when the suction pump is used. In filtering, allow the 
 filter pump to exhaust the air from the flask. The pres- 
 sure of the atmosphere then presses the liquid rapidly 
 down into the flask. 
 
 APPENDIX E. 
 
 Catch-Bottles. 
 
 It frequently becomes necessary to "wash," or purify, 
 a gas. For this purpose the gas is made to pass through 
 water, sulphuric acid, or some other liquid, contained 
 in a " catch-bottle." As it is usually necessary to dry 
 the gas after it has been washed, it is well to have on 
 hand two catch-bottles connected and arranged so that 
 at a moment's notice the wash-liquid may be put in 
 one and sulphuric acid in the other. 
 
APPENDICES. 245 
 
 Take two 2-oz. saltmouth bottles. Fit each with a 
 good two-hole cork, or, better, with a two-hole rubber 
 stopper. Pass a glass tube through one hole of the 
 stopper of the first bottle down to the very bottom. 
 This tube should be bent at a right angle just above 
 the cork, and to it should be attached the tube that is 
 delivering the gas which is to be purified. Through 
 the second hole of this first bottle pass another glass 
 tube, beginning just at the lower surface of the stopper 
 and extending over to the second bottle and passing 
 through one hole of the stopper of the latter and down 
 to the very bottom. The two bottles need not stand 
 more than an inch or two from each other. Through 
 the second hole in the stopper to the second bottle pass 
 another short piece of glass tube [bent at a right angle] 
 just through the stopper. This last is the exit tube 
 for the gas after it has been washed and dried. 
 
 Put -the wash-liquid in the first bottle, and fill the 
 second about half full of sulphuric acid. After the gas 
 
 -L O 
 
 has come in through the first tube of the first bottle 
 it should pass down under the liquid and bubble up ; 
 then it should pass through the tube to the second 
 bottle, where it should bubble up through the sulphuric 
 acid and pass out through the short exit tube. Be sure 
 all tubes are arranged properly, and that all joints are 
 tight before you pass any gas through the bottles. 
 
246 APPENDICES. 
 
 APPENDIX F. 
 
 Generator for Gases. 
 
 Take a common narrow-necked bottle of 8 to 10-oz. 
 capacity. Bore l one or two holes of 4 or 5 mm diameter 
 in the bottom of the bottle. Fit the bottle with a good 
 cork [better, a one-hole rubber stopper] and a short glass 
 delivery tube bent at a right angle and ending in a 
 short piece of rubber tube carrying a screw pinch-cock, 
 by which the flow of the gas may be regulated. Put a 
 layer of broken glass about one inch deep in the bottom 
 of the bottle, and set the bottle itself in a large beaker 
 [or, better, in a battery jar, or in a vessel made from a 
 large bottle whose top part has been cut off]. 
 
 To Generate Kon-Combustible Oxide of Carbon. 
 Put small lumps of hard marble in the generator. 
 Insert the stopper, close the pinch-cock, and pour 
 common muriatic acid in the outer vessel till the 
 surface of the liquid approaches within about one 
 inch of the top edge. Open the pinch-cock and the 
 acid will force its way into the bottle and act on the 
 marble. When the pinch-cock is closed the accumulat- 
 ing gas forces the acid down and out, and the action 
 ceases. The broken glass serves for draining the 
 marble, and causes the action to cease more promptly 
 than it would were the marble placed on the bottom. 
 After the gas has been generated it should be washed 
 and dried by being passed through two catch-bottles, 
 the first of which contains water and the second sul- 
 1 See Manipulations. 
 
APPENDICES. 247 
 
 phuric acid. The water serves to stop the passage 
 of any hydrochloric acid that may be driven over, 
 and the sulphuric acid removes the water with which 
 the gas at first is always charged. 
 
 To Generate Hydrogen Sulphide. Put sulphide of 
 iron instead of marble in the generator. The sulphide 
 should be broken in small pieces. Sulphuric acid some- 
 what diluted [five volumes of water to two volumes of 
 acid] may be used with advantage in the outer vessel. 
 
 To Generate Hydrogen. Put zinc in the generator, 
 and dilute sulphuric acid [five volumes of water to 
 one of acid] in the outer vessel. 
 
 APPENDIX G. 
 Hood. 
 
 There should be in the laboratory a small closet 
 provided with a flue leading up some chimney or into 
 the open air. This closet should have a glass window 
 that can be opened and closed so that articles put 
 "under the hood" can be shut off from the main 
 room. It is well, when possible, to have an artificial 
 draught produced by a steam coil, burning gas jet, or 
 the like; also to have gas, water, and a sink under 
 the hood. 
 
 APPENDIX H. 
 Preparation of Chlorine. 
 
 Fill a small flask about one quarter with small lumps 
 of black oxide of manganese. Add common muriatic 
 
248 APPENDICES. 
 
 acid till the liquid and the black oxide together fill 
 about one half of the flask. Insert a one-hole cork 
 and delivery tube. Set the flask with its charge in 
 a beaker, or a pot, of water. Heat the water, and 
 chlorine gas will pass off. The delivery tube should 
 be connected with two catch-bottles, 1 the first contain- 
 ing water, the second sulphuric acid. The first catch- 
 bottle serves to catch any hydrochloric acid that is 
 carried over, and the second to dry the chlorine. 
 
 APPENDIX I. 
 Sodium Amalgam. 
 
 For the preparation of sodium amalgam on the large 
 scale, have ready a large Hessian crucible capable of 
 holding at least ten times as much amalgam as it is 
 your intention to make. Put the mercury in the 
 ,crucible, and heat with a Bunsen burner. Take the 
 temperature of the mercury by means of a thermometer. 
 Have ready one tenth, by weight, as much sodium as 
 there is mercury. The sodium should be in a single 
 piece. When the temperature of the mercury has 
 -reached 200 remove the burner, drop the sodium in 
 the hot mercury, cover the crucible with an iron plate, 
 or with the bottom of some old iron pan, and at once 
 step back. The union takes place with considerable 
 commotion. Before the molten amalgam has time to 
 solidify, pour it out in a thin layer on some smooth 
 surface that will not be harmed by the heat. Just as 
 soon as the amalgam is cool enough to handle, break 
 1 See Appendix E. 
 
APPENDICES. 249 
 
 it in small pieces, and store it in a tightly-stoppered 
 bottle that the air may not give it a troublesome coat- 
 ing of hydroxide. 
 
 Amalgam that has been spoiled by standing long in 
 the air should not be thrown away, but should be 
 treated with water that the mercury may be recovered. 
 
 APPENDIX J. 
 Test Solutions. 
 
 Caution! Do not get any of either solution [1] or 
 solution [2] in the mouth. 
 
 [1] Preparation of an Arsenical Solution for Testing. 
 
 Weigh out exactly 0.01 g of the white oxide of arsenic, 
 put this in a 250 CC flask, add 250 CC of water and about a 
 gram of sodium hydroxide, and shake till solution takes 
 place. Use only a single cc of this solution at a time, 
 as the test is a very delicate one, and the arsenide of 
 hydrogen formed is a most terrible and deadly poison. 
 
 In adding the solution through the funnel-tube care 
 should be taken to let the solution trickle down the 
 tube in such a way that no air is carried into the bottle. 
 Why avoid letting air enter? 
 
 [2] Preparation of an Antimonial Solution for Testing. 
 
 Weigh out 0.03 g of tartar emetic [a compound which 
 contains about 40% of antimony]. Dissolve in 250 CC 
 of water and use one cc at a time, as in the case of the 
 arsenical solution. 
 
 Caution ! Do not get any of either of these solutions 
 in the mouth. 
 
250 APPENDICES. 
 
 APPENDIX K. 
 Use of the Mouth Blow-Pipe. 
 
 Rest the smaller end of the blow-pipe on the edge of 
 the Bunsen burner's top, and blow directly through the 
 flame. The gas will be carried along with the blast, 
 and a slender cone of blue flame will be projected at a 
 right angle to the original direction of the flame. If 
 the blast is not powerful enough to use all the gas, 
 turn off the supply of gas somewhat. This blast flame, 
 though small, will be found to be intensely hot. By 
 tipping the Bunsen burner you can direct the flame in 
 any direction. 
 
 In using the blow-pipe, make a reservoir of your 
 mouth, while you breathe entirely through the nose. 
 With a little experience you will be able to blow so 
 steadily that the small flame will show little or no 
 fluctuation for minutes at a time. 
 
 When it is desired to oxidize a substance care should 
 be taken that only the outer part of the blast flame 
 touches the substance. The inner part of the flame 
 is made up largely of unconsumed gas which, in its 
 eagerness to get oxygen, acts as a reducer. Hence 
 the inner part of the flame is often used to bring 
 about reductions on a small scale. 
 
 APPENDIX L. 
 Arsenical and Antimonial Papers for Testing 1 . 
 
 For the arsenical paper it is best, when possible, to 
 get a piece of wall paper that is known to contain 
 
APPENDICES. 251 
 
 arsenic. If this cannot be found, take a piece of 
 filter paper, and dip it in an arsenical solution made 
 five times as strong as that of Appendix J [1]. Hang 
 on a line to dry. Caution! Do not get poisoned. 
 
 The paper poisoned with antimony may be made by 
 dipping a piece of filter paper in a solution five times 
 as strong as that of Appendix J [2]. 
 
 APPENDIX M. 
 To Dry Precipitates. 
 
 Have ready a clean porcelain evaporating dish. Set 
 this dish on gauze above the flame of a Bunsen burner 
 that has been turned down to only one fourth of its 
 ordinary size. Carefully remove the precipitate, paper 
 and all, from the funnel, and place it in the evaporat- 
 ing dish. Watch the filter paper, and if it shows the 
 least sign of charring, turn the flame still lower. 
 
 If you are in no hurry, a good way is to leave the 
 precipitate in the funnel and set funnel and all into 
 a ring supported just above an iron plate which is 
 heated by the Bunsen burner. 
 
 Excellent little ovens are sold for the purpose of 
 drying precipitates and the like, but these are some- 
 what expensive. 
 
 APPENDIX N. 
 To Nurse a Crystal. 
 
 After a first crystallization has taken place, select 
 the best formed crystal, remove it from the "mother 
 
252 APPENDICES. 
 
 liquor " [as the liquid in which the crystals were 
 formed is called], and set it aside on a bit of filter 
 paper. Then dissolve the rest of the crystals, by 
 heat, in the mother liquor, and add a little more 
 water. Filter, if dirty. Cool the solution. Immerse 
 the reserved crystal in the solution, and set aside till 
 another deposit forms. Much of this second deposit 
 will take place on the large crystal which is thus made 
 to grow at the expense of the smaller. Again remove 
 the large crystal, and repeat the process. Repeat as 
 many times as desired. 
 
 It is well, in the beginning, to save two or three crystals 
 and nurse them together, as nursing is apt to distort 
 a crystal, particularly when the crystal lies each time 
 on the same face. Hence, it is well, also, to turn the 
 crystal occasionally. If you start with two or three 
 crystals, you improve your chances of getting a single 
 good one in the end. Of course, any crystal that has 
 become badly distorted best be dissolved, that it may 
 furnish material for the growth of others. 
 
 APPENDIX 0. 
 Distilled Water. 
 
 There are but few experiments in this book that 
 demand the use of distilled water. For those few the 
 water may be purchased from the nearest apothecary 
 shop, or it may be distilled by the student, as follows : 
 Take a glass retort [or a "boiling flask"] and fill it 
 half or two thirds with water from the tap. Any retort 
 
APPENDICES. 253 
 
 that holds 250-500 CC , or even the wash-bottle flask fitted 
 with a one-hole cork and delivery tube will do. Support 
 the retort on a stand in such a way that the water 
 may be heated by the Bunsen burner. Heat the water 
 rapidly till it boils. Keep it boiling gently. The steam 
 that passes down the neck of the retort will be con- 
 densed and drip down in drops of nearly pure water, 
 while the greater part of the impurities will be left 
 behind in the retort. If a boiling flask is used, it is 
 best to pass the steam on through a piece of glass tube 
 in order that more may be cooled and condensed. Do 
 not boil off more than three quarters of the total amount 
 of the water, as there is danger of impurities coming 
 over in the last quarter. It is also well to reject the 
 first quarter that distills over, as with this come any 
 gases the water may have dissolved. But there are not 
 enough of these gases in ordinary water to vitiate the 
 result of any experiment in this book. 
 
 Store your distilled water in a clean, well-stoppered 
 bottle. 
 
 When the laboratory is heated by steam it is advis- 
 able to condense steam from the heating apparatus and 
 to use distilled water in many other experiments besides 
 those in which its use is imperative. 
 
 A coil of small-bore tin pipe set in a water jacket 
 of sheet copper makes a good condenser. The tin pipe 
 should be connected at its upper end with the steam 
 pipes, and its lower end should project from the copper 
 jacket. The water jacket should be so arranged that 
 a stream of cold water may be let in at the bottom and 
 the warm water may flow out at the top. There should 
 
254 APPENDICES. 
 
 be a stop-cock, or valve, for the steam pipe, and one 
 for the water supply. 
 
 As solid impurities are often carried into the con- 
 denser from the steam pipes, it is best to let the distilled 
 water trickle through a large funnel containing an ordi- 
 nary filter paper. Collect the water in jugs or large 
 bottles. 
 
 Students should keep their wash-bottles filled with 
 distilled water when the supply is abundant. 
 
 APPENDIX P. 
 Directions for a Student who has no Instructor. 
 
 It is necessary, of course, to have a working room 
 that you can call your laboratory. It is not essential 
 that this room be large and built specially for your work. 
 Almost any room will do, provided it can be fitted with 
 a table, a sink, and gas or gasolene. 1 
 
 Do not think that it is necessary to have a fully- 
 equipped laboratory before you can commence to study 
 chemistry. Get enough apparatus to start with, and 
 begin your work. You will soon see what you need, 
 and how best to supply your wants. If you get into 
 difficulty, try to think your way out of it. Never for- 
 
 1 If it is necessary for you to use gasolene, you should be sure that 
 you state this fact to your dealer in apparatus, and have burners suit- 
 able for this fuel sent you. If you have neither gas nor gasolene, get 
 the largest and best alcohol lamp obtainable ; but even with the best 
 alcohol burners you may have to omit a number of experiments. 
 Before resorting to the use of alcohol, you should do your best to 
 obtain gas or gasolene. 
 
APPENDICES. 255 
 
 get that there are more ways than one for attaining 
 your end. 
 
 Your room best have a supply of water that can be 
 turned on and off by means of a faucet at the sink. 
 If you do not have town or city water delivered under 
 pressure, the best way is to arrange a small tank above 
 your sink. The higher this tank is above the sink the 
 better, although two or three feet will do for almost 
 all work. A wooden box serves well for the tank. Get 
 a plumber to line it with zinc or copper, and fit to it 
 a piece of pipe [of any kind], terminating with a faucet 
 over your sink. If the plumber can arrange a pump 
 to deliver water directly into your tank, so much the 
 better. Otherwise you must fill the tank by pails. It 
 is well to have a second faucet with a small delivery 
 tube over which you can slip a piece of quarter-inch 
 rubber tube. This second faucet should be a foot or 
 more above the bottom of the sink, and is needed in a 
 few cases, e.g., when the filter pump is required. This 
 second faucet, however, is not absolutely necessary, as 
 a good substitute may be obtained by inserting a one- 
 hole stopper in the opening of the other faucet, and 
 fitting a short piece of glass tube to the faucet by means 
 of the cork. Over this glass tube can be slipped the 
 rubber tube. 
 
 The arrangement for your gas supply is most simple. 
 All that is needed is a gas cock terminating in a cor- 
 rugated nozzle over which may be slipped the quarter- 
 inch rubber tube of the Bunsen burner. " Shut-oil's " 
 of this kind, ready to be screwed into a tee or an elbow, 
 come in trade. If your plumber does not have any, 
 
256 APPENDICES. 
 
 get him to fit the end of your gas pipe with a common 
 "shut-off," or cock, to the projecting end of which 
 has been fitted a brass "pillar" taken from a common 
 bat-wing burner. The clay tip should be removed 
 from the brass pillar before the rubber tube is slipped 
 on. It is well to have three of these delivery places 
 for gas, although almost all experiments can be per- 
 formed with a single gas tap. The blast-lamp does 
 not need any larger supply of gas than that furnished 
 by one of these taps. The three taps may be all close 
 together or at a distance from one another, as the 
 gas can easily be conveyed in rubber tubes wherever 
 needed. It is, however, best to have the taps all so 
 near the work table that, when standing at your work, 
 you can reach them and turn the gas on or off. A 
 special gas fitting is not absolutely essential, as the 
 rubber tube for the burner may be slipped on any 
 ordinary gas fixture. 
 
 Though almost any kind of sink will do, the best 
 form seems to be a small iron one about twenty inches 
 long, twelve inches wide, and five or six inches deep. 
 The outlet to the sink should be at one end, and best 
 be reamed out to fit an overflow plug that may be 
 inserted in order to convert the sink into a pneumatic 
 trough. The overflow plug is simply a piece of pipe 
 open at both ends, an inch or so shorter than the depth 
 of the sink, and tapered to fit the reaming of the out- 
 let to the sink. When the plug is put in the hole 
 and the faucet opened, the water can rise in the sink 
 no higher than the top of the plug, for at the top it 
 finds an outlet down the plug into the drain. As a 
 
APPENDICES. > 257 
 
 . 
 
 bridge for this pneumatic trough, provide a piece of 
 stout galvanized sheet-iron about two and a half inches 
 wide and twelve inches long. In the middle of this 
 strip of iron make a circular hole about half an inch 
 in diameter. Then, at points an inch and a half from 
 each end of the strip, bend the strip at right angles 
 and form a kind of platform, thus : , , on which 
 bottles, jars, etc., can be placed, in order to collect 
 gases when this iron bridge is set on the bottom of the 
 sink. If you cannot use your sink for a pneumatic 
 trough, order a small trough from the apparatus dealer, 
 or make use of a deep pan or, better, earthen dish. 
 
 You should also have some shelves and a drawer or 
 two for storing apparatus and chemicals. 
 
 There should be an earthen slop-jar for waste material. 
 
 Keep your taj>le neat. Do not let dirty dishes collect. 
 Have a clearing off of apparatus at the end of every 
 day's work, just as if you were a member of a class in 
 a laboratory where strict rules for neatness and order 
 are enforced. 
 
INDEX. 
 
INDEX. 
 
 Absolute scale, 145. 
 Acids, 
 
 carbonic, 33. 
 
 with lime water, 47. 
 
 with sodium hydroxide, 54. 
 hydriodic, 80. 
 hydrobromic, 78. 
 hydrochloric, 
 
 preparation, 56, 57. 
 
 solubility, 58. 
 
 with ammonium hydroxide, 
 71, 108, 131. 
 
 with marble, 58. 
 
 with sodium, 59. 
 
 with sodium hydroxide, 60. 
 hydrofluoric, 81-82. 
 muriatic, 58. 
 nitric, 64. 
 
 with ammonium hydroxide, 
 72. 
 
 with carbon, 66. 
 
 with copper, 65. 
 
 with magnesium, 65. 
 
 with potassium hydroxide, 67. 
 phosphoric, 33. 
 sulphuric, 29. 
 
 removal of hydrogen from, 30. 
 
 with ammonium hydroxide, 
 72. 
 
 with calcium hydroxide, 46. 
 
 Acids sulphuric, 
 
 with iron sulphide, 40. 
 
 with magnesium, 43. 
 
 with marble, 51. 
 
 with potassium hydroxide, 
 
 62. 
 
 with sodium carbonate, 55. 
 
 with sodium hydroxide, 54. 
 
 with water, 30, 106. 
 
 with zinc, 37. 
 
 with zinc oxide, 38. 
 sulphurous, 27. 
 Action of acids, 
 
 on aluminum, 99. 
 
 on gold, 96. 
 
 on lead, 91. 
 
 on platinum, 98. 
 
 on silver, 93. 
 
 on tin, 90. 
 Agricola, 122. 
 
 Aids for determining atomic 
 weights, 
 
 I. Law of Gay-Lussac and hy- 
 
 pothesis of Avogadro, 192. 
 
 II. Law of Dulong and Petit, 
 
 208-209. 
 
 III. Law of Isomorphism, 211. 
 
 IV. Periodic Law, 213. 
 Air, 
 
 with hydrogen, 21-22. 
 
 with iron, 11. 
 
 with phosphorus, 13. 
 
262 
 
 INDEX. 
 
 Air, 
 
 composition of, 153. 
 
 effect of pressure on, 126-129. 
 
 weight and specific gravity of, 
 
 141. 
 Alchemy, 
 
 period of, 114-119. 
 Alkaline substances, 53. 
 Alloy, 93. 
 
 fusible, 93. 
 Alum, 100. 
 Aluminum, 99. 
 
 properties, 99. 
 
 oxidation, 99. 
 
 with acids, 99. 
 
 sulphate, 99. 
 j Amalgam, 55. 
 I gold, 97. 
 
 sodium, 55. 
 i Ammonia, 68. 
 
 fountain, 70. 
 Ammonium, 71. 
 
 hydroxide, 71. 
 
 chloride, 71. 
 
 nitrate, 72. 
 
 sulphate, 72. 
 Ampere, 180. 
 Analysis, 16, 107, 131. 
 
 qualitative, 130-134. 
 
 quantitative, 164-167. 
 
 proximate, 107. 
 
 ultimate, 107. 
 
 of marble, 50-51. 
 
 of table salt, 165. 
 Analytical chemistry, 107. 
 Anhydride, 49. 
 Antimony, 87. 
 
 properties, 87. 
 
 oxide, 87. 
 
 chloride, 88. 
 
 hydride, 88. 
 
 Antimony, 
 
 solution for testing, 249. 
 Apparatus, 
 
 for chemical work, xxix. 
 
 for electrolysis of water, 239. 
 Aqua, 221. 
 
 ammonia, 70. 
 
 regia, 97. 
 Aqueous vapor, 
 
 effect on gas volume, 174. 
 Arabs, 115. 
 Aristotle, 112. 
 
 theory of the elements, 112-113. 
 Arsenic, 83. 
 
 properties, 83. 
 
 oxide, 83. 
 
 reduction of the oxide, 84. 
 
 hydride, 84. 
 
 mirror, 84, 85. 
 
 detection of, 85. 
 
 solution for testing, 249. 
 Arsenide of hydrogen, 84. 
 Arseniuretted hydrogen, 84. 
 Arsine, 84. 
 Assaying, 131. 
 Atom, 170. 
 Atomic 
 
 theory, 170. 
 
 weights, 171, 177. 
 
 table of, 216. 
 Aurum, 96. 
 Avogadro, 180. 
 
 his hypothesis, 180. 
 
 Barium, 134. 
 
 nitrate, 159. 
 Becher, 138. 
 Berthollet, 162. 
 Bismuth, 89. 
 
 properties, 89. 
 
INDEX. 
 
 263 
 
 Bismuth, 
 
 nitrate, 89. 
 
 basic nitrate, 89. 
 Black, 140. 
 Blank-books, xxiii. 
 Blast-lamp, 236. 
 Blow-pipe, 250. 
 Boyle, 125. 
 
 law of, 126. 
 
 tests of, 132. 
 
 chemical theory of, 135. 
 
 period of, 125-137. 
 Bromides, 
 
 hydrogen, 78. 
 
 sodium, 78. 
 Bromine, 77. 
 
 properties, 77. 
 
 replaced by chlorine, 78. 
 
 will replace iodine, 81. 
 Buddha, 113. 
 Burner, 
 
 alcohol, 254. 
 
 gasolene, 254. 
 
 Bunsen, 235. 
 
 Bunsen blast, 236. 
 
 C. 
 
 Calcium, 44. 
 properties, 44. 
 with water, 45. 
 oxide, 44. 
 
 with water, 45. 
 hydroxide, 45. 
 
 with carbonic acid, 47. 
 
 with sulphuric acid, 46. 
 hydrate [see hydroxide], 
 carbonate, 47. 
 chloride, 59. 
 fluoride, 81. 
 sulphate, 46, 52. 
 light, 50. 
 
 Carbon, 14. 
 properties, 14. 
 with oxygen, 18. 
 oxides, 
 
 non-combustible or dioxide, 
 19, 35. 
 
 with calcium hydroxide, 49. 
 with potassium, 61. 
 with sodium hydroxide, 55. 
 with water, 33. 
 with zinc, 35. 
 
 combustible or monoxide, 
 35-36. 
 with red oxide of mercury, 
 
 37. 
 
 action with nitric acid, 66. 
 sulphide, 24. 
 Carbonates, 
 calcium, 47. 
 sodium, 54. 
 
 with sulphuric acid, 561 
 Carbonic acid, 33. 
 
 with calcium hydroxide, 47-49. 
 with sodium hydroxide, 64. 
 Calorie, 204. 
 Calorimeter, 204. 
 Catch-bottle, 244. 
 Cavendish, 141. 
 Chalk, 47. 
 Changes, 103. 
 chemical, 103-104. 
 physical, 103. 
 analytical, 107. 
 metathetical, 109. 
 synthetical, 108. 
 caused by water, 105-103. 
 Charcoal, 14. 
 Charles, 
 
 law of, 143. 
 Chemeia, 115. 
 Chemi, 115. 
 
264 
 
 INDEX. 
 
 Chemical, 
 
 changes, 103-104. 
 
 symbols, 177, 218. 
 
 formulae, 219. 
 
 equations, 221-223. 
 
 Examination, 89. 
 
 Investigation, 63. 
 Chemicals, xxix. 
 Chinese, 
 
 early chemical knowledge of, 
 
 111. 
 Chlorate of potassium, 16, 25. 
 
 molecular weight of, 198. 
 Chlorides, 56. 
 
 ammonium, 71. 
 
 antimony, 88. 
 
 calcium, 59. 
 
 gold, 97. 
 
 hydrogen, 56. 
 
 lead, 92. 
 
 potassium, 199, 212. 
 
 sodium, 57. 
 Chlorine, 56. 
 
 preparation, 247. 
 
 properties, 56. 
 
 nascent, 97. 
 
 replaces bromine, 78. 
 
 replaces iodine, 80. 
 Combining number, 172. 
 
 for zinc, 172. 
 Combustion products, 
 
 of a candle, 157. 
 Compound, 12. 
 Conservation of mass, 157. 
 
 law of, 157. 
 Constant weight, 26. 
 Contents, 
 
 table of, xiii. 
 Cooke, 190. 
 Copper, 41. 
 
 properties, 41. 
 
 Copper, 
 
 oxide, 41. 
 reduction of the oxide, 42. 
 
 with nitric acid, 65. 
 
 replaces silver, 94, 95. 
 Corks, 
 
 to render tight, 230. 
 Crith, 178. 
 Crystallization, 
 
 water of, 31, 106. 
 Crystal, 
 
 to nurse a crystal, 251. 
 
 D. 
 
 Dalton's 
 
 law, 143-145. 
 
 atomic theory, 170. 
 Death of a metal, 117. 
 Decant, 47. 
 Definite proportions by volume, 
 
 law of, 179. 
 Definite proportions by weight, 
 
 law of, 163. 
 Deliquescence, 53. 
 Density, 142. 
 Diagrams, 
 
 to be drawn, 32, 56. 
 Diamond, 14, 156. 
 Displacement, 
 
 catch by, 25. 
 Drying, 
 
 of bottles, etc., 234. 
 Dulong and Petit, 202. 
 
 Earliest period, 111-113. 
 Efflorescence, 54. 
 Egypt, 115. 
 Egyptians, 
 
 early chemical knowledge of, 
 111. 
 
INDEX. 
 
 265 
 
 Electrolysis, 
 
 of water, 19-20, 180. 
 Elements, 
 
 list of common, 134. 
 
 list of all recognized, 219. 
 Empedocles, 113. 
 English system of weights and 
 
 measures, 5. 
 Equations, 
 
 chemical, 221-222. 
 Etching of glass, 
 
 by hydrofluoric acid, 82. 
 Examination, 
 
 a chemical, 89. 
 Expansion, 
 
 irregular of liquids, 184. 
 
 regular of gases, 185. 
 Explosion, 
 
 air and hydrogen, 21, 241. 
 
 tube, 42, 242. 
 
 F. 
 
 Factor, 38. 
 
 Ferric chloride, 110. 
 
 Filter, 
 
 paper, 233. 
 
 pump, 243. 
 Filtrate, 43. 
 Fluorides, 81. 
 
 calcium, 81. 
 
 hydrogen, 81. 
 
 etching of glass, 82. 
 Fluorine, 81. 
 Formulae, 219. 
 Fusible alloy, 93. 
 
 G. 
 
 Gas, 
 
 origin of the term, 121. 
 illuminating, 
 
 weight and specific gravity 
 of, 149. 
 
 Gas, 
 
 sylvestre, 121, 140. 
 Gas-retort carbon, 14. 
 Gay-Lussac, 179. 
 
 law of, 179. 
 Geber, 118. 
 
 sulphur-mercury theory, 118. 
 Generator, 246. 
 Glass, 
 
 to bend, 228. 
 
 to bore, 231. 
 
 to cut, 226. 
 
 to draw, 229. 
 
 to fire-polish, 228. 
 
 to mark, 226. 
 
 to pass through rubber, 231. 
 Glauber, 123. 
 Glauber's salt, 123. 
 Gold, 96. 
 
 properties, 96. 
 
 color, 97. 
 
 with acids, 96. 
 
 chloride, 97. 
 
 amalgam, 97. 
 Graphite, 14. 
 Gypsum, 46. 
 
 Halogen, 81. 
 Hard water, 
 temporarily, 48. 
 permanently, 48. 
 Heat, 203. 
 specific, 202. 
 of iron, 207. 
 of zinc, 205. 
 table, 208. 
 Historical periods, 
 earliest, 111-113. 
 of Alchemy, 114-119. 
 
266 
 
 INDEX. 
 
 Historical periods, 
 
 medical, 120-124. 
 
 of Boyle, 125-137. 
 
 of phlogiston, 138-139. 
 
 pneumatic, 140-160. 
 
 modern, 161-217. 
 Holder, 
 
 for test-tubes, etc., 232. 
 Hood, 247. 
 
 Hydrates [see hydroxides]. 
 Hydration, 106. 
 Hydriodic acid, 80. 
 Hydrobromic acid, 78. 
 Hydrofluoric acid, 81. 
 Hydrochloric acid, 56. 
 
 preparation, 56, 57. 
 
 properties, 58. 
 
 solubility, 58. 
 
 with marble, 58. 
 
 with sodium, 59. 
 
 with sodium hydroxide, 60. 
 Hydrogen, 
 
 preparation, 20, 30, 37. 
 
 properties, 20-23. 
 
 lightness, 22. 
 
 weight and specific gravity, 148. 
 
 with air, 22. 
 
 explosions, 21, 241. 
 
 atomic weight, 178, 193. 
 
 molecular weight, 193. 
 
 removed from sulphuric acid, 
 30, 37. 
 
 arsenide, 84. 
 
 antimonide, 88. 
 
 bromide, 78. 
 
 chloride, 56. 
 
 fluoride, 81. 
 
 sulphide, 39, 40. 
 
 sulphate [sulphuric acid]. 
 
 sulphuretted, 41. 
 
 arseniuretted, 84. 
 
 Hydroxides, 
 ammonium, 71. 
 calcium, 45. 
 potassium, 61. 
 sodium, 53. 
 
 I. 
 
 Illuminating gas, 
 
 weight and specific gravity of, 
 
 149. 
 
 Indestructibility of matter, 157. 
 Investigation, 
 
 a chemical, 63. 
 Iodides, 
 
 potassium, 80. 
 
 sodium, 211. 
 Iodine, 79. 
 
 properties, 79. 
 
 solubility, 79. 
 
 tincture, 79. 
 
 action on the skin, 79. 
 
 action on starch, 79. 
 
 replaced, 80, 81. 
 Iron, 11. 
 
 properties, 11. 
 
 with air, 11. 
 
 with oxygen, 17. 
 
 oxide, 12, 18. 
 with water, 32. 
 
 chloride, 110. 
 
 sulphate, 31. 
 
 sulphide, 39, 135. 
 Isomorphism, 211. 
 
 discovered, 211. 
 
 applied, 211-212. 
 
 J. 
 
 Jews, 
 
 early chemical knowledge of, 
 
 111. 
 Joints, 
 
 to render tight, 231. 
 
INDEX. 
 
 267 
 
 Kalium, 60. 
 
 King of metals, 96. 
 
 Kjeldahl flask, 16. 
 
 Language, 
 
 of chemistry, 218. 
 Laughing gas, 72. 
 Lavoisier, 153. 
 Law of, 
 
 Boyle, 126. 
 
 Charles [see Dalton's]. 
 
 conservation of mass, 157. 
 
 Dalton, 143-145. 
 
 definite proportions, 
 by volume, 179. 
 by weight, 163. 
 
 Dulong and Petit, 202. 
 
 Gay-Lussac, 179. 
 
 isomorphism, 211. 
 
 multiple proportions, 170. 
 
 periods, 214. 
 
 specific heats, 208-209. 
 Lead, 91. 
 
 properties, 91. 
 
 with acids, 91. 
 
 oxide, 91. 
 with water, 91. 
 
 chloride, 92. 
 
 sulphate, 92. 
 
 tree, 92. 
 
 replaced by zinc, 92. 
 Libavius, 
 
 first chemical text-book, 120. 
 Lime, 
 
 light, 50. 
 
 quick, 44. 
 
 slacked or slaked, 45. 
 
 water, 47. 
 Litmus papers, 27, 242. 
 
 M. 
 
 Magnesium, 43. 
 
 properties, 43. 
 
 with nitric acid, 65. 
 
 with sulphuric acid, 43. 
 
 oxide, 43. 
 
 with water, 43. 
 
 sulphate, 43. 
 Manganese, 26. 
 
 black oxide, 25. 
 Marble, 47. 
 
 analysis of, 50-51. 
 
 with sulphuric acid, 51. 
 
 with hydrochloric acid, 58. 
 Mass, 
 
 conservation of, 157. 
 Matrass, 15, 230. 
 Matter, 
 
 indestructibility of, 157. 
 Mayow, 155. 
 Measuring, 3. 
 Medical period, 120-124. 
 Mendele"eff, 213. 
 Mercury, 14. 
 
 properties, 14. 
 
 with gold, 97. 
 
 with sodium, 55. 
 
 oxide, 15, 37, 153. 
 Metal, 
 
 death of, 117. 
 
 resurrection of, 117. 
 Metals, 
 
 with platinum, 98. 
 
 noble, 97. 
 
 Metathesis, 109, 110. 
 Metric system, 
 
 of measures and weights, 3, 5. 
 Meyer, 213. 
 Microcrith, 178. 
 Millicalorie, 204. 
 
268 
 
 INDEX. 
 
 Mirror, 
 
 arsenic, 84, 85. 
 Mitscherlich, 211. 
 Mixture, 
 
 and chemical compound, 135. 
 Modern period, 161-217. 
 Molecular theory, 180. 
 Molecular weight, 192. 
 
 determined by Chemical Meth- 
 od, 197. 
 
 determined by Physical Meth- 
 od, 196. 
 
 of carbon dioxide, 196. 
 
 of chlorate of potassium, 198. 
 
 of chloride of potassium, 199. 
 
 of hydrochloric acid, 201. 
 
 of hydrogen, 193. 
 
 of oxygen, 194, 196. 
 
 of sulphate of potassium, 200. 
 
 of sulphuric acid, 200. 
 
 of water, 194. 
 Molecules, 176. 
 
 their size, 189-190. 
 
 their movements, 188-189. 
 Multiple Proportions, 
 
 law of, 170. 
 Muriatic acid, 58. 
 
 Nascent chlorine, 97. 
 Natrium, 52. 
 Neutral, 54. 
 Neutralization, 54. 
 Newlands, 213. 
 Nickel, 134. 
 Nitrates, 
 
 ammonium, 72. 
 
 bismuth, 89. 
 
 potassium, 67. 
 Nitre, 63. 
 
 Nitric acid, 64. 
 
 with ammonium hydroxide, 72. 
 
 with carbon, 66. 
 
 with copper, 65. 
 
 with magnesium, 65. 
 
 with potassium hydroxide, 67. 
 Nitric oxide, 72. 
 Nitrogen, 63. 
 
 discovered, 150. 
 
 properties, 63. 
 
 oxides, 72. 
 Nitrous oxide, 72. 
 Noble metals, 97. 
 Note-book, xxiii. 
 
 method of keeping, xxiv. 
 N. T. P., 146. 
 Nursing a crystal, 251. 
 
 O. 
 
 Oxides, 
 arsenic, 83. 
 
 reduction of, 84. 
 antimony, 87. 
 calcium, 44. 
 
 with water, 45. 
 carbon, 
 
 monoxide, 35-36. 
 
 oxidation of, 37. 
 dioxide, 19, 35. 
 
 with lime water, 49. 
 with potassium, 61. 
 with sodium hydroxide, 55. 
 with zinc, 35. 
 with water, 33. 
 copper, 41. 
 
 reduced by hydrogen, 42. 
 hydrogen, 22. 
 iron, 12, 18. 
 lead, 91. 
 
 with water, 91. 
 
INDEX. 
 
 269 
 
 Oxides, 
 
 magnesium, 43. 
 
 with water, 43. 
 manganese, 25. 
 mercury, 15, 37, 153. 
 nitrogen, 72. 
 phosphorus, 14. 
 
 with water, 33. 
 potassium, 61. 
 
 with water, 61. 
 silver, 95. 
 sodium, 52. 
 
 with water, 53. 
 sulphur, 27. 
 
 gaseous, 27. 
 with water, 27. 
 
 solid, 27-29. 
 
 with water, 29-30. 
 tin, 90. 
 zinc, 34. 
 
 with water, 34. 
 
 with sulphuric acid, 38. 
 Oxidation, 19, 37. 
 Oxygen, 12. 
 discovery, 153. 
 preparation, 15, 16, 19, 25. 
 properties, 15-20. 
 with iron, 12, 17. 
 with phosphorus, 13, 18. 
 with carbon, 18. 
 with sulphur, 25-27. 
 atomic weight, 172, 194. 
 molecular weight, 194, 196. 
 
 P. 
 
 Palissy, 122. 
 Paracelsus, 120. 
 Paris, 
 
 plaster of, 46. 
 Periodic law, 214. 
 Petit and Dulong, 202. 
 
 Phenomenon, 12. 
 Philosophers' stone, 118. 
 Phlogiston, 138. 
 
 period of, 138-139. 
 Phoenicians, 
 
 early chemical knowledge of, 
 
 111. 
 
 Phosphoric acid, 33. 
 Phosphorus, 12. 
 
 properties, 12. 
 
 with air, 13. 
 
 with oxygen, 18. 
 
 oxide, 14. 
 Pipette, 48. 
 Plaster of Paris, 46. 
 Platinum, 98. 
 
 properties, 98. 
 
 with acids, 98. 
 
 with metals, 98. 
 
 with other chemicals, 98. 
 
 sponge, 28, 98. 
 Plumbers' solder, 92. 
 Plumbum, 91. 
 Pneumatic period, 140-160. 
 Potassium, 60. 
 
 properties, 61. 
 
 with air, 61. 
 
 with water, 61. 
 
 with dioxide of carbon, 61. 
 
 oxide, 61. 
 with water, 61. 
 
 chlorate, 16, 25, 198. 
 
 chloride, 199, 212. 
 
 hydroxide, 61. 
 with wa'ter, 61. 
 with nitric acid, 67. 
 
 iodide, 80. 
 
 nitrate, 67. 
 
 sulphate, 62. 
 Precipitate, 43. 
 
 to dry, 251. 
 
270 
 
 INDEX. 
 
 Pressure, 
 
 effect on air, 126-129. 
 Priestly, 150. 
 Product, 38. 
 Proportions, 
 
 multiple, law of, 170. 
 
 by volume, law of, 179-180. 
 
 by weight, law of, 163. 
 Proust, 162, 168. 
 Prout, 175. 
 
 Proximate analysis, 107. 
 Pump, 
 
 air, 142. 
 
 filter, 243-244. 
 
 Q 
 
 Qualitative analysis, 131. 
 Qualitative tests, 132. 
 Quantitative analysis, 164. 
 Quick lime, 44. 
 
 Reaction, 43. 
 Reduction, 36. 
 
 of oxide of carbon, 35-36. 
 
 of oxide of copper, 42. 
 
 of oxide of mercury, 15, 37. 
 
 of chloride of silver, 96. 
 Resurrection, 
 
 of a metal, 117. 
 Richards, 216. 
 Richter, 161. 
 Rubber, 
 
 to cut, 231. 
 Rutherford, 150. 
 
 Sal soda, 54. 
 Salt, 
 
 definition, 67. 
 
 table, 57. 
 
 made, 57, 60. 
 
 S. 
 
 Salt, 
 
 analyzed, 165. 
 Scheele, 150. 
 Scheele's green, 152. 
 Silver, 93. 
 properties, 93. 
 oxidation, 93, 95. 
 oxide, 95. 
 with acids, 93. 
 chloride, 94, 96. 
 sulphide, 95. 
 replaced by copper, 95. 
 purification, 95. 
 Simple substance, 12. 
 Slaked lime, 45. 
 Solder, 92. 
 Soot, 14. 
 Sodium, 52. 
 properties, 52. 
 with air, 52. 
 with water, 53. 
 oxide, 52. 
 
 with water, 53. 
 amalgam, 55. 
 to prepare on a large scale, 
 
 248. 
 
 bromide, 78. 
 carbonate, 54. 
 
 with sulphuric acid, 55. 
 chloride, 57. 
 
 hydrate [see hydroxide], 
 hydroxide, 53. 
 with carbonic acid, 54. 
 with carbonic dioxide, 55. 
 with hydrochloric acid, 60. 
 with sulphuric acid, 54. 
 with hydrochloric acid, 59. 
 Solution, 103-106. 
 Spaces, 
 
 between the molecules, 182. 
 Spain, 115. 
 
INDEX. 
 
 271 
 
 Specific gravity, 142. 
 
 of air, 141. 
 
 of carbonic dioxide, 145. 
 
 of hydrogen, 148. 
 
 of illuminating gas, 149. 
 
 of oxygen, 196. 
 Specific heat, 202. 
 
 of iron, 207. 
 
 of zinc, 205. 
 
 table, 208. 
 Spencer, 171. 
 Sponge, 
 
 platinum, 28, 98. 
 Stahl, 138. 
 .Stalactite, 48. 
 Stalagmite, 48. 
 Stannum, 89. 
 Starch, 
 
 with iodine, 79. 
 Stibium, 87. 
 Stoichiometry, 224. 
 Stoppers, 
 
 to prevent mixing, 232. 
 
 to remove when stuck, 234. 
 Sublimation, 72. 
 Substances, 
 
 simple, 12. 
 
 compound, 12. 
 Suidas, 115. 
 Sulphates, 
 
 aluminum, 99. 
 
 ammonium, 72. 
 
 calcium, 46, 51. 
 
 iron, 31. 
 
 lead, 92. 
 
 magnesium, 43. 
 
 potassium, 62. 
 
 sodium, 55. 
 
 zinc, 38. 
 Sulphides, 
 
 carbon, 24. 
 
 Sulphides, 
 
 hydrogen, 39, 40. 
 
 iron, 39, 135. 
 
 silver, 95. 
 Sulphur, 23. 
 
 properties, 23. 
 
 modifications, 24. 
 
 oxides, 25, 27. 
 
 with hydrogen, 39. 
 
 with iron, 39, 135. 
 
 with zin<?, 136. 
 Sulphuretted hydrogen, 41. 
 Sulphuric acid, 29. 
 
 removal of hydrogen from, 
 30, 37. 
 
 with ammonium hydroxide, 72. 
 
 with calcium hydroxide, 46. 
 
 with iron sulphide, 40. 
 
 with magnesium, 43. 
 
 with marble, 51. 
 
 with potassium hydroxide, 62. 
 
 with sodium carbonate, 55. 
 
 with sodium hydroxide, 54. 
 
 with water, 30, 106. 
 
 with zinc, 37. 
 
 with zinc oxide, 38. 
 Sulphurous acid, 27. 
 Symbols, 
 
 Dalton's, 177. 
 
 modern chemical, 218. 
 Synthesis, 50, 108. 
 
 T. 
 
 Temperature, 202. 
 Terra pinguis, 138. 
 Test papers, 242. 
 Tests, 
 
 qualitative, 132. 
 
 used by Boyle, 132. 
 
 by chemical changes, 133. 
 
 by physical changes, 132. 
 
272 
 
 INDEX. 
 
 Time, 
 
 required in the laboratory, 
 
 xxvii. 
 Tin, 89. 
 
 properties, 89. 
 
 cry, 90. 
 
 crystalline structure, 90. 
 
 oxide, 90. 
 
 with acids, 90. 
 
 salts of, 90. 
 
 replaced by zinc, 91. 
 
 plate, 90. 
 Tincture, 
 
 of iodine," 79. 
 
 Transference of motion, 203. 
 Transmutation, 114, 116. 
 Turmeric paper, 242-243. 
 
 U. 
 
 Ultimate analysis, 107. 
 
 V. 
 
 Valentine, 119. 
 Van Helmont, 120. 
 
 W. 
 
 Wash-bottle, 6. 
 Water, 
 
 preparation, 22. 
 
 electrolysis, 19-20, 180. 
 
 with iron oxide, 32. 
 
 with phosphorus oxide, 33. 
 
 with carbonic dioxide, 33. 
 
 Water, 
 
 with gaseous oxide of sulphur, 
 27. 
 
 with the second oxide of sul- 
 phur, 29-30. 
 
 with zinc oxide, 34. 
 
 with magnesium oxide, 43. 
 
 with calcium oxide, 45. 
 
 with sodium oxide, 53. 
 
 with potassium oxide, 61. 
 
 with lead oxide, 91. 
 
 with sodium, 53. 
 
 with potassium, 61. 
 
 with sulphuric acid, 30, 106. 
 
 of crystallization, 31, 106. 
 
 permanently hard, 48. 
 
 temporarily hard, 48. 
 
 distilled, 252. 
 
 molecular weight, 194. 
 Water-bath, 26, 185. 
 Weighing, 4. 
 Weight, 
 
 constant, 26. 
 
 Z. 
 
 Zinc, 34. 
 properties, 34. 
 oxide, 34. 
 
 with sulphuric acid, 38. 
 replaces tin, 91. 
 replaces lead. 92. 
 combining number for, 172. 
 sulphate, 38. 
 with carbonic dioxide, 35. 
 
RETURN TO the circulation desk of any 
 University of California Library 
 or to the 
 
 NORTHERN REGIONAL LIBRARY FACILITY 
 Bldg. 400, Richmond Field Station 
 University of California 
 Richmond, CA 94804-4698 
 
 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS 
 2-month loans may be renewed by calling 
 
 (415) 642-6753 
 1-year loans may be recharged by bringing books 
 
 to NRLF 
 Renewals and recharges may be made 4 days 
 
 prior to due date 
 
 DUE AS STAMPED BELOW 
 
 1 8 1991 
 
YB 16879