The original of tliis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924068876436 
 
THE NEW 
 
 TEXT-BOOK OF CHEIISTEY 
 
 FOR use IN 
 
 HIGH SCHOOLS AND ACADEMIES 
 
 BT 
 
 Le Roy c. cooley, Ph. D. 
 
 PB0FES80B OF PHYSICS AND CHEMISTBY IN VABBAB COLLESE 
 
 NEW TORK .:• CINCINNATI .:• CHICAGO 
 
 AMEKICAN BOOK COMPANY 
 
Copyright, 1869. 
 
 Copyright, 1881, 
 
 By LE KOY C. COOLEY. 
 
 W. P. 4 
 
PEEFAOE. 
 
 TsR sole purpose of this volume is to provide an ele- 
 mentary course of chemistry suited to the wants of students 
 and teachers in high schools and academies. 
 
 With this purpose in view I have endeavored, — 
 
 I. To seize upon the fundamental facts and principles of 
 the science, and submit them to a simple and concise, but at 
 the same time a clear and accurate, treatment. 
 
 II. To present the subjects which will be of greatest value 
 to a student whose course of study must end when he leaves 
 the preparatory school, and which are, at the same time, 
 most desirable, as a preparation for higher courses, to those 
 who majj in future pursue them. 
 
 III. To thoroughly systematize the whole, securing a logi- 
 cal order of subjects and an arrangement of topics adapted 
 to encourage the best methods of study and to facilitate the 
 best methods of teaching. 
 
 IV. To encourage a complete mastery of what is under- 
 taken, by concentrating study upon a brief course, and pro- 
 viding for thorough reviews at short intervals by means of 
 summaries of principles and exercises with problems at the 
 ends of sections or chapters. 
 
 V. To present the science in the light of modern theories, 
 sparing no pains to make the work represent the present state 
 of chemistry fairly and fully, so far as its elementary char- 
 acter will permit. 
 
iv PREFACE. 
 
 VI. To make the experimental method of reaching facts 
 prominent and practicable, not by requiring the student to 
 read the descriptions of large numbers of experiments which 
 he can not make and may never see, but rather by inviting 
 his attention to a few which are within reach, or which may 
 be clearly understood by means of cuts, and then providing 
 an additional number which are easily and cheaply made, and 
 which are to he studied only when they are seen. 
 
 Chemistry is eminently an experimental science. Noth- 
 ing whatever can be learned in it by speculation, and very 
 little by direct observation of nature. All its laws and 
 principles have been established by experiment. The experi- 
 mental method is therefore the method of study which is 
 true to the character of this subject, and it should be promi- 
 nent in an elementary course. 
 
 Nevertheless it is not thought that a student should be 
 compelled to learn every thing in chemistry by the study of 
 experiments. He will acquire a larger knowledge and a 
 good discipline if he take many established facts and laws 
 without witnessing the experimental evidence on which they 
 rest. And, indeed, this he must do, or accomplish little, so 
 long as chemistry is compressed into the small space which 
 it usually occupies in our schools. But while so much of the 
 world's progress in art, in industry, and also in those beliefs 
 which sway the minds and characters of men, is based upon 
 the experimental method of reaching the facts and laws of 
 nature, chemistry, above all other sciences, should take to 
 itself the privilege and the duty of teaching the young to 
 know what an experiment really is, how to translate it, how 
 to weigh its testimony, and how, by means of this method, 
 facts may be revealed and laws established. 
 
 These considerations have prompted me to furnish two 
 sets of experiments. I have in the first place illustrated the 
 text by experiments, the study of which constitutes a part of 
 the student's daily preparation. These experiments should 
 be witnessed if possible, but will, in any case, impress the 
 
PREFACE. V 
 
 fact that the principles of chemistry rest on experiment for 
 their demonstration. In the second place, I have provided, 
 for the teacher's use, a selection of additional experiments, 
 easy, cheap, and appropriate for illustration, which may be 
 used at discretion, and which, having the charm of novelty 
 to the student, will more effectually fix his attention, and 
 arouse his thoughts. 
 
 LeE. C, C. 
 
COI^TTEI^TS. 
 
 CHAPTER I. 
 
 GENERAL PKINCIPLES OF THE SCIENCE. 
 Section 
 
 I. Phtsical and Chemical Changes 
 
 II. Chemical Attraction . 
 in. Indestructibility of Matter . 
 rv". Analysis and Synthesis 
 
 V. The Laws of Combination . 
 Vl. Chemical Symbols and Formulas 
 
 Paqb 
 1 
 
 10 
 
 17 
 
 23 
 
 29 
 
 CHAPTER II. 
 
 the non-metallic elements. 
 
 Section Page 
 
 I. General Description 52 
 
 II. Hydrogen 60 
 
 III. The Univalent Non-Metals ..... "70 
 
 IV. The Bivalent Non-Metals ..... 83 
 V. The Trivalent Non-Metals 115 
 
 VI. The Quadrivalent Non-Metals .... 143 
 
 VII. Combustion . 159 
 
 vii 
 
viii CONTENTS. 
 
 CHAPTER m. 
 
 the compounds of carbon. 
 
 Section Pa-BK 
 
 I. Genebal Statements 1^0 
 
 II. Maksh-Gas and the Maksh-Gas Seeibs . . • 182 
 
 III. The Alcohols 186 
 
 rV. The Etheks 189 
 
 v. Oleflant Gas and the Olefinbs .... 191 
 
 VI. Destbuctive Distillation 192 
 
 Vn. The Sugaes 203 
 
 CHAPTER IV. 
 
 the meCals. 
 
 Bbction PiSK 
 
 I. Genebal Description 214 
 
 II. Metals of the Alkalies 216 
 
 III. Metals of the Alkaline Earths .... 219 
 
 IV. Metals of the Earths 221 
 
 V. Metals op the Zinc Class 223 
 
 VI. Metals of the Iron Class 224 
 
 VII. Metals of the Tin Class 230 
 
 VIII. Metals of the Antimony Class .... 230 
 
 IX. Metals of the Lead Class 232 
 
 X. Metals of the Silver Class 233 
 
 XI. Metals op the Gold Class 242 
 
 APPENDIX. 
 
 Easy Experiments fob the Class-Room .... 251 
 
CHEMISTRY. 
 
 CHAPTER I. 
 GENERAL PRINCIPLES OF THE SCIENCE. 
 
 SECTION I. 
 PHYSICAL AND CHEMICAL CHANGES. 
 
 1. Physical Chang'es. — Bodies of matter are constantly 
 changing. They move : how varied are their motiops ! They 
 change their shapes, as when rocks are rounded by the flow 
 of water over them, or shattered by a blast of gunpowder. 
 They change from solid to liquid forms, as when the snows 
 of winter melt ; and from liquids to gases, as when water 
 passes into steam. In such changes as these, however, 
 the nature of the substance is not affected. After a body 
 has moved, it is the same body as before. Water, in the 
 forms of ice and dew and vapor, is water ; and, if it change 
 from one to another, it is water still. Such changes are 
 called Physicai. Changes. They are changes during which 
 the nature of a substance remains unaltered. 
 
 2. Illustrated by Experiment. — A simple experiment 
 with an apparatus shown in Fig. 1 will show that air will 
 yield to the slightest pressure, and suffer a change in its vol- 
 ume and in its density. 
 
 1 
 
CHEMISTEY. 
 
 A glass tube with a bulb at the upper end is joined to an- 
 other by a piece of rubber tubing. A colored liquid fills the 
 rubber, and stands at equal heights in the glass tubes. The 
 ^^ bulb and stem above the liquid are filled with air. 
 
 Let the lips be applied now to the top of the open 
 tube, and the breath be gently forced into it : the 
 fluid quickly responds to the pressure, and rises 
 towards the bulb, pushing the air before it into a 
 smaller space. The volume of the air is dimin- 
 ished, and its density is increased. 
 
 But the nature of the substance is not altered. 
 The same air remains, after the pressure is exerted, 
 as before. These changes in volume and density 
 are examples of physical changes. 
 
 3. Chemical Changes. — But all changes are 
 not like these. Wood burns : in doing so it ceases 
 to be wood ; it is changed to smoke and ash. 
 Gunpowder explodes : it is no longer gunpowder. 
 Fluids from the soil, and gases from the air, are 
 taken into the roots and leaves of plants, and are 
 there changed into substances which form the plant 
 Such as these are changes in the nature of sub- 
 They are called Chemical Changes. They are 
 changes in which we discover the production of new sub- 
 stances, substances totally unlike those which enter into the 
 action. 
 
 4. Illustrated by Experiment. — A piece of cardboard 
 is put over the top of an ale-glass (Fig. 2). A teaspoonful 
 of sugar and another of potassium chlorate are powdered and 
 mixed, and then laid upon the cardboard. Three or four 
 drops of strong sulphuric acid are allowed to fall from the end 
 of a glass tube upon this mixture. Almost upon the instant 
 when the acid touches the powder, violet-colored tongues of 
 flame leap up from it with a liissing sound, accompanied 
 with large volumes of white vapor passing off into the 
 
 Fig. 1. 
 
 itself, 
 stances. 
 
CHEMISTRY. 
 
 Fig. 2. 
 
 air. When the sound has ceased, and the colored flames 
 have died out, only a coal-black mass is left upon the card- 
 board. 
 
 The white mixture of sugar and potassium chlorate, with 
 the drops of oily-looking acid, have been 
 changed into vapors, which have gone into 
 the air, and a black coaly mass, which is left 
 behind. Not a particle of either of the sub- 
 stances used can be found remaining. 
 
 Burning of Sulphur in Oxygen. — An- 
 other illustration is seen in the action of 
 oxygen gas and" ignited sulphur. A large 
 bottle is filled with oxygen. A small pendant 
 spoon is fixed to tlie cork, and filled with 
 powdered sulphur. The sulphur, first-set on 
 fire, is thrust into the bottle (Fig. 3), when 
 the combustion goes on with a fine blue 
 flame, and the bottle is soon filled with whitish vapors. 
 
 The sulphur has now disappeared. Much of the oxygen has 
 been also used up. The new gas formed contains them both, 
 
 but its properties are not like 
 those of either. It is very 
 suffocating when breathed : 
 oxygen is not. Pour a little 
 solution of blue litmus into the 
 bottle : it is first reddened and 
 then bleached. Neither oxy- 
 gen nor sulphur can bleach 
 blue litmus. The mutual ac- 
 tion of the sulphur and oxygen 
 is called a Chemical Action, 
 because it has brought about 
 a change in the nature of these 
 substances, producing a, new 
 kind of matter having properties different from those of 
 either sulphur or oxygen. 
 
 Fig. 3. 
 
4 
 
 CHEMISTRY. 
 
 5. Chemical Combination. — In this chemical action of 
 sulphur and oxygen, we find two substances uniting to form a 
 third. Tliis is a case of chemical combination. 
 
 In the following experiment (Fig. 4), we may see another 
 example of the same kind of action. A small quantity of 
 pure mercury is put into a glass flask over a source of heat. 
 A bent glass tube reaches from the flask over into a vessel of 
 mercury. The flask and tube are filled with oxygen. The 
 end of the tube is bent upward ; and over it is placed a glass 
 
 Fig. 4. 
 
 jar, mouth downward, also filled with oxygen. Mercury and 
 oxygen are the only two substances in the flask. If the 
 mercury be heated for several hours, without boiling, two 
 things will be discovered : yellowish or red scales make their 
 appearance upon tlie surface of the mercury in the flask, in- 
 creasing in quantity until, if the heat be continued, the metal 
 is completely covered. At the same time the mercury rises 
 in the jar which contains the oxygen, showing that a part of 
 that gas has been removed. 
 
 Some of the mercury and some of the oxygen have united 
 to produce this new red substance. Their action is an 
 
CHEMISTRY. 
 
 example of chemical combination, since the product contains 
 them both, and is a substance quite unlike either. 
 
 6. ghfimicaJ Decomposition. — If the red powder, which 
 contains mercury and oxygen, and which the chemist calls 
 mercuric oxide, is heated, both the mercury and the oxygeu 
 can be regained. 
 
 For this purpose a tube (Fig. 5) containing a small 
 quantity of the oxide is tightly closed with a perforated 
 cork, from which a bent tube passes just through the cork of 
 a glass flask full of water. Another bent tube, through this 
 same cork, reaches to the bottom of the water, while its other 
 end passes into the neck 
 of a second flask. By 
 heating the tube, first 
 the red oxide becomes 
 black, and soon after a 
 colorless gas will push 
 the water over into the 
 second flask. '^" 
 
 Little globules of shining mercury will be found clinging 
 to the sides of the tube ; while, if the cork and tubes be 
 removed from the -first flask and a lighted taper be plunged 
 into it, the flame will burst into brilliant combustion, showing 
 the gas to be oxygen. 
 
 Here we find a single substance broken into two quite dif- 
 ferent ones. This is an example of chemical decomposition. 
 
 Of Water. — The decomposition of water is another ex- 
 ample of this kind of chemical action. It is done by means 
 of electricity in an apparatus shown in Fig. 6. 
 
 Two tall glass tubes are first filled with acidulated water, 
 and then inverted over two strips of platinum at the bottom 
 of a vessel containing the same liquid. These pieces of 
 platinum may be joined by wires to the poles of a galvanic 
 battery. The moment such a connection is made, bubbles of 
 gas begin to rise from each platinum, and are collected in the 
 
6 
 
 CHEinSTKY, 
 
 tubes above. After a little time the tubes will be full of the 
 colorless gases into which the water has been converted. 
 
 If then one tube be lifted from the water, a lighted taper 
 may be thrust into it, when the flame will instantly burst into 
 tenfold brilliancy, showing that the gas is oxygen. But if 
 the other tube be lifted, and the flame applied, the gas 
 instantly takes fire, and burns with a slight explosion. This 
 is characteristic of hydrogen. 
 
 The electricity has produced a chemical decomposition of 
 the water : it has changed it into oxygen and hydrogen, two 
 
 Fig. 6. 
 
 substances altogether different from that from which they 
 were derived. 
 
 7. Definition of Chemistry, — Chemistry is the science 
 which describes the chemical changes which occur in bodies 
 of matter, discovers the circumstances under which they take 
 place, and the laws by which they are governed. 
 
 8. Observation and Experiment. — Many things can 
 be learned by simply watching what occurs in the ordinary 
 operations of nature. The rusting of iron, for example, is 
 a very common occurrence. All have seen the bright metal. 
 
CHEMISTRY. 7 
 
 on exposure to moist air, become covered with a dull red 
 coating ; and, since iron-rust is a substance totally different 
 from either iron or moist air, we may say that these two 
 substances, on contact, enter into a chemical action. This 
 method of learning the truths of nature is called Obseeva- 
 
 TION. 
 
 But it is likely that we should never have learned by 
 observation that water is composed of two invisible gases, 
 because its decomposition does not happen in nature under 
 circumstances in which we are able to observe it. It was 
 discovered by means of an experiment. An experiment is 
 an operation performed under conditions ivhich we ourselves 
 arrange for the purpose. Nicholson and Carlisle, in the 
 year 1800, placed the poles of their galvanic battery in a 
 vessel of water, and in this way brought electricity to act 
 upon that liquid in a manner not to be seen in nature ; and 
 the result was the decomposition of the water into oxygen 
 and hydrogen. This method of learning the truths of nature 
 is called the Experimental Method. 
 
 Chemistry is an experimental science. Very little of 
 what it teaches has been discovered by observation. Nearly 
 every thing we know of chemistry has been established by 
 experiment ; and the student should pursue the study of it 
 by the experimental method. 
 
 An experiment in chemistry is of no value except as it 
 teaches some chemical truth. However attractive it may be, 
 or however startling, if it had no other merit than beauty 
 or novelty, it is worthless to the student of chemistry. 
 
 In order to learn by an experiment, one must see clearly 
 the conditions under which the substances are brought 
 together, obsei-ve accurately the changes which occur, and 
 the products of them ; and, finally, he must endeavor to see 
 that the fact or principle, which the experiment claims to 
 prove, is a correct interpretation of the results. 
 
CHEMISTRY. 
 
 REVIEW. 
 
 I. — SUMMARY OP PRINCIPLES. 
 
 9. Physical changes are such as do not affect the nature 
 of a substance. They are the result of mechanical action. 
 
 Chemical changes are such as cause an alteration in the 
 nature of a substance, converting it into a different kind of 
 matter. They are the result of chemical action. 
 
 Chemistry is the science which treats of the chemical 
 changes in all kinds of matter, discovers the conditions under 
 which they occur, the laws which govern them, and describes 
 the qualities of substances which take part in them, or are 
 produced by them. 
 
 Chemical combination is the uniting of two or more sub- 
 stances to form a single one with entirely different prop- 
 erties. 
 
 When sulphur burns in oxygen, these two substances unite 
 to form sulphurous oxide, a suffocating gas quite unlike 
 either sulphur or oxygen. When mercury is heated in 
 oxygen, these two unite to form mercuric oxide, which resem- 
 bles neither of them. These are examples of chemical 
 combination. 
 
 Chemical decomposition is the breaking-up of a single 
 substance into two or more simpler ones, with entirely dif- 
 ferent properties. 
 
 Mercuric oxide, when strongly heated, is changed into 
 mercury and oxygen. Water is broken, by the electric cur- 
 rent, into oxygen and hydrogen gases. These are examples 
 of chemical decomposition. 
 
 Neither oxygen, nor hydrogen, nor sulphur, nor mercury, 
 can be decomposed by any known process. On this account 
 they are called Elements. 
 
 An element is a substance which has never yet been 
 decomposed. 
 
 When two or more substances enter into chemical com- 
 bination, the new substance formed is called a Compound. 
 
CHEMISTKY. 9 
 
 A compound is a substance made up of two or more sim- 
 pler ones, and whose ■ properties are unlike tliose of eitlier 
 of them. 
 
 Besides elements and compounds, there are substances 
 called Mixtures. 
 
 A mixture is a substance made up of two or more which 
 have not combined. Its properties are the same as the prop- 
 erties of its constituents. 
 
 II.— EXERCISES. 
 
 How many kinds of changes occur in bodies ? 
 
 Give examples of physical changes. Why are these called 
 physical changes? 
 
 Give example of chemical changes. Why are these called 
 chemical changes? Salt dissolves in water: is the change 
 physical, or chemical? Iron rusts: is this a physical, or a 
 cliemical change? TJie loftiest tree may be shattered into 
 fragments by a lightning-stroke: which kind of change is 
 prodiiced? 
 
 Define chemistry. 
 
 What phenomena are to be studied in chemistry? In 
 natural philosophy? Which science explains the fall of a 
 stone? the decay of wood? the manufacture of glass out of 
 potash and sand ? 
 
 What is meant by chemical combination? 
 
 What is meant by chemical decomposition? 
 
 What is the experimental method? 
 
 What is the method of observation ? 
 
 What is an element? A compound? A mixture? 
 
 What is produced by burning sulphur in oxygen? By 
 heating mercury a long time in air? Why are these new 
 substances called compounds? 
 
 What are the elements in water? 
 
 How may water be decomposed^ 
 
10 
 
 CHEMISTRY. 
 
 SECTION II.- 
 
 Fig. 7. 
 
 CHEMICAL ATTRACTION. 
 
 10. Attraction. — If we suspend a long and light wooden 
 bar by means of a thread attached to its middle point, or 
 balance it on a pivot, and if then we briskly rub a glass tube 
 with a piece of silk or flannel, we shall find that the end of 
 
 the bar will swing 
 toward the glass, 
 even when the 
 glass is several 
 inches away from 
 it. (Fig. 7.) In 
 this experiment 
 we see the action 
 of a force which 
 tends to bring 
 these two bodies 
 together. Any 
 force by which bodies tend to approach is called Atteaction. 
 Varieties of Attraction. — We know that all bodies, if 
 not supported, will fall to the ground : this we learn by 
 observation. Experiments have been made which show that 
 there is also an attraction between bodies of every size and 
 kind. This attraction which acts between all separate 
 bodies, and throughout all distances however great, is called 
 Gravitation. 
 
 Again, we know that the parts of a solid body are not to 
 be separated with perfect ease ; and the attraction which 
 holds the particles of a body together is called Cohesion. 
 
 Neither gravitation nor cohesion produces any chemical 
 changes whatever. But we have seen that when sulphur and 
 oxygen are heated, they fall together into such intimate con- 
 tact, that neither sulphur nor oxygen can be distinguished, 
 but sulphurous oxide is found instead. The attraction which 
 
CHEMISTRY. 
 
 11 
 
 brings these two elements into chemical combination is called 
 Chemical Attraction. 
 
 The production of new substances, by uniting those on 
 which it acts, is the characteristic effect of chemical attrac- 
 tion. In a word, all chemical changes are effected by the 
 force of chemical attraction. 
 
 11. Influence of Coliesion on Chemical Action. — 
 
 If we place a crystal of potassium chlorate, about one- 
 half as large as a grain of wheat, in contact with a piece of 
 brimstone of about the same size, no chemical change occurs. 
 The particles of each are held together by cohesion, and 
 kept from uniting with those of the other. But if we grind 
 them together in a mortar, a sharp explosion follows. The 
 chemical action converts both into gases, which disappear in 
 the air. This experiment illustrates the fact, that, in the 
 solid forms of matter, cohesion is generally too strong to be 
 overcome by chemical attraction. 
 
 To weaken cohesive attraction is to facilitate chemical 
 action. In the experiment, cohesion was overcome hy pul- 
 verizing the solids. It may be overcome or weakened in 
 other ways, among which solution and 
 fusion are most important. 
 
 Effect of Dissolving the Sub- 
 stances. — If sodium carbonate and 
 tartaric acid, both in the finest pow- 
 der, be mixed most thoroughly, or 
 rubbed together violently, no chemi- 
 cal action will take place. But, when 
 a little water is added to this mixture, 
 a violent chemical action will quickly 
 follow. Let the mixture be made at 
 the bottom of a tall jar (Fig. 8), 
 and the vigor of the action will, very 
 likely, carry the foam to the top and over upon the plate 
 below. 
 
 Fig. 8. 
 
12 CHEMISTRY. 
 
 Now, in this ease, the water by dissolving the solids has 
 overcome cohesion to such an extent, that chemical attraction 
 can bring about a chemical change. In this way solution 
 very generally facilitates chemical action. 
 
 Eff'ect of Fusing: the Substances. — The melting of 
 solids together often has the same effect. If we take a little 
 sulphur, twice as much potassium carbonate (well dried), 
 and three times as much niter, powder them well sepa- 
 rately, then mix them thoroughly on paper, and introduce a 
 little of the mixture into an iron spoon, we may melt them 
 together over the gas-lamp. The cohesion is overcome by 
 the heat ; and the mixture explodes violently, announcing the 
 chemical action produced. In this way fusion very generally 
 facilitates chemical action. 
 
 Exceptions. — Yet we must not suppose that no two 
 solids can combine without their cohesion being first over- 
 come by the methods just described. If, for example, a 
 crystal of iodine is laid upon a thin slice of phosphorus, the 
 two will shortly burst into a rapid and curious combustion. 
 But such examples are quite rare : the liquid form is most 
 favorable to chemical action. 
 
 12. Influence of Heat. — Although the liquid state is 
 most favorable to chemical action, yet in many instances no 
 chemical change takes place until the mixture is heated. A 
 high temperature is favorable to chemical action. 
 
 We have .already seen the power of heat to produce chemi- 
 cal changes. Sulphur was ignited, before it would combine 
 with oxygen to form sulphurous oxide. Mercury was heated, 
 before it would combine with oxygen to form mercuric oxide. 
 
 Attraction of Pbosplioriis and Oxygen Phosphorus 
 
 and oxygen are two elements between which there is a pow- 
 erful chemical attraction. Nevertheless at ordinary tempera- 
 ture their combination is very slow. Phosphorus is kept 
 under water to prevent tlie action of oxygen in the air, which 
 will consume it slowly on exposure, and very rapidly if its 
 
CHKMISTRY, 13 
 
 temperature be raised. The heat of the fingers may start 
 the combustion, and hence phosphorus must be handled with 
 great caution. 
 
 Rapid Combination Tjy Heat. — But let us cut a thin 
 slice from the end of a stick of phosphorus under ivater, and 
 carefully dry it by very gentle pressure between two folds of 
 blotting-paper. We may then place it upon a piece of card- 
 board supported by a test-glass (Fig. 9). Delicate clouds 
 of white vapor float away : these are 
 the new substance formed by the slow 
 combination of phosphorus and oxy- 
 gen at ordinary temperature. Now 
 let a red-hot iron rod be brought near. 
 The phosphorus will burst into rapid 
 combustion, evolving large volumes 
 of dense white fumes, even while the 
 hot rod is several inches away. 
 
 All these are examples of chemical pig. 9. 
 
 combination ; but heat very often pro- 
 duces chemical decomposition also. We have already learned 
 that the red mercuric oxide is resolved into mercury and 
 oxygen when strongly heated. Chemical decomposition by 
 heat alone is called Dissociation. 
 
 Different Eflfects of High and Low Temperatures. — 
 The experiments with mercury and oxygen illustrate another 
 curious and inportant fact, — that a compound which is 
 fonned only at a high temperature, is again decomposed if 
 heated to a temperature still higher. In order to compel 
 mercury and oxygen to combine, we must heat them almost 
 to the boiling point of mercury ; and then by heating the 
 red oxide thus formed to a still higher temperature, we repro- 
 duce the elements. 
 
 Most compounds are more readily made under the influ- 
 ence of high temperature ; and yet at some higher tempera- 
 ture, it is thought, every compound may be resolved into its 
 elements again. 
 
14 
 
 CHEMISTRY. 
 
 13. The Influence of Electricity. — Electricity is also 
 a powerful agent in chemical action. - The decomposition of 
 water is an example. Many other liquids may be decom- 
 posed in a similar way. This decomposition by electricity is 
 called Electrolysis. 
 
 In the decomposition of water the oxygen was liberated at 
 the positive pole of the battery, and the hydrogen at the 
 negative pole. The oxygen is described as the electro-nega- 
 tive constituent, and the hydrogen as the electro-positive con- 
 stituent, of water. Whenever a compound is decomposed by 
 electricity, that constituent which is found at the negative 
 pole of the battery is called the electro-positive constituent, 
 the other is called the electro- negative constituent. 
 
 Cliemical Combination by Electricity. — But electri- 
 city may also produce chemical combination. 
 
 The tall glass tube represented in Fig. 
 10 is closed at the top, and open at the 
 bottom. Two platinum wires are fused 
 into the glass near the upper end : they 
 almost touch one another on the inside. 
 The tube was first filled with water. 
 Afterwards a few bubbles of oxygen 
 were introduced, and a little more than 
 twice as much hydrogen was added. 
 Now let a spark of electricity pass 
 through the gases by means of the plat- 
 inum wires, and a violent explosion in- 
 stantly follows. The gases combine 
 under the influence of the electricity, 
 and disappear, only the small excess of 
 Fig. 10. hydrogen remaining. 
 
 14. The Influence of Light. — Both decomposition and 
 combination are also brought about by light. 
 
 We may witness an example of decomposition if we will 
 dampen the surface of a piece of paper with a solution of 
 
CHEMISTRY. 
 
 15 
 
 silver nitrate, and expose it to the action of the sunlight. 
 Darker and darker the white surface becomes, until finally it 
 is almost black. This darkening of the surface is due to the 
 decomposition of the nitrate by light. 
 
 A large number of compounds of silver are darkened by 
 light. The art of photography is founded upon this decom- 
 posing action of light. 
 
 Combination by Ligbt. — Combination is also brought 
 about by light, as when hydrogen and chlorine gases are 
 mixed in a glass vessel. The direct rays of the sun will drive 
 them into sombination so rapidly as to produce explosion. A 
 new gas — hydrochloric acid gas — is formed by their union. 
 
 Let a strong tube or bottle be filled with a mixture of the 
 two gases, taking care to have a little more of one — say of 
 hydrogen — than of the other. Let 
 this mixture be prepared in a dark 
 room, the tube containing it being in- 
 verted in a vessel of water, firmly fixed 
 in place (Fig. 11), and covered with a 
 black cloth. Thus prepared, take the 
 apparatus at once to a place where the 
 direct rays of the sun may fall upon it, 
 and by means of a long handle remove 
 the cloth. A violent explosion will 
 quickly follow ■ the water, speedily dis- 
 solving the acid gas, will rise in the 
 tube, and would strike the top of it 
 with violence, did not the excess of 
 hydrogen act as a cushion to prevent it. 
 
 Exposed to diffuse light, the com- 
 bination of the mixed gases is gradual ; but, if prepared and 
 kept in the dark, no combination occurs. 
 
 These experiments clearly illustrate the fact, that sunlight 
 has power to produce chemical action. Other intense lights, 
 the electric light for example, may be used with similar 
 results. 
 
 ^11 
 
 Pig. H. 
 
16 CHEMISTRY. 
 
 REVIEW. 
 
 I. —SUMMARY OF PRINCIPLES. 
 
 15. Attraction is a force under whose influence bodies of 
 matter tend to approach one another. 
 
 Attraction is called gravitation when it acts between sepa- 
 rate masses of matter. It is called cohesion when it acts 
 between the particles of a body without causing any chemical 
 change. It is called chemical attraction when it causes two 
 or more substances to produce a single substance quite unlike 
 themselves. 
 
 Chemical attraction is opposed by cohesion. We facilitate 
 chemical action by reducing the strength of cohesion. 
 
 Cohesion may be reduced by pulverizing the solid, by dis- 
 solving it, and by melting it. All these processes are favor- 
 able to chemical action. 
 
 Chemical action is most likely to occur when the substances 
 are brought together in the liquid form. 
 
 The application of heat is favorable to chemical change. 
 Electricity and light also, in many cases, produce chemical 
 action. 
 
 Electrolysis is the decomposition of a compound by elec- 
 tricity. The constituents are distinguished as electro-positive 
 and electro-negative. 
 
 n.— EXERCISES. 
 
 Define attraction. Name the three varieties of attrac- 
 tion. Define each. To which of these are chemical changes 
 due? 
 
 What is the infiuence of cohesion on chemical action? 
 Why should pulverizing solids facilitate their chemical 
 action? By what other means may we weaken cohesion? 
 Name two solids whose cohesion does not prevent their 
 combination. 
 
 What is the general influence of heat on chemical action? 
 
CHEMISTRY. IT 
 
 Give an example of chemical combination, brought about by 
 heat. Give an example of chemical decomposition, brought 
 about by heat. Define dissociation. 
 
 Give an example of chemical decomposition by electricity. 
 Define electrolysis. "What is meant by electro-positive and 
 electro-negative constituents ? 
 
 Give an example of chemical combination by electricity. 
 
 What is the effect of light upon silver compouuds ? 
 
 What is the effect of light on mixed chlorine and hydrogen 
 gases ? 
 
 SECTION III. 
 
 THE INDESTRUCTIBILITY OF MATTER. 
 
 16. No Loss occm-s iu Chcinical Combination. — In 
 
 many cases of chemical action, substances disappear and seem 
 to be lost. This happens when a candle burns : its material 
 slowly wastes awaj-. Nevertheless, the quantity of matter 
 in all such cases remains unchanged. Mach or even all of 
 it may become invisible, but by appropriate tests its existence 
 can be demonstrated. 
 
 Test for the Presence of Matter. — Weight is the ap- 
 propriate measure of the quantity of matter, and experiment 
 will always decide whether the weight of the products of 
 chemical action is exactly equal to that of the substances 
 which take part in it. 
 
 Application of this Test. — Take a piece of phosphorus 
 as large as a pea, and support it on top of a small wire 
 whose lower end is bent into a flat spiral so that it will stand 
 upright. Select a thin, light beaker, and a large, thin, and 
 light flask, of about 1,500 cubic centimeters capacity. Puc 
 about 400 cubic centimeters of water, colored blue with lit- 
 mus, into the beaker, stand the phosphorus wire in it, and 
 then invert the flask over the phosphorus, with its neck rest- 
 ing on and completely closing the top of the beaker, and its 
 
18 
 
 CHEMISTEY. 
 
 mouth reaching almost to the bottom of the colored water. 
 The outside must be dry. 
 
 In this condition, let the whole apparatus be placed upon 
 one pan of a pair of scales, and exactly balanced by weights 
 in the other pan. (Fig. 12.) 
 
 If we leave the apparatus for several hours, — perhaps 
 until to-morrow, — we shall find that water has risen into 
 
 the flask, as shown in the 
 figure, as if a part of the 
 air had been annihilated. 
 Moreover, we think we can 
 see that the phosphorus has 
 wasted away, as if a part 
 of its substance also had 
 been destroyed. The bal- 
 ance, however, remains un- 
 disturbed : the apparatus 
 weighs exactly as much as 
 at first, showing that no loss 
 can be detected. And yet, 
 if what substance has disap- 
 peared had been destroyed, the apparatus would weigh at 
 least .43 of a gram less. A good common balance would 
 easily detect much less loss than that. 
 
 What has actually happened is this : The phosphorus has 
 combined with oxygen, which is one of the constituents of 
 the air in the flask. The compound, phosphorous oxide, is 
 adsorbed by the water, and remains unseen. This new sub- 
 stance contains all the oxygen and all the phosphorus which 
 seem to have been lost. 
 
 In all cases of chemical combination, the compound weighs 
 exactly the same as the constituents used up in producing it. 
 
 17. No Loss ill Clienilcal Decomposition. — In chemi- 
 cal decomposition, also, the quantity of matter remains 
 unchanged. The red mercuric oxide is decomposed by 
 
 Fig. 12. 
 
CHEMISTEr. 
 
 19 
 
 beat : let us get the facts by experiment with this substance. 
 We must make the experiment so that both constituents shall 
 be preserved in the apparatus. (Fig. 13.) 
 
 The Experiment. — Put about three grams of the red 
 powder into a small tube of hard glass, which is provided 
 with a bent tube reaching just through the cork of a flask of 
 about two hundred cubic centimeters capacity. Let this flask 
 be joined to another of equal size, by means of a bent tube 
 
 Fig. 13. 
 
 which reaches almost to its bottom, but only just through 
 the cork of the other. The first flask is to be nearly or 
 quite full of water, and must be air-tight at the cork ; while the 
 second is empty and loosely corked. Place the whole appa- 
 ratus, which should be perfectly dry outside, upon the scales, 
 as sliown in the figure, and accurately balance it by weights. 
 Then heat the tube, and decompose the red oxide. The 
 powder will waste away ; globules of metallic mercury will 
 collect on the side of the tube above the heat ; while the 
 oxygen will pass into the first flask, and drive the water over 
 into the second. 
 
 Leave the apparatus at rest for a time until the tube has 
 become cold, and it will be found that the balance is undis- 
 turbed. The whole weight is just the same as at first, 
 
20 
 
 CHEMISTRY. 
 
 showing that no loss of matter has occurred during the 
 decomposition. 
 ^ Grciieral Results. — Many accurate experiments have 
 proved beyond doubt, that matter is never desti-oyed nor 
 created by chemical action. During all tlie chemical changes 
 through which substances may go, tlie quantity of matter re- 
 mains unaltered. This is the foundation fact in the science 
 of chemistry. 
 
 18. Weighing. — In the study of the chemical action of 
 the elements, and of the properties of the compounds they 
 
 Pig. 14. 
 
 form, the determination of the weights of substances is an 
 operation of supreme importance. The chemist must do it 
 with the utmost precision. The instrument he employs is the 
 chemical balance (Fig. 14). 
 
 The worlvHiaiiship in this instrument is of the finest kind, 
 and the adjustments are m.ade with the nicest skill. Heavy 
 bodies are not to be weighed in the chemical balance, but 
 tlie weight of light ones can be found with marvelous accu- 
 racy. With two hundred grams in each scale-pan, the in- 
 strument shown in the figure will turn by the addition of the 
 
GHEMXSTEY. 
 
 21 
 
 twentieth of a milligram to either side. One-twentieth of a 
 milligram is about one thirteen-hundredth of a grain. 
 
 The French or metric system of weights is very generally 
 employed in chemistry. The student should be familiar with 
 it. In this system 
 
 10 milligrams = 1 centigram. 
 
 10 centigrams = 1 decigram. 
 
 10 decigrams = 1 gkam = 15.43+grs. 
 
 10 grams = 1 decagram. 
 
 10 decagrams = 1 hectogram. 
 
 10 hectograms= 1 kilogram = 2.2-f lbs. av. 
 
 10 kilograms = 1 myriagram. 
 
 19. Measuring. — But when the substance is a gas, 
 weighing is a difficult operation, and the quantity is usually 
 found by volume instead of by weight. For this purpose 
 glass tubes of various sizes are accurately graduated (Fig. 
 11). The divisions along the tube show the volume inside 
 in cubic inches or cubic 
 centimeters, and frac- 
 tions of these units. 
 
 Liquids also are more 
 easily measured than 
 weighed, and for many 
 purposes their volumes 
 are taken instead of 
 their weight. In Fig. 
 15 some forms of grad- 
 uated vessels for liquids 
 are represented. 
 
 The cubic centimeter 
 is the volume of one gram weight of pure water at 4° C. 
 The number of cubic centimeters, therefore, represents also 
 the weight of the water in grams. 
 
 As to any other liquid, if the number of cubic centimeters 
 is multiplied by the specific gravity, the product will represent 
 the weight of that liquid in grams. 
 
 Pig. 15. 
 
22 CHEMISTRY. 
 
 The cubic centimeter is also called milliliter. It and the 
 liter are the two denominations commonly used. The full 
 table is as follows : — 
 
 10 milliliters = 1 centiliter. 
 
 10 centiliters = 1 deciliter. 
 
 10 deciliters = 1 liter = .22 gal. 
 
 10 liters = 1 decaliter. 
 
 10 decahters = 1 hectoliter. 
 
 10 hectoliters = 1 kiloliter. 
 
 10 kiloliters = 1 myrioliter. 
 
 The operations of weighing and measuring require many 
 precautions, and the exercise of much skill, to insure the 
 nicest accuracy. We will not here enter upon the minute 
 details. 
 
 REVIEW. 
 
 I.— SUMMARY OF PRINCIPLES. 
 
 20. By chemical attraction substances are made to com- 
 bine. They disappear altogether, but new substances are 
 seen in their stead. 
 
 Moreover the products of chemical action are often in- 
 visible gases. 
 
 Nevertheless all the matter of the original substance ex- 
 ists in the products of the action. 
 
 During all chemical changes the quantity of matter remains 
 unaltered. 
 
 The quantity of matter in a body is found by taking its 
 weight, or in the case of gases, and often of liquids also, by 
 taking its volume. 
 
 Hence the operations of weighing and measuring are 
 fundamental and most important operations in chemistry. 
 Thi science is built upon the data given by them. 
 
 The French or metric system of weights and measures is 
 most largely employed in chemistry. 
 
jhbmistkv:. 
 
 The milligram, the gram, and the kilogram are the three 
 most useful units of weight. 
 
 The cubic centimeter and the liter are the most useful 
 units of volume. 1,000 milligrams=l gram ; 1,000 gram8= 
 1 kilogram; 1,000 cubic centime ters=l liter. 
 
 II. — EXERCISES. 
 
 By what means may we find out whether any gain or loss 
 occurs in chemical change ? 
 
 What are the results of experiment? 
 
 Of what importance is the balance in chemistry ? 
 
 What system of weights is generally used ? 
 
 Give the table. What is the value of the gram in ifing- 
 lish measure ? Of the kilogram ? 
 
 How many milligrams in one ounce Troy? 
 
 How many grains are equal to 500 m. g. ? I ' 
 
 How are the quantities of gases and liquids found? 
 
 What is a cubic centimeter ? 
 
 What is the weight of 100 cc. of alcohol, whose specific 
 gravity is .82? 
 
 What is the English value of the liter ? 
 
 Give the table of volumes in the metric system. 
 
 SECTION IV. 
 
 ANALYSIS AND SYNTHESIS. 
 
 21. Analysis. — Any process by which a compound may 
 be separated into its constituents, and its composition de- 
 termined, is called Analysis. If in the process only the 
 names of the constituents are found, the analysis is quali- 
 tative; if their proportions are found, the analysis is quan- 
 titative. 
 
 By Electricity. — Many substances maybe decomposed, 
 and their composition found, by the action of electricity. 
 We have already learned that such a process is called Elec- 
 
24 
 
 CHEMISTRY. 
 
 TROLTSis. The most interesting example of electrolysis is 
 that of water. Let us repeat the experiment, and study it 
 more in detail. 
 
 Two platinum strips are inserted in a jar of water ; and 
 over them are inverted two long and slender tubes, previously 
 Hlled with water. (See Fig. 16.) The wires of a galvanic 
 battery are then inserted in the screw cups, s s. Instantly a 
 
 torrent of gas-bub- 
 bles rises in each 
 tube, and will con- 
 tinue to do so until 
 the tubes are filled. 
 These two gases are 
 the constituents of 
 water. As the ex- 
 periment goes on, 
 it will be noticed 
 that one tube is 
 being filled faster 
 than the other ; 
 indeed, being of 
 equal size, one fills 
 twice as fast as the other. If the gases are tested, that 
 which is most rapidly set free is found to be hydrogen, the 
 other oxygen. 
 
 The experiment teaches that water is composed of hydro- 
 gen find oxygen, in the proportion by volume of two of hy- 
 drogen to one of oxygen. 
 
 Proportions toy Weight. - - This composition by volume 
 is shown directly by the tubes ; but, if we desii-e to know the 
 proportions of the gases by weight, we must make a calcula- 
 tion. 
 
 The specific gravity of oxygen is 16. By this is meant 
 that any volume of oxygen weighs just sixteen times as much 
 as an equal volume of hydrogen. If, then, there were equal 
 volumes of the two gases in water, their proportions by 
 
 Fig. 16. 
 
CHEMISTEY. 25 
 
 weight would be as 1 : 16. Since there are two Tolumes of 
 hydrogen, the proportions are as 2 ; 16. Eighteen parts 
 of water (16 + 2) contain sixteen parts of oxygen and two 
 parts of hydrogen. This being the ratio, it is easy to find 
 just what part of any quantity of water is hydrogen, and what 
 part oxygen. For example : one hundred of water must 
 contain -L<yx 2 = 11.11 of hydrogen, and Jj-^O-x 16 = 88.89 of 
 oxygen. 
 
 Percentage Composition. — The composition of a com- 
 pound is usually given by the hundred, and it is then called 
 the Percentage Composition. The results in the case of 
 water are written in this way : — 
 
 WATER. 
 
 Hydrogen ..... 11.11 
 Oxygen 88.89 
 
 100.00 
 
 By the Pi-ism. — When the light of a burning substance 
 Is passed through a prism, it is decomposed ; and the appear- 
 ance of the spectrum depends upon the nature of the burning 
 substance. Hence the constituents of a compound may be 
 told by the appearance of its spectrum. This method of 
 detecting the presence of substances is called Spectrum 
 Analysis. 
 
 For example : when the spectrum of burning sodium is 
 viewed through a telescope, a bright yellow line, of surpris- 
 ing brilliancy, is seen in the yellow part of the spectrum. 
 Or, if potassium is burned, a single crimson line and another 
 of blue, both of great beauty, will be seen in opposite ends 
 of the spectrum. Nor will the appearance of either set be 
 changed by the presence of the other ; for, if a mixture of 
 sodium and potassium is burned, the observer will see both 
 sets in the same spectrum, their place, size, and brightness 
 the same as when each was formed alone. The spectra of 
 many elements have been carefully studied ; they can be 
 
26 CHEMISTRY. 
 
 easily recognized by one who has previously made their ac- 
 quaintance. 
 
 By Chemical Action The methods of analysis just 
 
 described are limited in application. The general method is 
 by the chemical action of bodies upon each other. More 
 than a hint of this method would be out of place here. But 
 suppose, for example, that a solution of unknown substances 
 in water is to be analyzed. A few drops of hydrochloric 
 acid may be added. If a white, solid substance is formed, 
 it shows the presence of either silver, mercury, or lead. To 
 find out which of these metals is present, a little ammonia is 
 added : if the solid disappears again, the metal is silver ; if 
 it simply turns black, mercm-y is present ; but if it remains 
 unchanged, the metal is lead. If the acid fails to produce 
 the white solid, or Peecipitate, as any solid formed in this 
 way from solution, by the action of chemicals, is called, then 
 these three metals are counted absent, and some other agent 
 is used by which another group of metals may be detected. 
 
 So far the analysis is only qualitative. To obtain quanti- 
 tative results, the balance must be used. 
 
 The original substance is first weighed, and finally the 
 precipitate, clean and pure and dry. These two weights 
 enable the chemist to calculate the weight of the metal in 
 one hundred parts of the original compound. 
 
 22. Synthesis. — The composition of a compound may be 
 found by causing its constituents to combine, and noticing 
 the proportions required. This process is called Synthesis. 
 The synthesis of water may illustrate : it may be made iu 
 an apparatus called a Eudiometer. 
 
 This instrument is a glass tube, open at one end, and care- 
 fully graduated, having two metallic wires passing through 
 the glass near the closed end, and almost touching each 
 other inside. To use it, measured quantities of hydrogen 
 and oxygen, say fifty volumes of each, are put into it. The 
 tube should still be much less than full of the mixed gases, 
 
CHEMISTET. 
 
 27 
 
 and should be firmly held with its open end in the cistern. 
 
 (Fig. 17.) If now electricity from a Leyden-jar or a 
 
 Ruhmkorff-eoil is passed through the mixture, the two gases 
 
 combine with violent explosion; water will be formed by 
 
 their union ; and water or mercury from the cistern will rise 
 
 into the tube to fill the space 
 
 they occupied. The quantity 
 
 of gas left will be found to 
 
 be twenty-five volumes, and, 
 
 if tested, will be found to be 
 
 oxygen. 
 
 It is evident that fifty vol- 
 umes of hydrogen have taken 
 twenty-five volumes of oxygen 
 to form water ; and the experi- 
 ment therefore teaches that 
 water is composed of hydro- 
 gen and oxygen in the pro- 
 portions by volume of two of 
 hydrogen to one of oxygen. 
 
 By analysis or by synthesis, 
 the chemist is able to find out just what all kinds of matter 
 are composed of, and even the exact proportions by weight 
 or by volume, in which their constituents are united. 
 
 Fig. 17. 
 
 REVIEW. 
 
 I. — SUMMARY OF PRINCIPLES. 
 
 23. The composition of a compound may be found by 
 analysis or by synthesis. 
 
 Analysis is any process by which a compound is sepa- 
 rated into constituents, and its composition determined. 
 
 Synthesis is any process by which the constituents of a 
 compound may be made to combine and produce it. 
 
28 CHEMISTE'S, 
 
 Qualitative analysis is an analysis in which only the names 
 of the constituents are found. 
 
 Quantitative analysis is an analysis in which the propor- 
 tions by volume or by weight of the constituents are deter- 
 mined. 
 
 By the percentage composition of a compound, we mean 
 the proportional parts of all its constituents in one hundred 
 parts of the compound. 
 
 In one hundred ounces, grams, or other units, by weight, 
 of water, there are 88.89 ounces, grams, or other units of 
 oxygen, and 11.11 of the same units of hydrogen. 
 
 By volume, however, water consists of two volumes hydro- 
 gen to one volume oxygen. 
 
 A precipitate is any solid substance produced by the 
 chemical action of other substances in solution. 
 
 In the solution of a compound of either silver, mercury, or 
 lead, hydrochloric acid' will produce a white precipitate, and 
 in these only. 
 
 Hydrochloric acid is said, therefore, to be a Test for the 
 presence of these metals. 
 
 Conversely, any compound of these metals is a test for 
 hydrochloric acid. If a solution contains the slightest quan- 
 tity of this acid, a drop or two of silver nitrate will turn it 
 white. 
 
 II.— EXERCISES. 
 
 Define analysis. Define qualitative analysis. Define quan- 
 titative analysis. Describe the electrolysis of water. What 
 does this analysis of water show? 
 
 Define specific gravity. What is the specific gravity of 
 oxygen ? Knowing that water consists of one volume oxy- 
 gen and two volumes hydrogen, how would you calculate 
 the proportions by weight? Define percentage composition. 
 What is the percentage composition of water ? 
 
 Define spectrum analysis. What is a more general method 
 of analysis ? Define precipitate. How would you tell which 
 
CHEMISTEY. 29 
 
 of the metals, silver, mercury, or lead, is contained in a sub- 
 stance? How would you find out how much the original 
 substance contained? 
 
 Define synthesis. Describe the eudiometer. What does 
 the synthesis of water teach? 
 
 SECTION V. 
 THE LAWS OF COMBINATION. 
 
 24. The Law of Coustant Proportions. — The first 
 great law discovered by the use of the balance and the meas- 
 uring tube is that of the invariable proportions of the con- 
 stituents in any chemical compound. Whether we find the 
 composition of water by analysis or by synthesis ; whether 
 we operate upon water from the clouds, from the spring, or 
 from any other source, — we find it to consist of the same 
 elements, and in the same proportions by weight or vohimc 
 The same may be said of every other known compound. 
 The law states, that — 
 
 The same compound is always made up of the same con- 
 stituents, combined in the same definite proportions. This is 
 known as the law of "definite" or of "constant propor- 
 tions." 
 
 25. Composition of Hydrochloric Acid. — We may 
 
 study the combination of hydrogen and chlorine by experi- 
 ment, and determine their constant proportions in hydrochloric 
 acid. 
 
 The Experiment. — Let us provide a small cistern, partly 
 full of a strong solution of common salt. Let us fill two 
 graduated tubes (Fig. 18) also with this brine, and invert 
 them in the cistern. Into one of these we may pass up 20 
 cubic centimeters of hydrogen and 40 cubic centimeters of 
 chlorine. Into the other we will pass 20 cubic centimeters 
 of chlorine and 40 cubic centimeters of hydrogen. All this 
 
30 
 
 CHEMISTEY. 
 
 having been done quickly, we at once place the whole appa- 
 ratus for five minutes in direct sunlight. Now, chlorine is 
 a greenish-yellow gas, which will extinguish the flame of a 
 match ; while hydrogen is a colorless gas, which takes fire 
 
 instantly on contact with the 
 flame. 
 
 Finally it will be seen that 
 only 20 cubic centimeters of 
 gas remain in each tube. 
 That in the first tube is 
 greenish-yellow, and if tested 
 will extinguish a flame : it is 
 chlorine. That in the second 
 tube is colorless, and if tested 
 will take fire : it is hydrogen. 
 The Result by Volume. 
 — The 20 cubic centimeters 
 of hydrogen in the first, com- 
 bined with 20 cubic centi- 
 meters of chlorine. The 20 
 cubic centimeters of chlorine 
 in the second, combined with 
 20 cubic centimeters of hydrogen. The proportions by vol- 
 ume, in both cases, are 1:1. We can not make these two 
 gases combine in any other proportions. The composition 
 of hydrochloric acid is, invariably, hydrogen and chlorine in 
 equal volumes. 
 
 The Result by Weight. — Now, the weights of equal 
 volumes of these gases are as 1 to 35.5 : hence the composi- 
 tion of hydrochloric acid by weight is 1 of hydrogen to 35.5 
 of chlorine. These proportions are invariable. 
 
 Hydrochloric acid always consists of these same elements, 
 combined in these same proportions. 
 
 Fig. 18. 
 
 26. Combining Weights. — So definite and constant are 
 the weights of the elements in combination, that a number 
 
CHEMISTET. 31 
 
 is attached to each, which is called its Combining Weight. 
 It represents the smallest relative proportion, by weight, in 
 which the element can unite with others to form compounds. 
 For example, it is found that any given weight of hydrogen 
 must have at least 
 
 36.5 times as much chlorine to form a compound. 
 80 " " bromine " " 
 
 127 " " iodine " " 
 
 These numbers are the combining weights of chlorine, 
 bromine, and iodine, because they are the weights of the 
 smallest quantities of these elements which can combine with 
 a unit weight of hydrogen. 
 
 Again, if we examine some other compounds of chlorine, 
 we find that 
 
 !39 of potassium, 
 23 of sodium, 
 108 of silver. 
 
 These numbers are the combining weights of potassium, 
 sodium, and silver, because they are the smallest relative 
 quantities of these elements which can enter into combina- 
 tion. 
 
 The Unit of Combining Weights. — Hydrogen is the 
 standard of comparison for combining weights. Any given 
 weight of hydrogen may be regarded as the unit. -35.5 
 times that is the smallest weight of chlorine, and 108 times 
 that weight is the smallest weight of silver, which can com- 
 bine without excess of either. Thus every element has a 
 numerical value in chemical change. These combining 
 weights are to be found in the table of elements on p. 53. 
 
 27. The Law of Multiple Proportions. — Each ele- 
 ment has but one combining weight, and yet the same two 
 elements may form more than a single compound. 
 
 Some Facts. — Of oxygen and nitrogen, for example, no 
 less than five compounds are known to exist. Examine their 
 composition, and another law will be brought to light. 
 
32 CHEMISTRY, 
 
 (1) (2) (3) (4) (5) 
 Nitrogen 28 14 28 14 28 
 Oxygen 16 16 48 32 80 
 
 Now 16 is the combining weight of oxygen ; and we find 
 in this series that when the quantity of oxygen is not 16 it 
 is some multiple of 16. 
 
 Again, 14 is the combining weight of nitrogen ; and we 
 also find, that when the quantity of nitrogen is not 14 it is a 
 multiple of 14. 
 
 The Law. — This illustrates the law, that if one element 
 unites with another, in more than one proportion, these pro- 
 poHions will all be multiples of its combining weight. 
 
 If we attempt to combine these elements in any other pro- 
 portions, the result will be that all of one of them will be 
 used up to form one or more of these five compounds, while 
 the excess of the other will be left uncombined. 
 
 28. The Combining Weight of a Compound. — A 
 
 compound must contain the same quantity of matter as its 
 constituents : this follows from the indestructibility of mat- 
 ter. "Water contains two parts of hydrogen and sixteen 
 parts of oxygen. Its numerical value must therefore be 
 16-}- 2 = 18. Moreover, water combines with many other 
 substances, and its combining weight is found to be 18. 
 
 This illustrates the law, that the combining weight of a 
 compound is the sum of the combining proportions of its 
 constituents. 
 
 Combining Proportions. — It is important to notice that 
 the term "combining proportion," just now used, does not 
 mean combining weight in all cases. The combining weight 
 of hydrogen is 1 : the quantity which combines with 16 of 
 oxygen, however, is 2 ; and it is this which enters into the 
 combining weight of water. "We have applied the term 
 " combining weight" to the smallest proportion of any sub- 
 stance which may enter into combination : we apply the term 
 "combining proportion" to the relative weight actually 
 
CHEMISTRY. 33 
 
 existing in the compound. Thus the combining weight of 
 oxygen is 16 : its combining proportion is sometimes 16, and 
 sometimes 32 or 48 or 80, or some other multiple of 16. 
 
 2^. Dalton's Theory. — John Dalton, in the year 1808, 
 declared his belief that the combining weights of the ele- 
 ments are simply the relative weights of the very smallest 
 particles of them which can enter into chemical action. 
 
 We may divide a body into a multitude of pieces. Indeed, 
 we may grind it to the finest dust, and it may seem that there 
 is no end to its divisibility. But Dalton's theory assumes 
 that there is a point beyond which we can not carry the divis- 
 ion, and that when we reach this point we have minute 
 particles whose weights are not alike in different elements. 
 These ultimate particles of the elements are called Atoms. 
 The chemist defines the atom to be the smallest portion of an 
 element which can take part in a chemical action. 
 
 According to this theory, an atom of oxygen weighs sixteen 
 times as much as an atom of hydrogen ; and, in the same 
 way, the combining weights of chlorine, sodium, silver, and 
 of other elements, tell us how njany times the atoms of these 
 bodies are heavier than an atom of hydrogen. Hence the 
 terms ' ' combining weights ' ' and ' ' atomic weights ' ' mean 
 the same thing. 
 
 Dalton's theory assumes also that chemical action is an 
 action among atoms, that chemical attraction acts upon the 
 atoms of elements, and brings them together to produce the 
 compound. 
 
 This theory is known as the Atoshc Theokt. 
 
 Keasou for Accepting- this Theory. — The atomic 
 theory is generally believed ; for, while .it is impossible to get 
 at these atoms to weigh them separately, to handle them, or 
 to see them, still it seems impossible to discover any good 
 reason for the laws of combination, unless they do exist. On 
 the other hand, if we admit the existence of atoms, it is per- 
 fectly clear that the weights of the elements in a compound 
 
34 CHEMISTRY. 
 
 must be definite and constant. That theory in science is 
 accepted, wliich gives a clear and complete explanation of all 
 the facts which it embraces. This the atomic theory seems 
 to do, and this is the evidence of its truth. 
 
 30. The Molecule. — When hydrogen and chlorine com- 
 bine to form hydrochloric acid, each atom of chlorine seizes 
 an atom of hydrogen. In a tube full of the compound, we 
 have simply a multitude of these pairs of atoms. The 
 smallest quantity of hydrochloric acid which can be, must, 
 according to this theory, consist of these two atoms. So, 
 common salt is a compound of chlorine and sodium, and the 
 smallest piece of it which can exist as salt, must contain two 
 atoms, one of chlorine and one of sodium. These ultimate 
 particles of a compound are called Molecules. 
 
 It is believed that the atoms of the elements, also, when 
 they are in the free state, that is, not in combination, are 
 linked together in groups, generally of two ; and so the 
 chemist defines the molecule to be the smallest particle of an 
 element or compound which can exist in the free state. 
 
 31. Combination by VoUinie. — We have learned al- 
 ready that it is more easy to measure gases than to weigh 
 them. But the question arises. How much by volume of the 
 gases must be taken in order to produce compounds without 
 leaving any part of either constituent uncombined? This 
 question is answered by the law of Gay Lussac, discovered 
 by him in 1808. It states that " the weights of the combining 
 volumes of the gaseous elements hear a simple relation to their 
 atomic weights." 
 
 To find this Relation. — This simple relation is found 
 by the balance. By weighing equal volumes of these ele- 
 ments it is found that — 
 1 liter of oxygen weighs 16 times as much as a liter of hydi-or 
 
 gen. 
 1 liter of nitrogen weighs 14 times as much as a liter cf 
 
 hydrogen. 
 
CHEMISTRY. 36 
 
 1 liter of chlorine weighs 35.5 times as much as a liter of 
 
 hydrogen. 
 
 Here we see that these weights of equal volumes are the 
 same as the atomic weights of the elements. This is true of, 
 nearly all the elements when in the form of gas or vapor. 
 
 If, then, we bring such elements together in equal volumes, 
 or in some multiple of the equal volume, it will be the same in 
 effect as bringing them together in the proportions of their 
 combining weights or in some multiple of their combining 
 weights : no excess of either can remain after combination 
 has taken place. 
 
 Tlxe Volume of the Compound. — Experiments show 
 further that the simple relation extends to the volume of the 
 compound also. The following are some of the results of 
 exact experiment : — 
 
 1 vol. chlorine and 1 vol. hydrogen form 2 vols, hydrochloric acid. 
 1 vol. bromine and 1 vol. hydrogen form 2 vols, hydrobromic acid. 
 1 vol. iodine and 1 vol. hydrogen form 2 vols, hydriodic acid. 
 1 vol. oxygen and 2 vols, hydrogen form 2 vols, steam. 
 1 vol. nitrogen and 3 vols, hydrogen form 2 vols, ammonia. 
 
 "We here find that two volumes of the compound are 
 formed in every case ; and we discover the curious fact, that, 
 whether the sum of the constituent volumes be 2 or 3 or 4, 
 the volume of the compound is only 2. It is found in other 
 cases also, that, wlmtever the number of volumes which enter 
 into combination, the volume of the resulting compound 
 is 2. 
 
 Avogadro's Fiaw. — The simplest explanation we can 
 find of these facts is based upon two assumptions, viz. : — 
 
 Every molecule of each of these elementary gases contains 
 two atoms. 
 
 Equal volumes of all gases, simple and compound, contain 
 an equal number of molecules. 
 
 Let us study the case of steam in the above table, remem- 
 bering that, according to the atomic theory, two atoms of hy- 
 drogen and one atom of oxygen form one molecule of steam. 
 
36 CHEMISTRY. 
 
 If each molecule of oxygen contains two atoms of oxygen, 
 and only one is needed in a molecule of steam, there will be 
 just twice as many molecules of steam produced as there are 
 of oxygen required to form it. And then if equal volumes of 
 steam and oxygen contain the same number of molecules, 
 twice as many molecules of" steam must fill just twice the 
 volume of the oxygen. Hence the combination of one vol- 
 ume of oxygen with sufficient hydrogen must produce two 
 volumes of steam. The same kind of reasoning explains all 
 other cases, and hence it is believed that the assumptions on 
 which the explanations are founded are true. 
 
 The supposition that " Equal volumes of all gases, simple 
 and compound, contain equal numbers of molecules," was first 
 made by Avogadro in 1811. It is known Ss Avogadr&'s 
 Law, and is generally accepted, both in chemistry and in 
 physics. 
 
 REVIEW. 
 
 I. — SUMMARY OP PRINCIPLES. 
 
 32. Chemical changes occur in obedience to certain laws, 
 known as the laws of combination. 
 
 The " Law of Constant Proportions " states that the same 
 compound is always made up of the same constituents, com- 
 bined in the same definite proportions by weight. 
 
 Water always consists of hydrogen and oxygen in the 
 proportions, by weight, of two of hydrogen and sixteen of 
 oxygen. 
 
 Hydrochloric acid always consists of hydrogen and 
 chlorine, in the proportions, by weight, of one of hydrogen 
 to 35.5 of chlorine. 
 
 The combining weights of substances are the smallest 
 relative proportions, by weight, in which they enter into 
 combination. 
 
 Hydrogen is the standard of combining weights ; any given 
 weight of this gas may be considered the Unit. 
 
CHEMISTRY. 37 
 
 The "Law of Multiple Proportions " states, that if one 
 substance unites with another, in more than one proportion, 
 these proportions are all multiples of its combining weight. 
 
 The combining weight of a compound is the sum of the 
 combining proportions of its constituents. 
 
 The combining weight of water is eighteen, of hydro- 
 chloric acid 36.5. 
 
 These laws of combination have been established by 
 experiment. Our knowledge of them is quite independent of 
 any theory. Still the theory proposed by Dalton does explain 
 them. 
 
 This "Atomic Theory" assumes that every element con- 
 sists of Atoms, or minute particles, the smallest that can 
 take part in any chemical action. It assumes further, that 
 any compound is formed by the union of the atoms of its 
 elements, and that the combining weights of the elements 
 are the relative weights of their atoms. 
 
 A Molecule is the smallest particle of an element, or of 
 a compound, which can exist in the free state. 
 
 Chemical change consists in the breaking up of old mole- 
 cules, and the re- arrangement of their atoms to form new 
 ones. 
 
 A molecule of hydrochloric acid contains one atom of 
 hydrogen and one of chlorine. A molecule of water con- 
 tains two atoms of hydrogen and one of oxygen. A mole- 
 cule of ammonia contains four atoms, three of hydrogen and 
 one of nitrogen. 
 
 A molecule of an element generally contains two atoms. 
 
 Combining volumes are the relative proportions by volume 
 m which gaseous er volatile substances unite. 
 
 The weights of the combining volumes of the elementary 
 gases bear a simple ratio to their atomic weights. This is 
 Gay Lussac's Law. 
 
 Equal volumes of all gases, elementary or compound, at 
 the same temperature and pressure, contain an equal number 
 of molecules. This is Avogadro's Law. 
 
38 CHEMISTRY. 
 
 According to this law, the molecules of all gases or vapors 
 are of the same size. That is, the molecular volumes of all 
 gases, elementary or compound, are equal : the numerical 
 value is two. 
 
 Combining volume, combining or atomic weight, specific 
 gravity, and molecular weight, are all referred to hydrogen 
 as a standard of comparison. 
 
 Let us represent the names of a few elements by their 
 initial letters, and under each put its numerical values. We 
 
 shall huve 
 
 H O N P Hg. 
 
 1—1—1— -J- 2= combining vols. 
 
 Weights of these = 1 — 16 — 14 — 31 — 200=atomic weights. 
 
 Weights of equal vols. = 1 — 16 — 14 — 62 — 100=specific gravities. 
 Mol. of H = 2 atoms 2 — 32 — 28 — 124 — 200= molecular weights. 
 
 2—2—2— 2— 2=molecular vols. 
 
 From that we discover that — 
 
 Atomic weight =' specific gravity x combining volume : 
 
 Molecular weight = 2 x specific gravity. 
 
 II.— EXERCISES. 
 
 What is the composition of water? What is the compo- 
 sition of hydrochloric acid, by volume? By weight? Is 
 it always the same ? Is the same thing true of other sub- 
 stances ? State the law of constant proportions. 
 
 Define combining weight. What is the unit of measure 
 for combining weights ? The combining weight of chlorine 
 is 35.5 : what is meant by this statement? 
 
 Ten grams of hydrogen will require how much chlorine to 
 convert it all into hydrochloric acid ? 
 
 What would be the result if ten grams hydrogen, mixed 
 with 360 grams chlorine, are exposed to sunlight? 
 
 If 100 cubic centimeters of oxygen are mixed with 100 
 cubic centimeters of hydrogen, what will remain after pass- 
 ing the electric spark through the mixture ? 
 
 If 100 grams of oxygen are to be converted into water, 
 how much hydrogen must be used ? 
 
CHEMISTKY. 39 
 
 How many compounds of oxygen and nitrogen are known? 
 What law do their compositions illustrate? State this " law 
 of multiple proportions." 
 
 "What is the combining weight of water? State the law 
 which this illustrates. 
 
 Define atom. Define molecule. What is the atomic 
 theory ? On what ground is the atomic theory accepted ? 
 
 State Gay Lussac's Law. Compare the weights of one 
 liter of each, — oxygen, nitrogen, and hydrogen. What 
 relation between these weights and the atomic weights of 
 these elements? Define combining volume. What is the 
 combining volume of a gaseous or volatile compound ? 
 
 State Avogadro's Law. 
 
 How much oxygen is required to unite with 10 liters of 
 hydrogen ? 
 
 How many liters of water-vapor will be formed by the 
 union of 2,000 cubic centimeters of hydrogen and 1,000 cubic 
 centimeters of oxygen ? 
 
 Are the combining volumes of the elements the relative 
 volumes of their atoms, or of their molecules ? 
 
 SECTION VI. 
 
 CHEMICAL NOTATION AND NOMBNCLATUEE. 
 
 33. Symbols. — Instead of writing the names of elements 
 in full, chemists have agreed to use a set of symbols to rep- 
 resent them. These symbols are the capital initial letters of 
 the names (often of the Latin names) , or, in case two ele- 
 ments have the same initial, this capital with a small letter 
 added. Thus O stands for oxygen ; N for nitrogen ; H for 
 hydrogen. Of carbon, cobalt, and copper (Latin cuprum)^ 
 the symbols are C, Co, and Cu. The symbol not only repre- 
 sents the name of the element: it also represents just one 
 atom of it. The symbols of all the elements are given in the 
 table on p. 53. 
 
40 CHEMISTRY. 
 
 34. Formulas of Compounds. — Instead of writing the 
 names of compound bodies in full, a system of formulas has 
 been adopted. The formula of a compound is made up of 
 the symbols of its constituents, with figures placed a little 
 below to show the number of combining weights. Instead 
 of writing the statement that water consists of hydrogen and 
 oxygen, two combining weights of the one to one of the 
 other, we may with less trouble write the formula, H2 O, 
 which teaches the same thing. That nitric acid consists of 
 one part of hydrogen, one of nitrogen, and three of oxygen, 
 is shown by the simple expression, H N O3. When no 
 figure is used, one is understood. The formula not only 
 represents the name : it also represents just one molecule of 
 the compound. 
 
 TVliat they teach. — These formulas contain much valu- 
 able information about the compounds they represent. 
 
 They teach : — 
 
 1st, The names of the constituents, by the letters they 
 contain. 
 
 2d, The number of combining weights of each, by the 
 figures they contain. 
 
 3d, The number of combining volumes of gaseous or 
 volatile constituents, also by the figures they contain. 
 
 4th, The combining proportion of each, for this is equal 
 to the combining weight multiplied by the figures used. 
 
 5th, The number of atoms of each element in the molecule 
 of the compound. 
 
 Illustration. — The formula of potassium chlorate, for 
 example, is K CI O3, and it answers all of the following 
 questions : — 
 
 1st, What are the constituents of this compound? Potas- 
 sium, chlorine, and oxygen. 
 
 2d, How many combining weights of each? One of 
 potassium, one of chlorine, three of oxygen 
 
 3d, How many volumes of each? One of potassium, one 
 of chlorine, three of oxygen. 
 
CHEMISTRY. 
 
 41 
 
 4th, What combining proportion of each? K = 39.1, 
 CI = 35.5, = 48. 
 
 . 5th, How many atoms in one of its molecules ? One of 
 potassium, one of chlorine, and three of oxygen. 
 
 CHEMICAL NOMENCLATURE. 
 
 35. The Nomenclature. — Not until the year 1787 was 
 any attempt made to reduce the language of chemistry to a 
 system. But the number of compounds to be described 
 increased to such an extent that even the strongest memory 
 could not hope to keep their meaningless names. To avoid 
 this diflaculty, a system was proposed by Lavoisier, by which 
 the name of a substance should indicate its composition. 
 The simplicity of the system, and the accuracy with which it 
 expressed chemical theories, secured its universal adoption ; 
 but the theories themselves having now, in great part, been 
 rejected, new names have been introduced, and it can not 
 yet be said that the system is permanent. Nevertheless, 
 certain specific rules are observed. The object is to make 
 the name of a com- 
 pound show what ele- 
 ments it is composed 
 of, and, as nearly as 
 may be, also the rela- 
 tive proportions in ^5" 
 which they are present. 
 
 36. Binary Com- 
 pounds. — When only 
 two elements unite, 
 they form what is called 
 a Binary Compound. 
 Among the most nu- 
 merous and important are the binary compounds of oxygen. 
 
 For example, let a piece of magnesium, which can be had 
 in the form of wire or ribbon, be held in a' pair of forceps, 
 
42 CHEMISTEY. 
 
 while the other end is heated in the flame of a lamp. The 
 metal first becomes red-hot, and then takes fire (Fig. 19). 
 It burns with a vivid light, and throws off large volumes of - 
 white smoke. This white smoke is the compound of oxygen 
 with magnesium. It is called JVIagnesidm Oxide. 
 
 In like manner all the binary compounds of oxygen are 
 called Oxides, while the other part of the name signifies the 
 element with which the oxygen is united. 
 
 Prefixes. — It often happens that oxygen fonns several 
 binaries with the same other element, by combining in mul- 
 tiple proportions. This is true with the metal manganese. 
 Three distinct oxides of manganese are known. Their 
 formulas are : — 
 
 MnO . . 
 
 . 1 atom of in the molecule, 
 
 Mn O2 . . 
 
 . 2 atoms " " " 
 
 Muj O3 . . 
 
 3 (; (( (( a 
 
 To show that one atom of oxygen is present in the mole- 
 cule, the first is called manganese monoxide. The two 
 atoms of oxygen in the second are indicated by the name 
 manganese dioxide ; while the proportions three to two atoms 
 in the molecule of the third are shown by the name mangan- 
 ese sesquioside. 
 
 In general, we may say that the number of combining 
 weights, or of atoms, in the molecule, is shown by a prefix to 
 that part of the name which represents the element. 
 
 The prefix mon may be omitted ; the term ooeide alone 
 indicating the monoxide. And often the prefix jjee is given 
 in the name of the oxide which has the largest proportion of 
 oxygen, without regard to the number of atoms. 
 
 Terminations. — In case the same element forms two 
 oxides, it is customary to use the terminations ic and ous in 
 naming them. Thus sulphur and oxygen form 
 
 S Oj .... sulphuric oxide. 
 S Og .... sulphurous oxide. 
 
CHEMISTRY. 
 
 48 
 
 And the two compounds of mercury and Oxygen are called 
 mercuric oxide, Hg 0, and mercurous oxide, Hga 0. 
 
 Still these same substances may be named by the use of 
 prefixes ; and then, in the case of sulphur; we have, for the 
 first, sulphur trioxide, and, for the second, sulphur dioxide. 
 In very many other cases, also, the same compound may 
 have two or more different names. 
 
 Other Binary Compounds. — The very same rules for 
 naming these oxygen compounds apply to the naming of the 
 binaries of many other elements, such as chlorine and 
 sulphur. Thus, for example : — 
 
 Compounds of are called such as formula 
 
 Chlorine, chlorides, sodium chloride, Na CI. 
 
 Bromine, bromides, potassium bromide, K Br. 
 
 Iodine, iodides, lead iodide, Pb I^. 
 
 Sulphur, sulphides, iron sulphide, Fe S. 
 
 The same prefixes, and the terminations ic and ous, are 
 used for exactly the same purposes in naming these as in 
 naming the oxides. 
 
 37. Acids, and their Composition. — If we place a 
 piece of diy phosphorus upon a 
 little support, resting on a dry 
 plate, touch it with a hot wire, and 
 quickly invert over it a dry bell- jar 
 (Fig. 20), the burning phosphorus 
 will throw off large volumes of milli- 
 white vapors, much of which will 
 finally condense into snow-like flakes 
 upon the sides of the glass. 
 
 In this experiment the oxygen 
 of the air, and the phosphorus, 
 unite to form the new white sub- 
 stance, — the phosphorous pentox- 
 ide, whose formula is Pj O5 — a binary compound. 
 
 Next, let the jar be lifted, and a little water poured into it. 
 
 Fig. 20. 
 
44 CHEMISTRY. 
 
 The water combines with the white oxide, which disappears 
 with a hissing sound. The fluid becomes intensely sour to 
 the taste; and if a little of this solution be added to a 
 solution of blue litmus, the blw color will be instantly changed 
 to red. 
 
 This power to redden blue litmus, or other vegetable colors, 
 is characteristic of an all-important class of compounds 
 called Acids. The water and the oxide combined to form 
 Phosphoric Acid. 
 
 Composition of Acids. — The composition of this phos- 
 phoric acid is shown by its formula : H3 P O4. Its molecule 
 contains three atoms of hydrogen, one of phosphorus, and 
 four of oxygen. Below are the formulas of several other 
 acids for inspection : — 
 
 Sulphurous acid, H2 S O3. Hydrochloric acid, H CI. 
 
 Sulphuric acid, Hj S Oji Hydrobromic acid, H Br. 
 
 Nitric acid, H N O3. Hydriodic acid, H I. 
 
 Carbonic acid, H2 C O3. Hydrosulphuric acid, Hj S. 
 
 A glance at these formulas reveals the fact that hydrogen 
 is a constituent in every one of these acids. 
 
 From all these facts we may gather this description : viz., 
 an add is a hydrogen compound, which is generally sour to 
 the taste, and which will redden vegetable colors. 
 
 They are of Two Classes. — Another glance at the above 
 formulas reveals the fact that some acids contain oxygen, 
 and that others do not. Those which contain oxygen are 
 called Oxygen Acids, or Oxacids ; while those which do not 
 are called Hydeacids. The oxygen acids comprise far the 
 larger number of this class of bodies. 
 
 38. Names of the Oxygen Acids. — The terminations 
 «c and ous are used in the names of the oxygen acids, signi- 
 'ying the same thing as when used in the names of binaries. 
 That is, the ic indicates the larger proportion of oxygen in 
 the moleculo. Thus, for example, H N O3 is nitric acid, 
 
CHEMISTRY. 45 
 
 while H N O2 is nitrous acid. Two acids of sulphur are 
 distinguished in the same way. 
 
 The prefix hypo is also used, and always means tess. 
 HypomiTOMs acid, for example, is one which contains a still 
 smaller proportion of oxygen than the nitrous acid: its 
 formula is H N O. The prefix per is also sometimes used 
 to form the name of the acid which contains the largest pro- 
 portion of oxygen. 
 
 Names of the Hydracids. — The names of the hydra- 
 cids also end in ic, but they' are especially characterized by 
 the prefix hydro. Find this prefix in the names^ of acids in 
 the list already given. These four are the most important 
 acids of this class, and the name shows the constituents in 
 each. 
 
 The hydrogen acids are really binary compounds, and we 
 may name them as such if we choose. Instead of hydro- 
 chloric acid, we may speak of H CI as hydric chloride. 
 
 ^ 39. Salts. — Notice the following experiment. Into a 
 bottle put a few clippings of zinc, and upon them pour s„ 
 quantity of hydrochloric acid. A vigorous boiling quicklj 
 begins ; hydrogen gas escapes, and may be set on fire with 
 a match ; the zinc slowly disappears, and finally a quiet liquid 
 remains, which would be quite clear but for some, black 
 residue from the impurities of the zinc employed. By 
 evaporating the clear liquid we may obtain a white solid : 
 this proves to be zinc chloride. 
 
 The explanation is this : The zinc has decomposed the rtcid, 
 taking the place of the hydrogen which was in combination 
 with the chlorine. Before the action we had hydric chloride 
 and zinc : after the action we have zinc chloride and hy- 
 drogen. 
 
 Atoms of zinc take the place of atoms of hydrogen in the 
 molecules of the acid. This zinc chloride is not only a binary 
 compound : it is also called a Salt. If sodium takes the 
 place of hydrogen in the same acid, the salt, sodium chloride 
 (.common salt) , is formed. 
 
46 
 
 CHEMISTRY. 
 
 Again : if the two combining weights of hydrogen in 
 sulphuric acid are both replaced by sodium, a salt, sodium 
 sulphate, will be formed ; or, if only one of them is replaced 
 by sodium, the remaining compound is still a salt. From 
 these illustrations we gather this description : A salt is a 
 compound formed by substituting a metal for either the whole 
 or a part of the hydrogen in an acid. 
 
 40. Names of Salts. — The salts formed from hydracids 
 are named by the method already given for neutral binary 
 compounds. These salts were formerly called haloid salts. 
 
 Kanies of Oxy-Salts. — Of salts formed from oxacids, 
 the name is made by changing the ending of the name of 
 the acid from which they are derived, from ic to ate, or from 
 ous to ite. 
 
 A few examples will make this method clear. 
 
 Salts from 
 Sulphuric acid. 
 Sulphurous acid, 
 Nitric acid, 
 Nitrous acid, 
 Chloric acid, 
 Chlorous acid, 
 Hypochlorous acid, 
 
 sulphates, 
 
 sulphites, 
 
 nitrates, 
 
 nitrites, 
 
 chlorates, 
 
 chlorites, 
 
 hypochlorites. 
 
 such as 
 sodium sulphate, 
 sodium sulphite, 
 potassium nitrate, 
 potassium nitrite, 
 potassium chlorate, 
 sodium chlorite, 
 sodium hypochlorite. 
 
 In case only a part of the hydrogen of the acid is dis- 
 placed, the presence of the remainder is indicated in the 
 name by the prefix hydro. When, for example, all the 
 hydrogen of sulphuric acid Hj S 0^ is replaced by sodium, 
 the salt Na2 S O4 is called sodium sulphate ; but, if only one 
 of the two combining weights of hydrogen is displaced, the 
 presence of the metal and of the remaining hydrogen is 
 shown by the name hydro-sodium sulphate H Na S O4. 
 
 In the same way potassium and sulphuric acid may form 
 either potassium sulphate or hydro-potassium sulphate. 
 
 The acids are sometimes called Hydrogen Salts. Just 
 
OHEMISTBY. 
 
 47 
 
 as K N O3 is called potassium nitrate, so H N O3 may be 
 called hydrogen nitrate instead of nitric acid. 
 
 41. Bases. — Let a small piece of the metal potassium 
 be dropped upon the surface of water : it instantly takes Are 
 (Fig. 21), runs swiftly about over the 
 surface of the water, until finally it is 
 all wasted away. If now we prepare 
 some reddened litmus, by adding to blue 
 litmus a few drops of acid, and after- 
 ward add some of the water on which 
 the potassium burned, we find that the 
 blue color of the litmus is quickly re- 
 stored. 
 
 /^The power to neutralize an acid, 
 shown by the restoration of the blue 
 color to reddened litmus,' is characteristic of another large 
 and important class of compounds. They are called BasesJ7 
 
 Hydrates. — This whole class of bodies also receives the 
 name of Hydrates. A hydrate is a compound of hydrogen 
 and oxygen, with a third element, usually a metal. It is 
 often caustic to the taste, and restores the blue color of 
 reddened litmus. A hydrate receives the name of the metal 
 which it contains. We have, accordingly, sodium hydrate, 
 Na H O ; potassium hydrate, K H O ; silver hydrate, Ag H O ; 
 and lead hydrate, Pb Hj O2, or, as it is oftener written, 
 Pb (HO)s,. 
 
 Fig. 21. 
 
 REVIEW. 
 
 I. —SUMMARY OF PRINCIPLES. 
 
 42. The symbol of an element is the capital initial of its 
 name, sometimes accompanied by a small letter ; as, C for 
 carbon, and Co for cobalt. 
 
 The symbol represents not only the name, but also a single 
 atom, of the element. 
 
48 CHEMISTET. 
 
 The formula of a compound consists of the symbols of its 
 elements, with small figures J»ttached, to show the number of 
 combining weights of each. 
 
 The formula represents a single molecule of the compound. 
 
 Among the many classes of compounds are binaries, acids, 
 salts, and hydrates. 
 
 The name of a binary compound is known by its terminat- 
 ing in ide. Besides this its name combines the names of 
 both constituents, and prefixes are used to show how many 
 atoms of the constituents are present. 
 
 Acids are hydrogen compounds, which are sour, which are 
 able to redden vegetable colors, and which will exchange 
 hydrogen for a metal in chemical action. 
 
 Acids are called oxacids if they contain oxygen, and 
 hydracids if they do not. 
 
 The oxacids are named after the element which is com- 
 bined with their hydrogen and oxygen, the terminations k 
 and ous being used to indicate larger and smaller proportions 
 of oxygen. The prefix hyiM is also used to indicate a smaller 
 proportion of os.ygen, and per to show a larger proportion 
 of the same element. 
 
 The prefix hydro characterizes the name of a hydracid. 
 These acids may also be named as if they were simply binary 
 compounds. 
 
 Salts are described as substances which may be produced 
 by substituting atoms of metal for atoms of hydrogen in an 
 acid. 
 
 They are named after the acids from which they are 
 derived, by changing the ending of the name of the acid 
 from ic to ate, and from ous to ite. The name of the metal 
 is then prefixed. 
 
 Acids are sometimes regarded as hydrogen salts, and are 
 named as such. Instead of sulphuric acid, we may use the 
 name hydrogen sulphate. 
 
 Hydrates or Bases are described as compounds of hydro- 
 gen and oxygen with a metal having the power to neutralize 
 
CHEMISTRY. 49 
 
 an acid. They are usually caustic to the taste, and restore 
 the blue color of reddened litmus. 
 
 The hydrates are named after the metals which they 
 contain. 
 
 II. —EXERCISES. 
 
 Define symbol. Formula. 
 
 How much of an element does a symbol represent? 
 
 How much of a compound does a formula represent? 
 
 How many atoms in a molecule of alcohol, its formula 
 being Ca He O? 
 
 What is the symbol of Hydrogen? Oxygen? Nitrogen? 
 
 How would you represent a molecule of each ? 
 
 Define binary compound. 
 
 What are oxides ? How is any oxide named ? 
 
 What is a Monoxide ? A Dioxide ? A Trioxide ? A Ses- 
 quioxide ? A Peroxide ? 
 
 For what purpose are the terminations ic and ous used ? 
 
 What are Iodides ? Chlorides ? Bromides ? Sulphides ? 
 
 Mercury combines with oxygen ; what shall we call the 
 compound ? Ans. Mercuric oxide. 
 
 But there is another oxide of this metal, containing a less 
 proportion of oxygen ; what shall it be named ? 
 
 What are the elements of cupric oxide? 
 
 What are the elements of cuprous oxide ? 
 
 What are the elements and their proportions in chromium 
 trioxide ? 
 
 Name the compound of potassium and iodine. 
 
 Name the compound of lead and sulphur. 
 
 Name the compound of lead and iodine. 
 
 Name the compound of copper and chlorine. 
 
 What are the elements in arsenic sulphide ? 
 
 What are the elements in zinc sulphide? 
 
 What is the difference between cupric chloride and cuprous 
 chloride ? 
 
 What is an acid ? Name and distinguish the two classes. 
 
50 CHEMISTRY. 
 
 What terminations are used in naming the oxygen acids? 
 What do they indicate ? 
 
 What prefixes are used? What do they indicate? 
 
 What are the constituents of phosphoric acid? 
 
 Ans. Hydrogen, oxygen, and phosphorus. 
 
 By what part of the name is each one of these elements 
 suggested ? 
 
 What are the constituents of bromic acid? 
 
 Name the elements in sulphurous acid. 
 
 Name the elements in hyposulphurous acid. 
 
 What difference in the composition of the last two acids 
 named, is indicated by their names? 
 
 What difference in composition is indicated by the names 
 iodic acid and per-iodic acid? 
 
 What acid will be formed by the union of hydrogen, oxy- 
 gen, and bromine? 
 
 Name the acid which contains oxygen, manganese, and 
 hydrogen. Ans. Manganic acid. 
 
 AVhat other acid with the same elements, but with a larger 
 proportion of oxygen? 
 
 What are the elements in hydrofluoric acid? 
 
 Name the elements in hydriodic acid. 
 
 Name the elements in hydrosulphuric acid. 
 
 What is the difference in composition of hydrosulphuric 
 acid and sulphuric acid? 
 
 Name the acid compound of hydrogen and iodine. 
 
 What is a salt ? Haloid salts ? What are oxy-salts ? 
 
 How are the haloid salts named ? 
 
 How are the oxy-salts named ? 
 
 Name the salt from nitric acid and potassium. 
 
 Name the salt from copper and sulphuric acid. 
 
 Name the salt from hypochlorous acid and sodium. 
 
 Name the acid and tue metal from which calcium carbon- 
 ate may be derived. 
 
 Name the acid and the metal from which calcium hypo- 
 sulphite maj- be derived. 
 
CHEMISTRY. 51 
 
 What are the elements in ferrous sulphate? 
 
 What are the elements in barium sulphite ? 
 
 Of what elements is magnesium carbonate composed ? 
 
 What acid is required with copper to form copper nitrite r 
 
 What are the constituents of potassium chlorate ? 
 
 Name the metal in the aluminium silicate. 
 
 Name the metal and the acid in magnesium citrate. 
 
 Name the elements in calcium phosphate. 
 
 What are the constituents of hydrogen sulphate? 
 
 What other name may be given to the same compound ? 
 
 Name nitric acid as a salt. Chloric acid. Acetic acid. 
 
 Define base. What other name is given to this class? 
 
 How are the hydrates named? 
 
 What group of atoms occurs in the molecule of every 
 hydrate? Ans. H O. 
 
 What are the elements of calcium hydrate ? 
 
 What are the elements of magnesium hydrate ? 
 
 What are the elements of copper hydrate ? 
 
 Name the elements of silver hydrate. 
 
 Name the hydrate containing barium. What other ele- 
 ments does it contain ? 
 
52 CHRMISTBY. 
 
 CHAPTER II. 
 THE NON-METALLIC ELEMENTS. 
 
 SECTION I. 
 
 GENERAL DESCRIPTION. 
 
 43. The Number of the Elements. — The elements are 
 those simple substances which, up to the present time, have 
 not been decomposed. The existence of sixty-four has been 
 established, and very recent researches seem to show that 
 the existence of six or seven more is extremely probable. 
 
 These few elements are the alphabet of chemistry. They 
 are united in pairs, or in greater numbers, to form the solid, 
 liquid, and gaseous matter of the entire globe. 
 
 Not even all of this small number are found abundantly. 
 The greater part of the whole mass of our earth is made up 
 of less than half a score of these elements, while some of 
 the others are of such rare occurrence as to be of little 
 interest except to the chemist. 
 
 44. The following table contains the sixty-four elements, 
 arranged in alphabetical order, with their symbols and atomic 
 weights, for future reference. 
 
 To the chemist in his nice researches, the most exact values 
 'of atomic weights, which it is possible to obtain, are impor- 
 tant ; to the student, and for purposes of illustration, an 
 approximate value, the nearest whole number, is usually 
 sufficient. 
 
 The exact value for sodium, for example, is 22.99, but for 
 all practical purposes the atomic weight of this element is 23. 
 
CHEMISTRY. 
 
 53 
 
 Names. 
 
 Symbols. 
 
 Atomic 
 Weight. 
 
 Names. 
 
 Symbols. 
 
 Atomic 
 Weight. 
 
 Aluminium . 
 
 Al 
 
 21.3 
 
 Mercury , . . 
 
 Hg 
 
 199.8 
 
 Antimony 
 
 Sb 
 
 122.0 
 
 Molybdenum, 
 
 Mo 
 
 95.6 
 
 Arsenic . . 
 
 As 
 
 74.9 
 
 Nickel . . . 
 
 Ni 
 
 58.6 
 
 Barium . . 
 
 Ba 
 
 136.8 
 
 Niobium . . 
 
 Nb 
 
 94.0 
 
 Beyllium . . 
 
 Be 
 
 9.0 
 
 Nitrogen . . 
 
 N 
 
 14.01 
 
 Bismutli . . 
 
 Bi 
 
 210.0 
 
 Osmium . . 
 
 Os 
 
 198.6 
 
 Boron . . . 
 
 B 
 
 11.0 
 
 Oxygen . . 
 
 O 
 
 15.96 
 
 Bromine . . 
 
 Br 
 
 79.75 
 
 Palladium 
 
 Pd 
 
 106.2 
 
 Cadmium . . 
 
 Cd 
 
 111.6 
 
 Phosphorus . 
 
 P 
 
 30.96 
 
 Cffisium . . 
 
 Cs 
 
 133.0 
 
 Platinum . . 
 
 Pt 
 
 196.7 
 
 Calcium . . 
 
 Ca 
 
 39.9 
 
 Potassium . 
 
 K 
 
 39.04 
 
 Carbon . . . 
 
 C 
 
 ll;97 
 
 Rhodium . . 
 
 Rh 
 
 104.1 
 
 Cerium. . . 
 
 Ce 
 
 141.2 
 
 Rubidium . . 
 
 Rb 
 
 85.2 
 
 » Chlorine . . 
 
 CI 
 
 35.37 
 
 Ruthenium . 
 
 Ru 
 
 103.5 
 
 Cliromium . 
 
 Cr 
 
 52.4 
 
 Selenium . . 
 
 Se 
 
 78.0 
 
 Cobalt . . . 
 
 Co 
 
 58.6 
 
 Silver . . . 
 
 Ag 
 
 107.66 
 
 Copper . . . 
 
 Cu 
 
 63.0 
 
 Silicon . . . 
 
 Si 
 
 28.0 
 
 Didymium 
 
 Di 
 
 147.0 
 
 Sodium . . 
 
 Na 
 
 22.99 
 
 Erbium . . 
 
 Er 
 
 169.0 . 
 
 Strontium . . 
 
 Sr 
 
 87.2 
 
 Fluorine . . 
 
 F 
 
 19.1 
 
 Sulphur . . 
 
 S 
 
 31.98 
 
 Gallium . . 
 
 Ga 
 
 ■ t * . 
 
 Tantalum . . 
 
 Ta 
 
 182.0 ■ 
 
 Gold . . . 
 
 Au 
 
 196.2 
 
 Tellurium 
 
 Te 
 
 128.0 
 
 Hydrogen . . 
 
 H 
 
 1.0 
 
 Thallium . . 
 
 Tl 
 
 203.6 
 
 Indium . . 
 
 In 
 
 113.4 
 
 Thorium . . 
 
 Th 
 
 231.5 
 
 Iodine . . . 
 
 I 
 
 126.53 
 
 Tin ... . 
 
 Sn 
 
 117.8 
 
 Iridium . . 
 
 Ir 
 
 196.7 
 
 Titanium . . 
 
 Ti 
 
 48.0 
 
 Irpn. . . . 
 
 Fe 
 
 55.9 
 
 Tungsten . . 
 
 W 
 
 184.0 
 
 Lanthanum . 
 
 La 
 
 139.0 
 
 Uranium . . 
 
 U 
 
 240.0 
 
 Lead . . . 
 
 Pb 
 
 206.4 
 
 Vanadium 
 
 V 
 
 51.2 
 
 Lithium . . 
 
 Li 
 
 7.01 
 
 Ytrlum. . . 
 
 Y 
 
 93.0 
 
 Magnesium . 
 
 Mg 
 
 23.94 
 
 Zinc. . . . 
 
 Zn 
 
 64.9 •- 
 
 Manganese . 
 
 Mn 
 
 54.8 
 
 Zirconium 
 
 Zr 
 
 90.0 
 
 It is well to remember that the chemist defines an element 
 to be a substance which has never yet been decomposed. He 
 does not claim to know that these sixty-four kinds of matter 
 are really the ultimate simples of material bodies. Indeed, ' 
 the science of Spectrum Analysis, in the hands of Mr. 
 Lockyer, is giving some reason for supposing that they are 
 in reality compounds of still more elementary forms. It is 
 not impossible that more powerful analyses may yet decom- 
 pose them. 
 
64 CHEMISTRY. 
 
 45. Metals and Non-Metals. — The elements are usually 
 divided into two classes, — the metals, SiUd the .non-metals or 
 metalloids. The first includes such substances as iron, gold, 
 silver, and copper ; the second, such as sulphur, oxygen, 
 nitrogen, and hydrogen. This division is purely arbitrary. 
 It is not found in nature, but is made for the convenience 
 of study. No line of division can distinctly mark the 
 separation between the metals and the non-metals. Several 
 elements, of which arsenic is one, have neither distinctly 
 metallic nor non-metallic properties. 
 
 46. Classification. — The non-metals are divided into 
 four groups. This division is founded on the relation 
 between the number of their atoms which may enter a mole- 
 cule together. This relation is seen by comparing the 
 formulas of 
 
 Hydrochloric acid . . . . CI H, 
 
 Water O H2, 
 
 Ammonia ...... N H3, 
 
 Marsh-gas C H4, 
 
 for in them we see that one atom of chlorine can hold but 
 one atom of hydrogen in the molecule, while one atom of 
 oxygen is able to hold two, one of nitrogen three, and one 
 of carbon four. 
 
 Now, an atom of chlorine is never known to combine with 
 more than one of hydrogen. We must consider it equivalent 
 to one of hydrogen. So we say that an atom of oxygen is 
 equivalent to two atoms of hydrogen, that one of nitrogen 
 is equivalent to three, and one of carbon is equivalent to four 
 of hydrogen. 
 
 To express this different equivalence, — 
 
 Chlorine is called a univalent element or a monad. 
 Oxygen " bivalent " " dyad. 
 
 Nitrogen " trivalent " " triad. 
 
 Carbon " quadrivalent" " tetrad. 
 
CHEMISTRY. SS^ 
 
 The Groups But chlorine is not the only element 
 
 whose atom is equivalent to one of hydrogen : there are 
 bromine, iodine, and fluorine besides. And these four are 
 grouped together, and called the Univalent Group of non- 
 metals. 
 
 Others are like oxygen, and with it form the Bivjv.lent 
 Group : they are sulphur, selenium, and tellurium. In the 
 same way we have the Trivalent Group, consisting oi nitro- 
 gen, phosphorus, arseijic, and boron ; and the Quadrivalent 
 Group, containing only carbon and silicon. These four 
 groups include all the non-metals. 
 
 Quantivalence. — Thus the atoms of the different ele- 
 ments have different values in chemical change. The atom 
 of hydrogen is the unit by which to measure these atomic 
 values. What is the value of a chlorine atom ? One unit, 
 because it is able to bind only one atom of hydrogen in a 
 molecule. For a similar reason, the atom of any bivalent 
 substance has a value of two units, of a trivalent substance 
 three units, and of a quadrivalent substance four units. 
 
 This atomic value of a substance is called its Quantiv- 
 alence. We accordingly say that the quantivalence of 
 chlorine is 1, that of oxygen 2, of carbon 4. And we may 
 define quantivalence to be the combining power of a sub- 
 stance as measured by the number of hydrogen atoms, or 
 their equivalent, which one of its atoms can bind together in 
 a molecule. 
 
 47. Graphic Symbols and Formulas. — The quantiv- 
 alence of an element is represented by Roman numerals, 
 or by primes or dashes attached to its symbol. For ex- 
 ample : — 
 
 1 vmivalent atom of chlorine 
 
 . CI* or 
 
 CI' or 
 
 CI—. 
 
 1 bivalent " 
 
 oxygen 
 
 . 0" or 
 
 0" or 
 
 — 0— . 
 
 1 
 
 1 trivalent " 
 
 nitrogen . 
 
 . N"* or 
 
 W" or 
 
 1 
 
 1 quadrivalent " 
 
 carbon 
 
 . C'^ or 
 
 C"" or 
 
 --, 
 
56 CHEMISTKY. 
 
 The symbol of an element with its quantivalence shown 
 by dashes attached to it is a Graphic Symbol. 
 
 The formula for a compound may then be made to show 
 whether all the unit values of its elements are satisfied, and 
 in what way. For example, in the molecule of water an 
 atom of oxygen holds two of hydrogen. Put the symbols 
 of hydrogen and oxygen together in this way, H — O — H, 
 and we see that each of the two unit values of the oxygen is 
 balanced by a unit value of hydrogen. A similar formula for 
 
 Hydrochloric acid is written .... h — CI, 
 
 H 
 I 
 
 Ammonia is written H— N— H, 
 
 H 
 I 
 Marsh-gas is written H— C— H, 
 
 H 
 in which we can see how every unit of quantivalence of CI, 
 of N, and of C, is balanced by a unit of hydrogen. Such 
 formulas are called Graphic Formulas. 
 
 Unsaturated Molecules. — There is a compound of 
 carbon and nitrogen called cyanogen. Its molecule contains 
 one atom of each element, and its common formula is there- 
 fore C N. Its graphic formula is N^C — . This graphic 
 formula shows at a glance that three of the four units of the 
 carbon atom are balanced by the three units of the nitrogen 
 atom, and the fourth is unbalanced or free. A molecule 
 like this, in which there is one or more unbalanced units of 
 quantivalence, is called an Unsaturated molecule ; while a 
 molecule like that of water, in which all the units of quan- 
 tivalence are balanced, is said to be Saturated. 
 
 The quantivalence of a molecule is the number of its 
 unbalanced units. Thus the quantivalence of cyanogen, 
 N^C — , is 1, while that of water, H — 0— H, is 0. 
 
 Constitutional Formula — Now, these graphic formulas 
 tell us something about the way in which the atoms are put 
 together to make a molecule. For instance, in the formula for 
 
CHEMISTRY. 67 
 
 water, H — O — H, it appears that the atom of oxygen binds 
 the two atoms of hydrogen to itself. The hydrogen atoms 
 do not seem to be bound to one anotlier at all. Nor can 
 they be. Let us try to make the molecule by binding them 
 together, and we have H— H and —0—, but the quantiv- 
 alence of the hydrogen is already exhausted: there is not 
 a single unit left free by which it can bind the oxygen. 
 
 H 
 So in the molecule of marsh-gas, h— C— H, the carbon 
 
 H 
 
 atom must be the nucleus about which the hydrogen atoms 
 are arranged. 
 
 Since these graphic formulas show what is believed to be 
 the way in which the atoms are grouped to constitute a mole- 
 cule, they are called Constitutional Formulas. 
 
 Caution. — We must not for a moment suppose that 
 these formulas show the shapes of the molecules, or the 
 geometrical arrangement of the atoms in them. We are not 
 to infer that the molecule of water is a line of atoms 
 
 H — O — H : it may be a triangle, O , or it may have some 
 
 other form. We know nothing of its shape. 
 
 The molecule of marsh-gas may be represented by 
 
 ^N/S ,^ /i UK? 
 
 H— C— H , C <„ , as well as by h— C— H . 
 ^ H I 
 
 H 
 
 What the formula docs mean to teach is, that all the atoms 
 of hydrogen are bound by chemical attraction to the single 
 atom of carbon, and not to one another. 
 
 The chemist studies the grouping of the atoms in the mole- 
 cules, as the astronomer studies the grouping of the planets 
 and the stars in cosmic systems, and represents the results in 
 these constitutional formulas. 
 
 I^^H ^H ^H 
 
68 CHEMISTRY. 
 
 48. Variable Quantlvalence. — The quantivalence of an 
 atom is not always the same. In different compounds the 
 same atom may have different values. For example, in the 
 
 molecule of ammonia, N , nitrogen is a trivalent atom, 
 
 I 
 H 
 
 but in a molecule of ammonium chloride, N H4 CI, it is 
 H 
 
 pentivalent, N— CI. Its value is increased from 3 to 5. 
 
 H 
 Whenever the quantivalence of an atom changes, it changes 
 by two units, as in the example just given. If the quantiv- 
 alence of an atom is even at one time, it is always even. If the 
 quantivalence of an atom is odd in one compound, it is odd 
 in all compounds. Hence the elements are divided into two 
 classes ; one class containing all those whose quantivalence is 
 represented by an even number, and the other class containing 
 all those whose quantivalence is represented by an odd num- 
 ber. The members of the first class are called Artiads, and 
 those of the second are called Perissads. An artiad may have . 
 a value represented by any even number, as 2, 4, 6, or 8, and a 
 perissad may have a value represented by any odd number, 
 as 1, 3, 5, or 7. 
 
 REVIEW. 
 I. — SUMMARY OF PRINCIPLES. 
 
 49. An element is a substance which has never yet been 
 decomposed. 
 
 There are sixty-four elements whose existence is at present 
 well established. 
 
 The elements are, for convenience of study, divided into 
 two classes, metals and non-metals. 
 
 The quantivalence of an element is the chemical value of 
 its atom, measured by the number of hydrogen atoms, or 
 their equivalent, which it can hold in combination. 
 
CHEMISTRY. 59 
 
 A univalent element is one whose atom is equivalent to one 
 atom of hydrogen. 
 
 A bivalent element is one whose atom is equivalent to two 
 atoms of hydrogen. 
 
 A trivalent element is one whose atom is equivalent to 
 three atoms of hydrogen. 
 
 A quadrivalent element is one whose atom is equivalent 
 to four atoms of hydrogen. 
 
 Among the non-metals we find no elements whose quantiv- 
 alence is not one or another of these four values. Hence 
 the non-metals are placed in four groups : the Univalent, the 
 Bivalent, the Trivalent, and the Quadrivalent. 
 
 The quantivalence of an element is represented to the eye 
 sometimes by a Roman numeral, sometimes by primes, some- 
 times by dashes attached to its symbol. 
 
 The quantivalence of an element is not always the same : 
 it varies, however, only by the addition or subtraction of two 
 units. 
 
 The formula for a compound is a combination of the 
 symbols of its elements to represent the composition of a 
 molecule. 
 
 A formula which shows nothing but what is actually known 
 by experiment, the names and proportions of the elements, 
 is an Empirical Formula. 
 
 A formula which represents any theory in regard to the 
 arrangement of the atoms in the molecule is a Rational 
 Formula. 
 
 A formula which represents the quantivalence of the 
 atoms, and shows how the atoms are grouped in the molecule, 
 is a Constitutional Formula. 
 
 II. —EXERCISES. 
 
 Define element. How many elements are at present 
 recognized? Are they known to be absolutely simple sub- 
 stances ? Into what classes are they usually divided ? 
 
 "What relation gives a better classification? Illustrate the 
 
60 
 
 CHEMISTRY. 
 
 equivalence of CI, O, N, and C atoms. Define tlie terms 
 univalent, bivalent, trivalent, and quadrivalent. Define 
 quantivalence. 
 
 How is the quantivalence of an atom represented? What 
 
 I 
 do F", B/, S", N = , -0-, and-C- represent? 
 
 I 
 
 What is a graphic formula? Write the graphic formula 
 for water, for hydrochloric acid, for ammonia, and for marsh- 
 gas. 
 
 When is a molecule said to be saturated? Unsaturated? 
 Write the graphic formula for cyanogen. What is the 
 quantivalence of cyanogen? Describe the quantivalence of 
 any molecule. 
 
 What is a constitutional formula? What caution are we 
 to observe in the use of constitutional formulas? 
 
 What is an «*mpirical formula? What is a rational 
 formula? 
 
 SECTION II. 
 
 HYDROGEN. 
 
 50. Preparation. — Pure water consists of hydrogen and 
 
 oxygen, and there are many 
 ways in which the hydrogen 
 may be obtained from it. 
 Many of the metals have 
 power to take the oxygen 
 alone from water. If a 
 piece of sodium be dropped 
 ■ upon water, it melts into a 
 globule, floats, and runs 
 briskly around over the sur- 
 face, taking the oxygen' to 
 itself, and letting the hydro- 
 
 JTig. 22. 
 
 gen go free. If the sodium be confined in a net of wire- 
 
CHEMISTEY. 
 
 61 
 
 gauze, it may be brought under the mouth of a test-tube 
 previously filled with water. (Fig. 22.) The hydrogen will 
 then be collected in the tube. 
 
 A more Practical Way. — Into a bottle, B, Fig. 23, are 
 put some fragments of zin'j. Through the well-fitting cork 
 passi two tubes, one a funnel-shaped tube reaching down into 
 the bottle, the other a bent tube reaching over to the cistern 
 of ivater. If now a mixture of water and sulphuric acid is 
 poured through the funnel until the lower end of its tube 
 is covered, hydrogen will flow rapidly through the bent tube, 
 
 Fig. 23. 
 
 and may be collected in jars upon the shelf of the cistern. 
 None should be collected, however, until all the air in the 
 apparatus has been driven out. 
 
 Fixplanation. — The molecule of sulphuric acid contains 
 two atoms of hydrogen, one of sulphur, and four of oxygen. 
 An atom of zinc takes the place of the two atoms of hydrogen : 
 they are driven away, while a new molecule containing the 
 atom of zinc and those of sulphur and oxygen is formed. 
 This new molecule is zinc sulphate. 
 
 51. Reactions. — We may represent this chemical change 
 to the eye by formulas and algebraic signs^ Thus : — 
 
62 CHEMISTEY. 
 
 H2 S O4 + Zn = Zn S O4 + Hj. 
 
 Sulph. acid. Zinc. Zinc sulphate. Hydrogen. 
 
 The formulas for the substances which were put together 
 in the experiment are joined by the sign of addition in this 
 expression, and made the first member of an equation ; while 
 the new substances made by the chemical action are repre- 
 sented by their formulas in the second member. 
 
 Chemical changes are very generally called Reactions, and 
 are represented by ciiemical equations like the one above. 
 
 Reaction of Sortiiiin and Water. — For another exam- 
 ple let us tvrite the reaction when hydrogen is obtained by the 
 action of sodium. In the experiment we put the metal in 
 contact with water ; lot us add their formulas for the first 
 member of our equation, and the formulas for the-substances 
 produced for the second. 
 
 H2O + Na = NaHO + H. 
 
 Water. Sodium. Sodium Hydrate. Hydrogen. 
 
 This equation shows us that one atom of sodium takes the- 
 place of one atom of hydrogen in the molecule of water, and 
 produces one molecule of sodium hydrate, and sets free one 
 atom of hydrogen. 
 
 No Loss nor Gain. — Not an atom is lost, nor an atom 
 gained, in these exchanges. The second member must show 
 the same number of atoms of every element found in the 
 first, but differently arranged to make the formulas of the new 
 compounds. The precision of exchanges is, beyond com- 
 parison, perfect. To illustrate this, let us write the same 
 equation with the combining weights of the elements (see 
 table, p. 53). 
 
 H2 -I- Na = Na H O -f H. 
 
 (2 X 1 -I- 16) -1- 23 = (23 -h 1 -F 16) -I- 1. 
 
 18 + 23 = 40 -f- 1. 
 
 The two members of this equation are exactly equal. 
 
CHEMISTRY. 
 
 63 
 
 This symbolic language of chemistry is of the greatest 
 value. It shows, at a glance, an amount of information 
 which, if spread out in ordinary language, would often be 
 tedious or obscure, and reveals relations which in the ordi- 
 nary language would be unseen. 
 
 The equation above tells us that every eighteen grams of 
 water will require exactly twenty-three grams of sodium to 
 completely decompose it, and that exactly forty grams of 
 sodium hydrate will be produced, and just one gram of hy- 
 drogen will be set free. 
 
 Fig. 24. 
 
 Beaction of Zinc and HydrocMoric Acid. — When 
 we use zinc and hydrochloric acid as we may in the hydrogen 
 generator (Fig. 24) , the reaction may be written 
 
 Zn H- 2 H 01 = Zn Cl^ -f H2, 
 
 65 -f 73 = 136 -I- 2 ; 
 
 which shows at a glance that in order to obtain two grams of 
 hydrogen we must use sixty-flve grams of zinc and seventy- 
 three of hydrochloric acid. 
 
 52. Pliysical Properties. — Hydrogen is a colorless 
 gas, and when pure has neither taste nor odor. It is the 
 
64 
 
 CHEMISTRY. 
 
 lightest of known substances ; its specific gravity is only 
 .0692 (air=l). It is eleven thousand times lighter than 
 water. 
 
 Let us take two small glass vessels, and fill one with hydro- 
 gen, the other with air. Then suppose we bring their mouths 
 together closely, so that the one containing hydrogen shall be 
 
 above the other (Fig. 25). 
 Next turn them quickly over, 
 to bring the air-vessel to the 
 top. A moment afterward 
 we may remove the lower jar, 
 and then touch the mouth of 
 the upper one with a lighted 
 match : a sharp explosion tells 
 us that the hydrogen is there. 
 It has risen through the air 
 to the top, just as oil will rise 
 through water to its surface. 
 Soap-bubbles blown with 
 cold air will fall to the floor, 
 but if blown with hydrogen they will rise quickly to the ceil- 
 ing (Fig. 26). 
 
 This gas is slightly soluble in water, one hundred cubic 
 inches of which will absorb one and a half of hydrogen. 
 
 Hydrogen is capable of being absorbed by many metals 
 when heated to temperatures more or less elevated. The 
 most remarkable absorption is by the metal palladium, which, 
 at ordinary temperatures, will take up more than nine hun- 
 dred times its own volume. Such absorption of gases by 
 metals is called Occlusion. 
 
 Hydrogen, by intense cold and enormous pressure, may be 
 reduced to the liquid form. This was first done by two 
 experimenters, M. Cailletet and M. Pictet, working inde- 
 pendently, but succeeding at the same time, both in Decem- 
 ber, 1877. M. Cailletet brought the gas under a pressure of 
 nearly three hundred atmospheres, and then suddenly released 
 
 Pig. 25. 
 
CHEMISTRY. 
 
 65 
 
 it. By the sudden expansion of a portion of tlie gas the 
 temperature of the rest was enormously reduced, and the 
 hydrogen took the form of mist. 
 
 M. Pictet subjected the gas to a temperature of —140 C, 
 and a pressure of six hundred and fifty atmospheres. On 
 opening a valve the hydrogen came out in a jet of steel-blue 
 color. But after a little while, on opening the valve a second 
 time, and although the pressure was still three hundred and 
 
 Fig. 26. 
 
 fifteen atmospheres, no hydrogen came out. The fact that 
 no gas issued when under such pressure showed that the 
 hydrogen was not only liquefied but actually reduced to the 
 solid form : it was frozen. 
 
 53. Chemical Properties. — Hydrogen is a combustible 
 gas. If a small jar, filled with it, is carefully lifted from the 
 cistern, and a lighted taper is quickly pushed up into it (Fig. 
 27), the gas takes fire with a slight explosion. 
 
66 
 
 CHEMISTKY. 
 
 Fig. 27. 
 
 We may study the flame by means of the apparatus shown 
 in Fig. 28. The hydrogen generator is connected with a 
 
 second bottle by a bent 
 tube reaching down 
 nearly to the bottom. 
 This bottle contains 
 some water, and is pro- 
 vided with a tall tube 
 whose upper end is 
 drawn to a small open- 
 ing. Let the acid be 
 poured through the fun- 
 nel upon the zinc, until 
 a rapid evolution of the 
 gas is produced, and 
 wait until the gas Jias 
 driven the air completely 
 from the apparatus. Then touch the jet of escaping hy- 
 drogen with a match-flame : it will take fire, and continue to 
 burn as long as the gas is supplied. 
 
 The flame of pure hydro- 
 gen yields almost no light, 
 but its heat is intense. One 
 gram of hydrogen will yield 
 heat enough to raise 34,462 
 grams of water from 0° to 
 ]°C. 
 
 The mixture of hydrogen 
 with air is explosive. When 
 the mixture is made with ^ 
 oxygen, in the proportions p 
 of two volumes hydrogen to 
 one volume oxygen, the ex- 
 plosion is deafening. If it ' 
 
 takes place in free air, it is 
 
 A 
 
 uot dangerous ; but, if 
 
 Fig. 28. 
 
 the mixture is confined in a tight 
 
CHEMISTRY. 67 
 
 bottle, the fragments of the bottle will be driven with vio- 
 lence as by a charge of gunpowder. 
 
 The combustibility and the explosibility of hydrogen are 
 due to the strong chemical attraction between it and oxygen. 
 It also enters into combination with the other non-metals 
 with the exception of boron ; but its compounds with the 
 metals are rare. By some chemists it is regarded as itself a 
 metal, and has been called Hydrogenium. This view is 
 based upon the general resemblance of the chemical actions 
 of hydrogen and the metals. 
 
 The molecule of hydrogen is supposed to contain two 
 atoms. Its symbol is H, which represents one atom, but its 
 molecule is represented by H — H, or Hj. 
 
 54. Occurrence. — Hydrogen rarely occurs in nature 
 free ; it has been found among the gases given off in volcanic 
 eruptions ; but in compounds it is a very abundant element. 
 One-ninth, by weight, of all the water of the globe, is hydro- 
 gen ; and besides this it is an important element in all animal 
 and vegetable bodies. 
 
 55. Hydrogen as a Standard. — This element has been 
 adopted as the standard of atomic weight, of equivalence, of 
 density of gases, and of molecular weight. 
 
 Tlie weight of its atom is 1 = unit of atomic and molecular weight. 
 
 Its atom value or quan- 
 
 tivalence is . . 1 = " quantivalence. 
 
 The weight of a unit vol- 
 ume is . . . 1 = " density or specific gravity. 
 
 Its molecular weight = 2 atomic weights is ... 2 
 
 The weight of 1 liter is 0.08936 gram. 
 
 ^^ 
 
 REVIEW. 
 
 I. — SUMMARY OP PRINCIPLBS. 
 
 56. Hydrogen may be obtained from water by the action 
 of sodium or of potassium at ordinary temperature. 
 
 It may also be obtained from water by iron and some other 
 metals at a red heat. 
 
68 CHEMISTRY. 
 
 It may also be obtained from water by electrolysis. 
 
 It is usually obtained by the action of zinc upon dilute 
 sulphuric or hydrochloric acid. 
 
 Hydrogen is the lightest known substance : it is 14.4 times 
 lighter than atmospheric air. 
 
 With air it is combustible and explosive. It will not 
 support combustion nor animal life. 
 
 Its symbol is H, and its atomic weight is 1. Its molecule 
 is represented by H — H, and its molecular weight is 2. Its 
 density is 1, and its quantivalence is 1. 
 
 Chemical changes are called reactions. Reactions are 
 written in the form of equations. The -formulas of the sub- 
 stances entering into the action are connected by the sign of 
 addition to form the first member, while the formulas of the 
 substances produced by the action, joined by the same sign, 
 form the second member, of the equation. 
 
 The molecular weights of the various substances repre- 
 sented in the equation show the relative quantities of them 
 which take part in the reaction. 
 
 II. —EXERCISES. 
 
 Describe the preparation of hydrogen by the use of 
 sodium. By the use of zinc. Give the explanation. 
 
 What is a chemical reaction? How are reactions writ- 
 ten? Write the reaction of sodium and water in the 
 preparation of hydrogen. What does the equation show? 
 Write the equation with the numerical values of the sub- 
 stances. What does this numerical equation show? 
 
 In the equation we find that eighteen grams of water will 
 yield just one gram of hydrogen : then how much water 
 would be needed to yield twenty grams of hydrogen ? 
 
 How much sodium would be needed with it? 
 
 How much sodium hydrate would be formed? 
 
 How much water would be required to yield seventy-five 
 grams of hydrogen? Ans. 1,350 grams. 
 
CHEMISTRY. 69 
 
 How many liters of hydrogen will be liberated from oo« 
 hundred grams of water by sodium ? 
 
 Ans. 100 grams HjO yield of I gram H = 5.6554-. 
 
 18 
 
 K KKK 
 
 A liter of H weighs 0.08936 gram ; hence = the 
 
 ^ 0.08936 
 
 number of liters = 62.16 + . 
 
 Write the reaction of zinc and hydrochloric acid. Change 
 it to a numerical equation. 
 
 How much zinc must be used to prepare seventy-five grams 
 of hydrogen? 
 
 How many liters of hydrogen will be set free by using one 
 hundred grams of zinc ? 
 
 How much hydrochloric acid will be required to liberate 
 one hundred liters of hydrogen ? 
 
 Ans. 0.08936 x 100 = 8.936 grams, the weight of 100 
 liters H ; to liberate 2 grams H, requires 73 of H CI (see 
 
 reaction) ; hence — x 73 = 326.164 grams H CI will 
 
 be required for 100 liters of H. 
 
 How many grams of Hj S O4 must be decomposed by zinc 
 to yield one hundred liters of H ? 
 
 Give the physical properties of hydrogen. What is 
 occlusion ? 
 
 Why is hydrogen combustible ? How much heat is evolved 
 by the combustion of one gram of hydrogen ? 
 
 Where is hydrogen found in nature? Give the symbol 
 of hydrogen. Atomic weight. Quantivalence. Density. 
 Molecular weight. How is the molecule of hydrogen repre- 
 sented in symbols ? 
 
70 
 
 CHEMISTBY. 
 
 SECTION ni. 
 
 THE UNIVALENT NON-METALS. 
 
 I. — Chlorine. 
 
 "^57. Preparation from Hydrocliloric Acid. — The 
 
 chlorihe in hydrochloric acid may be set free by the action 
 
 of manganese diox- 
 ide. For this pur- 
 pose the acid, with 
 about one-third of 
 its weight of the di- 
 oxide, is put into a 
 largeflask(Fig. 29), 
 provided with a tight 
 cork and suitable 
 tubes as represented 
 in the cut. By heat- 
 ing the mixture gen- 
 tly, the chlorine is 
 given off in abun- 
 dance ; passes over 
 through the tube to 
 
 the bottom of the jar. A, in which it gradually rises, until 
 
 the jar is filled. 
 
 The reaction is as follows : — 
 
 Fig. 29. 
 
 Mn O2 -f 4 H CI = 2 Hj O -f- Mn Clj -F 2 CI. 
 
 This equation is read in this way : One molecule of 
 manganese dioxide with four molecules of hydrochloric acid, 
 yield two molecules of water, one of manganese dichloride, 
 and two atoms (one molecule) of chloj-ine. 
 
 The oxygen of the dioxide, combining with the hydrogen 
 of tlie acid, forms water ; while a part of the chlorine, taking 
 
CHEMISTEY. 
 
 71 
 
 the manganese, forms manganic chloride, and the rest of the 
 gas is set free. 
 
 Preparation by Use of Common Salt. -^ In place of 
 hydrochloric acid we may use sodium chloride and sulphuric 
 acid : these with the manganese dioxide, gently heated, 
 evolve the gas abundantly. The following equation shows 
 the chemical changes which occur : — 
 
 2NaCl + 3H2S04+Mn02 = 2NaHS04+MnS04+2CH-2H2 0, 
 
 Manga- 
 nese 
 Dioxide, 
 
 Sodium Sulphuric 
 Chloride. Acid. 
 
 Hydro- 
 Sodium 
 Sulphate. 
 
 Manga- 
 nese Chlorine. Water. 
 Sulphate. 
 
 ^ MlMi!'l^l^Milll'iii'ilfcilliiiiliWiiii^^ 
 
 To Obtain the Gas Pure and Dry, — To purify and 
 
 dry the gas, obtained by either of these methods, it is passed 
 from the flask first through water contained in a wash- 
 bottle, — the three-neeked bottle in Fig. 30, — and then 
 through a vessel — the tall jar in the figure — containing 
 
72 CHEMISTRY. 
 
 calcium chloride. The water washes out the impurities, and 
 the chloride absorbs the moisture. The pure, dry chlorine 
 may then be collected in bottles or jars. 
 
 58. Physical Properties. — Chlorine is a transparent 
 gas, having a greenish-yellow color and a characteristic 
 suffocating smell. When inhaled, it powerfully initates the 
 air-passages,' and produces coughing, even when mixed with 
 large portions of air. If breathed pure it even causes 
 death. 
 
 Chlorine is nearly two and a half (2.45) times heavier 
 than an equal volume of air. Its density, hydrogen being 
 the standard, is 35.37. 
 
 Chlorine is very soluble in cold water. Water, at ordinary 
 temperature, dissolves about twice its own bulk. It dissolves 
 less and less as the temperature rises, until at 100° C. it dis- 
 solves none. 
 
 The solution of chlorine is useful in the laboratory ; and it 
 is prepared by passing the gas from the generator through 
 water, as shown in Fig. 31. The gas is washed in the small 
 bottle, and dissolved in those which follow. 
 
 Under a pressure of four atmospheres, chlorine becomes a 
 yellow liquid at ordinary temperature. If cooled to —34° C, 
 the same effect is produced without any extra pressure. 
 
 59. Chemical Character. — Chlorine combines readily 
 with hydrogen. The application of either heat or light will 
 cause them to unite. When a mixture of the two is placed 
 in the direct rays of the sun, the combination is rapid, some- 
 times with explosion. Diffuse light causes the combination 
 gradually ; while, if mixed and kept in the dark, no chemical 
 action takes place. 
 
 So strong is the chemical force, or aiBnity, between these 
 elements, that chlorine will decompose many compounds of 
 hydrogen. An instructive experiment illustrates this. A 
 lighted wax-taper, plunged into a jar of chlorine, is extin- 
 guished ; but, curiously enough, it is at once relighted, bum- 
 
CHEMISTRY. 
 
 73 
 
 ing afterward with a dark red flame, and giving off a dense 
 black smoke. The explanation is this : the white flame in 
 the air is due to the action of oxygen ; and since there is 
 none of this element in the jar, the flame dies. But the wax 
 contains hydrogen ; and the chlorine decomposes the wax, 
 and combines with this element so vigorously as to produce 
 a dull red flame. 
 
 - k 
 
 ,-A 
 
 
 ^Jji^ i^^, .i^. 
 
 I 
 
 
 mJ±.^^ 
 
 
 I 
 
 Fig. 31. 
 
 Application of this Affinity. — Chlorine is largely used 
 in the arts of bleaching and disinfecting. But dry chlorine 
 will not bleach : it must be moist. Its power to destroy 
 colors and odors is due to its attraction for hydrogen. 
 
 In bleaching, the chlorine decomposes the water present, 
 and combines with its hydrogeni The oxygen of the water 
 
74 
 
 CHEMISTRY. 
 
 then attacks the coloring matter, decomposing it and destroy- 
 ing the color. 
 
 Chlorine and the Metals. — Chlorine combines, also, 
 with most metals readily. Powdered antimony sprinkled 
 
 into a bottle of chlo- 
 rine takes fire (Fig. 
 32), and falls to the 
 bottom in a shower 
 of sparks. Metals 
 which, like gold, re- 
 sist the action of ox- 
 ygen and the acids, 
 are attacked by chlo- 
 rine. Neither nitric 
 acid nor hydrochloric 
 acid alone will act 
 upon gold, but when 
 mixed they form 
 what is called agua- 
 regia, in which there 
 is free chlorine ; by 
 this mixture gold tri- 
 chloride is speedily 
 formed. 
 - Chlorine is not found free in nature, 
 it is one of the most abundant ele- 
 
 Fig. 
 
 than half 
 
 the weight of this substance is chlorine ; 
 
 60. Occurrence. - 
 
 but in combination 
 ments. Sodium chloride (common salt, Na CI) is distributed 
 throughout the air, the soil, the rocks, and the sea. More 
 ^35.5N 
 
 and calculating from the amount of salt in sea-water, we 
 may find that something more than five gallons of this gas 
 is contained in the salt of one gallon of sea-water. Other 
 chlorides exist in the water of the sea : potassium and mag- 
 nesium chlorides are the most abundant. Chlorides are 
 found also in the bodies of plants and animals. 
 
CHEMISTRY. 76 
 
 II. — Bromine, Iodine, and Flijokine. 
 
 61. Bromine. — Bromine is found in small quantities 
 combined with metals in the waters of the sea. It is a dark 
 brown-red liquid, having a strong affinity for hydrogen and 
 the metals. Its compounds are used to some extent in 
 medicine, and quite largely in photography. 
 
 62. Iodine. — Iodine, like chlorine and bromine, is not 
 found free in nature, but combined with metals it is found 
 in sea-wa;ter, in sea-plants, and in some mineral springs. 
 
 It is a blue-black crystalline solid, very volatile, giving off 
 a superb violet- colored vapor when warmed, i It has a strong 
 affinity for hydrogen and the metals. Its compounds are 
 used in photography, and are highly prized in medicine. 
 
 63. Fluorine. — Fluorine is found combined with metals 
 in certain minerals — fluor-spar, (calcium fluoride, Ca Flj) 
 being the most common. It is obtained free only with the 
 greatest difHculty, and on this account its physical properties 
 are imperfectly known. It seems to be a gas, having a 
 violent affinity for, hydrogen, for the metals, and, indeed, for 
 many other elements. 
 
 III. -—The Group. 
 
 64. Comparison of tlieir Physical Properties. — 
 
 Leaving fluorine out of the account, we notice that chlorine 
 is a gas at ordinary temperature, bromine a liquid, and 
 iodine a solid. At a little higher temperature all three are 
 gaseous. In the colors of these gases we notice a curious 
 gradation. That of bromine represents one end of the 
 spectrum, dark-red ; that of chlorine represents the middle 
 part, greenish-yellow ; and that of iodine represents the 
 other end, a beautiful violet. 
 
 Comparison of their Chemical Properties. — These 
 four elements closely resemble each other in their chemical 
 properties. They combine with the same substances, and 
 
76 
 
 CHEMISTRY- 
 
 generally in the same proportions. For hydrogen and the 
 metals they all have strong attraction ; with oxygen they (with 
 the possible exception of fluorine) unite, although with a 
 feeble force ; with nitrogen they form explosive compounds. 
 They are all univalent, and the single compound which each 
 one forms with hydrogen is an acid. 
 
 The following formulas illustrate the analogous composi- 
 tion of the hydrogen compounds of these elements : — 
 
 HCl 
 HBr 
 HI 
 HF 
 
 Hydrochloric acid. 
 Hydrobromic acid. 
 Hydriodic acid. 
 Hydrofluoric acid. 
 
 IV. — HrDROCHLORic Acid. 
 
 65. Hydrocliloric Acid is a Gas. — The hydrochloric 
 acid found in commerce is a liquid, but a simple experiment 
 will show that this liquid is the solution of a gas in water. 
 
 Fig. 33. 
 
 Some of the liquid is put into a flask (Fig. 33), and heated : 
 a colorless gas is by this means driven over through the bent 
 tube, and, being dried while going through sulphuric acid in 
 the bottle B, finally enters a jar, previously filled with mer- 
 
CHEMISTRY. 
 
 77 
 
 cury, and inverted over a small cistern of the same fluid. 
 If, when the jar is full of gas, it be taken from the mercury 
 and its open mouth inserted in water, the gas will b» dis- 
 solved, the water rising into the jar at the same time with 
 surprising swiftness. Now, the solution thus obtained is 
 found to be weak hydrochloric acid, and we hence learn that 
 the real acid is a gas. 
 
 Fig. 34. 
 
 66. Preparation. — For some purposes the gas may be 
 obtained in small quantity, by the process just described. 
 
 It may, however, be made by the reaction of common salt 
 with sulphuric acid. 
 
 For this purpose six parts by weight of salt are put into a 
 
78 
 
 CHEMISTRY. 
 
 large flask, and eleven parts of strong acid are slowly poured 
 through a funnel-tube upon it. The gas is rapidly set free, 
 and is purified by passing through a little water in a wash- 
 bottle ; after which it may be collected over mercury, as 
 shown in Fig. 34, or by displacement like chlorine, or it may 
 be dissolved by passing it into water. 
 
 The Reaction. — The salt furnishes the chlorine, and the 
 sulphuric acid furnishes the hydrogen, to form the hydro- 
 chloric acid. The chemical change is as follows : — 
 
 NaCl-fH2S04 = NaHSOi + HCl. 
 
 A molecule of sodium chloride, with a molecule of sul- 
 phuric acid, yields a molecule of hydro-sodium sulphate and 
 one molecule of hydrochloric acid. 
 
 Fig, 
 
 67. Physical Properties. — Hydrochloric acid is a color- 
 less gas, a little heavier than air, and 18.2 times heavier than 
 hydrogen. 
 
 One of its most remarkable properties is its solubility in 
 water ; and it is this solution which is found in commerce 
 
CHEMISTRY. 79 
 
 and used in the laboratory, as hydrochloric acid. The great 
 solubility of this gas may be demonstrated by experiment 
 with apparatus shown in Fig. 35. Some commercial acid is 
 heated in the small flask. The acid gas is rapidly evolved. 
 It passes into the upper bottle, and drives the air before it, 
 out through the side tube, which reaches over to the surface 
 of water in a beaker. When the air has been all driven out, 
 this side tube is closed by a spring-clamp. The gas then 
 passes down the vertical tube, which reaches from the upper 
 bottle to the bottom of another below containing water colored 
 blue with litmus. The flame is then withdrawn from the 
 flask, and the other clamp immediately closed. At this mo- 
 ment the upper bottle and the vertical tube are filled with 
 the acid gas. The water then quickly absorbs the gas, and 
 ascends the vertical tube. It enters the upper bottle in the 
 form of a fountain, and continues to rise as long as any gas 
 remains to be absorbed. At 15° C, water dissolves four hun- 
 dred and fifty times its own volume of hydrochloric gas. On 
 contact with air the colorless gas takes moisture, and yields 
 dense white fumes. 
 
 68. Chemical Properties. — Hydrochloric acid is an 
 energetic acid. It reddens litmus, and it readily yields its 
 hydrogen when acted on by metals. For example : — 
 
 HCl + Na' = NaCl + H. 
 Acid. Sodium. Sodium Chloride. Hydrogen. 
 
 2HC1 + Zn" = ZnClz + 2H. 
 Acid. Zinc. Zinc Chloride. Hydrogen. 
 
 The metals take the place of the hydrogen of the acid, 
 and produce chlorides. 
 
 The gas is wholly irrespirable. It will neither burn nor 
 support combustion. 
 
 The molecular weight of hydrochloric acid is 36.5 
 
 (H = l, CI = 35.5), and its molecular volume is two. 
 
 35.5 
 Hence its density is —^=18.25. 
 
80 CHEMISTRY. 
 
 69. Uses. — In the manufacture of many commercial procl- 
 nets, such, for example, as gelatine, " bleaching- powder," 
 and many chemicals, hydrochloric acid is used in very great 
 quantities. In the laboratory of the chemist it is an indis- 
 pensable reagent. 
 
 REVIEW. 
 I. —SUMMARY OF PRINCIPLES. 
 
 70. Chlorine is obtained by gently heating a mixture of 
 hydrochloric acid and manganese dioxide. 
 
 It is a heavy greenish-yellow gas, with a penetrating and 
 characteristic odor. It is soluble in one-half its volume of 
 cold water. 
 
 Its most characteristic attractions are for hydrogen and the 
 metals. With hydrogen it combines in equal volumes, and 
 forms hydrochloric acid ; with the metals it forms a large 
 class of compounds called chlorides. 
 
 Its affinity for hydrogen is taken advantage of in the pro- 
 cess of bleach itg cotton fabrics. Only moist chlorine will 
 remove color or destroy bad odors. 
 
 The gas is not found in nature free, but its compounds are 
 very abundant. The most abundant chloride is common 
 salt, — the sodmm chloride (NaCl). 
 
 Chlorine, Bromine, Iodine, and Fluorine form a well- 
 marked chemical group. They are all univalent elements. 
 They enter into combination with the same elements, and 
 their compounds have similar composition. 
 
 Hydrochloric acid is the only known compound of chlorine 
 and hydrogen. It was formerly called Muriatic Acid. 
 
 It is manufactured in large quantities for many commercial 
 purposes. Common salt and sulphuric acid are the materials 
 employed. When heated together they evolve large volumes 
 of the gas, which is dissolved in water to constitute the 
 commercial acid. 
 
 The commercial acid is usually highly colored yellow by 
 
CHEMISTRY. 81 
 
 the presence of organic impurities. The pure article is 
 perfectly colorless. 
 
 Hydro-sodium sulphate (Na H S O4) or sodium sulphate 
 (Naa S O4) is formed at the same time with tlie acid : the 
 first, if one molecule of salt to one of sulphuric acid are the 
 proportions used ; and the second, if two molecules of salt 
 are used to one of the acid, thus : — 
 
 2NaCl + H2SO4 = Na^SO^ + 2HC1. 
 
 This sodium sulphate (Naj S O4) is used in the manufac- 
 ture of sodium carbonate. It is the well-known Glauber's 
 Salts. 
 
 Hydrochloric acid changes many metals into chlorides. 
 The chemical action consists in the substitution of an atom 
 of the metal for the hydrogen, in one or more molecules of 
 the acid. 
 
 The substitution will be for hydrogen in one molecule of 
 acid if the metal is univalent, in two molecules of the acid 
 if the metal is bivalent, and in three if the metal is trivalent. 
 
 These chlorides are all very soluble in water, except three. 
 Silver chloride ( Ag CI) , mercurous chloride (Hgj Clj) , and 
 lead chloride (Pb CI2), are the three exceptions. 
 
 A mixture of hydrochloric acid and nitric acid is called 
 Aqua Eegia. Neither of these acids alone can attack gold, 
 but aqua-regia quickly converts gold into a chloride 
 ( Au CI3) . Aqua-regia owes this power to .dissolve gold to 
 the free chlorine which it contains. 
 
 II. —EXERCISES. 
 
 Describe the preparation of chlorine. 
 
 Give the reaction. Take the needed atomic weights from 
 the table of elements, p. 53. and wiite the numerical equa- 
 tion in the reaction. 
 
 How many grams of CI may be obtained by using fifty 
 grams of hydrochloric acid? Ans. 24.315. 
 
82 CHEMISTRY. 
 
 How many liters in this weight of chlorine : its densitj 
 being 35.5? 
 
 Ans. 0.08936 x 35.5 = weight of 1 liter of CI. 
 
 '■ ?i = number of liters of CI. 
 
 weight of 1 liter 
 
 What volume of chlorine will fifty grams of Mn Oj liberate 
 from H CI when the two are heated together ? 
 
 What is the weight of 2,500 cubic centimeters of chlorine 
 gas? 
 
 What are the physical properties of chlorine ? Illustrate 
 the chemical attraction of chlorine and hydrogen. To what 
 useful purposes is this property of chlorine applied ? Explain 
 the bleaching action of chlorine. 
 
 Illustrate the chemical attraction of chlorine and the 
 metals. What class of compounds does chlorine form? 
 What is aqua-regia? 
 
 In what form is chlorine abundant in nature ? 
 
 Give a brief description of bromine. 
 
 Give a brief description of iodine. 
 
 Give a brief description of fluorine. 
 
 Compare the physical properties of chlorine, bromine, and 
 iodine. Compare their chemical properties. Give the 
 formulas and names of their hydrogen compounds. What 
 is the quantivalence of the members of this group? 
 
 What is the liquid hydrochloric acid of commerce ? How 
 may the gas itself be obtained? Write the reaction when 
 salt is used with sulphuric acid. 
 
 What are some of the properties of this gas ? 
 
 Describe its solubility. 
 
 What chemical change occurs when sodium and hydro- 
 chloric acid are brought together? 
 
 What chemical change when zinc and hydrocb'oric acid 
 are brought together? 
 
 What class of substances are formed by the action ol 
 metals on this acid ? 
 
 What are the uses of this acid? 
 
CHEMISTEY. 
 
 83 
 
 SECTION IV. 
 
 THE BIVALENT NON-METALS. 
 I. — Oxygen. 
 
 71. Preparation. — Oxygen may be obtained by heating 
 potassium chlorate. This is the best and usual method. 
 Potassium chlorate is a white solid, about 39.2 per cent of 
 its weight being oxygen. It gives up all this oxygen when 
 heated. For this purpose it is finely powdered, mixed with 
 about an equal weight of black oxide of manganese, and put 
 
 Pig. 36. 
 
 Into a flask, F (Fig. 36). A bent tube reaches through tne 
 cork of the flask and over into the water of the cistern ; and 
 upon the shelf of the cistern there stands an inverted jar 
 filled with water. Now, when the flask is heated, the 
 chlorate is decomposed, and oxygen, being set free, passes 
 through the bent tube, and bubbles out of the water. If the 
 end of the tube is brought under the mouth of the jar, the 
 oxygen will rise into the jar, which in a little time will be 
 filled. The reaction is as follows : — 
 
84 
 
 CHEMISTRY. 
 
 KCIO3 
 
 KCl 
 
 + 
 
 o,. 
 
 Potassium chlorate = Potassium chloride + Oxygen. 
 122.6 = 74.6 " + 48. 
 
 The manganese dioxide is used in order to obtain the, gas 
 at a lower temperature. It takes no part in the chemical 
 action, and, in the end, is found mixed with the potassium 
 chloride in the flask. 
 
 72. Its Physical Properties. — Oxygen is a colorless 
 and transparent gas ; without odor or taste ; a little heavier 
 than air, its specific gravity being 1.1056 (air = 1), or 16 
 when hydrogen is the unit. 
 
 This gas is slightly soluble in water, one hundred volumes 
 of water absorbing about three volumes of oxygen at ordinary 
 temperatures. 
 
 When submitted to a pressure of three hundred atmos- 
 pheres, and a cold of —140° C, if the pressure be suddenly 
 removed oxygen is reduced to the liquid 
 form. This liquefaction was accom- 
 plished by Pictet in December, 1877. 
 
 73. Its Cliemical Properties. — A 
 
 lighted taper lowered into a jar of oxy- 
 gen burns with sui"prising brilliancy. 
 A glowing spark upon the wick is all 
 that is needed : the oxygen instantly, 
 and with a slight explosion, kindles it 
 into a vivid flame. 
 
 Into a jar of oxygen, hang, by means 
 L ]^P of a wire, a piece of charcoal bark on 
 '^ _ which there is a spark of fire (Fig. 37). 
 Quickly the charcoal bursts into a beau- 
 tiful and vigorous combustion. The 
 carbon combines with the oxygen, and produces carbon di- 
 oxide, thus : — 
 
 C -f O2 = CO2 
 
 Carbon -f- Oxygen = Carbon dioxide. 
 
 Fig. 37. 
 
CHBMISTEY. 
 
 85 
 
 Experiments like tlieae illustrate the fact that bodies which 
 bum in air will burn with greater vigor in oxygen. 
 
 Again : let an iron wire or a steel watch-spring be tipped 
 with a bit of wood. Set fire to the wood, and at ouce^pluuge 
 it into a jar of oxygen. Quickly the metal takes fire, and 
 burns (Fig. 38), the iron with a steady and beautiful light, 
 or the steel with a multitude of star-like sparks. Iron 
 sesquioxide (Fez O3) is pro- 
 duced by this chemical ac- 
 tion. Experiments such as 
 this illustrate the fact tliat 
 substances which do not burn 
 in air may burn with great 
 rapidity in oxygen. 
 
 .This gas not only supports 
 combustion, it is also neces- 
 sary to the life of animals. 
 It is in the air, and animals 
 breathe it ; it goes into their 
 blood, and purifies it. By 
 being mixed with nitrogen, 
 its violent action is toned 
 down so that the most deli- 
 
 Fig. 38. 
 
 cate organ may not only withstand it, but be invigorated by 
 its presence. 
 
 Oxygen unites with all other elements with the exception 
 of fluorine, and its compounds are very numerous and 
 abundant. 
 
 Its combining weight is 16. Its molecule is supposed 
 to contam two atoms ; so that while the symbol of oxygen is 
 O, its molecule is represented by O ^ O or O2, and its molec- 
 ular weight is therefore 32, and molecular volume 2. 
 
 74. Occurrence. — Oxygen is the most abundant element 
 in nature : minerals, plants, and animals alike contain large 
 quantities of it. One-fifth part of the air by weight is 
 
86 CHEMISTRY. 
 
 oxygen, eight-ninths of all tha water on the globe, and about 
 one-half of all the solid rocks. Besides this about four-fifths 
 of the weight of vegetable bodies is oxygen, and about three- 
 fourths of that of animals. It is, perhaps, not too much to 
 say, that one-half of all the matter of the world, as far as it 
 has been examined, is oxygen. And yet, when freed from 
 its prisons in solid and liquid bodies, oxygen is a gas, invis- 
 ible as air and but little heavier. 
 
 75. Ozone. — Let strips of unsized paper be soaked in a 
 solution of potassium iodide mixed with starch. If these 
 strips be hung iu a jar of air, no action 
 or change will occur; but if a few 
 drops of ether be added, and a hot 
 glass rod be put into the jar (Fig. 
 39), the paper will very soon become 
 colored blue. The oxygen, which at 
 first could not attack the iodide, has 
 been changed by the ether and the 
 heat so that it can. This more active 
 form of oxygen is called Ozone. 
 
 That ozone is nothing but oxygen, 
 may be proved. By passing electric 
 sparks through pure oxygen, ozone is 
 formed. Now, electricity is not a 
 kind of matter, and hence can add 
 nothing to, nor can it take any thing 
 from, the element oxygen. Ozone is therefore but another 
 form of oxygen. Moreover, if left alone in the jar, ozone 
 will in time return to the form of oxygen. 
 
 Vigorous as is the chemical action of ordinary oxygen, it 
 is still more vigorous in the form of ozone. This is the. chief 
 difference in the action of these two foiTns of oxygen. 
 
 Ozone by Slow Combustion of Pbospborixs Let a 
 
 stick of phosphorus be laid on a plate with water deep 
 enough to half immerse it. Then let a glass jar be inverted 
 
 Fig. 39. 
 
CHEMISTRY. 87 
 
 over it. White fumes arise from the phosphorus, due to its 
 combination with oxygen, and, during tliis sloiv combustion 
 of the phosphorus, a portion of the oxygen of the air is 
 changed to ozone. Its presence may be shown by the starch 
 paper. 
 
 By Electricity. — A silent discharge of electricity through 
 air is able to convert a considerable portion of its oxygen 
 into ozone. Indeed, a stronger ozone mixture can be 
 obt6,ined in this way than in any other. There is no way 
 known in which oxygen can be wholly changed into ozone. 
 
 Allotropism. — Ozone is called an allotropic form of 
 oxygen. "Whenever the same element exists in two forms, 
 they are said to be allotropic. And the property of an ele- 
 ment in virtue of which it can show different properties under 
 different conditions, is called Allotropism. 
 
 76. Density of Ozone. — Whenever oxygen is changed 
 into ozone, it is reduced in volume ; and when the ozone is 
 changed back to oxygen again the original volume is restored. 
 This proves that ozone is denser than oxygen. Experiments 
 indicate that three volumes" of oxygen form two volumes of 
 ozone. If so, ozone is one and a half times heavier than 
 oxygen, and its density is 24 (H = 1). 
 
 Explanation. — This can be best explained by supposing 
 that the molecule of ozone contains three atoms, while that 
 of oxygen contains only two. We should then have 
 
 3 O2 = 2 O3. 
 
 Oxygen. Ozone. 
 
 That is, three molecules of oxygen produce two of ozone. 
 
 Thus the molecule of oxygen is = 0, 
 
 O 
 
 and the molecule of ozone is / \ • 
 
 — 
 
 It is believed that it is because the molecule of ozone 
 contains this extra atom of oxygen, that ozone is able to 
 convert substances into oxides more vigorously than can 
 
88 
 
 CHEMISTRY. 
 
 oxygen itself. This extra atom is easily given up to unite 
 with other substances, with silver for example, while the two 
 remaining atoms form a molecule of oxygen. 
 
 77. Occurrence. — Ozone occurs in the atmosphere. The 
 quantity varies from time to time. It is often more abun- 
 dant after a thunder-storm, being formed by the action of 
 atmospheric electricity. It is a powerful agent in cleansing 
 the atmosphere from organic impurities : it decomposes them, 
 and converts their constituents into oxides. 
 
 II. — Oxygen and Hydrogen. 
 
 7tf. The Combustion of Hydrogen. — We have seen 
 that hydrogen is a very combustible gas. Now, the product 
 
 Fig. 40. 
 
 of its combustion is Water. This may be demonstrated 
 by an experiment represented in Fig. 40. Hydrogen is set 
 free in the bottle seen at the left in the picture. It passes 
 
CHEMISTRY. 89 
 
 over through the bent tube to the bottom of a tall upright 
 jar. This jar contains some calcium chloride, a substance 
 which has a very strong attraction for water, but none for 
 hydrogen. The gas, passing out at the top of the jar, will 
 be thoroughly dry. Finally the hydrogen issues from the 
 other end of the bent tube reaching from the top of the 
 drying-jar, and is set on fire. A cold glass vessel is then 
 brought down over the flame of burning hydrogen. 
 
 What is the result ? Instantly the walls of the cold vessel 
 are dimmed with dew ! The dew rapidly accumulates ; and, 
 if the jar is kept cold, it collects into little globules. The 
 little globules, grown larger and larger, at length trickle 
 down the sloping sides of the vessel, and slowly drop from 
 its mouth. 
 
 79. Properties of Water. — Water is a colorless, taste- 
 less liquid. It evaporates at all temperatures, keeping the 
 atmosphere charged with its invisible vapor, which, when 
 condensed, produces fogs and mists, dews and rain. It boils 
 at 100° C, (212° F.). At 15° C. (59° F.) water is 819 times 
 heavier than an equal volume of air. Its greatest density is 
 at a temperature of 4° C. (39° F.). 
 
 Freezinsf. — The freezing point of water is 0° C. (32° F.), 
 and on freezing it expands nearly ^ of its bulk. Ice is 
 therefore lighter than water (.917) when equal volumes are 
 compared. 
 
 Ice is crystallized water. In solid masses the crystalline 
 form is obscured, but it is distinctly seen when the ice begins 
 to form. It is beautifully exhibited in the frost figures often 
 found upon the window-pane in winter, and- also in the snow- 
 flakes when just fallen. (Fig. 41.) <_/. ^'iL^_t^ 
 
 80. Water as a Solvent. — A great many substances are 
 soluble in water. A substance is said to be dissolved in 
 water when its particles are so completely separated and 
 scattered through the liquid as to be invisible. Its cohesion 
 is entirely overcome by the stronger force of adhesion be- 
 
90 
 
 CHEMISTRY. 
 
 tween its particles and those of water. A substance that 
 may thus disappear is said to be soluble; and the fluid which 
 contains it is called a Solutiok, while that which dissolves it 
 is called a Solvent. Salt is soluble in water : the brine is a 
 solution, the water a solvent. 
 
 Fig. 41. 
 
 But it is well known that only a certain quantity of salt 
 can be dissolved in water : all added beyond that, will remain 
 undissolved. It is so with other solids : water can only dis- 
 solve a limited quantity. A solution in which the fluid has 
 all it can hold of a soluble body is said to be Saturated. 
 
 ££fect of Heat. — The solvent power of water may be 
 
CHEMISTRY. 
 
 91 
 
 increased by heat. To this, however, there are some excep- 
 tion. Common salt, for example, will dissolve about equally 
 m hot and cold water, and lime better in cold than in hot 
 water. 
 
 Solubility of Gases — Many gases, also, are soluble in 
 water. Oxygen and nitrogen are examples : small quantities 
 of both these gases, taken from the air, may be found in all 
 natural waters. The presence of this dissolved air in water 
 
 Fig. 42. 
 
 may be proved easily. We only need to place the liquid in 
 a glass flask, and gently warm it. Little bubbles of gas will 
 shortly be seen clinging to the bottom and sides of the vessel. 
 More and more numerous and larger and larger they become, 
 until, as the heat increases, they break away, and escape at 
 the surface of the water. These bubbles are bubbles of air. 
 It was in solution in the water, and the heat has driven it out. 
 It may be caught in another vessel (Fig. 42) if desired. 
 
92 CHEMISTRY. 
 
 The experiment illustrates the fact that we may expel certain 
 gaseous impurities from water by boiling. 
 
 Like solids, each gas has its own degree of solubility. 
 Oxygen, for example, is more soluble than nitrogen, while 
 carbon dioxide is much more soluble than either. Of this 
 gas, water will dissolve about its own volume. Others are 
 still more soluble : of ammonia gas, water at 0° C. will dis- 
 solve 1,148 times its volume. 
 
 81. Natural Waters. — Because water can dissolve so 
 many other bodies, we may not expect to find pure water 
 upon the earth. Coming from the clouds, it dissolves the 
 gases of the atmosphere ; sinking into the soil, it dissolves 
 the minerals it meets ; and flowing over rocks, it dis- 
 solves their materials. Hence the waters of all seas, lakes, 
 rivers, and wells, are, without exception, impure ; the kind 
 and quantity of their impurities depending on the material 
 over which they have passed. 
 
 Mineral Springs. — Salt springs are those whose waters 
 have dissolved out the salt from the soil through which they 
 Lave flowed. In another place some other substances may 
 exist in the soil or rocks ; and the water, dissolving these, 
 forms other kinds of mineral springs. 
 
 The water may, for example, contain some salt of iron in 
 solution, in sufficient quantity to give it an astringent taste 
 and other special properties. In this case it is called 
 Chalybeate Water. 
 
 The Saltness of the Sea. — In a similar way we may- 
 account for the saltness of the sea. Common salt is scat- 
 tered in small quautities through most soils, and is dissolved 
 by water which trickles through them. This water collects 
 in rivers, and finds its way to the sea. From the sea, water 
 can only escape by evaporation. But, by this process, only 
 pure water passes away : the salt is left behind. Age after 
 age this work goes on, and large quantities of salt have thus 
 already been accumulated in the sea. 
 
CHEMISTRY.. 
 
 93 
 
 Salt lakes are found, such as the Great Salt Lake of Utah. 
 They are lakes without an outlet ; so that, while the water 
 may escape by evaporation, there is no escape for the salt. 
 
 Such Solid Impurities increase the Weight of the 
 Water. — A very pretty experiment shows that brine is 
 heavier than fresh water. In 
 the first place, a small vial is 
 partly filled with a colored liquid, 
 so that when corked it will just 
 sink in fresh water. Into a tall 
 jar (Fig. 43), put fresh water 
 several inches deep, and into 
 this the little vial. Now by 
 means of a long funnel-tube a 
 saturated solution of salt may, 
 with care, be poured to the 
 bottom of the jar without mixing 
 with the fresh water above. 
 The fresh water will be lifted, 
 floating on the brine, while the 
 vial, also lifted, marks the dividing line between them. 
 
 82. To Purify Water. — Water very often contains- 
 sediment, — solid matter not in solution, but 
 held suspended in the liquid. By long 
 standing this solid matter is likely to fall 
 to the bottom. Nevertheless it is often 
 desirable to separate it more perfectly or 
 more quickly. 
 
 Filtration. — When a solid in fine di- 
 vision is mixed with a liquid, it may be 
 separated by passing the liquid through 
 f some porous substance which will not let 
 the particles of the solid pass. The pro- 
 cess is called Filtration. The porous 
 body through which the fluid passes is called a Filtee, and 
 
 Fig. 44. 
 
94 
 
 CHEMISTBY. 
 
 the clear liquid which issues is called the Filtrate. A filter 
 of common form is made of unsized paper. Cut in the 
 shape of a ckcle, it is folded so as to fit into a funnel (Fig. 
 44) . The turbid fluid poured upon it filters through ; and 
 tlie clear liquid is caught in the vessel below, while the sedi- 
 ment is left upon the filter. 
 
 On a large scale water is freed from its suspended matter 
 by passing it through filtering beds of sand or gravel. 
 
 Fig. 45. 
 
 Distillation. — Impurities dissolved in water may be 
 either fixed or volatile -matter. When the water is boiled, 
 only the gaseous impm-ities will pass away with the steam. 
 The solid impurities will be left behind in the boiler, and if 
 the steam be- collected and cooled back into water, the fluid 
 
CHEMISTEY. 95 
 
 will be free from them. This process of boiling and then 
 condensing the vapor is called Distillation. 
 
 In Fig. 45, one form of a Still, as the apparatus for 
 distilling liquids is called, is represented. It consists of the 
 boiler and the worm. The boiler is a close vessel standing 
 over a furnace. The worm is a pipe, usually of tin, bent 
 into a coil, and placed in a vessel which is kept full of cold 
 water. The boiler and worm are connected by a steam-pipe. 
 
 The steam passing over from the boiler enters the worm, 
 where, condensed by the low temperature, it becomes water 
 again, and may be caught as it flows from the bottom. , 
 
 To Remove Volatile Impurities. — By boiling water in 
 an open vessel, such gases as air and carbon dioxide are 
 driven away. But ammonia and sorganic substances, which 
 may be present, cannot be removed so easily. It is necessary 
 to put potassium permanganate and potassium hydrate with 
 the distilled water, and then distill it a second time. These 
 substances decompose the organic-' matter ; and if the first 
 portion of the water which coihes over in this second distil- 
 lation be thrown away, another may be collected which is 
 likely to be pure distilled water. 
 
 By Freezingr. — If the quantity of solid impurities in 
 solution be small, water may be purified from them by freez- 
 ing. The water only will become ice, while the impurities 
 will be left in the fluid which remains unfrozen. On 
 re-melting the ice a purer water is obtained. 
 
 But where the quantity of salt in the water is large, there 
 is a different result. The fluid must be cooled to a much 
 lower degree, and then a portion of the salt enters into com- 
 bination with the water to form the crystals which are 
 deposited. In the case of common salt the crystals begin 
 to form at —7° C, and they are composed of salt and water 
 in proportion represented by 
 
 NaCl + 2H20. 
 On remelting these crystals, salt-water is obtained. Many 
 
96 CHEMISTRY. 
 
 other salts, in the same way, combine with ice ; and these 
 new compounds have been called Cryohydrates. 
 
 83. Hard and Soft Water. — Water which contains 
 compounds of lime or magnesia in solution is familiarly 
 called Hard Water. The magnesia may be present as a 
 sulphate, and the lime as a carbonate, which is soluble in 
 water containing carbon dioxide. 
 
 A water is hard when it requires much soap to make a 
 lather. Now, soap is a salt, which contains a fatty acid 
 combined with a base ; and these salts of lime and magnesia 
 decompose the soap, and combine with its acid constituent. 
 The new compound is insoluble in water, and adheres to the 
 surface of whatever is being washed. 
 
 To Soften Hard Water. — If the water is hard, because 
 of the presence of lime carbonate, it may be softened by 
 boiling ; for, by boiling, the carbon dioxide is driven away, 
 and the carbonate, no longer soluble, will settle as a precipi- 
 tate. Or, by adding some "milk of lime" (calcium 
 hydrate, Ca H^ O2, and water) , the free carbon dioxide may 
 be removed, and the water softened. If water is hardened 
 by a sulphate, it can not be softened in these ways : its hard- 
 ness is permanent. 
 
 84. Hydrogen Dioxide A second compound of hydro- 
 gen and oxygen, and the only one beside water, is Hj, O2, 
 called Hydrogen Dioxide. It is prepared by the action of 
 dilute sulphuric acid on pure barium dioxide ; thus, — 
 
 BaOz + H2SO4 = BaSO^ -|- H^Oj. 
 Barium , Sulphuric _ Barium . Hydrogen 
 dioxide acid ~ sulphate dioxide. 
 
 The dioxide, Hj O2, remains dissolved in water, but by care- 
 fully evaporating the water the dioxide may be obtained. 
 
 85. Properties. — Hydrogen dioxide is a colorless, oily 
 liquid, almost one and a half (1.452) times heavier than 
 water. It has no smell, but it has an astringent taste. If in 
 
CHEMISTKY. 97 
 
 contact with the skin, it raises a white blister. It destroys 
 vegetable colors. 
 
 This compound is very unstable, decomposing sponta- 
 neously at 15° C, and at 100° C. so rapidly as sometimes 
 to produce explosion. The products are water and oxygen. 
 The presence of finely divided silver or gold decomposes it 
 with great violence, while, curiously enough, the metal itself 
 remains unchanged. 
 
 86. Hydroxyl. — Hydroxyl is the name given to half a 
 molecule of the hydrogen dioxide : the formula for the di- 
 oxide being Hj O2, that of hydroxyl is H O. 
 
 This group of atoms, H O, is found in a large number of 
 compounds. Thus we find it in sodium hydrate, Na H O ; in 
 potassium hydrate, KHO; in calcium hydrate, Ca (H0)2; 
 and in alcohol, Cj H5 H O. 
 
 It is believed that in a great many chemical changes this 
 group remains unbroken. The hydrogen and the oxygen 
 atoms cling together, and go together into combination, and 
 stay together in the new molecule. The group is univalent. 
 This is shown by its constitutional formula, H — O — . 
 
 III. — Oxygen and Chlorine. 
 
 87. Oxides and Acids of Chlorine. — The chemical at- 
 traction between chlorine and oxygen is very feeble. Still 
 there are three oxides of chlorine known, — the monoxide 
 CI2O, the trioxide CI2O3, and the peroxide CI O2. 
 
 The first two of these oxides combine with water to form 
 acids ; thus : — 
 
 CVO + H2O = 2HC10, 
 
 Chlorine monoxide -f- Water = Hypochlorous acid. 
 
 CI2O3 + H2O = 2HCIO2, 
 
 Chlorine trioxide 4- "Water = Chlorous acid. 
 
 In addition to these, there are two other acids of chlorine : 
 
 Chloric acid HCIO3, 
 
 Perchloric acid H CI O4. 
 
98 CHEMISTRY. 
 
 88. Chloric Acid. — In this series of seven compounds, 
 the chloric acid Is the most important. Even this one is im- 
 portant, only because It yields a valuable class of salts, — 
 the chlorates. Potassium chlorate is an example. 
 
 Hypochlorous Acid. — Next in importance is the hypo- 
 chlorous acid, which is of interest chiefly because it is a 
 constituent in " bleaching-powder. " This useful substance 
 contains calcium hypochlorite, Ca (CI 0)2, and its bleaching 
 power depends on this substance. The addition of hydro- 
 chloric or sulphuric acid liberates its chlorine, and this 
 chlorine then attacks the coloring matter. 
 
 All these compounds of chlorine and oxygen are very 
 unstable bodies, decomposing easily, and some of them spon- 
 taneously, often with explosive violence. 
 
 REVIEW. 
 
 I. — SUMMARY OP PRINCIPLES. 
 
 89. Oxygen may be obtained in many ways. It is usually 
 obtained by heating potassium chlorate, K CI O3. 
 
 It is produced by heating mercuric oxide, Hg O. Also by 
 the electrolysis of water. 
 
 Oxygen is colorless, tasteless, odorless, a little heavier than 
 air, and slightly soluble in water. 
 
 It enters into combination with all the elements, with the 
 possible exception of fluorine. 
 
 Substances which burn in air burn with increased vigor in 
 oxygen, and many substances which will not burn in air wQl 
 burn when heated in this gas. 
 
 The combining weight of oxygen is 1 6 : its molecular 
 weight is 32 :. its molecular formula is O^ or O ^ 0. 
 
 Oxygen exists in an allotropic form, called Ozone. In this 
 condition it attacks and combines with many things for 
 which, in its ordinary state, it has no afHnitv. 
 
CHEMISTEY. 99 
 
 The molecular formula for ozone is O3, or / \ . Having 
 
 — 
 three atoms in the molecule instead of two, its density is f , 
 or 1.5, that of oxygen. 
 
 The compounds of oxygen are very numerous. Whether 
 produced by common oxygen or by ozone, their composition 
 is the same : they are called oxides. 
 
 Oxygen is the most abundant element in nature. 
 
 Oxygen and hydrogen form two compounds, viz. : Water 
 or Hydrogen Oxide, H^O, and Hydrogen Dioxide, H2O2. 
 
 Water is the sole product of the combustion of pure hydro- 
 gen. 
 
 Water consists of hydrogen and oxygen in the proportion 
 of 1 : 8 by weight. By volume the proportions are two of 
 hydrogen to one of oxygen. 
 
 The graphic formula for water is H — — H. An atom 
 of oxygen links together two atoms of hydrogen to form a 
 molecule. 
 
 The power of water as a solvent is very great. Heat 
 generally increases the solubility of solid bodies in water ; it 
 diminishes the solubility of gases. 
 
 Rain-water, caught after much has fallen, is the purest 
 form of water to be found in nature. 
 
 All spring-water contains soluble salts and gases. If these 
 substances are present in sufficient quantity to impart special 
 properties to the water, it is called mineral water. 
 
 Water may be purified by filtration or by distillation : by 
 filtration it may be freed from sediment ; by distillation it may 
 be freed from all solids and most of its gaseous impurities. 
 
 The presence of salts of lime and magnesia renders water 
 unable to dissolve soap readily ; such waters are called hard 
 waters. 
 
 Hydrogen dioxide is a colorless liquid, nearly one and a 
 half times heavier than water. It readily decomposes into 
 oxygen and water. 
 
100 CHEMISTRY. 
 
 Its graphic formula is H — O — — H. 
 
 Hydroxyl is a compound of one atom eaci of hydrogen 
 and oxygen. Its graphic formula is H — O — . One of the 
 bonds of the oxygen atom is free. In other words, the mole- 
 cule is univalent. 
 
 This group, H O, is found in a large number of com- 
 pounds. 
 
 Oxygen and chlorine form three oxides of chlorine. There 
 are also foui- acids with chlorine. 
 
 All these compounds are very unstable. 
 
 Chloric acid is important because if forms a large and use- 
 ful class of compounds, the Chlorates. 
 
 Hypochlorous acid is important because some of its salts 
 are bleaching agents. The calcic hypochlorite is the bleach- 
 ing agent in " bleaching powder," often called "chloride of 
 lime." 
 
 II. —EXERCISES. 
 
 describe the preparation of oxygen. Write the reaction. 
 
 What weight of oxygen will be furnished by one thousand 
 grams of potassium chlorate ? 
 
 How much by volume, the density of oxygen being 16? 
 
 What weight of potassium chlorate must be used to 
 obtain ten liters of oxygen? 
 
 What volume of oxygen may be obtained from one hun- 
 dred grams of the mercuric oxide, Hg ? 
 
 What are the physical properties of oxygen ? What is the 
 chemical action when carbon burns in oxygen ? When iron 
 burns in oxygen ? What is the relation of oxygen to animal 
 life ? What class of compounds does oxygen form ? 
 
 Give the atomic weight' of oxygen. Its atomic volume. 
 Its molecular weight. Its molecular volume. Its density. 
 
 Where does oxygen occur m nature ? 
 
 How may ozone be produced ? By what test may it be 
 recognized ? In chemical character how does it differ from 
 oxygen ? 
 
CHEMISTRY. 10] 
 
 Define allotropism. What evidence that ozone is an 
 allotropic form of oxygen ? What is the density of ozone ? 
 What explanation is given ? 
 
 What is the product when hydrogen is burned ? 
 
 What is the composition of water by volume ? By weight ? 
 What is its freezing point ? Its boiling point ? What is the 
 temperature of water at its greatest density ? 
 
 Define solution. Solvent. What is a saturated solution ? 
 
 What is the effect of heat upon solubility ? 
 
 What are mineral waters ? 
 
 Define filtration. Evaporation. Distillation. Filtrate. 
 Distillate. Describe the process of distillation. 
 
 What are cryohydrates ? 
 
 What are ' ' hard waters ' ' ? How may hard water be soft- 
 ened? 
 
 What is the composition of hydrogen dioxide ? How may 
 it be obtained? What are its properties? What are the 
 products of its decomposition? 
 
 What is hydroxyl ? In what is this group of atoms found ? 
 What is its quantivalence ? 
 
 Name the oxides of chlorine. How many acids of chlo- 
 rine are known ? Which of these are important ? What is 
 bleaching-powder ? 
 
 IV. — Sulphur. 
 
 90. Preparation. — By far the greater part of sulphur in 
 commerce has been obtained from the ' ' native sulphur, ' ' 
 such as is found in Sicily, simply by the application of heat. 
 The sulphur is vaporized, and, passing over into large cold 
 chambers, the vapor is again condensed. In this way sul- 
 phur in the finest powder, known in commerce as Flowers 
 OF Sulphur, is obtained. 
 
 When smaller chambers are used, their walls soon become 
 so heated by the hot vapors, that the sulphur is kept in a 
 melted state. This liquid, drawn off into molds and cooled, 
 forms what is known as Eoll Brimstone. 
 
102 CHEMISTEY. 
 
 91. Properties. — Sulphur is a solid at ordinary tempera- 
 tures. It is tasteless and without odor. 
 
 The effects of heat on this element are very unusual- Let 
 a small quantity of sulphur be laid on a piece of writing- 
 paper, and held over the flame of a candle ; in a little time it 
 melts to a clear, yellow liquid. The melting occurs at about 
 115° C. Again : put more of it into a test-tube, and heat it 
 gradually. After melting, it remains a clear, limpid liquid 
 up to about 132° C, and then begins to get thick and dark- 
 colored. At about 250° C. it is so viscid that it can scarcely 
 be poured from the tube ; but, as the heat increases, it 
 becomes less viscid again, and finally, at about 450° C. it 
 boils. 
 
 If, when heated to almost the boiling point, the mobile 
 liquid is poured into cold water, it becomes curiously unlike 
 common sulphur ; it cools into a dark-colored solid, with a 
 considerable degree of elasticity. In this condition it is 
 called Plastic Sulphur. On standing, it soon becomes 
 yellow and brittle again. 
 
 92. Crystalline Forms. — Sulphur may be obtained in 
 crystals, either by melting it or by dissolving it. 
 
 If we fill a test-tube one-half full of sulphur, and melt it, 
 and then let it cool slowly, we may soon see the formation of 
 crystals, which grow from the cool sides of the tube toward 
 the center of the liquid. These crystals will multiply until 
 they crowd one another more and more so that the whole 
 finally becomes a compact mass. 
 
 If we desire to keep the crystals separate, we may melt the 
 sulphur in a beaker, let it cool slowly until a good crop has 
 formed, then pierce the crust on top, and pour off the remain- 
 ing liquid. Fine transparent needle-shaped crystals of sul- 
 phur will line the walls of the beaker. 
 
 These experiments illustrate the production of crystals by 
 the method of fusion. Crystals may also be obtained by the 
 method of solution. 
 
CHEMISTS, Y. 103 
 
 Crystals by Solution Sulphur is not at all soluble in 
 
 water, but it dissolves easily in carbon disulphide. The car- 
 bon disulphide is very volatile : it rapidly evaporates on 
 exposure to air, and deposits the sulphur in the form of 
 crystals. These crystals are not needle-shaped like those 
 obtained by fusion : they are rhombic octahedrons instead. 
 
 Sulphur is not the only substance which is able to crystallize 
 in two distinct forms. Such substances are said to be 
 Dimorphous. 
 
 93. Cliemical Properties. — Sulphur has a wide range 
 of attractions. It unites with oxygen and with hydrogen to 
 form important acids. With the metals it forms a numerous 
 class of compounds called Sulphides. These were formerly 
 called sulphurets. 
 
 94. Sulphur in Nature. — In some volcanic districts 
 sulphur is found free. The mines of sulphur on the island 
 of Sicily contain the sulphur mixed with earthy matter, and 
 much more rarely in the form of very pure and beautiful 
 crystals. 
 
 Sulphur is found in combination with metals in the earth 
 almost everywhere. Iron pyrites, so common and familiar, 
 is a disulphide (Fe S2) . In combination with hydrogen it is 
 found in the water of what are called sulphur-springs. And, 
 besides all this, sulphur is an important element in many 
 animal and vegetable substances. 
 
 95. Its Uses. — Sulphur is very largely used in the arts. 
 It is a constituent of gunpowder and of sulphuric acid. It 
 is used in the manufacture of friction-matches, in medicine 
 also ; and in its elastic state, produced under the influence of 
 heat, it is used in taking casts of coins and medals. 
 
 V. SULPHUH AND HyDROGEN. 
 
 96. Sulphuretted Hydrogen. — Two compounds of 
 sulphur and hydrogen are known. They are represented by 
 the formulas Hj S and Hj %. The first of these, hydi'ogeu 
 
104 
 
 CHEMISTEY. 
 
 sulphide, or, as it has long been called, sulphuretted hydro- 
 gen (Hg S) , is an indispensable substance in the laboratof-y, 
 and it is that which is dissolved in the waters of the so-called 
 sulphur-springs, giving to them their odor, taste, and medici- 
 nal qualities. 
 
 Fig. 46. 
 
 97. Preparation. — Fragments of ferrous sulphide (Fe S) 
 are placed in a bottle (Fig. 46), which is provided with a 
 tightly fitting cork and two tubes, one a funnel-tube reach- 
 ing nearly to the bottom, the other a bent tube reaching from 
 the cork over into the water of a cistern. Dilute sulphuric 
 acid is poured through the funnel- tube. Chemical action at 
 once begins, and the sulphuretted hydrogen is set free. 
 
 FeS + H2SO4 = FeSOi -f H2S, 
 Ferrous , Sulphuric _ Ferrous , Sulphuretted 
 
 + 
 
 + 
 
 sulphide acid sulphate hydrogen. 
 
 98. Properties. — Hydrogen sulphide is a colorless gas, 
 having a powerful and unpleasant odor, resembling the odor 
 of rottfi]i_eggs. Very small proportions of the gas mixed 
 with air render it unpleasant ; while the gas itself, when 
 inhaled, acts as a powerful poison. Very dilute chlorine is 
 an antidote to this poison. Should an antidote ever be re- 
 quired, then moisten a towel with dilute acetic acid, sprinkle 
 a few grains of bleaching-powder upon it, fold the powder 
 
CHEMISTRY. 
 
 105 
 
 inside, and apply the outside to the nose. The acid liberates 
 the chlorine, and the chlorine attacks the hydrogen sulphide. 
 Reaction with Metals. — Sulphuretted hydrogen is very 
 readily decomposed by many metallic compounds, whose 
 metals are in this way converted into sulphides. Thus, — 
 
 CUSO4 + 
 
 Copper 
 
 sulphate sulphide 
 
 H2S = H2SO4 + CuS, 
 Hydrogen _ Sulphuric Copper 
 
 acid ''" sulphide. 
 
 This power to convert metals into sulphides renders 
 hydrogen sulphide an indispensable reagent in the laboratory. 
 
 Solubility. — This gas is freely^oluble in cold water. 
 The solution is easily prepared by passing the gas through 
 
 ^ 
 
 Fig. 47. 
 
 successive bottles of water, arranged, as represented in 
 Fig. 47. The sulphide still retains its odor and its chemical 
 power, and the solution can be used for chemical purposes 
 instead of the gas. 
 
 VI. — Sulphur and Oxygen. 
 
 99. Oxides and Acids. — Sulphur and oxygen form two 
 oxides : — 
 
 Sulphurous oxide S Oj, 
 
 Sulphuric oxide S O3. 
 
106 
 
 CHBMISTBY. 
 
 By combining with the elements of water, these yield two 
 very important acids : — 
 
 Sulphurous acid H2 S O3, 
 
 Sulphuric acid H2 S O4. 
 
 Oxides which form acids by uniting with water are often 
 called Anhydrides. The S O2 may be called sulphurous 
 anhydride, and the S O3, sulphuric anhydride. 
 
 SO2 + H2O 
 
 Sulphurous anhydride + Water 
 
 Hj S Oj, 
 Sulphurous acid. 
 
 In addition to the two acids just named, six others are 
 known. One of these is thiosulphuric acid : it was formerly 
 known as hyposulphurous acid. Its salts, then known as 
 hyposulphites, are now called thiosulphates instead. Sodium 
 thiosulphate is an example, and a useful substance. 
 
 Pig. 48. 
 
 100. Sulphurous Oxide. — Set fire to a piece of sulphur 
 in a deflagrating spoon, and thrust it into a bottle of air 
 (Fig. 3). The sulphur burns, combining with the oxygen, 
 and forms sulphurous oxide. 
 
 To obtain this gas in a pm-er state, we may treat copper 
 
/chemistry. 107 
 
 with sulphuric acid. The operation may be conducted in an 
 apparatus shown in Fig. 48. The copper and acid are 
 brought together in a retort, and heated. The gas may be 
 collected over mercury. Three new substances are produced : 
 viz. , copper sulphate, water, and sulphurous oxide, thus : — 
 
 Cu + 2H2SO4 = CUSO4 + 2H2O + SO2, 
 COPP- + 'tSr = sSpTaTe + ^^*er + ^^xidr 
 
 101. Properties. — Sulphurous oxide is a colorless gas, 
 with a very stifling odor. It is very soluble in water, but 
 when dissolved it is no longer sulphurous oxide : it has com- 
 bined with water, and has become sulphurous acid. This is 
 easily demonstrated by pouring a little water into a bottle-'in 
 which sulphur has been burned, and then adding a little of 
 this liquid to a beaker of blue litmus solution. The red- 
 dening of the litmus, which immediately occurs, declares the 
 acid character of the solution. 
 
 102. BleacMag. — Both the gas and its solution have 
 power to remove colors. If, for example, a brightly tinted 
 flower, be held over burning sulphur, its color disappears. 
 
 This action is employed in the arts for bleaching silk, 
 woolen, and straw goods. For example, if a milliner wishes 
 to whiten her straw, she may hang it in a small chamber, 
 which may be nothing more than an inverted barrel, and then 
 bum some sulphur under it. The sulphurous oxide enters 
 the straw, and discharges its color. 
 
 On a large scale the slightly moistened articles are hung 
 in large chambers in which sulphur-flres are kindled. 
 
 103. A Reducing Agrent. — Sulphurous oxide takes oxy- 
 gen out of many other substances, and reduces therii to sim- 
 pler forms of combination. If, for example, we fill a bottle 
 with the gas, by burning in it some sulphur, and then thrust 
 into it a glass rod, or, better, a shaving of wood, moistened 
 with strong nitric acid, dark red fumes will soon make their 
 
108 CHEMISTRY. 
 
 appearance. These red fumes show that a compound of 
 nitrogen and oxygen, N Oj, is set free. 
 
 The chemical action may be written as follows : — 
 
 2HNO3 + SO2 = H2SO4 + 2NO2, 
 
 Nitric acid + ^^P^}^'^^^ = Sulphuric Nitrogen 
 ' oxide acid ' peroxide. 
 
 A substance which readily takes oxygen out of others is 
 called a Reducing Agent. Sulphurous oxide is valuable to 
 the chemist as a reducing agent. 
 
 Nitric acid, on the other hand, readily imparts oxygen to 
 other substances. In the above illustration it gives oxygen 
 to the S O2, and oxidizes it to S O3, which then combines with 
 2 Hj O to produce the Hj S O4. A substance which readily 
 parts with oxygen to other substances, as nitric acid does, is 
 called an Oxidizing, Agent. Nitric acid is valuable to the 
 chemist as an oxidizing agent. 
 
 104. Preparation of Sulphuric Acid. — Sulphuric, acid 
 is made by oxidizing sulphurous oxide in presence of water. 
 The oxidizing agent employed is nitric acid, or a compound 
 of nitrogen and oxygen such as the nitrogen peroxide, N Oo. 
 -. On a large scale the sulphurous oxide is obtained by burn- 
 ing sulphur, or iron pyrites (Fe Sj) which yield sulphur when 
 heated. This sulphurous oxide is carried over into immense 
 chambers, which are made of sheet-lead. As it enters the 
 first lead chamber, it meets with nitric acid, which falls 
 through it in fine streams, and also with steam, which is 
 blown in from a boiler. The sulphurous oxide is changed 
 into sulphuric acid, which condenses on the walls of the 
 chamber, and trickles down to the floor, where it remains 
 dissolved in water. 
 
 The nitric acid is thus reduced to nitrogen monoxide, N ; 
 but this unites at once with the oxygen of the air in the 
 chamber, and becomes nitrogen peroxide, N O2. 
 
 This nitrogen peroxide gives half its oxygen to change 
 
CHEMISTRY. 109 
 
 another portion of S O2 to S Og, which, in presence of steam, 
 becomes Hj S O4, and is itself again reduced to N 0. 
 
 Again, the N becomes N O2 by taking oxygen from air ; 
 and, again, the NO2 oxidizes another portion of S Oj. In 
 this way the N O is a carriage which conveys oxygen from 
 the air to the sulphurous oxide, continually. 
 
 The fluid which collects on the floors of the lead chambers 
 is very dilute sulphuric acid, having a specific gravity of 1.55. 
 
 Oil of Vitriol. — The dilute acid is made stronger by 
 drawing it off into leaden pans, and heating it. The water 
 passes off as steam, and the acid remains. In this way the 
 acid is concentrated until it contains only twenty-two per 
 cent of water, or has a specific gravity of 1.71. In this 
 form it is called Oil of Vitriol. Put up in large bottles, 
 incased in wood, called carboys, it is sold in great quantities. 
 
 Oil of vitriol always contains lead sulphate taken from the 
 lead pans. To avoid this impurity the concentration is often 
 made in vessels of glass or of platinum. Even then the acid 
 may contain other impurities, especially arsenic, which comes 
 from the pyrites employed. To obtain pure sulphuric acid, 
 the commercial acid is distilled in glass retorts. 
 
 105. Properties. — Pure sulphuric acid is a colorless, 
 very heavy, and oily liquid. The usual brown color of the 
 "oil of vitriol " is due to a little organic matter which it 
 contains. 
 
 Its attraction for water is one of the most remarkable 
 characters of this acid. Left in an open bottle, it speedily 
 takes moisture from the atmosphere, and increases in volume. 
 
 The combination of the acid with liquid water is a source 
 of heat. Let a little water be put into a beaker, and about 
 four times as much strong acid added. The beaker will be 
 found too hot to be handled with convenience ; and if a test- 
 tube containing alcohol, or even a little water, be placed in 
 the mixture, its contents will boil vigorously. 
 
 Many organic bodies are decomposed by sulphuric acid. 
 
110 CHEMISTRY. 
 
 They are composed of carbon, hydrogen, and oxygen ; and 
 the acid seizes their hydi'ogen and oxygen in the proportions 
 which form water, leaving the carbon behind. A piece of 
 white pine wood is almost instantly blackened in this way 
 by contact with the acid, and paper is also charred as if by 
 fire. Let about 50 centimeters of the strong acid be mixed 
 with the same volume of a thick sirup of sugar in a tall jar : 
 the chemical action is violent, and the sugar is converted into 
 a bulky mass of porous charcoal. 
 
 106. Uses. — Sulphuric acid is regarded as the most use- 
 ful acid known. Its manufacture is one of the important 
 branches of industry. Probably more than a million tons is 
 made yearly in Great Britain and the United States. 
 
 It is used in the manufacture of almost all other chemicals, 
 in the preparation of fertilizers, in the art of bleaching, in 
 dyeing, and in calico-printing. 
 
 "7^-107. The Sulphates. — By action on the metals, sulphuric 
 acid forms a large class of compounds, called Sulphates. 
 Both atoms of hydrogen in its molecule (Hj S O4) , or one 
 alone, may be displaced by atoms of metal, and hence two 
 classes of sulphates exist. Thus with sodium we may have 
 Naj S O4, or Na H S O4. The first is the Normai sodium 
 sulphate ; the second is the Acid sodium sulphate. A nor- 
 mal salt is one in which all the replaceable hydrogen of the 
 acid is removed. An acid salt is one in which only a part of 
 the replaceable hydrogen of the acid is removed. 
 
 The hydrogen of an acid which can be replaced by metals 
 is called Basic hydrogen. And sulphuric acid is said to be a 
 Dibasic acid, because its molecule contains two atoms of 
 hydrogen, for which metallic atoms may be substituted. 
 
 Most of the sulphates are freely soluble in water. Lead 
 sulphate and a few others are but little soluble, while barium 
 sulphate is quite insoluble. 
 
 108. Tests. — • If a little barium chloride is added to a 
 solution containing a sulphate, or sulphuric acid itself, the 
 
CHEMISTRY. Ill 
 
 insoluble barium sulphate will be invariably produced. If 
 will appear as a white precipitate, which will not dissolve 
 in hydrochloric acid. The appearance of this precipitate 
 declares the presence of the acid, or its compounds, in the 
 suspected liquid. 
 
 Free sulphuric acid may be detected by its charring organic 
 bodies. Vinegar has been known to contain this acid. To 
 detect the adulteration , add a little white sugar, and then 
 evaporate the vinegar to dryness at a gentle heat. If a 
 black r esidue r emains, it indicates the presence of the acid. 
 
 Vn. — Selenium and Tellurium. 
 
 109. Selenium. — Selenium is a solid element found in 
 small quantities, usually in combination, as selenides of 
 metals. Copper, lead, and silver selenides are examples. 
 The element exists in two allotropic forms. In one it is 
 soluble in carbon disulphide (C Sj) , in the other it is not. 
 
 The relations of selenium to electricity are most curious 
 and important. When cooled suddenly from a melted state, 
 it is very brilliant, dark-colored, and a non-conductor of 
 electricity. When cooled slowly from fusion, it has a dull 
 lead-colored surface, is crystalline, and is a conductor of 
 electricity. Its power to conduct is increased by heat. So 
 exceedingly sensitive is it, that even the heat of a candle- 
 flame, at a distance, wiU diminish its resistance to the 
 passage of the current. Even when the radiation from 
 the candle passes through a layer of water, it still affects the 
 selenium, indicating that the element is affected not only by 
 heat but by light alone, since water transmits the light but 
 absorbs heat. 
 
 110. Application. — The rapidity with which selenium 
 will respond to the touch of light is remarkable. Let the 
 light be flashed on and off in quick succession, and the 
 resistance of the selenium changes with equal rapidity. 
 
 This principle has been applied by Graham Bell io hia 
 
1V2 GHBMISTEY. 
 
 photophone. Light is thrown upon a mirror which reflects it 
 to a distant selenium receiver, lenses being employed to con- 
 centrate it. This receiver is placed in circuit with a battery 
 and a Bell telephone. If the voice is thrown against the 
 back of the mirror, the mirror will vibrate and put the beam 
 of light in motion. The motion of this light on the surface 
 of the selenium varies its resistance. The current of elec- 
 tricity passing through it is thus thrown into undulation. 
 These undulations of the current correspond to those of the 
 voice, and affect the ear at the telephone in the same way. 
 Thus has this property of selenium been made useful in the 
 transmission of sound by light. 
 
 111. Tellurium. — Tellurium is even more rare than 
 selenium. When pure this element is bluish- white and 
 lustrous. In physical properties it resembles the metals, but 
 its cliemical actions are much like those of selenium and 
 sulphur. 
 
 VIII. — The Bivalent oe Oxygen Grotip. 
 
 112. Chemical Resemblance of these Elements. — 
 
 Oxygen, sulphur, selenium, and tellurium form a well-marked 
 natural group. They enter into combination with the same 
 substances, and their compounds have similar composition. 
 
 This analogy is seen in their hydrogen compounds. 
 Thus : — 
 
 HjO, HjS, H^Se, U^Te. 
 
 Their bivalent character is clearly shown by these formulas. 
 The last three elements of the group form analogous com- 
 pounds with oxygen. Notice the formulas : — 
 
 502, SeOg, TeOj, 
 
 503, SeOs, TeOg, 
 
 in which this resemblance clearly appears. 
 
CHEMISTRY. 113 
 
 By combining with water, these oxides all form acids. 
 Thus : — 
 
 SeOj + H2O = HaSeOa, 
 
 Selenium dioxide + Water = Selenious acid. 
 
 EEVTEW. 
 
 I. — SUMMARY OF PRINCIPLES. 
 
 113. Sulphur is found in nature uncombined. 
 
 This element is a yellow solid, at ordinary temperatures 
 very fusible, easily vaporized, but quite insoluble in water. 
 
 An allotropic form of sulphur is produced by heating it 
 to near its boiling-point, and suddenly cooling it by cold 
 water. In this condition it is dark-colored and elastic. 
 
 The compounds of sulphur are very numerous and 
 important. 
 
 With hydrogen it forms the useful but unpleasant ' ' sul- 
 phuretted hydrogen " or hydric sulphide, H2S. 
 
 This gas is readily decomposed by many salts : their 
 metals take the sulphur, and become sulphides. 
 
 With oxygen sulphur forms two oxides, or anhydrides, 
 SO2 and SO3; and these unite with water to form the 
 sulphurous and the sulphuric acids. 
 
 Both sulphurous oxide and sulphurous acid are good 
 bleaching agents. They are used for bleaching silk, woolen, 
 and straw goods. 
 
 Sulphurous oxide is a reducing agent. 
 
 Sulphuric acid is obtained by burning native sulphur, or 
 iron sulphide, and oxidizing the sulphurous oxide thus 
 formed by means of nitric acid and the nitrogen oxides. 
 
 This acid is the most useful among chemicals. It is a 
 heavy, oily liquid, having a strong attraction for water. It 
 combines directly with water, and also decomposes many 
 organic substances in order to obtain their hydrogen and 
 
114 CHEMISTRY. 
 
 oxygen, which it takes from them in the proportions which 
 form water. 
 
 This acid is dibasic. Its salts are sulphates, and these are 
 either normal sulphates or acid sulphates. 
 
 The barium sulphate is the most' insoluble in water or 
 acids. It is formed whenever a barium compound is added 
 to a solution of any sulphate. It appears as a white pre- 
 cipitate. This is a test for the presence of sulphuric acid, 
 either when it is free or in combination. 
 
 Selenium and tellurium are rare elements, much resembling 
 sulphur in their chemical actions. 
 
 Oxygen, sulphur, selenium, and tellurium are bivalent, and 
 constitute a well-marked group, known as the oxygen or 
 bivalent group of non-metals. 
 
 II.— EXERCISES. 
 
 Describe the preparation of sulphur. Describe the effect 
 of heat on sulphur. 
 
 In what two ways may crystals be obtained? How may 
 we obtain crystals of sulphur by fusion? How may we 
 obtain crystals of sulphur by solution ? Why is sulphur said 
 to be a dimorphous substance? What class of compounds 
 does sulphur form? How does sulphur occur in nature? 
 What are some of the uses of this element? 
 
 What is sulphuretted hydrogen ? How may it be prepared ? 
 Write the reaction. What are the properties of this sub- 
 stance ? What is the chemical action of this gas on metals ? 
 Write the reaction with Cu S O4. 
 
 Name the oxides of sulphur. Give their composition. Name 
 the corresponding acids. Define anhydride. Show by the 
 equation that the addition of the elements of water converts 
 these oxides into acids. 
 
 What compounds of chlorine are anhydrides ? 
 
 How may sulphurous oxide be obtained? Describe thQ 
 gas. For what purpose is it useful ? 
 
CHEMISTRY. 115 
 
 What is a reducing agent? What is an oxidizing agent? 
 Show by the equation how S O2 reduces nitric acid. 
 
 How is sulphuric acid made? 
 
 Describe the process as conducted on a large scale. What 
 is oil of vitriol ? 
 
 What is the result of bringing sulphuric acid and water 
 together ? What action does Hg S O4 exert on organic bodies ? 
 What are some of its uses ? 
 
 What class of compounds does sulphuric acid produce? 
 What is a normal salt? What is an acid salt? What is a 
 dibasic acid? A monobasic acid? A tribasic acid? What 
 is basic hydrogen ? 
 
 What is the test for sulphuric acid? How would you 
 detect this acid in vinegar? 
 
 Name the members of the bivalent group of non-metals. 
 Give the formulas of their hydrogen compounds. Give the 
 anhydrides of sulphur, selenium, and tellurium. 
 
 1/) A;^^^ SECTION V, 
 IT 
 
 THE TRIVALENT NON-METALS. :i- 
 I. — Nitrogen. 
 
 114. Preparation. — There are large quantities of nitro- 
 gen in the atmosphere, but there are large quantities of 
 oxygen with it. By burning phosphorus in a portion of air, 
 the oxygen will be taken away, and the nitrogen left. For 
 this purpose let a piece of phosphorus the size of a large 
 pea be placed on a cork floating upon the water of a cistern. 
 Touch it with a hot iron, and quickly invert over it a gallon 
 jar. (See Fig. 49.) The phosphorus burns with a beautiful 
 light, while milk-white vapors fill the jar. These vapors will 
 be g'radually absorbed by the water which will rise iuto the 
 jar. The space above the water at last is filled with nitrogen. 
 
116 
 
 CHEMISTRY. 
 
 115. Its Physical Properties. — The nitrogen is now 
 seen to be a gas, perfectly colorless and transparent. It is 
 without odor or taste, and a little lighter than air, its speeifle 
 gravity (air =1) being .972. It is slightly soluble in water, 
 one hundred volumes of water absorbing about 1.5 volumes 
 at ordinary temperature. 
 
 Fig. 49. 
 
 116. Its Chemical Properties. — If a lighted taper be 
 lowered into a jar of nitrogen, it will be extinguished as 
 quickly as if plunged into water. The gas will neither burn, 
 nor allow other things to burn in it. So, too, if an animal 
 were put into this gas, death would soon follow. It is not 
 poisonous, but kills simply because it has no power to sup- 
 port life. A bandage over the face, which would shut all air 
 away from the lungs, would kill in the same way. These 
 facts illustrate the feeble disposition of nitrogen to combine 
 with other elements. It can be made to combine with many 
 
CHEMISTRY. 117 
 
 of the elementary bodies ; but the compounds are for the 
 most part unstable, that is, easily decomposed. On this 
 account the compounds of nitrogen are among the most 
 energetic substances in chemical actions. 
 
 The atomic weight of nitrogen and its density, hydrogen 
 being 1, are 14. 
 
 117. Occurrence in Nature. — Nitrogen is a very abun- 
 dant element. It forms about four-fifths by weight of all 
 the atmosphere, and besides this it is an important constituent 
 in many animal and vegetable bodies. 
 
 ^/ ' II. — NiTEOGEN AND HydROGBN. 
 
 118. Ammonia. — Nitrogen unites with hydrogen to form 
 a single compound : it is the hydrogen nitride, or, as it is 
 commonly called, ammonia. 
 
 Ammonia exists in small quantities in the atmosphere, not 
 free but in combination as a carbonate and some other salts. 
 Its compounds occur in small quantities in rain-water, and 
 are to be found also in all fertUe soils. 
 
 Nitrogen is a constituent in many of the substances which 
 compose animal and some vegetable bodies, and by their 
 putrefaction and decay ammonia is set free. 
 
 In this case the nitrogen and hydrogen are brought together 
 just at the moment when they are liberated from combina- 
 tion. At this moment they unite in ammonia. Substances 
 at the moment when set free from combination are said to be 
 in the Nascent State. Their chemical activity seems to 
 be greater at this time than at others : the hydrogen and 
 nitrogen, for example, which readily unite in the nascent 
 ' state, show no disposition at all to unite when simply mixed 
 together. 
 
 119. Preparation. — Ammonia is usually obtained by 
 heating together some ammonium chloride and ' ' slaked 
 lime." 
 
118 CHEMISTRY. 
 
 The chemical change is as follows : — 
 
 2NH4CI +Ca(0H)2= CaCl2 + 2H2O + 2NH3, 
 
 Ammonmm ^ime = ^^}''''^^ + Water + Ammonia, 
 
 chloride chloride 
 
 That is : two molecules of ammonium chloride with one of 
 calcium hydrate, yield one molecule of calcium chloride, two 
 of water, and two of ammonia. 
 
 120. Physical Properties. — The ammonia obtained is 
 a gas, having a well-known pungent odor. It is much lighter- 
 than air (.586)- But its most remarkable physical property 
 is its solubility in water ; one volume of water at 0° C. 
 absorbing no less than 1,148 volumes of the gas. As in the 
 case of all gases, its solubility is less at higher tempera- 
 tures, but at 15° C. one volume of water still dissolves 
 783 volumes of ammonia. Its solubility may be shown by 
 experiment, using the same apparatus as for hydrochloric 
 acid. The lower bottle should contain a little reddened 
 litmus, and the ammonia may be obtained by heating the 
 " liquor ammoniae " of the shops. 
 
 This "liquor ammonise " is simply the solution of the 
 ammoniargas in water, and it parts with the gas at a gentle 
 heat. 
 
 121. Chemical Properties. — Ammonia combines with 
 the elements of water, and forms ammonium hydrate. 
 Thus : — 
 
 NHs + H2O = ' NH4OH, 
 Ammonia -f- "Water = Ammonium hydrate. 
 
 The ammonium hydrate of the laboratory is made by pass- 
 ing ammonia-gas through water. A few drops of this solu- 
 tion turns reddened litmus blue, which shows it to be a 
 hydrate. Indeed, it is one of the strongest. But on expos- 
 ure to air the hydrate is decomposed, and the ammonia-gas 
 escapes. 
 
CHEMISTEY. 119 
 
 Ammonia has a strong attraction for hydrochloric acid. 
 Let two little cups stand side by side : into one pour ' ' liquor 
 ammoniae"; into the other, hydrochloric acid. The two 
 gases arise, mix, combine, and a cloud of white fumes is 
 produced. The new substance is ammonium chloride, or, as 
 it was formerly called, sal-ammoniac. The presence of N Hg 
 may be tested in this way. 
 
 — Nitrogen and Oxygen. 
 
 122. Nitrogen Oxides and Acids. — No less than five 
 compounds of nitrogen and oxygen are well known. Three 
 of these, by uniting with the elements of water, yield acids. 
 The most important of all these eight compounds is nitric 
 acid, H N O3. 
 
 123. Nitric Acid. — This acid is one of the most impor- 
 tant in chemistry. It is largely used in the laboratory, and 
 in great quantities, also, for many purposes in the arts. The 
 nitrates are a numerous class of salts, many of which occur 
 in large quantities in the earth. From these the acid is 
 obtained. 
 
 124. Preparation. — Let potassium nitrate, often called 
 saltpeter and sometimes niter, and sulphuric acid be heated 
 together : the nitrate will be changed to a sulphate, and the 
 nitric acid will be set free. Thus : — 
 
 KNO3 + H2SO4 = KHSO4 -I- HNO3, 
 
 Potassium , Sulphuric _ Potassium acid , -^j.. . ■-, 
 nitrate acid ~ sulphate 
 
 The nitrate is put into the retort (Fig. 50) , whose neck is 
 thrust into a receiver upon which a stream of cold water runs. 
 The nitric acid goes over in vapor into the receiver, and is 
 there condensed into liquid form. This liquid has a yellow- 
 ish color due to the presence of nitric peroxide. 
 
 Sodium nitrate is much cheaper than niter, and is used 
 instead for the manufacture of the acid for commerce. 
 
120 
 
 CHBMISTEY. 
 
 125. Properties. — Nitric acid is a colorless liquid when 
 pure, intensely acid, corrosive, and poisonous. Let it touch 
 the skin, and it gives a yellow stain which time alone can 
 
 Pig. 50. 
 
 remove ; and, if long in contact, it occasions painful corro- 
 sion. Silk, wool, wood, and most organic bodies receive a 
 bright yellow tint by its action. 
 
 It is a powerful oxidizing agent, as a single experiment 
 
 Pig. 51. 
 
 may illustrate. Place a little tin-foil in a cup, and pour dilute 
 nitric acid upon it. Quickly volumes of red fumes arise, and 
 the tin rapidly changes into a white compound of tin and 
 oxygen. The tin is oxidized by the acid. 
 
CHEMISTRY. 
 
 121 
 
 126. Nitrous Oxide. — First in importance among the 
 nitrogen oxides is the lowest in the-series, the nitrous oxide. 
 It may be obtained by heating ammonium nitrate. The 
 nitrate is put into a flask (Fig. 51), from which a bent tube 
 reaches over into a small bottle standing in a vessel of cold 
 water. Another tube passes from this bottle over to a jar on 
 the shelf of the cistern. By heat the nitrate is melted, 
 and afterward decomposed. Water and nitrous oxide are 
 formed. The water is condensed in the cold bottle, while 
 the oxide is collected in the jar. 
 
 NH4NO, = 2H2O + N2O, 
 
 Ammonium nitrate = Water + Nitrous oxide. 
 
 Properties. — Nitrous oxide is a colorless gas, a little 
 heavier than air. The chemical force between its constitu- 
 ents is weak ; a lighted taper decomposes it, and, taking its 
 oxygen, burns with almost as great brilliancy as in oxygen 
 itself. When breathed, its effects upon 
 the system are peculiar. It often causes 
 a lively intoxication, with a disposition 
 to laughter : for this reason it has 
 been called laughing-gas. It often 
 produces entu'e insensibility, and is 
 administered for this purpose, by sur- 
 geons, to patients upon whom they are 
 to operate. If impure, or carelessly 
 given, it may produce serious results. 
 
 Composition. — Nitrous oxide is 
 composed of nitrogen and oxygen in the 
 proportions by volume of two of nitro- 
 gen to one of oxygen. This composi- 
 tion is represented by the foimula Nj O. 
 
 The Experiment. — The apparatus consists of a eudio- 
 meter, shown in Fig. 52. Four equal divisions are marked 
 off from the closed end of the tube. Two of these divisions 
 are filled with nitrous oxide ; the remaining two are afterward 
 
 A 
 
 -^ 
 
 Fig. 52. 
 
122 
 
 CHEMISTRY. 
 
 filled with pure hydrogen. By an electric spark a violent 
 explosion is made ; steam is condensed on the side of the 
 tube, and water from the cistern will rise, leaving the two 
 upper divisions only filled with gas. This gas, when tested, 
 is found to be nitrogen. 
 
 The Reasoning'. — It is clear that the two volumes of 
 hydrogen have taken oxygen enough — one volume — from 
 the oxide, to form the water that was condensed on the tube, 
 and have left two volumes of nitrogen. The nitrous oxide, 
 then, was composed of two volumes of nitrogen and one of 
 oxygen. 
 
 If we represent equal volumes of the two gases by equal 
 squares, and their names by their symbols, the composition 
 of the compound may be shown to the eye by the following 
 diagram : — 
 
 N 
 
 N 
 
 + 
 
 
 
 and represented also by the formula N2 0. 
 
 127. Nitric Oxide. — Nitric oxide may be obtained by 
 the action of copper upon dilute nitric acid, in an apparatus 
 
 similar to that used in the 
 preparation of hydrogen. 
 (Fig. 53.) 
 
 The copper decom- 
 poses the nitric acid ; red 
 fumes flit the bottle ; but 
 when the nitric oxide 
 bubbles through the wa- 
 ter into the jar it is seen 
 to be colorless and trans- 
 j,jg_ gg parent. A lighted taper 
 
 will be instantly extin- 
 guished by this gas ; but burning phosphorus will decompose it, 
 take the oxygen from it, and burn with exceeding brilliancy. 
 
CHEMISTRY. 
 
 123 
 
 Composition. — This gas is decomposed also by lieated 
 potassium, and when a measured quantity is used the com- 
 position of the gas may be found. It is composed of one 
 volume of nitrogen and one volume of oxygen. This compo- 
 sition is represented to the eye by the following diagram : — 
 
 N 
 
 + 
 
 
 
 and its formula must therefore be written N O. 
 
 128. Nitrous Anhydride. — Nitrous anhydride is a third 
 compound of nitrogen and oxygen, obtained with difficulty 
 and imperfectly known. It has been found to consist of two 
 volumes of nitrogen and three of oxygen. Thus : — 
 
 N 
 
 N 
 
 -1- 
 
 
 
 
 
 
 
 The foi-mula is therefore written N, Oa. 
 
 129. Ifitric Peroxide. — If nitric oxide is allowed to 
 escape into the air, the dark cherry-red vapors which appear 
 announce its combination with oxygen. This red substance 
 IS nitric peroxide. By measuring the volumes of nitric oxide 
 and pure oxygen needed to produce this compound, its com- 
 position has been found to be, one volume of nitrogen to two 
 volumes of oxygen. Hence the diagram : — 
 
 N 
 
 H- 
 
 
 
 
 
 and the formula which represents it is N Og. 
 
 The production of this cherry-red gas is a useful test for 
 the presence of free oxygen. Whenever the presence of 
 oxygen is suspected, we may decide by passing into it a little 
 nitric oxide, which instantly unites with oxygen to yield the 
 red fumes of nitric peroxide. 
 
124 ' CHEMISTBY. 
 
 ■J 
 
 130. Nitric Anliydrlde. — Finally we have a compound 
 which, analyzed, is found to contain five volumes of oxygen 
 and two of nitrogen. Thus : — 
 
 N 
 
 N 
 
 + 
 
 
 
 
 
 
 
 
 
 
 
 Its formula is Nj O5. It is called nitric anhydride because 
 it unites with water to form nitric acid. Thus : — 
 
 N2O5 + H2O = 2HNO3. 
 
 IV. — The Atmospheke. 
 131. Nitrogen is a Constituent of Air. — Let a jet of 
 
 hydrogen be burned in a bottle of air. For this purpose an 
 india-rubber tube from the bottle B (Fig. 54), ends in a jet- 
 pipe, which passes tightly through one of two holes in a cork 
 which fits the air-bottle A. Set fire to the jet of hydrogen, 
 
 Fig. 54. 
 
 and insert it in the air-bottle, whose neck may then be 
 quickly lowered into water. The hydrogen burns for a while, 
 and then ceases, the water in the mean time rising a little 
 distance into the bottle. 
 
 If the jet-pipe be now removed, and the remaining gas 
 tested, it will be found to be nitrogen. Hence nitrogen is a 
 constituent of the air. 
 
CHEMISTRY. 126 
 
 ^'' 132. Oxygren is a Constituent of Air. — We have seeu 
 that mercury, when heated for a long time in air, is changed 
 to a red oxide of mercury, and that if this oxide is lieated to 
 a higher temperature the metallic mercury will be restored 
 while oxygen will be given off. Now observe : the oxygen 
 set free from the oxide in the last heatmg must have been 
 taken from the air in the first. The experiment teaches that 
 oxygen is a constituent of air. 
 
 ^_ Carbon Dioxide is a Constituent of Air. — Let a 
 goblet of lime-water stand for a few hours exposed to the 
 air : a crust will be formed on its surface. This crust con- 
 sists of the well-known calcium carbonate. This substance 
 is alwaj's formed when lime-water comes in contact with car- 
 bon dioxide, and its presence in this experiment shows that 
 this contact has occurred, and hence that air contains carbon 
 dioxide. 
 
 133. Water is a Constituent of Air. — That a vessel 
 — of ice- water on a warm day will in a little time be covered 
 
 with drops Of dew, is a fact sufficiently familiar. Now, the 
 water, collected on the vessel, can have come only from the 
 air. It must have been in the air in the form of invisible 
 vapor, which, cooled by the cold sides of the vessel, is 
 condensed. Hence water is a constituent of the air. 
 
 134. Tlie Proportions of Nitrogen and Oxygen. — 
 
 By far the larger part of the atmosphere consists of nitrogen 
 and oxygen : their proportions may be found by experiment. 
 A vessel, V (Fig. 55) , has two openings closed with stop- 
 cocks, c and d. To the upper stop-cock is attached a series 
 of tubes, one, t, with a bulb in which is put some copper to 
 be heated by a lamp below ; others, p p, containing potash ; 
 and others still, a a, containing sulphuric acid. 
 
 The capacity of the vessel is accurately known, and at the 
 beginning of the experiment it is quite full of water. When 
 the stop-cocks are opened, air will flow through the series of 
 tubes, entering at o, until the vessel is filled. In passing 
 
126 
 
 CHEMISTEY. 
 
 through a a, all its water will be taken out by the acid ; in 
 going through p p, all its carbon dioxide will be taken by 
 the potash ; in passing over the heated copper in the bulb 
 it will give up all its oxygen ; and the nitrogen will be left 
 to enter the globe alone. 
 
 Fig. 55. 
 
 Now notice : if the tube t be accurately weighed before 
 and after the experiment, what it has gained will be the 
 weight of the oxygen taken from the air that passed through 
 it. The vessel V is filled with the nitrogen from the same 
 air; and, since the capacity, of the vessel is known, the 
 weight of the gas may 1)6 calculated. By this means it has 
 been found that one liundred parts of air from which water 
 and carbon dioxide have been taken, contain, by weight, 
 ^76.9 parts of nitrogen to 23 . 1 parts of oxygenT^ 
 
 135. Tlie Proportions of Water and Carbon Dioxide. 
 
 — Now, the quantities of water and carbon dioxide might 
 also be found in this experiment by weighing the tubes in 
 which they are left, were it not that in so small a quantity as 
 the vessel full of air they are too small to be very appre- 
 ciable. If, however, larger quantities of air are passed, the 
 increase in weight will be quite enough. It has been found 
 that the quantities of these substances vary at different times 
 and places, being always very small. 
 
 The quantity of water is exceedingly variable. It depends 
 
CHEMISTRY. 127 
 
 upon locality and temperature. At 15° C. the largest quan- 
 tity that air can hold is ^ of its own weight. Commonly 
 the amount is far less than this. 
 
 The proportion of carbon dioxide is usually given by 
 volume. It varies from -g^^ to more than -^wtrui averaging 
 about ^Vtt- 
 
 136. The Air is a Mixture. — In the properties of the 
 atmosphere we discover none that do not belong to one or 
 another of its constituents. The oxygen causes bodies to 
 burn, not so freely, of course, as if it were pure. The 
 nitrogen, if pure, would quench all flames ; in the air it 
 hinders the burning which it can not quench. So, too, the 
 water-vapor, by being cooled, is condensed into clouds and 
 rain-water, just as this substance when pure first becomes 
 visible as white vapor and then changes to water. And 
 finally, the carbon dioxide of the air turns lime-water white 
 just as the pure gas would do, only in a less degree. Hence 
 the air is a mixture of its constituents, not a compound. 
 
 137. Diffusion. — The gases of the atmosphere have very 
 different densities. The oxygen is heavier than the nitrogen, 
 and the carbon dioxide is still heavier than oxygen. Yet the 
 atmosphere is a uniform mixture of these gases ; the heavy and 
 the light remain mixed at all heights above the earth. Left 
 to the force of gravity they would separate into layers, the 
 heaviest at the bottom. Evidently they are under some other 
 influence which overcomes this tendency ; and this mixing of 
 gases of different densities, when brought in contact, is called 
 Diffusion. The same action is also observed in liquids. 
 
 138. The Diffusion of Liquids. — If in a tall jar some 
 colored water is placed, alcohol may, with care, be poured 
 upon it without mixing the fluids. Being lighter than water, 
 the alcohol floats ; and, being colorless, the line of division 
 may be distinctly seen. After a few hours the liquids in the 
 jar will be found colored uniformly throughout. The heavy 
 
128 
 
 CHEMISTRY. 
 
 water has risen ; the lighter alcohol has sunk, and a uniform 
 mixture is formed. Liquids, which when shaken together, 
 wUl remain mixed, will diffuse when brought in contact ; but 
 those which separate again when standing a while will not 
 diffuse. 
 
 Osmose of Liquids. — A thin membrane or porous sub- 
 stance will not prevent liquids from mixing. To illustrate : 
 let a bladder be firmly tied over the end 
 of A lamp-chimney, or other glass tube ; 
 and, being filled with alcohol, let it be 
 pressed a little way into a vessel of 
 water (Fig. 56). After a time the 
 fluid will be seen gradually rising in 
 the chimney. The water flows in to 
 mix with the alcohol, and a smaller 
 quantity of alcohol flows out at the 
 same time. This mixing of liquids 
 through porous solids is called Osmose. 
 
 Pig. 56. 
 
 139. The Diffusion of Gases 
 
 Diffusion among gases is more rapid 
 than among liquids. The following 
 experiment will clearly illustrate this important property. 
 Two strong bottles with narrow necks, one filled with oxygen, 
 the other with hydrogen, are placed with their open necks 
 together, the oxygen being at the bottom. After considerable 
 time the gases in both bottles will explode at the touch of a 
 lighted taper. Neither oxygen nor hydrogen is explosive, 
 but their mixture is. The oxygen must have risen into the 
 upper jar, and the hydrogen must have fallen into the lower 
 one, until a mixture was formed in both. Gases diffuse in 
 spite of gravitation ; nor will other mechanical forces pre- 
 vent them : a gas will spread in direct opposition to a current 
 of air. 
 
 On examination it is found that hydrogen will diffuse four 
 times as fast as oxygen. Now, the densities of these gases 
 
CHEMISTET. 
 
 129 
 
 
 are as 1 : 16 ; but notice, their diffusive rates are as 4 : 1. In 
 other words, their diffusive rates are inversely as the square 
 roots of their densities. This law applies to the diffusion of 
 all-gases. 
 
 The Osmose of Gases. — Porous substances can not 
 stop the mixing of gases. Hydrogen can not for any length 
 of time be kept pure in india-rubber bags : it will pass 
 through the pores to mix with the air outside. 
 The osmose of hydrogen and air may be 
 shown very beautifully with the apparatus 
 seen in.Fig. 57. A porous cup (of Grove's 
 battery) is fitted air-tiglit to a tube which 
 reaches into colored liquid, contained in a 
 bottle. If a jar of hydrogen is held over the 
 cup, bubbles instantly rush out of the tube, 
 showing that hydrogen has entered to mix 
 with the air inside. Nor is this all : if the 
 jar is removed, the liquid quickly rises in the 
 tube, showing that the hydrogen leaves the 
 cup, to mix with the air outside, and that it 
 flows out so much faster than air can flow in, 
 that a partial vacuum is formed. 
 
 Application to the Air. — We can now 
 see how gases of such different weights as 
 those which form the atmosphere are kept 
 uniformly distributed, instead of forming 
 layers with the heaviest at the bottom. In 
 obedience to this law of diffusion, the heavier 
 gases are compelled to rise, and the lighter ones to fall, until 
 the proportions of them all are the same throughout. Think, 
 moreover, how vast the quantities of unwholesome, and even 
 poisonous gases, which are given off by decaying substances, 
 and from sewers, swamps and marshes. Were gases subject 
 only to the laws of gravitation, the heavy and poisonous car- 
 bon dioxide, with miasms and effluvia, would render animal 
 life impossible. 
 
 Fig. 57. 
 
130 
 
 CHEMISTRY. 
 
 v. — Phosphortts. 
 
 140. Phosphorus in Nature. — Compounds containing 
 phosphorus are quite common in soils and rocks. Plants re- 
 ceive them from the soil ; while animals, living upon vegetable 
 food, take these compounds from the plant. They are found 
 in wheat and other grains, and in the brain and secretions of 
 animals ; so that, while not a very abundant element, phospho- 
 rus is widely distributed and very important. Its most com- 
 mon compounds are the phosphates, and of these the most com- 
 mon is the calcium phosphate. This compound of phosphorus 
 occurs iu bones, and from these the element is obtained. 
 
 14L Its Physical Properties. — Phosphorus is a solid 
 element, having a pale yellow color, rather soft and wax-like 
 at common temperature, but brittle at 
 0° C. In a dark room its clean sur- 
 face shines with a feeble, pearl-white 
 light. Its vapor also is beautifully 
 phosphorescent. To show this, put a 
 few small fragments of the solid into 
 a flask of water, and boil it. The 
 mixed vapors of water and phospho- 
 rus escape (Fig. 58), and, in a dark 
 room, look like livid flames issuing 
 from the mouth of the flask, while at 
 the same time globules of melted 
 phosphorus, on the surfaces of the 
 water and the glass, appear like little 
 balls of pearl. 
 
 This element is insoluble in water ; but it dissolves freely in 
 ether, and still more freely in carbon disulphide. 
 
 142. Its Chemical Properties. — Phosphorus combines 
 most readily with oxygen. From a piece of the solid 
 exposed to air, white fumes are continually falling, which 
 consist of a compound of phosphorus and oxygen. A gentle 
 
 Fig. 58. 
 
CHEMISTRY. 131 
 
 heat — that of the fingers handling it is often enough — 
 causes it to burst into violent combustion, forming the fumes 
 in great abundance. On this account the element must be 
 kept under water ; and it should be held under water when 
 cut, lest the friction of the knife set it on fire. The pieces 
 to be used should be afterward dried by gentle pressure 
 between layers of blotting-paper. 
 
 There is, however, an allotropic form of phosphorus, 
 called red phosphorus, which will not produce the phenom- 
 ena of combustion under a temperature of 260° C. Ex- 
 perim^ts with this variety are, of course, far less dangerous 
 than with the common form. Sticks of the solid, exposed 
 to light, gradually change to red phosphorus. 
 
 This element is a violent poison : even its vapors, inhaled, 
 will cause wasting disease. 
 
 143. Uses. — The most important use of phosphorus is 
 in the manufacture of matches, hundreds of tons being 
 employed annually for this purpose. 
 
 Formerly the match was made by first dipping the end of 
 the wood into melted sulphur and afterward into a paste of 
 gum-water, phosphorus, and either niter or potassium chlorate. 
 By friction the phosphorus is set on fire. The heat of the 
 burning phosphorus is intense enough to ignite the sulphur, 
 which in turn inflames the wood. But sulphur is seldom no.w 
 employed, its place having been taken by parafHne or stearic 
 acid. When potassium chlorate is used, the match burns 
 with an explosive combustion. 
 
 The " safety match," now in quite common use, contains 
 no phosphorus. This element is put upon the box, the sur- 
 face on which the match is rubbed, instead of upon the 
 match itself. The matter on the tip of this match contains 
 potassium chlorate and sulphur or antimony sulphide, and 
 sometimes red lead and potassium bichromate. The matter 
 on the side of the box contains i-ed phosphorus. Only by 
 rubbing the match against this surface, can it be easily fired. 
 
132 
 
 CHEMISTRY. 
 
 VI. — Phosphorus and Hydrogen. 
 
 144. Hydrogen Phosphide. — Three compounds of 
 phosphorus and hydrogen are known. One, PHj, is a gas 
 at ordinary temperatures ; another, Pj H^, is a liquid ; and a 
 third, P2H, is a solid. 
 
 The gaseous compound may be obtained by the action of 
 pliosphorus on a solution of " caustic potash," KHO. The 
 experiment is represented in Fig. 59. 
 
 Fig. 59. 
 
 The small flask is two-thirds filled with a moderately strong 
 solution of potassium hydrate, and a small piece of phos- 
 phorus is added. A few drops of ether are poured in, and 
 the flask is then closed. The delivery tube dips into a cistern 
 of water. 
 
 On applying a gentle heat the ether evaporates, and its 
 vapor expels the air from the flask and tube. Very soon 
 bubbles of gas arise from the phosphorus ; and after a time 
 larger bubbles emerge from the tube in the water, come in 
 contact with the air, and instantly take fire with explosion. 
 The bright white flame is followed by a beautiful vortex-ring 
 of white vapor (P2O5) rising and expanding, and finally 
 breaking and vanishing in the air. 
 
CHEMISTRY. 133 
 
 And yet the gaseous phosphide is not spontaneously 
 inflammable, as it would appear to be : it has been found 
 that, made in this way, it contains some vapor of the liquid 
 phosphide, and to this the spontaneous combustion is due. 
 
 VII. — Phosphorus and Oxygen. 
 
 145. Phosphoric Oxide and Acid. — "When phos- 
 phorus burns in dry oxygen, or in a full supply of dry air, a 
 snow-white solid is produced : it is the phosphorus pentoxide, 
 PjOs, also called phosphoric anhydride. This snow-like 
 solid has so strong an attraction for water, that exposed to 
 the air it takes moisture and melts away, or if brought in 
 contact with water itself the two unite with such vigor as to 
 produce a hissing sound, and much heat. The powder can 
 be preserved only in hermetically sealed flasks. 
 
 If now some drops of the solution of this oxide are added 
 to blue litmus, the color instantly changes to red, showing 
 the liquid to be an acid. The Pj O5 has combined with 3 Hj O, 
 yielding 2 H3PO4, or two molecules of phosplwric acid. 
 
 146. Phosphorous Oxide and Acid. — If, instead of 
 burning the phosphorus rapidly, it be made to burn slowly 
 in a small supply of dry air, it produces a different com- 
 pound. The phosphorous trioxide, P2 O3, is formed. 
 
 This phosphorous oxide is also a white solid, and when 
 brought into contact with water instantly unites with it. 
 The P2 O3 takes 3 Hj O, and yields 2 H 3 P O3, or two molecules 
 of phosphorous acid. 
 
 147. Other Acids. — Besides the two acids of phos- 
 phorus just mentioned, there are three others, whose names 
 and composition are here given for reference : — 
 
 Hypophosphorous acid H3 P O2, 
 
 Metaphosphoric acid H P O3, 
 
 Pyrophosphoric acid H4 Pa O,. 
 
134 CHEMISTBY. 
 
 Vlll. — Arsenic. 
 
 148. Arsenic in Nature. — Arsenic sometimes occurs in 
 the eartli uncombined with other substances ; but generally 
 it is found as an oxide or a sulphide, mixed with similar 
 compounds of the metals. "It was at one time supposed 
 that arsenic entered into the composition of the flesh and 
 bones of animals as a normal constituent ; but it has been 
 clearly proved that it is never found in the tissues, either ol 
 animals or vegetables, except when it has been introduced 
 into them by accident or design." (Brande & Taylor.) 
 
 Its Pliysical Properties. — Arsenic is a very brittle 
 solid, in appearance much like metals. It may be sublimed 
 by heat ; that is to say, it may be changed from the solid to 
 the vapor state, directly, without melting. 
 
 Its Cliemical Properties. — Heated in the open air, 
 arsenic rapidly combines with oxygen, and even on simple 
 exposure to air it forms an oxade. With some of the metals 
 it forms arsenides. Owing to the criminal use of its poison- 
 ous compounds, this element has been most thoroughly and 
 successfully studied. 
 
 IX. — Arsenic and Hydrogen. 
 
 149. Hydrog-en Arsenide. — Let fragments of zinc be 
 put into a- bottle (Fig. 60) with water enough to cover them. 
 Let sulphuric acid be poured through the funnel-tube until 
 a brisk evolution of hydrogen begins. Patiently wait until all 
 air has been driven out of the bottle, and then touch a match- 
 flame to the tip of the taller tube from which the gas is 
 escaping. The almost colorless flame of hydrogen is thus 
 obtained. 
 
 Next pour in through the funnel a few cubic centimeters 
 of a solution of arsenious oxide Asj Og : a moment afterward 
 the flame will become enlarged, and shine with a livid white- 
 ness. 
 
 The hydrogen has decomposed the arsenious oxide, and 
 
CHEMISTRY. 
 
 135 
 
 taken its arsenic to form hydrie arsenide, AsHa, commonly 
 called arseniuretted hydrogen. 
 
 Properties. — This substance is a colorless gas of 
 unpleasant odor, and very poisonous. 
 It is very combustible, and the prod- 
 ucts of combustion are water and 
 arsenious oxide. If the flame be 
 cooled by holding the cold surface of 
 a piece of porcelain across it, then 
 only the hydrogen will burn away ; 
 the arsenic will be deposited on the 
 porcelain in the form of a brown and 
 lustrous mirror. 
 
 150. Marsh's Test. — This repro- 
 duction of arsenic as a mirror on 
 porcelain is a most delicate and im- 
 portant test for the presence of the 
 compounds of this poisonous sub- ^.^ g^ 
 
 stance. It is known as Marsh's test. 
 It is applied by means of the apparatus shown in Fig. 61. 
 
 Fig. 61. 
 
 Into the bottle A are put pure zinc, water, and sulphuric acid 
 for the evolution of hydrogen gas. This gas is allowed to 
 
136 CHEMISTRY. 
 
 flow until all air is expelled from the apparatus. The liquid 
 supposed to contain the poison may be afterward poured 
 through the funnel-tube. The gas formed in the bottle, 
 passing through the bulb, b, loses a part of the water carried 
 over with it, and going over calcic chloride in c, it is 
 thoroughly dried. It finally escapes at the pointed end of 
 the tube, d. After the air of the apparatus has been all 
 driven out by the stream of gas, the hydrogen may be burned 
 as it issues. 
 
 Now, if the liquid contain arsenic, there is at once formed 
 arseniuretted hydrogen (HgAs). In presence of much 
 arsenic the color of the flame turns to a livid hue, and 
 sometimes gives off white fumes of arsenious oxide. But 
 now comes the decisive test. A cold, clean, white porcelain 
 surface, is held in the small flame for a moment ; metallic 
 arsenic condenses on its surface, if the poison is present, 
 and, when cold, appears a blackish-brown stain, with a bright 
 metallic luster. The substance of this stain may be still 
 further tested, until the last doubt of its character is 
 removed. 
 
 The experiment is varied by applying heat to the middle 
 part, 0, of the small tube. The arseniuretted hydrogen, if 
 present, will be decomposed, and the metallic arsenic will 
 lodge upon the inside surface of the tube, forming a brilliant, 
 mirror-like ring. 
 
 By Marsh's test, even so little as 0.01 of a milligram 
 (tt^utt E^-) ^^^ tie detected with certainty. 
 
 This is only one of many tests by which, taken together, 
 the chemist can pronounce upon the presence of arsenic with 
 absolute certainty. 
 
 151. Some other Compounds of Arsenic. — The 
 
 arsenious oxide (AsjOg) is the common "arsenious acid" 
 or " white arsenic," — the well-known poison. It is a white 
 solid, slightly soluble in water, with which it forms an acid, 
 and this acid combines with metals to form arsenites. 
 
CHEjfiSTEY. ISi/ 
 
 These, also, are violent poisons ; and yet some of them are 
 used quite largely in the manufacture of aniline dyes, in 
 calico-printing, and as pigments. Green wall-papers, many 
 of them, have been colored with copper arsenite, well known 
 as Scheele's green. Nor is green the only color of wall- 
 papers containing arsenic : it has been found in yellow, pink, 
 blue, and drab. These arsenical papers are guilty of 
 poisonous action upon those who inhabit the rooms. 
 
 Another compound of arsenic and oxygen has the formula, 
 As2 O5 : it is the arsenic oxide. This oxide is also an anhy- 
 dride, since it unites with water to form arsenic acid. This 
 acid is represented by the formula, H3ASO4. 
 
 AsjOs -1- 3 H2O = 2 H3ASO4. 
 
 By passing sulphuretted hydrogen through a solution of 
 arsenious oxide, made acid by a few drops of hydrochloric 
 acid, a fine yellow precipitate is formed at once. This yellow 
 solid is arsenious sulphide, As2 Sj. It has long been known 
 under the name of orpiment, and was formerly much used 
 as a pigment called king's yellow. 
 
 X. — Boron. 
 
 152. Boron in Ifature. — The element boron is not 
 found free in nature, but several of its compounds exist in 
 considerable quantities. The most important of these are 
 boric or boracic acid, and sodium biborate, commonly called 
 borax. 
 
 The Element. — Boron is sometimes a dark-brown pow- 
 der, and sometimes it occurs as lustrous crystals almost as 
 hard as diamond. In neither of these allotropic forms does 
 boron show much chemical activity. Boron is the only non- 
 metal which forms no compound with hydrogen. 
 
 153. Boracic Acid. — The waters of the lagoons of 
 Tuscany hold this acid in solution. These waters, evaporated 
 by the heat of volcanic jets of steam issuing in the neigh- 
 
138 CHEMISTRY. 
 
 borhood, yield the acid in solid form. This is the source of 
 it for the European market. 
 
 In the United States it is manufactured from the native 
 borax found in sufficient quantity in the water of the borax 
 lake in California. 
 
 Let a little borax be dissolved in two and a half times its 
 weight of boiling water, and add a little more than half its 
 weight of strong hydrochloric acid. On cooling, this solution 
 will deposit glistening plate-like crystals. These crystals are 
 boracic acid. 
 
 Place a little of this crystallized acid in a capsule, and add 
 a spoonful of alcohol. After stirring it well, to dissolve the 
 acid, set fire to the solution, stirring it the while, and the 
 flame wiU exhibit a fine green color. This is a characteristic 
 test for this acid. 
 
 154. The Borates. — With sodium this acid forms 
 sodium biborate, or borax, Na2B4 07. With other metals 
 other borates are produced, the class being quite numerous. 
 
 Many of these are crystalline, and in the form of crystals 
 almost always contain water. Borax, for example, in crys- 
 tallizing, takes up ten parts of water, so that its formula 
 becomes Na2B4 07 -1-10 H2O. This water contained in crys- 
 tals is called Water of Crystallization. Oftentimes, when 
 gently heated, the crystals, wUl dissolve in this water which 
 they contain. Heat crystals of borax in an iron spoon, and 
 they " melt in their water of crystallization." 
 
 XI. — The Tkivalent Group. 
 
 155. The Group. — Ntoegen, phosphorus, areenie_and 
 Ijoron are trivalent elements. Many other chemical relations 
 also mark them, with the exception of boron, as members of 
 a natural group. 
 
 They are Trivalent. — The compounds of these elements 
 with hydrogen have the following symbols : — 
 
 H3N, HaP, HjAs, 
 
CHEMISTEY. 139 
 
 from which we learn that an atom of each can hold three 
 atoms of hydrogen in combination. These three compounds 
 are gases. 
 
 Other Chemical Relations. — The complete analogy in 
 the composition of the compounds of these elements may be 
 seen by a glance at the following formulas : — 
 
 N2O3, N2O4, N2O,, NCl3(?), 
 
 Pa O3, ... Pg O5, P CI3, Pj Sg, P2 S5, 
 
 ASaOs, . . . AS2O5, AsClj, AS2S3, ASaSj. 
 
 KEVIEW. 
 I. —SUMMARY OF PRINCIPLES. 
 
 156. Nitrogen, phosphorus, arsenic, and boron are the 
 members of the trivalent group of non-metals, one atom of 
 each being equivalent to three atoms of hydrogen. 
 
 Nitrogen does not directly combine with oxygen. Phos- 
 phorus and arsenic do. 
 
 Nitrogen is a colorless gas ; phosphorus, a translucent 
 solid ; arsenic also, a solid, steel-gray and metallic. 
 
 Nitrogen and hydrogen form a single compound, ammonia, 
 a gas, very soluble in water with which it combines to form 
 liquor ammonise, a strong base. 
 
 Ammonia combines directly with hydrochloric acid to form 
 ammonium chloride. 
 
 Nitrogen unites with oxygen to form five compounds, 
 illustrating well the " law of multiple proportions." 
 
 Two of these oxides are anhydrides ; with water one forms 
 nitrous acid, and the other nitric acid. 
 
 Nitric acid is a powerful oxidizing agent. 
 
 Nitrous oxide is an anaesthetic much used by dentists. 
 
 Nitric oxide is a test for the presence of oxygen, with 
 which it instantly forms red vapors of nitric peroxide. 
 
 The atmosphere is a mixture of nitrogen, oxygen, carbon 
 
140 CHEMISTRY. 
 
 dioxide, and water-vapor, together with small and variable 
 quantities of ammonia, and several other gases. 
 
 Compared with the nitrogen and the oxygen, the quantity 
 of all other constituents is small. 
 
 By volume, the air consists of : — 
 
 Oxygen 20.77 
 
 Nitrogen 79.23 
 
 100.00 
 By weight, the air consists of : — 
 
 Oxygen 22.92 
 
 Nitrogen 77.08 
 
 100.00 
 
 For most purposes it is sufficient to say that four-fifths of 
 the air is nitrogen, and one-fifth is oxygen. 
 
 Diffusion is the tendency of fluids or of gases to mix when 
 brought in contact. The principle of diffusion is well illus- 
 trated by the uniform mixture of gases throughout the 
 atmosphere. 
 
 Phosphorus burned in a full supply of air or oxygen yields 
 phosphoric pentoxide, P2 Oj ; but burned in a limited supply 
 it yields phosphorous trioxide, P2 O3. 
 
 These oxides are anhydrides : one of them with water 
 forms phosphoric acid, the other phosphorous acid. 
 
 These acids form large classes of salts, one the phosphites, 
 the other the phosphates. 
 
 The compounds of arsenic are remarkable for their poison- 
 ous character. Nevertheless some of them are used in many 
 industrial arts. 
 
 There are two oxides of arsenic ; viz. , the arsenious oxide, 
 AS2O3, and the arsenic oxide, AsjOs. 
 
 These oxides are anhydrides : with water, one yields 
 arsenious acid, the other arsenic acid. 
 
 "With metals these acids form salts : the first yields 
 arsenites, and the second arsenates. " Scheele's green " is 
 
CHEMISTRY. 141 
 
 a copper arsenite, and Schweinfurt's green consists of coppei 
 arsenite and acetate. Both are used as pigments in coloring 
 wall-paper. 
 
 The arsenic in paper can be easily detected. Moisten the 
 paper with hydrochloric acid, and then add water. Into 
 this solution thrust a bright copper wire. Arsenic, if 
 present, will be deposited on the wire, giving it a gray 
 coating. 
 
 The most sensitive and reliable test for arsenical poison is 
 Marsh's test. 
 
 The antidote to arsenical poison is moist ferric hydrate, 
 which can be made by adding ammonia-water to a solution 
 of iron sulphate (copperas), after having first heated the 
 solution with a little nitric acid. In absence of this antidote 
 milk, or white of eggs, may be used. Or a powerful emetic 
 may be administered. 
 
 Boron has two allotropic forms, one amorphous, the other 
 crystalline. 
 
 It is the only non-metal which has no known compound 
 with hydrogen. 
 
 Its most important compounds are boric acid and borax. 
 
 II. —EXERCISES. 
 
 Give the preparation of nitrogen. "What are its physical 
 properties? What is its chemical character? 
 
 What are its atomic weight and density ? 
 
 How does it occur in nature ? 
 
 What compound does nitrogen form with hydrogen ? What 
 is the source of the ammonia in the air? Define nascent 
 state. What influence has the nascent state on combination ? 
 
 How is ammonia usually obtained? Give the reaction. 
 Consult the table of elements, and convert this reaction into 
 a numerical equation. What does this numerical equation 
 show? How much ammonium chloride is required to yield 
 one hundred grams of ammonia? To yield one hundred 
 liters of ammonia? 
 
142 CHEMISTRY. 
 
 What are the physical properties of ammonia? What 
 is ammonium hydrate? How is this hydrate made in the 
 laboratory ? 
 
 How many oxides of nitrogen are known? How many 
 oxygen acids? 
 
 How is nitric acid prepared ? Give the reaction. 
 
 What are the properties of nitric acid ? Why is it called 
 an oxidizing agent? 
 
 Describe the preparation of nitrous oxide. What are its 
 properties ? For what is it useful ? How is its composition 
 represented? Describe the experiment to determine its 
 composition. Give the reasoning. 
 
 How may nitric oxide be obtained ? What is the composi- 
 tion of nitric oxide ? Wha,t formula represents its molecule ? 
 How does it serve to test the presence of oxygen ? 
 
 Give the formula for nitrous anhydride. The formula for 
 nitric peroxide. The formula for nitric anhydride. 
 
 What acid comes from nitric anhydride? Show by an 
 equation the composition of the acid derived from nitrous 
 anhydride. 
 
 Name the two most abundant constituents of the atmos- 
 phere. Name other constituents. Give the composition of 
 the air by volume. By weight. How are these proportions 
 determined ? 
 
 What are the proportions of water- vapor and carbon 
 dioxide ? Why is the air called a mixture ? 
 
 Is this mixture uniform at all heights ? On what principle 
 are the ases kept from settling into layers? Define 
 diffusion. State the law of diffusion of gases. 
 
 How does phosphorus occur in nature? What are its 
 physical properties? With what element has oxygen the 
 strongest inclination to combine? Describe the allotropic 
 form of phosphorus. Describe the composition of the 
 match. What is the safety-match ? 
 
 How does arsenic occur in nature ? What are its physical 
 properties ? Its chemical properties ? 
 
CHEMISTRY. 143 
 
 How may arseniuretted hydrogen be prepared? What is 
 its formula? Describe its combustion. 
 
 What is Marsh's test? Describe the apparatus employed. 
 How is the experiment conducted? 
 
 What is the so-called " arsenious acid " ? What is its true 
 chemical name? 
 
 What is the most remarkable general character of the 
 arsenic compounds? 
 
 To what uses are many arsenical compounds applied? 
 How can the arsenic in wall-paper be detected ? 
 
 Name the members of the trivalent group of non-metals. 
 Show that they are trivalent by means of the formulas for 
 their hydrogen compounds. In what else are they analogous ? 
 
 SECTION VI. 
 
 THE QUADRIVALENT NOK-METALS. 
 
 I. — Silicon. 
 
 157. The Element. — Sihcon is a solid substance, some- 
 times obtained as a brown powder, sometimes as crystals 
 with an iron-gray color and metallic luster. It is very hard, 
 very insoluble, and very difficult to melt ; but when heated in 
 air it burns because of its attraction for oxygen. 
 
 158. Its Compounds. — Silicon is never found free in 
 nature, but its compounds are very abundant. With oxygen 
 it forms a silicon oxide, Si O2, more commonly called silica. 
 
 This compound is one of the most abundant substances in 
 the earth. The beautiful opal and amethyst and some other 
 gems are almost pure silica : so is the more common rock 
 crystal or quartz, while the sand of the sea-shore and every 
 variety of sandstone rock are the impure forms of the same 
 substance. 
 
 Silica is also an important constituent in organic bodies. 
 It gives strength to the stalks of grains and grasses, while it 
 
144 CHEMISTRY. 
 
 constitutes the skeleton of whole tribes of some of the lower 
 orders of animals. 
 
 Silica is used largely in the manufacture of glass. 
 
 Silicic acid, Hj Si O3, is a limpid liquid of little known 
 importance ; but its salts, the silicates, occur in large 
 quantities and are widely distributed in the earth. 
 
 159. Glass. — Glass is made from silica and the bases, 
 potash, soda, lime, and some others, according to the variety 
 required. These materials, being intensely heated, melt into 
 a transparent pasty mass, portions of which may be taken 
 from the furnace, and blown or molded into the different 
 forms in which glass articles are made. These articles, 
 being afterward annealed, are ready for the market. We 
 may study the manufacture of glass a little more in detail. 
 
 The Materials. — In all true glasses silica is one con- 
 stituent. This substance exists in almost pure form in flint, 
 agate, and quartz ; while all varieties of sand consist of the 
 same in various degrees of purity. Flint was formerly used 
 in the manufacture of glass : hence the name, flint glass, 
 which one variety still retains. Sand is now the more 
 general source of silica, great care being used to select a 
 pure material. 
 
 Potash, soda, and lime are the most important bases used 
 with the silica ; but, besides these, lead oxide and oxides of 
 tin and manganese_are often employed. 
 
 The Varieties of Glass There are several varieties of 
 
 glass, chief among which are four, viz. : green bottle-glass, 
 Bohemian glass, window-glass, and flint-glass. 
 
 Green bottle-glass is made of cheaper and coarser material 
 than any other variety. Its bases are more numerous : they 
 are chiefly soda and lime ; but the oxides of iron and manga- 
 nese are among them, and to the first of these the glass 
 owes its familiar color. 
 
 Bohemian glass is made from purer material than bottle- 
 glass, and care is taken to have it free from color. Its bases 
 
CHBMISTEY. 145 
 
 are potash, lime, and manganese. Its lightness, the absence 
 of color, and its power to stand high heat and sudden 
 changes of temperature, make it very valuable for chemical 
 purposes. 
 
 Window-glass consists chiefly of silica, soda, and lime. 
 
 Flint-glass consists chiefly of silica, potassa, and lead 
 oxide (PbaOg). This very beautiful variety of glass, some- 
 times called crystal glass, is chiefly made into such articles 
 of domestic and ornamental use as tumblers, decanters, 
 wine-glasses, and vases. It is very transparent, and refracts 
 light powerfully : on this account it is valuable for lenses, 
 and other optical instruments. 
 
 The Melting. — The raw material is heated in pots made 
 of the purest and most infusible clay, and set in a conical 
 furnace. When the heat is sufficient, the silica and the 
 bases form silicates. In the case of window-glass, for ex- 
 ample, the silica, soda, and lime form Sodium and Calcium 
 Silicates. The compound of these silicates is a transparent 
 half -fluid or pasty mass of glass, ready to be wrought into 
 any desired form. 
 
 The Blowing. — By means of an iron tube four or five 
 feet long, the workman takes out of the furnace a portion of 
 the pasty and adhesive glass. He gives it regular shape by 
 rolling it upon a smooth hard surface, and makes it hollow by 
 blowing air through the tube. By keeping the tube in con- 
 stant rotary motion while he blows, the bulb is enlarged into 
 a globe ; or if, at the same time, he swings his tube, pendu- 
 lum like, a pear-shaped flask is made. 
 
 Some idea of the interesting process of making window- 
 glass may be gained by studying the following cuts found in 
 Muspratt's Applied Chemistry. In Fig. 62 some of the first 
 stages of the process are shown. In front of each opening 
 of the furnace is a stage, built over a pit about ten feet 
 deep. Upon these stages the workmen stand. The ball of 
 glass having been taken from the furnace, the workman blows 
 through his pipe, while he at the same time skillfully rotates 
 
146 
 
 CHEMISTRY. 
 
 it in his hand, and swings it backward and forward, some- 
 times below his feet, sometimes over his head, until he has 
 lengthened and enlarged it into a cylinder with uniform sides 
 as long as the pane of glass is expected to be. The ends or 
 this cylinder are then cut off, and a slit is made along one 
 side. It is afterward placed upon a smooth and even stone 
 plate, and heated in an oven. As the glass softens, the 
 
 Fig. 62. 
 
 workman, with an iron rod, presses the sides of the cylinder 
 open (see Fig. 63), and finally smooths it out upon the flat' 
 surface of the stone. It is then a pa?ie of glass, needing 
 only to be carefully cooled. 
 
 Tlie Annealing. — Annealing is a process of slow cool- 
 ing. All articles of glass must be annealed. For this pur- 
 pose they are placed in hot ovens, whose temperature grows 
 gradually less, until, at the end of four or five days, they 
 
casMrsTHY. 
 
 147 
 
 Fig. 63. 
 
 are quite cold. The process is necessary, because if glass is 
 cooled suddenly it becomes exceedingly brittle, and will some- 
 times break even without apparent cause ; but when slowly 
 cooled it is able to stand much pressure and sudden blows. 
 
 " Considered only with reference to its application in the 
 study of natural phenomena, it is impossible to doubt the 
 singular influence glass has exerted 
 on the progress of science. It is 
 chiefly by its aid that astronomy 
 has attained a perfection so won- 
 derful ; by it, also, naturalists have 
 been enabled to study under the 
 microscope a host of phenomena 
 which before escaped notice. But 
 perhaps of still greater importance 
 is the use made of it by chemists 
 in their experiments. It requires no profound chemical 
 knowledge to recognize the fact that to glass is chiefly owing 
 the present advanced state of the sciences, so fruitful in 
 marvelous application." 
 
 II. — Carbon. 
 
 160. Charcoal obtained from Wood. — When splin- 
 ters of wood are heated in a test-tube closed with a cork 
 through which passes a small tube, considerable quantities of 
 vapor and gas escape, and the wood turns black. The black 
 mass that remains when the gas is no longer given off is 
 charcoal, one form of carbon. In the same way, on a large 
 scale, wood is put into retorts, and heated intensely ; its 
 liquid and gaseous constituents are driven off, while the solid 
 carbon remains. 
 
 Or, again : if we light one end of a splinter of wood, and 
 slowly push the burning part into the mouth of a test-tube, 
 the part in the tube will only glimmer in the small supply of 
 air, or be extinguished altogether. The black residue is 
 carbon. 
 
148 
 
 CHEMISTET. 
 
 On a Large Scale. — In a similar way, when charcoal is 
 required in large quantities, piles of wood are burned under 
 a covering of sod and moist earth, where but little air can 
 
 reach them. Figs. 
 64 and 65 represent 
 the way in which the 
 method is carried 
 out. In the former 
 we see how the sticks 
 lire piled ; in the lat- 
 ter we see the pile in 
 
 Fig 64. 
 
 its slow combustion. 
 Air can enter only through holes in the earthy covering near 
 the base. Smoldering sometimes for weeks, the gaseous 
 
 Fig. 65. 
 
 parts of the wood are at last all driven off ; while the carbon, 
 keeping the form of the original sticks, with knots and 
 
CHEMISTEY. 
 
 149 
 
 annular rings still perfect, all, however, much reduced in 
 size and weight, remains. 
 
 Charcoal is without crystalline form, and on this account it 
 is said to be Amorphous. 
 
 
 161. Other Forms of Amorphous Carbon. — Beside 
 charcoal there are several other forms of amorphous carbon, 
 among which we may mention lamp-black, c_okej and animal, 
 c harcoal . 
 
 Animal charcoal is carbon obtained from animal sub- 
 stances. Bone-black, for example, is animal charcoal ob- 
 tained by charring bones in iron cylinders. 
 
 Coke is the carbon which remains when soft coal is heated 
 to redness in the ab- 
 sence of air. Large 
 quantities of soft, or 
 bituminous coal, are 
 used for the manufac- 
 ture of illuminating 
 gas, and large quan- 
 tities of coke are left 
 behind. It is a fuel 
 of considerable value. 
 
 Lamp - Black. — 
 Bodies which contain 
 large proportions of 
 carbon are likely to 
 burn with a smoky 
 flame. They are sure 
 to do so if the supply 
 of air in which they 
 burn is limited. The 
 blackness of the smoke 
 is due to minute par- 
 ticles of carbon. Let a metallic plate be held over the flame 
 of an oil-lamp, and we shall find an abundance of this finely 
 
 Pig. 66. 
 
150 
 
 CHEMISTRY. 
 
 divided carbon deposited on it. In this form the carbon is 
 called Lamp-black. 
 
 This form of carbon is much used in the arts. On 
 a large scale it is made by burning tar, resin, or petro- 
 leum, in such a way that but little air will reach it. The 
 dense black smoke is drawn over into large chambers 
 (Fig. 66), on whose walls the soot, or lamp-black, is 
 deposited. 
 
 Lamp-black is used as a black paint, and when mixed with 
 oil it constitutes printer's ink. The finest kind is also used 
 for preparing India ink and in calico-printing. 
 
 162. The Diamond. — The diamond is crystallized car- 
 bon. A roughly rounded 
 pebble found in the sand 
 and clay of India or 
 Brazil, the diamond would 
 hardly be picked up by 
 one whose eye had not 
 been trained to recognize 
 it ; but when polished it is 
 at once the most beautiful 
 and the most indestructible 
 of gems. It can neither 
 be melted nor dissolved : it 
 may, however, be burned 
 when heated intensely in 
 oxygen-gas. 
 
 Its great power to re- 
 fract light and its wonder- 
 ful hardness are character- 
 istic properties : these are 
 pj g„ the properties which render 
 
 the gem so valuable in the 
 arts. The light flashing from the different sides of the crys- 
 tal makes it the most brilliant of ornaments : its extreme 
 
CHEMISTRY. 
 
 151 
 
 hardness renders it valuable in the construction of pivots in 
 delicate instruments where friction is to be avoided. 
 
 There are two principal forms of this most elegant jewel. 
 They are called the brilliant and the rose. The first of these 
 is regarded as the finest. Its shape is well shown in Fig. 67. 
 Look at the gem sidewise, and it appears as seen in the upper 
 part of the picture ; look at the top of it, and it appears as 
 seen in the lower part. The form of the rose is seen in 
 Fig. 68 ; a side view above and a top view below. 
 
 Value of the Diamond. — The diamond is the most 
 highly prized of precious 
 stones. Its value depends 
 on its weight, and its freedom 
 from color and from flaws. 
 The weight of a diamond is 
 described as so many carats, 
 a carat being .2054 grm. 
 (3.17 grains). 
 
 One of the finest diamonds 
 in the world is known as the 
 Pitt or Regent diamond, 
 which weighs 136.25 carats, 
 and is worth £125,000, equal 
 to about $625,000. The lar- 
 gest diamond in Europe 
 weighs 194|^ carats : it be- ^'s. 68. 
 
 longs to Russia, and is set in one end of the einperor's 
 scepter. The famous Koh-i-noor is the property of the Eng- 
 lish crown. Originally it weighed 186 carats, but its 
 weight has been reduced to 106 carats by the recutting to 
 which it has been subjected. 
 
 163. Grapliite. — Graphite is another crystalline form of 
 carbon. It is also called plumbago, and is still more famil- 
 iarly known as black-lead. It is taken from the earth in 
 large quantities for the manufacture of lead-pencils. It 
 
152 CHEMISTRY. 
 
 ^ 
 
 has a shining steel-gray color, and it is a good con- 
 ductor of electricity, being in these respects much like 
 metals. 
 
 164. AUotropic Forms. — Chai^coal, the diamond, and 
 graghite, are but different forms of the element carbon. 
 They differ in hardness, in color, in weight, and in many 
 other physical properties. They are alike infusible, alike 
 able to resist the action of substances which attack most 
 other bodies, alike in being combustible, and alike in yield- 
 ing the same substance (carbon dioxide) when burned. That 
 they are also alike in being of vegetable origin, is believed ; 
 but of the mode in which the diamond and graphite have been 
 made from vegetable matter, little, if any thing, is known. 
 
 It is Found in Nature. — All the different varieties of 
 coal are but different impure forms of carbon, the remains 
 of a vegetation which grew ages before the period of man's 
 creation. 
 
 Enormous beds of limestone are found on every continent, 
 but not a molecule of limestone occurs which does not contain 
 an atom of carbon. 
 
 And more : not a single organized body, from the lowest 
 form of plant to the highest form of animal, exists, in which 
 carbon is not an important element. 
 
 III. — Carbon and Oxygen. 
 
 165. Oxides of Carbon. — With oxygen carbon unites 
 in two proportions. "We have 
 
 Carbon monoxide CO, 
 
 Carbon dioxide C Oj. 
 
 166. Carbon Monoxide. — ■ Carbon monoxide may be 
 prepared by heating gently, in a flask, four or five grams of 
 potassium ferro-cyanide with about ten times as much strong 
 sulphuric acid. It is a gas, and may be collected over 
 water. 
 
CHEMISTRY. 
 
 153 
 
 Properties. — Carbon monoxide is colorless, hut has a 
 slight odor of a peculiar kind. It is very inflammable, and 
 burns with a blue flame, which may be seen playing over the 
 surface of a brisk and new-made coal fire. 
 
 This gas is very poisonous. Even when breathed in small 
 quantities it produces headache and giddiness : if the quan- 
 tity is increased, insensibility and death follow. Accidents, 
 not a few, have arisen from burning charcoal in open fires in 
 rooms. The carbon takes oxygen from air to form this 
 poisonous oxide, which escaping into the room destroys 
 life. 
 
 Pig. 69. 
 
 167. Carbon Dioxide. — Carbon dioxide may he obtained 
 from marble by the following process. Small fragments of 
 marble are put into a bottle whose cork is provided with two 
 tubes, one reaching to the cistern, the other a funuel-tube 
 reaching nearly to the bottom of the bottle. (Fig. 69.) 
 "Water is poured through the funnel until the lower end of 
 its tube is covered, and hydrochloric acid is then added. 
 A violent agitation quickly begins in the bottle : carbon 
 dioxide is set free, and is collected in the jar over the 
 water. 
 
154 
 
 CHEMISTKY. 
 
 Marble is the calcium carbonate represented by Ca C O3. 
 The reaction with hydrochloric acid is as follows : — 
 
 CaCOs + 2HCI = 
 Calcium . 
 carbonate 
 
 CaClj + H2O + CO, 
 
 _ Calcium 
 "~ chloride 
 
 '2, 
 
 , Carbon 
 dioxide. 
 
 Its Properties. — Carbon dioxide is a colorless gas. If 
 a lighted taper is plunged into it, the flame is instantly 
 extinguished ; in this respect carbon dioxide resembles 
 nitrogen. If lime-water is exposed to its action it will 
 be turned milky : this effect can not be produced by other 
 gases. 
 
 Carbon dioxide is much heavier than air ; its density being 
 1.524. To illustrate : let the end of the bent tube from the 
 
 bottle in which this gas is made 
 be placed in a jar, standing with 
 its open mouth upward In a 
 little time a lighted taper, low- 
 ered into the jar, is quenched, 
 showing that the jar is full of 
 the gas. The gas remains in 
 the open vessel as water would, 
 and just for the same reason, 
 — it is heavier than air. In- 
 deed, it may be poured from one 
 vessel to another like water : its 
 flow can not be seen, but a light- 
 ed taper (Fig. 70) or lime-water 
 will show its presence in the second vessel and its absence 
 from the first. 
 
 Carbon dioxide may be condensed to a liquid and even 
 to a solid state. As steam when cooled becomes water, so 
 this gas when made cold enough becomes a liquid : the 
 temperature required is —78.2° C. And as by being cooled 
 still further water is frozen, so carbon dioxide may be 
 changed from the liquid to the solid form. To reduce the 
 
 Fig. 70. 
 
CHBMISTEY. 155 
 
 temperature low enough, the liquid oxide is suddenly exposed 
 to air at ordinary temperature and pressure : it evaporates 
 so swiftly that the large amount of heat taken up by the 
 change from tlie liquid to the gaseous form, leaves the rest 
 of the liquid so cold that it freezes. 
 
 Gases may be liquefied, not only by cooling them : the same 
 effect may be produced by pressure. Thus steam, whose 
 temperature is kept up to 100° C, will be changed to water 
 by pressure : so carbon dioxide, by a greater pressure, may 
 be liquefied. At a temperature of 0° C. this requires a 
 pressure of thirty-six atmospheres, equal to 540 pounds to 
 the square inch. 
 
 168. Solubility. — Carbon dioxide is quite soluble in 
 water. This liquid at 15° C. dissolves its own volume of the 
 gas. At lower temperatures it will dissolve more, and at 
 higher temperatures less. 
 
 The quantity which water will absorb, not only depends 
 on its temperature, but also on the pressure to which it 
 is subjected. If under twice the pressure of the at- 
 mosphere, the quantity of gas dissolved is doubled ; and 
 in all cases the quantity of carbon dioxide dissolved by 
 water will be directly proportional to the pressure upon 
 it. 
 
 Soda Water. — The refreshing summer drink known as 
 ' ' soda-water ' ' is nothing but common water holding carbon 
 dioxide in solution. The violent foaming of soda-water, 
 when drawn from the "fountain," is due to the escape of 
 carbon dioxide gas, which it has been made to dissolve by 
 high pressure, but which it can not hold when under only the 
 pressure of the atmosphere. 
 
 Water so highly charged with carbon dioxide is sometimes 
 also called seltzer water. The true seltzer water comes from 
 the celebrated spring of this name, and contains in solution 
 many other things beside carbon dioxide. The artificial 
 waters are greatly inferior to the natural waters, which are 
 
156 CHEMISTRY. 
 
 found, as at Saratoga, in such abundance. Yet they are 
 wholesome and everywhere highly esteemed. 
 
 169. Carbon Dioxide and Respiration. — The pres- 
 ence of this gas in any considerable proportion is injurious to 
 animals breathing it ; and, in sufficient quantities, it produces 
 death by suflfocation. It is, however, generally admitted 
 that the gas does not possess the poisonous character once 
 attributed to it. It is given off in the breath ; and the air in 
 unventilated rooms quickly becomes charged with it, and 
 unfit for respiration. Still the unpleasant odor of such air, 
 and its poisonous effects when breathed, are believed to be 
 due to other gases furnished by the breath, rather than to 
 carbon dioxide. 
 
 Test for its Presence. — This gas is so heavy that it 
 is likely to accumulate in wells, in cellars, and in coal-pits. 
 Indeed, it is often found in coal-mines : the miners call it 
 choke-damp. Before entering a place where its presence may 
 be suspected, let a lighted candle be introduced. If the 
 caudle continues to burn, the air is pure enough to be 
 breathed ; but if the flame is extinguished, life would be also. 
 
 170. Carbonic Acid. — Carbon dioxide is an anhydride. 
 With water it combines, and forms carbonic acid, Hj C O3. 
 
 CO, -h H2O = H2CO3. 
 
 This acid can not be obtained pure and free ; but its pres- 
 ence in water, which has dissolved C O2, is demonstrated by 
 adding a little blue litmus solution, which becomes red. 
 
 IV. — The Group. 
 
 171. The Quadrivalent Group Carbon and silico n. 
 
 are the two quadrivalent non-metals. One atom of carbo n 
 can hold four of hydrogen in combination ; one of silicon 
 can do the same. The symbols of these compounds are 
 C Hj and Si H4. Carbon forms a host of other compounds 
 with hydrogen, some of which will be noticed in due time. 
 
CHEMISTRY. 157 
 
 Other Properties. — These two elements have each 
 three allotropic forms. The common form of carbon is 
 charcoal : its crystalline forms are graphite and the diamond. 
 So the common form of silicon is a dark-colored solid, which 
 may be changed to two crystalline forms, like graphite and 
 diamond. 
 
 Both these elements are very hard, very infusible, and 
 able to resist the action of chemicals in greater degree than 
 most others. 
 
 The compounds of carbon are especially numerous among 
 organic substances, while those of silicon are to be found 
 almost wholly among minerals. 
 
 REVIEW. 
 I.— SUMMARY OF PRINCIPLES. 
 
 172. vSilicon and carbon are the only quadrivalent non- 
 metals. 
 
 Each exists in three allotropic forms. 
 
 Silica is the compound of silicon with oxygen, represented 
 by the formula Si Oj. It is very abundant in the earth. 
 
 Silicic acid is represented by Hj Si O3. The salts of this 
 acid are silicates, and are very numerous. 
 
 Glass is a silicate containing two or more metals. It is 
 made by melting together silica and such bases as soda, 
 potash, and lime. The character of tlie glass depends on 
 tlie bases used. 
 
 Carbon is found in the form of coal, of diamond, and of 
 graphite. 
 
 With oxygen, carbon forms two oxides, carbon oxide or 
 monoxide, and carbon dioxide. They are represented by 
 C O and C O2. 
 
 Carbon oxide is a colorless, combustible, and very poison- 
 ous gas. 
 
 Carbon dioxide is also colorless, but not combustible. It 
 does not support respiration. 
 
158 CHEMISTRY. 
 
 It may be obtained by the action of any strong acid upon 
 a carbonate. Hydrocliloric acid and marble are conveniently 
 chosen. 
 
 This gas is soluble in water, the quantity depending on the 
 temperature and the pressure. 
 
 The presence of carbon dioxide may be determined in wells 
 and mines by means of a candle-flame, which it will extin- 
 guish. 
 
 The test used by chemists is lime-water, which the gas 
 renders milky. 
 
 Carbonic acid is represented by Hj C O3. The salts of this 
 acid arc the carbonates, and are very abundant in nature. 
 They are among tlie useful substances in the laboratory also, 
 and in many arts. 
 
 II. — EXERCISES. 
 
 Describe the element silicon. 
 
 What is silica? Where is it found? What is silicic acid? 
 What are silicates ? 
 
 From what is glass made ? Give a brief description of the 
 process. 
 
 Describe the materials used in malting glass. 
 
 Name four varieties of glass. Of what different materials 
 are they made ? 
 
 Describe the process of melting. 
 
 Of blowing. Tell how a pane of glass is made. 
 
 Describe the process of annealing. 
 
 How many ways of making charcoal are given ? Describe 
 the first. The second. 
 
 What is said of the abundance of carbon ? 
 
 What properties make tlie diamond so valuable? What is 
 said of its occurrence? In what two forms is it cut? What 
 is a carat? Mention a few of the largest diamonds. 
 
 What is said of graphite ? 
 
 Name the three allotropic forms of carbon. How do they 
 differ ? In what respects are they alike ? 
 
CHEMISTBY. 
 
 159 
 
 Name the compounds of carbon and oxygen. Give the 
 formula for each. 
 
 Describe carbon oxide briefly. 
 
 Of what is carbon dioxide composed ? 
 
 How may this gas be obtained ? 
 
 In what respects does it resemble other gases ? In what 
 action does it differ from all others ? How may we show it to 
 be heavier than air ? How can this substance be obtained in 
 a liquid state ? In a solid state ? "What is the effect when 
 this gas is breathed? 
 
 What is carbonic acid ? 
 
 What is the quantivalence of silicon and of carbon ? How 
 are these elements related by other properties? 
 
 SECTION VII. 
 
 COMBUSTION. 
 
 1. — Nature and Products of Combustion. 
 
 173. Combustion. — Combustion is a mutual chemical 
 action, generally between oxygen and some other siibstance, 
 and which, when rapid 
 enough, evolves heat and 
 light. 
 
 When a substance will 
 burn in air, it is said to be 
 combustible : the air at the 
 same time is said to be the 
 supporter of combustion. 
 But really there is no dif- 
 ference in the part played 
 by the two things in the 
 
 Fig. 71. 
 
 action : the chemical change is mutual. 
 
 Illustrated by Experiments. — Experiments may be 
 'Tiade to illustrate this fact. Fig. 71 represents a jar of 
 
160 
 
 CHEMISTRY. 
 
 oxygen, with a jet of hydrogen burning in it. It is the 
 hydrogen which appears to burn. In Fig. 72 oxygen is flow- 
 ing from a jet, and burning in a vessel kept full of hydro- 
 gen : in this ease the oxygen appears to burn. The truth 
 is, that in both eases alilie the two gases are combining 
 to form the liquid water. 
 
 Take an alcohol lamp, and, by spreading its wick, make a 
 large flame. The center of this flame is dark, and is filled 
 
 with the vapor of al- 
 cohol. Let the oxy- 
 gen in a gas-bag be 
 forced out bj' a very 
 gentle pressure, and 
 while it is thus flow- 
 ing in a gentle stream 
 let the end of the 
 jet-pipe be slowly 
 pushed into the edge 
 of the dark center of 
 the alcohol flame. 
 The jet of oxygen 
 will take fire while 
 entering the flame, 
 and then continue to 
 burn with a very dis- 
 tinct and pretty light. In this little flame the oxygen seems 
 to be the combustible, and the alcohol vapor the supporter ; 
 while in the large flame around it the alcohol seems to be the 
 combustible, and the oxygen of the ah the supporter. The 
 fact is, both are equally combustible. 
 
 Fig. 72. 
 
 174. Combustion is an Oxidation. — In all. ordinary 
 combustion oxygen is one of the active substances. When 
 wood burns in air, it is because the carbon and hydrogen of 
 the wood combine with the oxygen of the air. Few, indeed, 
 are the exceptions to this : the burning of a wax taper in a 
 jar of chlorine is ouq. 
 
CHEMISTRY. 161 
 
 The products of combustion must, therefore, be oxides. 
 
 Evolving: Light and Heat. — The evokition of light 
 and heat accompanies all familiar cases of burning ; but the 
 same chemical action, going on more slowly, gives off heat 
 without light. An iron wire, when burned in moist oxygen, 
 produces a splendid light, but when allowed to slowly rust in 
 air, no light is ever seen. The chemical action is the same 
 in both eases, — oxygen combines with the iron, and they 
 form an oxide. Moreover, to change the iron to an oxide 
 takes the same amount of oxygen in the two cases ; and, 
 still further, the same aggregate quantity of heat is given 
 off. Both are cases of combustion ; the one being rapid, the 
 other slow. 
 
 The amount of heat depends upon the amount of material 
 taking part in the action : the intensity depends upon the 
 rapidity with which the action goes on. 
 
 175. The Kindling Temperature. — Thin shavings of 
 the dryest pine wood, as is well known, will rest in air for 
 any length of time unburned ; but when heated by a burning 
 match how quickly do they disappear ! The match, by its 
 heat, simply raises the temperature of the wood until, having 
 reached a certain point, the oxygen of the air begins rapidly 
 to combine with its elements. The temperature at which a 
 substance begins to burn is tolerably constant, and it may 
 be called its Kindling Point. The kindling point varies 
 greatly in different substances : phosphorus, for example, in- 
 flames sometimes by the gentle heat of the hand ; while sul- 
 l)hur must be heated to about 560° F. before it will take fire, 
 and ordinary fuels to about 1,000° F. 
 
 Temperature kept up hy Chemical Action. — But 
 let the burning once begin, and the kindling point is kept up 
 by the combustion itself : a match may kindle the fire which 
 destroys a city, but if by any means the burning body can be 
 cooled below the kindling point the fire is quenched. Over 
 the flame of a gas-jet press down a sheet of wire-gauze 
 
162 CHBMISTEY. 
 
 (Fig. 73) : the gas goes through the gauze, the flame does 
 not. The cold metal reduces the heat, cooHug the gas below 
 its kindling point. The metal finally be- 
 comes red-hot, after which the flame freely 
 passes it. 
 
 Upon this principle the ' ' safety-lamp ' ' is 
 made (Fig. 74). It consists of a wire-gauze 
 cylinder completely enveloping the burner of 
 the lamp. The combustible " flre-damp " of 
 a mine may burn some time inside the cylin- 
 der, warning the miners of its dangerous 
 presence, before the cold meshes of the gauze 
 will allow the flame to pass out and explode the mine. 
 
 Fig. 73. 
 
 176. The Composition of Fuel. — All fuel is of vege- 
 ' table origin. That wood and charcoal are so, is evident; 
 not less so are all forms of coal found in the 
 earth. Tliey are the remains of an ancient 
 vegetable or forest growth, which, under the 
 influence of heat and pressure, has at last 
 parted with its oxygen and hj-drogen, while 
 the carbon still remains. The resins, oils like 
 l)etroleum, and coal-gas, more rarely used for 
 fuel, are substances which have also come 
 from the decomposition of plants. But all 
 these substances are compounds of carbon and 
 hydrogen in different proportions. In all or- 
 dinary fuels, carbon and hydrogen are the chief 
 constituents. 
 
 The Products of Comhustion. — Upon 
 the bottom of a plate or pan stand a burning 
 wax taper, and cover it with a glass jar (Fig. 
 75). The flame soon grows dim, and is finally extinguished. 
 Let the taper be removed, and a small quantity of lime-water 
 poured into the jar. The milkiness of the fluid shows the 
 presence of carbon dioxide. The carbon of the wax has 
 
 Fig. 74. 
 
CHEMISTRY. 
 
 163 
 
 united with the oxygen of the air, and carbon dioxide is a 
 product of tlie combustion. 
 
 Again, over the flame of a burning gas-jet hold a cold 
 glass jar. The sides of the jar are quickly dimmed with 
 dew, which must have been 
 formed by the hydrogen of the 
 gas uniting with the oxygen of 
 the air. 
 
 Water and carbon dioxide are 
 the important products of all 
 ordinary combustions. 
 
 177. Gases only burn with 
 Flame. — The flames which ac- 
 company the combustion of 
 most substances are due to 
 burning gases. The flame of 
 
 Fig. 75. 
 
 a candle is as truly a gas 
 
 flame as is the flame of a jet of illuminating gas. The 
 
 solid wax or tallow in the wick must be first melted and then 
 
 vaporized by the heat of the match before it will take Are. 
 
 The gas once lighted causes a flame, whose 
 
 heat melts the wax below ; and the 'liquid, 
 
 lifted by capillary force through the wick, 
 
 is changed to vapor as fast as it is needed 
 
 in the flame. Take the wax in a test-tube 
 
 with a jet-pipe through its tight cork, and 
 
 heat it. The wax melts, then boils, and 
 
 the vapor at length issues from the jet, 
 
 when, if touched with a hghted match, it 
 
 burns (Fig. 76) with exactly the same kind 
 
 of flame, only less steady. 
 
 Alcohol and oil burn with flame only after 
 heat has changed them to vapors. Bitumi- 
 nous coal and wood burn with flame because 
 they contain substances which the heat applied can vaporize ; 
 while hard coal burns with uo flame, because it gives off no 
 gases when heated. 
 
 Fig. 76. 
 
164 
 
 CHEMISTRY. 
 
 The fine blue flame which is often seen over an anthracite 
 fire has been already explained as due, not to the combustion 
 of the coal, but to the combustion of carbon oxide. The 
 carbon at first takes oxygen, and becomes carbon oxide ; and 
 then this gas, coming in contact with oxygen at the surface 
 of the fire, combines with additional oxygen, and becomes 
 carbon dioxide. 
 
 CO + O = CO2. 
 
 This combustion of the gas, C O, yields the blue flame. 
 
 178. Three Parts to a Common Flame. — The dark 
 center and the luminous cone of common flames have been 
 noticed by us' all. Tliis dark center or 
 nucleus consists of the gases formed from 
 the fuel ; but they are not in a burning 
 condition. The luminous envelope consists 
 of these gases combining with the oxygen 
 of the air. In this part of the flame only 
 does combustion occur. Outside of this, is 
 an envelope made up of water-vapor and 
 carbon dioxide produced by the burning. 
 
 The three parts may be easily seen in a 
 common candle flame (Fig. 77). 
 
 The micleus is not burning: for the end 
 of a match, plunged to the center of the 
 flame, does not burn while there ; it takes 
 fire while coming out. And even gunpow- 
 der may rest in this center of a flame un- 
 harmed ! This can be easily proved. For 
 this purpose invert a dluuer-plate or com- 
 mon bowl upon the table : its bottom is a 
 very shallow dish which will hold a small 
 quantity of alcohol. Put some gunpowder on the end of a 
 small cork, and place it at the middle of the plate, and then 
 touch the alcohol with a match. A large flame is formed, in 
 the center of which the powder remains unburned (Fig. 78) , 
 
 Fig, 
 
CHEMISTRY. 
 
 16fi 
 
 until some air-curreut wafts the flame, or until the alcohol is 
 nearly consumed. 
 
 The hnrning takes place in the luminous envelope. We 
 are taught this by the fol- 
 lowing experiment : over the 
 flame ai an alcohol-lamp 
 suddenly lower a sheet of 
 writing-paper, holding it for 
 a moment across the middle 
 of the flame (Fig. 79). Re- 
 move it, and a scorched ring 
 will be seen ; the paper is 
 burned just where it was in 
 contact with the luminous Fig. 78. 
 
 envelope. 
 
 Hold a cold glass plate in place of the sheet of paper for 
 a moment on the flame : a ring of dew is condensed upon it 
 where it comes in contact with the non-luminous envelope. 
 
 II. — Light and Heat. 
 
 179. The Practical Value 
 
 Fig. 79. 
 
 of Combustion. — Most 
 chemical processes are 
 valuable on account of 
 their products ; but the 
 products of combustion, 
 water and carbon _diQX7 
 ide, are of no practical 
 value as products, and 
 combustion is never re- 
 sorted to for their sake. 
 This process is useful 
 
 simply for the light and heat which accompany it. 
 
 180. Conditions for Production of Light. — Witness 
 the following experiments. Let a glass jar be inverted over 
 a burmng taper (Fig. 80) . The flame continues for a tune, 
 
166 
 
 CHEMISTRY. 
 
 Fig. 80. 
 
 and jthen dies. It goes out because its supply of oxygen is 
 
 exhausted. Nor does it help the matter much to raise the 
 jar a little space above the plate on 
 which the taper stands, for the jar 
 remains full of impure air which 
 keeps the pure air out. 
 
 Now again, put the taper at the 
 bottom of a jar whose open mouth 
 is upward, and, if necessary, partly 
 cover it (Fig. 81). The flame dies 
 almost as quickly as before, and for 
 the same reason. "We learn from 
 these experiments that a supply of 
 fresh air is absolutely needed for 
 combustion. 
 A Full Supply. — Go further : take a lamp-chiraney, 
 
 and so place it that a very small opening admits air at the 
 
 ))ottom : the flame does not die, but 
 
 burns diml}'. And now, again, almost 
 
 cover the top of the chimney, leaving 
 
 the bottom open : the taper burns, but 
 
 with a dim or smoky flame. Finally, 
 
 open both top and bottom. A cur- 
 rent of air passes freely up through 
 
 the cliimney, and we see the taper 
 
 burning brightly. These experiments 
 
 teach us that a full supply of air 
 
 is necessary to produce a luminous 
 
 flame. 
 To the Surface of the Flame. — But it will not do to 
 
 mix the air with the combustible gas : such a mixture burns 
 
 with an almost lightless flame. 
 
 This effect is shown in the Bunsen's burner (Fig. 82). 
 
 The gas is brought from the chandelier by means of the 
 
 rubber tube, and issues from a jet-pipe inside the tube A. 
 
 Just below the end of this jet are two large holes on 
 
 Fig. 81. 
 
CHBMISTET. 
 
 167 
 
 Fig. 82. 
 
 its flame is without 
 
 opposite sides of the tube, one of which is shown at 6. A 
 
 movable collar c, with corresponding holes, may be turned 
 
 around the tube so as to open and 
 
 close these holes at pleasure. Now 
 
 a constant supply of gas from the jet,- 
 
 and of air entering at the holes, keeps 
 
 the tube (A) full of a mixture, which 
 
 is lighted as it issues from the upper 
 
 end. This burning mixture gives an 
 
 intense heat, — a glass tube may be 
 
 quickly softened or melted by it ; but 
 
 the light is very feeble. 
 
 The instrument is much used in llie 
 laboratory for heating glass vessels, 
 for which it is well adapted, because 
 smoke and deposits no soot. 
 
 A full supply of air must be brought in contact with the 
 surface of the gas-jet if the greatest light is to be obtained. 
 
 This is done in the Common Lamp. — The oil or 
 kerosene lamp is too familiar to need description. Notice 
 that the Jlal wick usually employed, exposes a large surface 
 to the air, and that the chimney, open at the top and bottom, 
 allows a constant current of fresh air to pass up through it. 
 By this means an abundance of air is brought in contact 
 with the flame, at its surface only, and the bright light is the 
 result. 
 
 Tlie Argrand Burner. — In the argand burner an artifice 
 is resorted to, by which the surface of the flame exposed to 
 air is increased. The wick is a hollow cylinder, and the an- 
 passes up through the inside of it as well as around its out- 
 side. The gases from the wick expose a double surface to 
 the air, and give off a greater light accordingly. 
 
 The Gas Burner. — The burner of a gas-chandelier is 
 so made that the gas escapes in a fan-shaped jet. This is 
 done in many ways. In the end of some burners we may 
 notice two small holes ; and by putting pins into these we 
 
168 CHEMISTRY. 
 
 find them to be the ends of two little tubes slanting toward 
 each other, so that if continued outward they would meet. 
 Now, the two jets of gas from these tubes strike against 
 each other with force enough to flatten both out into a single 
 fan-shaped jet. In this way a large surface of gas is 
 exposed to air without making a mixtm-e of the two sub- 
 stances, and the luminous flame is produced. 
 
 181. Source of the Light. — Sift some finely-powdered 
 charcoal into the almost non-luminous flame of a Bunsen's 
 burner, and we find that the flame becomes more or less 
 luminous. What happens is this : The small particles in 
 the hot flame are heated to whiteness, and shine with a bright 
 light. The light quickly vanishes, however ; because when 
 these hot particles of carbon come in contact with air, they 
 instantlj' combine with oxygen, and become carbon dioxide. 
 The light is due, while it lasts, to the intensely heated solid 
 particles. 
 
 Doubtless on this principle we may. in part, account for 
 the light of common flames. We know that the burning gas 
 is being decomposed, and that one of its constituents is 
 carbon. We know, too, that carbon is a solid, even at the 
 highest heat, but that heated in air it combines with oxygen. 
 At the instant, then, when set free from the burning gas, 
 and before its union with oxygen, each little molecule of 
 carbon is heated white-hot, and, shining brightly, adds its 
 mite to the light of the flame. 
 
 The Oxyhydrogen Light. — The luminous power of 
 solid bodies in a heat-flame is illustrated by the so-called 
 oxyliydrogcn or lime light. It is made by simply placing a 
 piece of lime in tlie flame of the oxyhydrogen blow-pipe. 
 (Fig. 84.) So very intense is this light, that the eye is 
 blinded by its direct rays ; and, used in light-houses, it has 
 been seen miles away at sea. 
 
 Observe now : lime remains solid, even in the most intense 
 heat of the blow-pipe ; but the burning mixture gives heat 
 
CHEMISTRY. 169 
 
 enough to raise the lime to a white heat, and in this condition 
 it shines with a blinding light. 
 
 Light Due also to Dense Vapors. — But that all the 
 light of flames is not to be explained in this way, is seen 
 clearly from the fact that in some of the most dazzling there 
 is no substance present which can remain solid at the tem- 
 perature of the flame. Remember the blinding light of 
 phosphorus burning in oxygen-gas. " Now, phosphoric 
 anhydride, the product of this combustion, is volatile at a 
 red-heat ; and it is, therefore, manifestly impossible that this 
 substance should exist in the solid form at the temperature 
 of the phosphorus flame, which far transcends the melting 
 point of platinum." {Dr. Frankland.) Many other exam- 
 ples of a similar kind might be given. The light of such 
 flames, and doubtless much of the light of all flames, is due 
 to intensely heated dense vapors. 
 
 182. Conditions for the Production of Heat. — If 
 
 heat is the object sought for in the process of combustion, 
 two conditions should be fulfilled. There should be & proper 
 supply of air provided, and this supply should be thoroughly 
 mixed with the fuel. 
 
 Object of Mixing the Air and Fuel. — By mixing 
 the air with the fuel we enable the combustion to take place 
 in every part at once. It is therefore more rapid and 
 complete, and the heat is more intense. 
 
 In the common stove and furnace, for example, the air 
 entering at the draught mixes very thoroughly with the fuel ; 
 and the heat is much more intense than it would be if the 
 two came in contact only at the surface. 
 
 The Proper Supply of Air. — By the proper supply 
 of air we mean just so much as is needed to furnish oxygen 
 enough to combine with all the fuel. 
 
 Too little air will leave some of the fuel unburned, and heat 
 will be lost. Too much air will cool the fire by carrying 
 away some heat into the draught. 
 
170 
 
 CHEMISTRY. 
 
 To Calculate the Quantity. — If we know the composi- 
 tion of tlie fuel, we can then calculate the quantity of air 
 needed for its combustion. Suppose, for example, we have 
 ten liters of hydrogen, and wish to get the most intense heat 
 by burning it : how much air must we give it? We first find 
 how much oxygen it requires to combine with it. We know 
 that two volumes of hydrogen take one volume of oxygen to 
 form water. Hence our ten liters of hydrogen must have five 
 of oxygen. We next find how much air is required to furnish 
 the necessary oxygen. We know that oxygen constitutes 
 very nearly one-fifth of the air ; hence it will need twenty-five 
 liters of air to give the five liters of oxygen to bum the ten 
 of hydrogen. 
 
 Whatever the composition of the fuel may be, knowing it 
 we can calculate just how much oxygen will exactly oxidize 
 all its constituents, and then the quantity of ai»- required to 
 furnish this amount. 
 
 183. The Intensity of the Heat. — The intensity of 
 heat produced depends on the rapidity of the combustion, 
 g A brisk fire is a hot fire. A smolder- 
 
 ing fire may burn longer, and in the 
 end give out as much heat, but at no 
 time is it able to scorch, consume, or 
 fuse with vigor. 
 
 The Oxyhydrogen Blow-pipe. 
 — A mixture of hydrogen and oxy- 
 gen, in the right proportions to form 
 water, burns with heat of surprising 
 intensity. By means of the oxyhy- 
 drogen, or compound blow-pipe, this 
 
 flame may be obtained with little dan- 
 
 — ger of explosion. Notice Fig. 83, 
 which shows a section of one form of 
 the jet, and Fig. 84, which shows the instrument in use. 
 The gases are stored in separate bags, or other reservoirs. 
 
 Fig. 83. 
 
CHEMISTRY. 171 
 
 Hydrogen passes from one of these into the larger or outside 
 tube of the jet, and flows out at c; while oxygen from the 
 
 Pig. 84. 
 
 other passes through the inside tube, and out at the same 
 point. It will be seen that the two gases mix just at the 
 point of the jet, and that here the combustion takes place. 
 This is called the concentric jet. In another form the jet 
 contains no inner tube. The two gases are brought into the 
 base of the jet, where they mix, and the mixture issues from 
 the tip. This is called the mixed jet. 
 
 The heating effects of this flame are astonishing. Zinc 
 and antimony are vaporized by it. Iron and steel (Fig. 84) 
 burn in it like thread in a lamp-flame. Platinum, and even 
 quartz and other rocky matter, may be melted or softened. 
 Only the heat of the electric arc exceeds this in intensity. 
 
 184. The Quantity of Heat. — It has been proved by 
 numerous experiments that the quantity of heat evolved by 
 combustion does not depend on the rapidity of the action, but 
 only on the weight of the material burned. The burning of a 
 pound of hydrogen will yield precisely the same amount of 
 heat, whether it burn swiftly or slowly. A pound of carbon 
 will yield always exactly the same quantity of heat when it 
 is changed into carbon dioxide by combustion. If, however, 
 the carbon burns to carbon monoxide, the pound will yield 
 less, because the quantity of oxygen burned is less. The 
 general principle may be stated as follows : — 
 
172 
 
 CHEMISTRY. 
 
 Tlie same weight of the same substance will invariably yield 
 the same amount of heat when the products of combustion are 
 the same. 
 
 A slow fire will in the end give just as much heat as a 
 brisk one, if the same quantity of fuel and air are consumed. 
 
 "^ \i,xA^ III. _ Respiration. 
 
 185. Respiration. -— The walls of the air-cells of the 
 lungs are covered with a net-work of minute capillary blood- 
 vessels. Into the air-cells successive portions of fresh air 
 enter, to be at once thrown out again, while, at the same 
 time, the impure blood of the system is constantly coursing 
 through these vessels. We must consider what changes are 
 being made, first in the air, and second in the blood. 
 
 The Chemical Changes. — If one breathes through 
 a tube into a vessel of lime-water, its milky color soon 
 shows the presence of carbon dioxide. If he breathe on a 
 cold surface, the moisture condensed there shows the pres- 
 ence of water-vapor. To determine what other substance 
 is exhaled, we may make an experiment, which is repre- 
 
 Fig. 85. 
 
 sented in Fig. 85. A bell-jar is placed with its open mouth 
 in a vessel of water. The jar is provided with a cork. 
 
CHEMISTRY. 173 
 
 through which passes a tube which joins it to the bottom of 
 a tall jar containing caustic potash, K H O. The top of this 
 potash jar is also provided with a tube terminating with a 
 mouth-piece. Applying the lips to this mouth-piece, the air 
 in the jar may be drawn into the lungs, and then returned to 
 the jar. Let this be done two or three times. In going 
 back and forth between the jar and the lips, the air must 
 pass over the caustic potash, which will effectually remove 
 from it, both the water-vapor and the carbon dioxide. Let 
 the flame of a taper be afterward plunged into the jar, and 
 it will be extinguished, showing the absence of oxygen and 
 the presence of nitrogen. 
 
 From all these experiments we conclude that the air whUe 
 in the lungs gives up its oxygen, and receives carbon dioxide 
 and water-vapor. 
 
 Could we examine the blood, we should find that while in 
 the lungs its color changes from purple to bright red, due to 
 the loss of carbon dioxide and water-vapor, and the receipt 
 of oxygen. 
 
 A Process of Slow Combiistioii. — Now, how can 
 these changes be explained? It has been found that 
 particles of the body itself are constantly being worn out. 
 Not an act can be done, a word spoken, nor can a thought 
 occur, without the disintegration of some portion of the 
 organs. These waste particles are in great part thrown into 
 the blood : they are its impurities. These particles are com- 
 posed chiefly of carbon and hydrogen. The pure blood is 
 charged with oxygen ; and, as it flows, this gas combines with 
 the carbon and hydrogen of the waste, at all points in its 
 course ; and the carbon dioxide and water-vapor, thus formed, 
 pass into the lung-cells, to be finally exhaled from the system. 
 The action is a process of slow combustion. The waste par- 
 ticles are the fuel, oxygen is supplied, and carbon dioxide 
 and water-vapor are the products. 
 
 Moreover, it is by the heat evolved in this combustion that 
 the body is kept warm. 
 
174 CHEMISTRY. 
 
 Large Quantities of Air Spoiled. — It will be at once 
 seen that the air of our rooms is being constantly made unfit 
 to keep up this action by wliich the blood is purified. In the 
 first place, its oxygen is being taken out ; and, in the second 
 place, impurities are being thrown into it. Not only does it 
 receive the worn-out matter of the system from the breath, 
 but we may here add that other portions of waste, even more 
 offensive, are incessantly being given into it from the body 
 by perspiration. The total amount of impurity thus added 
 to the air of a close room is frightful ; since, upon the aver- 
 age, about twenty thousand cubic inches of air pass through 
 the lungs of a single person every hour ! 
 
 Hence the Need of Ventilation. — As the fiame of a 
 taper dies in a closed jar, so a human being would die if 
 confined long enough in an air-tight room. As the flame 
 flickers and burns dim when a small supply of air is fur- 
 nished, or the products of combustion are not removed, so 
 the life of human beings flickers and grows feeble in rooms 
 where fresh air is not supplied. 
 
 rv. — Decay. 
 
 186. Decay. — The decay of wood or other vegetable 
 matter is a slow process of combustion. By the gradual loss 
 of carbon dioxide and water, the decaying wood is finally 
 changed into a brown or black mold, to which the name 
 humus is given. 
 
 The Decay of Wood. — If fine sawdust is thoroughly 
 moistened, and put into a stoppered bottle containing air, and 
 afterward exposed to a temperature of about 16° C. (60° F), 
 it will, after a long time, be found partially decayed. By 
 the usual tests it will be found that the air in the bottle has 
 given up a part of its oxygen, and received carbon dioxide 
 in return. 
 
 "Wood, of whatever kind, when exposed to the continued 
 action of moist air and warmth, will, like the sawdust in the 
 experiment, be gradually decomposed. Moisture and warmth 
 
CHBMISTEY. 
 
 175 
 
 Pig. 86. 
 
 are essential to decay ; since it is found that wood, exposed 
 to the cold of the arctic regions, or to the dry air of Egypt, 
 will remain, even for 
 centuries, in good con- 
 dition. 
 
 Other Vegetable 
 Matter. — If a flask 
 (Fig. 86) partly filled 
 with peas and water is 
 furnished with a bent 
 tube reaching over to 
 an inverted larger tube 
 filled with water, there 
 may, after a time, be seen bubbles of gas rising into the 
 tube. This gas, if tested, will be found to be carbon diox- 
 ide ; and when the peas are examined they will be found to 
 be partially decayed. 
 
 A Slow Combustion. — Now, the experiments with the 
 sawdust and the peas are simple illustrations of what occurs 
 whenever any kind of vegetable matter is long exposed to 
 the action of air under the influence of moisture and warmth. 
 They are slowly decomposed : a part of their carbon and of 
 their hydrogen unites with oxygen to form carbon dioxide 
 and water ; while the rest of these elements, in combination 
 with oxygen, remains in the form of a loose, solid, black 
 mold. 
 
 The chemical action in the process of decay is, clearly, 
 very similar to that of combustion. Indeed, it differs from 
 combustion, chiefly in being less rapid. Heat is evolved in 
 decay as in combustion, and from equal quantities of material 
 the same amount. In some rare cases a feeble light is also 
 given off by decaying vegetable matter. Decay is to be 
 considered as but a process of slow combustion. 
 
 The combustion is, however, very incomplete. A large 
 part of the carbon, and much of the hydrogen, of the 
 decaying body, is left unoxidized. 
 
176 CHEMISTRY. 
 
 Humus. — The brown or black mold that is left after the 
 decay of plants is called Humds. This term, however, is 
 not the name of a single substance, but rather of a mixture 
 of several compounds of carbon, hydrogen, and oxygen in 
 various proportions. Humus gives to fertUe soils their rich 
 brown or black appearance. 
 
 REVIEW. 
 I. — SUMMARY OF PRINCIPLIIS. 
 
 187. Combustion is a mutual chemical action, generally 
 between oxygen and some other substance, and which, when 
 rapid enough, evolves heat and light. 
 
 A certain temperature must be reached before a substance 
 will kindle ; but once started, the chemical action will pro- 
 duce heat enough to keep the action going. 
 
 Every combustible has a kindling point peculiar to itself. 
 Phosphoretted hydrogen kindles on contact with air at ordi- 
 nary temperatures. When this is the case, the burning is 
 said to be Spontaneous Combustion. On the other hand, 
 ordinary fuels have a kindling point of about 1000° F. 
 
 Flame is extinguished by being cooled below the kindling 
 point of the substance. For this reason flames will not 
 pass through small openings in cold bodies, as, for example, 
 the interstices in wire-gauze. 
 
 All fuel is of vegetable origin, and consists chiefly of 
 carbon and hydrogen. 
 
 Combustion is the oxidation of the elements of the fuel. 
 
 Carbon dioxide and water are therefore the chief products 
 of combustion. 
 
 Flame is produced only by the burning of gaseous matter. 
 A solid, burning as such, yields a glow of light but no flame. 
 
 Combustion is resorted to merely for the heat and the light 
 it produces ; not as in other chemical processes, for the 
 material which it forms. 
 
 To give the greatest light, there should be a full supply of 
 
CHEMISTRY. 177 
 
 air to the surface of the gas-jet, as in the common lamp, the 
 argand burner, and ordinary gas flames. 
 
 To give the greatest heat, the air should be thoroughly 
 mixed with the burning gas. 
 
 The proper supply of air is that which will furnish just 
 oxygen enough to unite with the elements of the fuel. 
 
 The quantity of heat depends on the weight of the material 
 burned. 
 
 The intensity of the heat depends on the rapidity of the 
 combustion. 
 
 When the oxidation takes place so slowly that no light is 
 evolved, it is described as stow combustion. 
 
 Respiration is a process of slow combustion. The waste 
 particles of the body are the fuel : they are oxidized by the 
 oxygen of the air which is absorbed by the blood in its 
 passage through the lungs : carbon dioxide and water- vapor 
 are produced and exhaled in breathing. 
 
 The heat of this slow combustion is the natural heat of 
 the body. 
 
 The decay of organic bodies is also an analogous process 
 of slow combustion. 
 
 II.— EXERCISES. 
 
 What is combustion ? By what experiment is it shown to 
 be a mutual action ? 
 
 Between what substances does it occur? 
 
 Do light and heat always accompany combustion? Illus- 
 trate by the combustion of iron. Upon what does the amount 
 of heat depend ? Upon what, its intensity ? 
 
 Why do not substances take fire when simply exposed to 
 air? What is meant by the term, kindling temperature? 
 Give examples. 
 
 How is the temperature kept up? Illustrate. Describe 
 the experiment with the wire-gauze. What does this 
 experiment teach? What application has been made of 
 this principle ? 
 
178 CHEMISTRY. 
 
 Of what is fuel composed ? "What are the chief products 
 of combustion? 
 
 What is the origin of all fuel ? How can this be true of 
 coal ? Of resins and petroleum ? 
 
 Describe the experiment with the wax taper. What does 
 it teach ? The experiment with the gas-jet. What does it 
 teach ? 
 
 Do solids, liquids, or gases burn with flame? How can 
 this be true of the candle flame? Of alcohol? Of wood? 
 Of hard coal? 
 
 Name the three parts of a common flame. Of what is 
 each formed ? Prove that the nucleus is not burning. How 
 may we learn that the burning takes place in the luminous 
 envelope ? How can we prove that there is water in the non- 
 luminous envelope? 
 
 For what is combustion resorted to ? 
 
 In what way is the greatest heat produced? 
 
 Describe the Bunsen's burner. Explain its action. 
 
 Describe the oxyhydrogen blow-pipe. What effects may 
 be produced by it? 
 
 To get the greatest l^ht from combustion, what is 
 necessary ? 
 
 Describe the first experiment with the burning taper. The 
 second. What do these experiments teach? Describe the 
 experiments with the lamp-chimney. What do they teach? 
 Should the air and gas be mixed? 
 
 How is the full supply of air in contact with the surface of 
 the flame secured in the common lamp ? 
 
 In the argand-burner ? 
 
 In the gas-burner? 
 
 To what is the light of a flame due ? 
 
 Illustrate by the lime-light. 
 
 What reason have we to suppose that all the light is not 
 due to solid particles ? To what is it, then, due ? 
 
 What kind of an action is respiration ? 
 
 By what means are the air and blood in the lungs brought 
 
CHEMISTRY. 179 
 
 in contact? How may the presence of carbon dioxide in 
 the breath be proved ? Of water- vapor ? How may we prove 
 the absence of oxygen and the presence of nitrogen in the 
 breath? What change, then, occurs in the air while in the 
 lungs ? What change occurs in the blood there at the same 
 time? Explain these changes. 
 
 How, then, is the air of inhabited rooms being spoiled? 
 How much impurity is thus being added to the air? 
 
 Why is ventilation absolutely necessary? 
 
 What kind of a process is decay? What change takes 
 place in decaying bodies ? 
 
 Describe the experiment with sawdust. How do we know 
 that moisture and warmth are necessary to cause decay ? 
 
 Describe the experiment with the peas. 
 
 What do these experiments illustrate ? In what respects 
 are decay and combustion alike ? 
 
 What is left after the decay of plants ? 
 
180 CHEMISTKY. 
 
 CHAPTER III. 
 THE COMPOUNDS OF CARBON. 
 
 SECTION I. 
 
 GENERAL STATEMENTS. 
 
 188. Orgauic Clieniistry. — The compounds of carbon 
 are more numerous than those of all other elements taken 
 together. Many of them are very complex in composition. 
 They are, for the most part, constituents of, or products 
 from, organic bodies. For these reasons they have usually 
 been studied by themselves, in what is called Organic 
 Chejiistry. 
 
 Organic chemistry is now defined to be the chemistry of 
 the carbon compounds. 
 
 Carbon Compounds. — By the carbon compounds we 
 here refer to compounds of carbon containing hydrogen. 
 These two elements alone unite to form a very large num- 
 ber of bodies, which are called Hydrocarbons. 
 
 Another very large class contains carbon and hydrogen 
 with oxygen ; and a smaller class contains a few other ele- 
 ments also, among which are nitrogen and sulphur. 
 
 189. Organized Bodies. — Plants and animals are 
 organized bodies. Their bodies have been nourished and 
 enlarged by means of food taken into and distributed 
 throughout their interior. The plant, by means of certain 
 organs, receives the sap into its roots, and sends it to every 
 part. Every leaf and stem is built of substance which is 
 taken from this sap and from the air. The animal takes its 
 
CHEMISTRY, 181 
 
 food, converts it into blood, distributes it to the most minute 
 fibers tiirougiiout, and every part of its body is built from 
 material thus furnished. 
 
 Every distinct part of these bodies is also organized. The 
 leaf, the twig, and the tendril are organized bodies ; and so 
 ai'e the hairs, the claws, and the tissues of animals. 
 
 Org-anic Substances. — These organized bodies consist 
 almost entirely of the compounds of carbon and hydrogen, 
 oxygen and nitrogen. Sugar (C,2 H 22O11) , starch (Cg Hjo O5) , 
 and alcohol (CjHgO) are three among the thousands of sub- 
 stances which the chemist is able to get by decomposing 
 organic bodies. Such compounds may be called Organic 
 Substances, in distinction from Organized Bodies from 
 which they are obtained. 
 
 Many of these organic substances exist ready formed in 
 the organized body, but many more do not. These last are 
 produced only by the decomposition of the organized tissues. 
 
 190. Chemistry deals only with Organic Sub- 
 stances. — Now, it would seem that Nature has fixed a 
 barrier, which the chemist may not pass, between organic 
 substances and the organized bodies which they form. The 
 chemist can, by synthesis, make a few of the simplest 
 organic substances, and he has good reason to believe that 
 even the most complex are produced by chemical force, 
 governed by the ordinary laws of combination. But, on the 
 other hand, the simplest organized body, although it consists 
 of the same elements, is entirely beyond his reach. He can 
 not make a single cell. By what. chemistry the leaf and the 
 flower are made, he does not know. His laboratory teems 
 with elegant crystals whose growth he has himself guided ; 
 but his garden is filled with still more delicate forms, the 
 secrets of whose chemistry are known only to the Divine 
 Chemist who made the earth and the sun, and all that they 
 contain. 
 
182 
 
 CHEMISTRY. 
 
 SECTION II. 
 
 MARSH-GAS AND THE MARSH-GAS SERIES. 
 
 191. Marsh-Gas. — The simplest hydrocarbon known is 
 marsh-gas (C H4) , in which one atom of carbon is united 
 with four atoms of hydrogen. 
 
 This gas is found in nature. It is the principal part of 
 the gas which escapes in bubbles when the muddy bottom 
 of a stagnant pool is disturbed. 
 
 It may be collected by receiving these bubWes in an 
 inverted bottle (Fig. 87). 
 
 Fig. 87. 
 
 In this case marsh-gas has been produced by the decay of 
 dead leaves, or other organic matter ; and its name comes 
 from the fact of its occurrence in such places. This same 
 gas collects sometimes in mines ; and, by explosions of which 
 we have all heard, now and then extinguishes the lamps and 
 the lives of the miners. On this account it has also been 
 called Fire-Damp. 
 
 Properties. — Marsh-gas is colorless, and only eight 
 times heavier than hydrogen, or a little more than half as 
 heavy as air (.558). It burns vigorously, with a bluish 
 
CHEMISTRY. 183 
 
 flame which is slightly luminous. Its mixture with twice 
 its volume of oxygen explodes with great violence. 
 
 Composition. — The composition of marsh-gas is repre- 
 sented by its formula, C H4. That the molecule contains 
 four atoms of hydrogen, may be proved in this way : We 
 remember that a molecular volume is always two : hence two 
 volumes represent a molecule of the gas. Now pass electric 
 sparks through two volumes of marsh-gas : it will be decom- 
 posed, and will yield just four volumes of hydrogen. But 
 the atomic volume of hydrogen is one, and hence four vol- 
 umes must represent four atoms. Therefore, the molecule of 
 marsh-gas yields four atoms of hydrogen. 
 
 Names. — Marsh-gas is the old and common name of this 
 substance ; but the chemist calls it Methane, and at other 
 times he calls it Methyl Hydride. 
 
 This last name, methyl hydride, is intended to show that 
 the gas is a binary compound of hydrogen and methyl. If 
 we write the formula C H3 H instead of C II4 we show what 
 that methyl is : it is C Kg, which with hydrogen forms the 
 hydride. Chemists have much reason to suppose that the 
 molecule, CH4, is made up of two paHs, viz., CHg and H ; 
 and the name, methyl hydride, expresses this view, the name 
 of the C H3 being methyl. 
 
 192. The Marsh-Gas Series. — Methane is the simplest 
 of a large number of compounds, which contain carbon and 
 hydrogen holding a very curious relation. The relation is 
 this : each one in the series may he obtained by adding C H^ 
 to the one before it. Let us start with C II4 in the following 
 table, and illustrate this relation : — 
 
 C H4 . . . . Methane, 
 
 C II4 -|- C H2 = C2 H(j 
 C2 Hg -|- C H2 = C3 Hg 
 Cg Hj -)- C H2 ^ C4 Hio 
 C4HM 4- CH2= G5H12 
 etc. + etc. = etc. 
 
 Ethane, 
 Propane, 
 Butane, 
 Pentane, 
 etc. 
 
184 CHEMISTRY. 
 
 All these compounds actually exist, and many more whose 
 formulas the reader can make for himself by continuing to 
 add C H,. 
 
 This series of hydrocarbons, beginning with methane, and 
 increasing in complexity by the constant addition of C H,, is 
 called the Marsh-Gas Series. They are also sometimes 
 called the Paraffines. 
 
 Explanation. — Carbon alone among the elements is able 
 to form so many hydrogen compounds. Chemists try as 
 follows to explain this fact : In the first place, the carbon 
 atom is quadrivalent ; and, in the second place, one atom can 
 combine with another atom of carbon, and saturate one or 
 more of its units of quantivalence, leaving the other units to 
 be saturated by atoms of hydrogen. This explanation is 
 considered very satisfactory. 
 
 Illustration. — If we write the graphic formula for the 
 first one in the series, it stands thus : — 
 
 H 
 
 H— C— H CH4, Methane. 
 
 I 
 H 
 
 If, now, we put two atoms of carbon together, we must 
 add two atoms of hydrogen in order to saturate them. 
 Thus : — 
 
 H H 
 I I 
 
 H— C— C— H C2 He, Ethane. 
 
 I I 
 H H 
 
 If, again, we add a third atom of carbon, we must add two 
 more atoms of hydrogen to give the saturated molecule. 
 Thus : — 
 
 H H H 
 I I I 
 11— C— C— C— H . . . . CaHg, Propane 
 III 
 H H H 
 
CHEMISTRY. 185 
 
 Thus we see, that, carbon remaining quadrivalent, and its 
 atoms combining together by one unit, the constant addition 
 of C H2 must produce the successive members of the series. 
 
 193. Properties of the Marsh-Gas Series. — The first 
 five members of this series are gases at ordinary tempera- 
 tures. Several which follow are liquids, while from Cjo H42 
 onward in the series the substances are solids. 
 
 Each one of the liquids has its own boiling-point. Pen- 
 tane, for example, boils at 30° C, and hexane at about 60° C. 
 Jlie boiling-point rises about 30° C. for each addition of C H^. 
 
 The series is remarkably indifferent to nearly all chemical 
 agents. Its members are all combustible, and in other chemi- 
 cal actions they exchange atoms of hydrogen for atoms of 
 other elements. 
 
 194. Petroleum. — Petroleum is an oily liquid of a 
 greenish color, found in the rocks of various parts of the 
 world. It is especially abundant in Pennsylvania, where it 
 is obtained in large quantities for commercial purposes. 
 
 Composition. — Petroleum is a mixture of hydrocarbons ; 
 and these are chiefly, but not wholly, of the marsh-gas series. 
 All the members of the series from Ci Hjo to C9 Hjo are present. 
 
 Fractional Distillation. — Since each hydrocarbon has 
 its own boiling-point, it is possible to separate several, when 
 mixed, by distillation. Let the mixture be heated up to the 
 lowest boiling-point, and kept steadily at that temperature ; 
 only the vapors of the one substance having that boiling- 
 point will be driven off, and these may be condensed in a 
 receiver. "When these vapors cease to flow, let the tempera- 
 ture be raised up to the next boiling-point, and maintained : 
 only the vapors of the substance having this next higher 
 boiling-point will be driven off, and these may be condensed 
 in a separate receiver. Similarly each one in the mixture 
 may be obtained in a separate vessel. This distillation of a 
 liquid at the successive boiling-points of its constituents is 
 called Fractional Distillation. 
 
186 CHEMISTEY. 
 
 For Commercial Purposes. — Kerosene oil, naphtha, 
 and gasoline are among the products obtained from petro- 
 leum for various uses in the arts. None of these are single 
 compounds : each is a mixture of several hydrocarbons. 
 They are obtained from petroleum by fractional distillation ; 
 although the temperatures used are not the successive boiling- 
 points of its chemical constituents, but are arbitrarily chosen 
 instead. On this account each product is a mixture. 
 
 The following table, from Wagner's Chemical Technology 
 (Crookes), shows temperatures used, and names the commer- 
 cial product obtained : — 
 
 Below 37. 7° C Rhigoline, 
 
 At 76.6° " GasoUne, 
 
 At 137.0° " Naphtha, 
 
 At 148.0° " Benzine, 
 
 At 183.0° - 219.0° C Kerosene. 
 
 SECTION III. 
 
 THE ALCOHOLS. 
 
 ^"y 
 
 IBS. Common Alcobol. — When the juices of fruits 
 containing sugar are kept warm for several hours, a peculiar 
 change occurs. Their sweetness becomes less and less ; 
 bubbles of carbon dioxide escape ; and, at the same time, 
 alcohol is formed in the liquid. The chemical action, called 
 fermentation, is to be described more fully in the future. 
 
 The alcohol may be separated by distilling the liquid in 
 which it is formed ; its boiling-point being about 85.5° C. 
 (186° F.). 
 
 But mere distillation from the fermented liquor, while it 
 may furnish a concentrated spirit, can not give one entirely 
 free from water. The attraction of alcohol for water is so 
 strong that a small portion will be retained by it after tlie 
 most careful distillation. It can be removed by the stronger 
 
CHEMISTRY. 187 
 
 attraction of quicklime, and when this is done the product 
 is called absolute alcohol ; but on exposure to air it soon 
 absorbs water again, so that absolute alcohol is of rare 
 occurrence. The specific gravity of absolute alcohol is .794 ; 
 of the strongest commercial alcohol, which contains about 
 ten per cent of water, it is .825. 
 
 Properties. — Alcohol is a colorless, limpid liquid, lighter 
 than water. It burns readily with a hot, but not a bright, 
 flame. It is able to dissolve resins and oils, and many other 
 substances which water can not ; and this solvent power 
 renders it useful in the arts. 
 
 Composition. — The composition of alcohol is shown by 
 its formula CjHeO. This is its empirical formula. It is 
 often written also C2H5HO, which represents the belief that 
 its molecule consists of two groups of atoms, CgHj and 
 HO. 
 
 It is interesting to know why the chemist should feel 
 inclined to arrange the atoms in the molecule in these two 
 groups, and a little attention will show the reason. 
 
 Constitution of tlie Molecule. — He finds, that if he 
 mixes ethane, C2H6, and chlorine, he may bring about the 
 following reaction : — 
 
 CaHs + 2C1 = C2H5CI + HCl, 
 
 Ethane + Chlorine = Ethyl chloride + Hydrochloric acid ; 
 
 and, if he then treats the ethyl chloride with silver hydrate, he 
 produces alcohol. Thus, — 
 
 QH^Cl + AgHO = C2H5HO + AgCl, 
 
 Ethyl , Silver _ Ai„„r,^i , Silver 
 
 chloride + hydi-ate " ^iconoi + chloride. 
 
 Now, the C, H5 seems to have come along down from the 
 ethane unbroken, while the H 0, from the silver hydrate, has 
 been added to it ; and the union of these two groups, CgHj, 
 H O, seems to give the molecule of alcohol. 
 
 This is only one of the chemical actions which can be best 
 
188 CHEMISTKY. 
 
 explained by this view of tlie arrangement of atoms in the 
 molecule of alcohol. It is very generally accepted. 
 
 Derived from Ethane. — Compare C2 He with C2 H5 H O, 
 and we see that the latter would be obtained by substituting 
 H for H in the former. 
 
 That is, alcohol may he derived from ethane by substituting 
 a molecule of hydroxyl for one atom of hydrogen. This may 
 be clearly shown by the constitutional formula : — 
 
 II H n n 
 
 II XI 
 
 H— C— C— H H— C— C— O— H 
 
 II II 
 
 H H H H 
 
 Ethane Alcohol 
 
 where it is seen that if we only put the two atoms, OH, in 
 phice of the right-hand atom of liydrogen in ethane, we 
 change the molecule of ethane into a molecule of alcohol. 
 
 196. The Series of Alcohols. — Now, hydroxyl may be 
 substituted for an atom of hydi'ogen in other members of the 
 marsh-gas series as well as in ethane. 
 
 Methane, C H4 , becomes C H3 O H, 
 Ethane, CjHe, " C2H5 OH, 
 Propane, CsHg, " C3H7 OH, 
 Butane, C^Hio, " C4H9OH, 
 Pentane, C5H12, " C5H11OH. 
 
 The new compounds are all of them Alcohols. Alcohol 
 is, therefore,' the name of a large class of bodies, instead of 
 a single compound. An alcohol is a substance derived from 
 a member of the marsh-gas series by substituting hydroxyl for 
 hydrogen. 
 
 Their Names. — The first in the series is called methyl 
 alcohol, from the hydrocarbon group, C H3, the name of 
 which is methyl. The second is called ethyl alcohol, from 
 the group CgHj, or ethyl. The third is propyl alcohol, from 
 
CHEMISTRY. 189 
 
 propyl, C3H,. In every case the name of the ahohol is the 
 name of the hydrocarbon in it; and the name of the hydro- 
 carbon in it is the name of the corresponding member of the 
 marsh-gas series with the ending ane changed to yl. 
 
 197. liadicals. — These hydrocarbons in the alcohols are 
 called Alcohol Radicals. This term radical is applied to 
 any group of atoms which is not broken up during chemical 
 changes, but which seems to go bodily from one molecule 
 into another. 
 
 Let us take the case of methane, C H4, and represent it as 
 methyl hydride, C H, H. Now, if we mix chlorine with this, 
 the molecule C H3 H will be changed into C H3 CI ; and then, 
 if we treat this with silver hydrate, Ag O H, the molecule 
 CHsClwill be changed into CH3OH. "We here see that 
 the group C Hg remains unbroken while the substance 
 changes. This is what the term radical implies. 
 
 These alcohol radicals are all unsaturated molecules with 
 one free unit of quantivalence : they are univalent. 
 
 SECTION IV. 
 
 THE ETHERS. 
 
 198. Ether. — Ether is a transparent liquid, with a 
 peculiar odor, and a sweetish taste. "When breathed, it 
 causes exhilaration at first, but perfect insensibility at last. 
 On this account ether has been used to render patients 
 insensible to the pain of surgical operations. 
 
 The evaporation of ether produces intense cold : a pretty 
 experiment can illustrate this. Let a drop or two of water 
 be covered with a few drops of ether, and by a bellows or a 
 blow-pipe let a current of air be blown against the ether. 
 By its rapid evaporation the ether takes away the heat, until 
 the water is frozen. A mixture of ether with solid carbon 
 dioxide will produce a temperature of —110° C. ( — 166°F.). 
 Pure ether has never been frozen. 
 
190 CHEMISTRY. 
 
 Liquid ether is mucli lighter than water, but its vapor is 
 mucli heavier than air. 
 
 Ether is very combustible, burning with a bright flame ; 
 and a mixture of its vapor with air is explosive. 
 
 Ether is used in medicine, and extensively by the chemist 
 as a solvent. Oils and resins, caoutchouc, and many other 
 organic substances, are soluble in this liquid. It is a more 
 powerful solvent than alcohol. 
 
 Preparation. — When a mixture of concentrated sulphuric 
 acid and alcohol is heated to about 140° C, a very volatile 
 substance is formed, whose vapors may be condensed in a 
 separate vessel. It is sulphuric ether; or, since it is the only 
 ether of commercial importance, it is called simply Ether. 
 The chemical change is complicated ; but the result of it all 
 is, that the alcohol is changed into ether and water. 
 
 2C2H,OH = (C2H5)20 + H2O, 
 Alcohol = Ether + Water. 
 
 Two molecules of alcohol yield one molecule of ether and 
 one of water. 
 
 199. The Series. — Just as common or ethyl alcohol 
 yields common ether when treated with sulphuric acid, so 
 each alcohol will yield a corresponding ether. Thus : — 
 
 Methyl alcohol yields Methyl ether. 
 Ethyl alcohol " Ethyl ether. 
 Propyl alcohol " Propyl ether. 
 
 Hence the term ether, like alcohol, is the name of a large 
 class of compounds. Indeed, this series of simple ethers is 
 only one of several series. Nitric acid, also, converts the 
 alcohols into ethers ; and any other strong acid will yield a 
 series of compounds belonging to this same large family. 
 An ether is a compound produced by the action of a strong 
 acid on an alcohol. 
 
 We may notice that common ether is an oxide of the 
 
CHBMISTKY. 191 
 
 radical ethyl. This is shown by its formula (02115)20. So 
 all this series of ethers obtained by sulphuric acid are oxides 
 in which one atom of oxygen is combined with two molecules 
 of a radical. ' ' 
 
 SECTION V. 
 
 OLEPIANT GAS AND THE OLEFINES. 
 
 200. Oleflant Gas. — Oleflant gas is Another compound 
 of carbon and hydrogen, whose composition is shown by the 
 formula C2 H^. It is a colorless and very combustible gas, 
 and burns with a bright flame. It is found in small quanti- 
 ties in illuminating gas, and was formerly thought to be the 
 most important constituent in it ; but this idea has been aban- 
 doned. Mixed with air it explodes violently. 
 
 Oleflant gas is sometimes called Ethylene, and sometimes 
 Ethene. 
 
 201. The Oleflnes. — We have seen that marsh-gas is the 
 simplest or first member of a long series of hydrocarbons, in 
 which there is a constant difference of C Ho. Oleflant gas is 
 like marsh-gas in this respect ; for it is also the simplest or 
 first -member of a long series, in which there is a constant 
 difference of C Ho. Thus we have 
 
 
 C2 H4 . . 
 
 . . Ethene, 
 
 C2 H4 -f- C H2 
 
 = CjHe . . 
 
 . . Propene, 
 
 C3 He -f- C Hg 
 
 = C4H8 . . 
 
 . . Butene, 
 
 C4 Hs -f- C H2 
 
 = CsHio . . 
 
 . . Pentene. 
 
 The members of this series are produced by distilling 
 organic bodies, and they are found also in petroleum. 
 
 202. Homologous Series. — Any series of compounds, 
 the members of which differ by tlje cojnmon difference, C H.j, 
 is called a Homologous Series. The parafflnes and the 
 oleflnes are only two homologous series of hydrocarbons ■ 
 
192 
 
 CHEMISTET. 
 
 many others are known, and all together include a multitude 
 of compounds. The members of each series agree in cer- 
 tain relations and properties, so that a description of one is 
 to some extent a description of them all. Were it not that 
 they may be arranged in these natural groups, any thing like 
 an exhaustive study of the hydrocarbons would be an over- 
 whelming task. y . 
 
 SECTION VI. "^ "^^ 
 
 DESTRUCTIVE DISTILLATION. 
 
 203. Destructive Distillation. — When wood or othet 
 vegetable substance is heated in close vessels, it is decom- 
 posed. The process is called Destructive Distillation. 
 Some of the products are solid, some are liquid, and some 
 are gaseous : these three classes of substances are always 
 produced by destructive distillation. 
 
 204. Destructive Distillation of Wood. — Let the fol- 
 lowing experiment be tried. Into a small flask (Fig. 88) 
 
 put some fine splint- 
 ers of some hard 
 wood : beech-wood 
 answers the purpose 
 well. Let the flask 
 be tightly corked, 
 and provided with a 
 bent tube reaching 
 over into a bottle 
 which is kept cold 
 by the water which 
 surrounds it. On 
 heating the flask the wood soon turns black : volatile matter 
 is driven over, some of it being condensed in the bottle, 
 while another part escapes in the form of gas. This gas 
 may be collected in a second bottle over water, by passing it 
 
 rig. 88. 
 
CHEMISTRY. 193 
 
 through a rubber tube reaching from the short tube t. The 
 black solid left in the flask is charcoal : the gas collected is a 
 mixture of several, — marsh-gas and oleflant gas being among 
 them ; while the fluid in the first bottle consists of pyrolig- 
 neous acid and wood-tar. 
 
 Charcoal and the gases have already been described. 
 
 205. Pyroligiieous Acid. — Pyroligneous acid is often 
 called wood-vinegar. Dry beech-wood yields it in greatest 
 abundance. It is a dark-brown liquid, with a sour, smoky 
 taste. It contains acetic acid ; and on this account has been 
 largely used in making such acetates as are employed in the 
 arts, especially in calico-printing and dyeing. Sodium ace- 
 tate and lead acetate are examples. 
 
 206. Wood-Tar. — Wood-tar is a very dark-colored resi- 
 nous fluid. There are several varieties. One, largely used 
 in ship-building and other arts, is obtained by a rude distilla- 
 tion of resinous pine- wood : another is obtained from hard 
 wood. It is sometimes used as a covering for wood to pre- 
 serve it from decay : the more volatile constituents of the 
 tar passing away, leave the harder part (pitch) in the pores 
 of the wood. Water is thus kept out of the pores of the 
 wood ; and this, together with the action of creosote, to be 
 soon noticed, prevents decay. 
 
 207. Methyl Alcohol. — When pyroligneous acid is dis- 
 tilled, a very volatile liquid may be obtained, which, being 
 afterward rectifled by the use of quicklime, constitutes the 
 Methyl Alcohol of commerce. It is a limpid liquid, very 
 inflammable. It may be used instead of alcohol for many 
 purposes, especially for dissolving resins in making varnish. 
 It is the simplest member of the alcohol series. 
 
 208. Creosote. — The smoky taste of pyroligneous acid, 
 and the power of both this acid and wood-tar to prevent 
 decay, is due to the presence of a curious compound of car- 
 bon, hydrogen, and oxygen (CjHjoO), called Ckeosotb- 
 
194 CHEMISTRY. 
 
 One pound of the acid contains about a quarter of an ounce 
 of it in solution. Its most curious and valuable property is 
 its power to prevent decay : indeed, it is among the most 
 powerful antiseptics known. Flesh remaining a few hours 
 in a fluid made by dissolving one part of creosote in one 
 hundred parts of water will not afterward decay. That 
 meats are often cured by exposure to smoke, is familiar to 
 all : now, the preservation and the peculiar flavor of smoked 
 meat is due to the action of creosote in the smoke. This sub- 
 stance is often used in medicine ; but when taken internally, 
 except in very small quantities, it is a corrosive poison. 
 
 209. Parafflne. — ParafHne may be obtained by distilling 
 wood-tar. It is a crystalline solid, with neither taste, color, 
 nor smell. Its most remarkable property is its indifference 
 to the chemical action of other substances. It can resist the 
 action of the strongest alkalies and of the most corrosive 
 acids. It is, however, combustible, and its flame is white 
 and smokeless. ParaflSne candles rival the most costly wax 
 candles in luster and in the strength and beauty of then- 
 light. 
 
 210. Other Substances. — Numerous substances, be- 
 sides the few just described, may be obtained by the 
 destructive distillation of wood. Each different kind of 
 wood and of other vegetable matter yields some different 
 products ; but for the most part they are all compounds of 
 carbon with either hydrogen or oxygen, often with both. 
 
 It should be noticed that none of these products are 
 supposed to exist ready formed in the plant. By heat the 
 substance of the plant is broken up ; its elements are re- 
 arranged, and these hydrocarbons formed thereby. 
 
 Application of this Process. — Destructive distillation 
 is used on a large scale in the manufacture of illuminating- 
 gas. In this manufacture the solid and liquid products are 
 of secondary importance, while the gaseous products are 
 secured as pure as possible. 
 
CHEMISTRY. 
 
 195 
 
 Any complete apparatus for illustrating the process of 
 destructive distillation illustrates also the essential parts of 
 the apparatus of the gas-house. Foi example, in Fig. 89, 
 
 there is a, flask, in which the organic matter is heated ; a bottle 
 surrounded by cold water, in which impurities are condensed ; 
 and a receiver over water, in which the gas is collected. 
 These three parts of the apparatus are represented in every 
 " gas-works." 
 
 211. Manufacture of Illuminating' Gas. — By the 
 
 destructive distillation of bituminous coal, and sometimes of 
 other substances, illuminating-gas is made. The material 
 being heated in iron retorts, its volatile constituents are 
 driven off. The gas thus formed is purified by passing first 
 through cold pipes, and then over lime. It is afterward 
 collected in gas-holders, from which it is pressed out into 
 the pipes of the city, and through these into the chandeliers 
 of the houses. 
 
 The following is an outline of this important manufacture. 
 
 212. Bituminous Coal. — In the. United States alone, 
 there are about 130,000 square miles of workable coal-fields. 
 The coal found so abundantly in -nature is called Mineral 
 Coal : it consists of carbon mixed with other matter, espe- 
 cially with volatile compounds of carbon and hydrogen. The 
 
196 
 
 CHEMISTRY. 
 
 two varieties of mineral coal, anthracite and bituminous, 
 differ chiefly in the amount of their volatile constituents. 
 The first contains very little of the hydrocarbons, is very 
 hard, and burns with a very feeble bluish flame ; the second 
 contains a large amount of , volatile compounds, is much 
 softer, and burns with a bright flame. From bituminous 
 coal illuminating-gas is generally made. 
 
 Heated in Iron Retorts. — The vessels in which the 
 coal is heated are called retorts. They are usually of iron, 
 about seven feet long, and scarcely more than a foot in 
 diameter. Fig. 90 shows the ends of Ave of these retorts 
 
 placed in a single 
 furnace. Each one, 
 after receiving a 
 charge of from one 
 hundred pounds to 
 one hundred and fifty 
 pounds, is closed air- 
 tight as shown at 
 G, and made red-hot 
 by the fire in the 
 furnace, whose doors 
 ^^' ■ are shown at A. In 
 
 the course of a few hours the volatile matter of the coal is 
 driven off : the residue, called coke, is then raked out, cooled, 
 and used for fuel. 
 
 Its Volatile Constituents. — The gaseous mixture 
 driven off by heat contains marsh-gas and many other 
 hydrocarbons, carbon dioxide, hydrogen, ammonia, hydro- 
 sulphuric acid, and coaL-tar, besides other substances. This 
 mixture is totally unfit for use, and must be purified. 
 
 Pass through the Hydraulic Main. — From each 
 retort a vertical pipe {Hi, Fig. 90) is an outlet for this 
 mixture of gases. This pipe, bending over at the top, 
 reaches down into a larger and horizontal tube or trunk, H, 
 called the Hyueaulic Main. In the beginning of this pro- 
 
 «■ , 
 
 i i 
 
 > 
 
 
 1 1 
 
 ' 
 
 ^^ ' 'y ll 
 
 1 
 
 n :i 1 
 
 ' t 
 
 I>1 ll 1 
 
 1 1 
 
 n 1 1 1 
 
 -1 t. J 'I'J 
 
 1_J ' 
 
 w'^^'~r 
 
 Jrn • 1 ' 1 
 
 -f^ji i>„ 1 
 
 
 i^^u t^m.\ . 1 
 
 Ft"^ 
 
 \ ■' 1 
 
 ' ' t 1 
 
 [^ 1 1 
 
 : 1 1 
 
 1 { 
 
 1 
 
 t 1 
 
 1 1 1 
 
 1 J 1 
 
 
 ' 1 
 
 1 1 1 
 
 1 1 i 
 
 U^fc 
 
 J- 
 
 ti 
 
 1 1 
 
 1 i 1 
 
 -M 
 
 Hi 
 
 II 1 
 
 1 1 1 
 
 W 
 
 1 1 
 
 - 1 1 jJ 
 
 -^11 ll 
 
 ij^'^r Ji 
 
 1 
 
 1 1 -a'^ 
 
 
 ^^^ik,i^r^ii::=^:i^r 1 
 
 1 1 ^ 
 
 =^ 1 %?fcSf,- < '«i£=d# -I 1 1 
 
 1 1 . , i 1 -r 1 1- II 1 
 
 1 1 1 o' t 1 - t 1 , -J, 1 n 
 
 1 1 4 
 
 __t 1 iJ — * 1 
 
 \X^A 1 1 
 
 ' \ 1 1 
 
 
 1 
 
 ■ 
 
 I MM 1 II 
 
CHEMISTRY. 
 
 197 
 
 cess this main, is filled half full of water, and the pipes i i 
 dip into this fluid. The gas coming over from the retorts 
 bubbles up through the water, which prevents its return. 
 Now the vapors of coal-tar will be condensed, in part, by 
 the lower temperature of the main ; but, as the fluid increases, 
 it runs off through the tube L to a tar-cistern.- Much of the 
 coal-tar is left in the hydraulic main, while the gas passes 
 out of it through the pipe K. 
 
 Through the Condensers. — This pipe, K, leads the 
 
 /F^i 
 
 ooy 
 
 ^ 
 
 ^r>\ 
 
 r 
 
 gases over to a series of upright 
 
 pipes, CC (Fig., 91), called the 
 
 condensers. Passing up one, and 
 
 down another, until they have 
 
 traversed the whole series, the 
 
 gases are exposed to a large 
 
 extent of cold surface, and the 
 
 condensable gases are changed 
 
 to a liquid state. The tar and 
 
 ammoniacal liquor thus con ^is- 91- 
 
 densed run into a cistern below, from which they may be 
 
 drawn off at pleasure. 
 
 Tlirough the Lime Purifier. — The gas, still contain- 
 ing sulphur compounds and carbonic 
 acid, passes from the condensers 
 through a pipe (L) into a chamber 
 (Fig. 92) in which are several sieve- 
 like shelves covered with slaked lime. 
 In passing through the lime the gas 
 loses its carbon dioxide and hydro- 
 ^is. 92. sulphuric acid. 
 
 Into the Gasometer. — The purified gas, leaving the 
 
 lime chamber through a pipe (P) , passes into the gas-holder 
 
 (Fig. 93) , an immense sheet-iron cylinder, closed at the top 
 
 and opened at the bottom, hung by chains which run over 
 
 pulleys at the top, and which carry weights to balance it. 
 
 Below it is a well of water large enough and deep enough 
 
198 
 
 CHEMISTRY. 
 
 to let this cylinder down until it is filled with water. As 
 the gas enters it the gas-holder rises ; and, when it is filled, 
 
 the gas is ready to be pushed 
 out through the pipe S into 
 the streets, and finally into 
 the houses of the city, fur- 
 nishing to all a convenient 
 and beautiful light. 
 
 ' ' In the iron arteries under 
 towns, in the coustellations 
 of burners that rule the nights 
 of favored days, rising over 
 the chaotic oil-lamps of old, 
 what a creation ! ' ' 
 
 Fig 93 
 
 213. Gas from Petrole- 
 um. — A very elegant and 
 successful process of making gas from petroleum has in 
 recent years been successfully carried out. In this process 
 petroleum vapor, and water-gas are brought together in a 
 white-hot retort, from which lliey issue as a mixture of per- 
 manent gases of good illuminating power. The following 
 outline will show the principles of the process. 
 
 Water-Gas. — Steam from a boiler is carried into a 
 furnace, and heated to a high temperature. This " super- 
 heated steam " is driven into a retort containing some red- 
 hot anthracite coal. Here a chemical reaction occurs. 
 
 C -f- H2O = 
 
 Carbon -|- Steam = 
 
 CO + H.2. 
 
 Carbon monoxide + Hydrogen.. 
 
 This mixture of carbon monoxide and hydrogen is called 
 'Water-Gas. 
 
 Decomposition of the Petroleum. — The water-gas 
 passes over into another retort kept intensely hot, into which 
 petroleum is introduced. This liquid is at once vaporized 
 and decomposed. Its heavy hydrocarbons CoHjo, CgHij, 
 
CHEMISTRY. 199 
 
 etc., are broken into light hydrocarbons, such as marsh-gas, 
 olefiant-gas, and other permanent gases. 
 
 The Illuminating: Gras. — These hydrocarbons, mixed 
 with carbon monoxide and hydrogen, constitute the illumi- 
 nating gas. Several of the hydrocarbons are rich in carbon, 
 and would burn with a smoky flame if they were alone ; but 
 they are diluted with the marsh-gas, carbon oxide, and hy- 
 drogen, until they are able to burn with a clean and brilliant 
 light. Because the marsh-gas, carbon oxide, and hydrogen 
 are useful to dilute the heavy hydrocarbons, these constitu- 
 ents ai-e called the Diluents, while the light-giving gases 
 are called the Luminants. 
 
 214. Coal-Tar. — The coal-tar of the gas-works is a 
 very complex substance. When distilled, vapors containing 
 ammonia first pass over, and then a light oil, known as coal 
 naphtha, followed by a heavier one called dead oil, contain- 
 ing a small portion of parafflne. A black pitch or asphalt 
 is left. 
 
 But these are only proximate constituents of the tar : each 
 is itself made up of many simpler ones. The naphtha, for 
 example, is made up of several distinct kinds of oil which 
 may be separated by careful distillation, each having its own 
 peculiar boiling-point. 
 
 215. Carbolic Acid. — One of the most important sub- 
 stances obtained from coal-tfir is carbolic acid or phenol 
 (Ce He O) . It is not a direct product of distillation ; but it is 
 obtained from the naphtha which comes over betweein 300° 
 and 400° F., by the action of sodium hydrate (caustic soda). 
 When pure, it is a white solid, soluble in alkalies, with a 
 smell like creosote. Its most important property is its 
 power to interrupt decay : it is a good disinfectant, and is 
 in much demand for this purpose. It is used to some ex- 
 tent in medicine, and quite largely in the manufacture of 
 colors for dyeing silk and woolen goods. 
 
 216. Benzol. — Benzol (CeHe) is another important con- 
 
200 CHBMISTEY. 
 
 stituent of coal-tar. It is a colorless liquid, very volatile 
 and very combustible. It is a powerful solvent of oils and 
 other fatty substances, and may be used to remove grease 
 spots from silk or woolen fabrics. 
 
 217. Nitro-lienzol. — By mixing benzol with strong 
 nitric acid a reaction is brought about, shown in the equa- 
 tion, 
 
 CeHe + HNO3 = CeH.NOs + H,0. 
 
 It win be noticed that one atom of hydrogen in the benzol 
 is replaced by one molecule of the radical NO2, forming 
 Ce Hj N Oa. This new substance is called Nitho-Benzol. 
 
 Nitro-benzol is a fluid having the odor of bitter almonds. 
 It is used to some extent in making perfumes, but its most 
 important use is in the production of aniline. 
 
 218. Aniline. — Nitro-benzol may be changed to aniline 
 in different ways. Hofmann's method consists in acting 
 upon it by hydrogen set free from sulphuric acid by zinc. 
 The following reaction takes place : — 
 
 CeHjNO^ + 6H = CeHjN -|- 2H2O. 
 
 Losing two combining weights of oxygen, and gaining two 
 of hydrogen, the nitro-benzol is changed to CeH^X. This 
 new substance is aniline. 
 
 Manufacture. — On a large scale aniline is made by a 
 more economical method (Bechamps'), in which the change 
 is effected by iron and acetic acid. One hundred parts of 
 the crude nitro-benzol is mixed with nearly its own weight 
 of strong acetic acid ; and to this is added, little by little, 
 about one hundred and fifty parts of iron-turnings. A com- 
 plicated reaction takes place ; and when the mixture is after- 
 ward heated, impure aniline is obtained. It is purified by 
 treating it with lime or soda, and re-distilling it. By this 
 means the crude aniline of commerce is obtained. 
 
 Properties. — Aniline, when pure, is a colorless liquid, 
 heavier than water, soluble in alcohol and ether, and \'ery 
 
CHEMISTRY. 201 
 
 slightly in water. Its most remarkable property is that ot 
 acquiring various and rich colors by the action of different 
 oxidizing agents. 
 
 Aniline Red. — If, for exaniple, aniline is heated with 
 arsenic acid to about 150° C, a part of its hydrogen will be 
 extracted as water, and there will remain what is called 
 RosANiLiNE, in combination with the arsenic. Sodium 
 hydrate may then be added : it will remove the arsenic, and 
 precipitate the rosaniline. 
 
 Let this rosaniline be treated with hydrochloric acid, and a 
 rosaniline chloride will be formed. This salt is the so-called 
 Aniline Red. It occurs in crystals, having a green luster, 
 but its solution in water or in alcohol is a beautiful red. 
 
 Aniline Dyes. — By the action of . other chemicals oji 
 aniline or its salts, many coloring matters are obtained. 
 Various rich shades of red, yellow, green, blue, and black, 
 indeed, almost every variety of tint, are made, and largely 
 used in the arts. 
 
 219. Slow Destructive Distillation. — The decay of 
 vegetable matter, when buried in the moist earth, or covered 
 by the water and mud of bogs and marshes, is somewhat 
 different from its decay when exposed to the air. Instead 
 of giving off carbon dioxide and water, and crumbling to a 
 black mold, it gives off marsh-gas and other hydrocarbons, 
 and yields _a residue of coal. 
 
 The chief constituents of wood ai-e carbon, hydrogen, and 
 oxygen ; the first two being far the most abundant. On 
 exposure to air, oxygen from the atmosphere combines with 
 hydrogen and carbon of the wood to form water and carbon 
 dioxide, leaving oxygen in combination with what remains of 
 both these elements, forming humus ; but when the air is 
 excluded, the process of decay must consist chiefly in the 
 re-arranging of the elements of the wood itself. Its oxygen 
 takes carbon enough to form carbon dioxide ; its hydrogen 
 takes carbon also, and forms gaseous or liquid compounds ; 
 
202 CHEMISTRY. 
 
 while the excess of carbon, not thus used, is left in the form 
 of coal. 
 
 Varieties of Coal. — Vast quantities of vegetable mat- 
 ter, accumulating in low wet lands of warm countries, 
 gradually beeome covered with water ; and sometimes, by 
 the sinking of the land, they are buried under mud and sand 
 brought over them by streams or floods. Thus shut off from 
 the air, a slow decay goes on, by which they are at last 
 changed to coal. The different varieties of coal mark the 
 different stages of the process. In peat the change is only 
 well begun : in anthracite coal the process is at an end. 
 The warmth of the earth assists the change ; and the great 
 pressure of the material, accumulating for ages upon it, 
 must have had much to do with the final compactness of the 
 remaining coal. In bituminous coal the liquid hydrocarbons 
 remain, but may be driven away by heat : from anthracite 
 they have already escaped. 
 
 Origin of Petroleum. — Numerous and extensive beds 
 of coal have thus been produced by the slow distillation of 
 vegetable matter during past ages of the earth's history. 
 
 But what has become of the liquid hydrocarbons which 
 must have been formed, but which are no longer held in the 
 hard coal ? Moreover, during the deposition of other rocks 
 in which no coal is found, there is abundant evidence that 
 plants were growing, and they, too, must have been decom- 
 posed in a similar way : what has become of the products of 
 their decay? 
 
 The gaseous products would, of course, for the most part, 
 escape into the air ; and it would be natural to suppose that 
 the liquid products would gradually collect in cavities and 
 fissures in the rocks. Now, inflammable, oily substances, 
 issuing often in large quantities from the fissures of rocks, 
 have been long known. To them the general name of petro- 
 leum has been given. They resemble the liquid products 
 obtained by destructive distillation of wood; and it is 
 believed that they are the products of the slow decom- 
 
CHEMISTRY. 203 
 
 position of organic matter, chiefly vegetable. Petroleum, 
 or rock-oil, is, then, the liquid hydrocarbon substances given 
 off in the slow process of the decay of vegetable matter long 
 buried in the earth. 
 
 • SECTION VII. 
 
 THE SUGARS. 
 
 220. Sugar. — The term " sugar," when used in chem- 
 istry, is not the name of any single substance, but the 
 name of a class. The sugars are, all of them, compounds 
 of carbon, hydrogen, and oxygen ; and in their composition 
 there is this peculiarity, viz., Tlie hydrogen and oxygen are 
 in the proportions to form water. There are many varieties 
 of sugars ; but they may be grouped in three classes, — the 
 SMCi'oses, the glucoses, and the amyloses. 
 
 The Sucroses. — Cane-sugar, so common and well 
 known, and milk-sugar, or lactose, obtained by evaporating 
 the whey of fresh milk, are members of the first class. 
 Cane-sugar occurs in the juices of many plants. It is 
 obtained by evaporating the sap of the sugar-maple, or the 
 juice of the beet, and in far larger quantities from the juice 
 of the sugar-cane. Its general character is well known. Its 
 composition is represented by the formula C12 H22 Ou. When 
 strongly heated, it yields water and a dark-colored residue 
 called caramel. One of its most curious properties is shown 
 ■ in its action upon, polarized light: it turns the plane of 
 polarization to the right hand. 
 
 The Glucoses. — Grape-sugar and fruit-sugar are glu- 
 coses. They are found together in many kinds of fruit, 
 especially in the grape. They have the same composition, 
 Co H12 Og, and yet differ in several properties. Grape-sugar 
 easily crystallizes : fruit-sugar never does. The latter is 
 more soluble, and rotates the plane of polarization to the left, 
 the foi-mer to the right. 
 
204 CHEMISTEY. 
 
 Sucrose Changed to Glucose. — When cane-sugar is 
 acted on by dilute sulphuric acid, a reaction takes place by 
 which the cane-sugar is changed into grape-sugar and fniit- 
 sugar, by taking the elements of a molecule of water : — 
 
 C12H22OH + HjO = CeHjoOo + C8H,2 0e, 
 Cane-sugar + Water = Grape-sugar + Fruit-sugar. 
 
 The Amyloses. — • Starch is the most familar example of 
 the amyloses. It consists of a white powder, composed of 
 granules, which have different size and shape in different 
 varieties : those of potato-starch being about .007 inches in 
 diameter ; of beet- root, about .0002 inches. These granules 
 are not soluble in cold water, but when heated in water 
 they swell and split open ; and, if the paste thus formed is 
 boiled in a larger quantity, the starch is at last dissolved. 
 
 When free iodine is brought in contact with starch, a com- 
 pound, having a rich blue color, is made. This action is the 
 most delicate test for the presence of starch. To show its 
 presence in a potato, for example, let the freshly cut surface 
 of the vegetable be washed with a solution of iodine. 
 
 The composition of starch is shown by its formula, 
 Cs Hio O5. By the action of dilute sulphuric acid, starch is 
 changed into dextrine and grape-sugar. 
 
 Dextrine. — Dextrine, or, as it is more commonly called, 
 British gum, is another amylose. It is very soluble in water, 
 and it is used sometimes instead of gum-arabic in calico- 
 printing and other arts. It is made from starch, not only by 
 means of dilate sulphuric acid, but by simply heating the 
 starch to about 150° C. (302° F.), or by the action of 
 diastase (a substance contained in malt) . By the continued 
 action of the diastase the starch is first changed into dextrine 
 and grape-sugar, and the dextrine is finally changed also into 
 grape-sugar. 
 
 SCCsHioOs) + H2O = 2(CeH,oO,) + CeH^Oe, 
 Starch -|- Water = Dextrine -|- Grape-sugar. 
 
CHEMISTRY. 205 
 
 Dextrine and starch have the same composition, CeHmOj. 
 but their properties are different. Dextrine is soluble in 
 water, and i§ reddened, instead of being turned blue, by 
 iodine. Bodies having the same composition, but different 
 properties, are said to be isomeric. Dextrine and starch are 
 isomeric substances. 
 
 221. Ferment. — By the term ferment we mean an 
 organic compound containing nitrogen, and which readily 
 decomposes on exposure to air. Any substance containing 
 nitrogen, and partially decomposed, will act as a ferment. 
 Yeast is the most familar example. When the sweet juices 
 of vegetables are exposed to the air, a ferment is soon 
 formed in them ; aud, the smallest quantity of ferment being 
 present, an action is started by it which goes on until the 
 entire body of liquid is decomposed. 
 
 Fermentation. — The decomposition caused by ferments 
 is called Fermentation. It may be easily illustrated by 
 experiment. Dissolve about one hundred grains of honey, 
 or it may be molasses, in a pint of water ; fill a small flask 
 with the solution, and add a few drops of brewer's yeast. 
 Close the neck of the flask with the hand, and invert it in a 
 dish holding some of the same sirup, and leave it in a warm 
 place for twenty-four hours. Fermentation soon begins ; a 
 colorless gas collects in the flask, which, by lime-water, may 
 be shown to be carbon dioxide, while alcohol remains in the 
 fluid. Thus : — 
 
 Cs Hi2 O5 = 2 Cj Hj O -f- 2 C O2, 
 
 Sugar = Alcohol -f- Carbon dioxide. 
 
 All fermentation which produces chiefly alcohol and carbon 
 dioxide is called the~ Alcoholic or Vinous fermentation. 
 The process goes on best at a temperature of 25° or 30° C. 
 
 Spirituous Liquors. — The spirituous l iquors of com- 
 merce, such as brandj, gm, and whiskey, are produced by 
 distilling fermented liquids. The fermented liquid obtained 
 
206 CHEMIST^Hf. — 
 
 from malted grain is called Beerj that from the juice of the 
 grape is called Wine. By distilling these, and adding various 
 substances to color and flavor the result, different kinds of 
 liquor are made. Brandy is made by distilling wine ; gin is 
 made from different kinds of corn spirits, its flavor being 
 given by juniper-berries, sweet-flag, licorice-powder, and 
 several other substances. Whiskxis also obtained by distill- 
 ing the fennented liquor from corn. 
 
 The intoxicating principle in all these liquors is alcohol, 
 which has been produced by fermentation. 
 
 222. Tlie Acetous Fermentation. — An alcoholic 
 liquid, which contains a small quantity of a ferment, and 
 is in the presence of air, yields acetic acid. Acetic acid is 
 the acid which gives sourness to vinegar. 
 
 Fermentation in which acetic acid is the chief product is 
 called the Acetous Fermentation. 
 
 Production of Vinejjar. — When an alcoholic liquid is 
 exposed to the air in a warm place, a little yeast or other 
 nitrogenous matter in it will start an action by which the 
 alcohol is clianged into ^'iuegar. " A good extemporaneous 
 vinegar may be prepared by dissolving one part of sugar in 
 six of water, with one part of brandy, and a little yeast. 
 The mixture is put into a cask, with the bung-hole open, and 
 kept at a temperature between 70° and 80° F. In from four 
 to six weeks the clear vinegar may be drawn off." (JBrande 
 & Taylor.) A still more simple process consists in soaking 
 crushed apple-skins in soft water for a few days, straining 
 the juice, and letting it stand exposed to the air in a warm 
 place for several days : an excellent vinegar is the result. 
 
 Acetic Acid. — Common vinegar is a very dilute acetic 
 acid. Its quality depends upon the proportion of acid it 
 contains, and the absence of other impurities. The compo- 
 sition of acetic acid is shown by the symbol C^ H4 0^. It is 
 a colorless liquid, with a powerful and peculiar odor, which, 
 once experienced, is afterward easily recognized. 
 
CHEMISTRY. 207 
 
 Fermentation of Alcohol. — The chemical action by 
 which alcohol is changed to acetic acid is called the acetous 
 fermentation. And yet it is not in all respects a true fer- 
 mentation. It is not a decomposition, but rather an oxida- 
 tion, as may be seen by comparing the symbols of alcohol 
 and acetic aei-d. In this respect the action is a ease of com- 
 bustion rather than of fermentation. It can take place only 
 in the presence of air, so that the action is not entirely due 
 to a ferment. Yet, on the other hand, it will not occur, 
 except in presence of a nitrogenous substance, to which the 
 term ferment has been given ; and hence the reaction is very 
 naturally called a fermentation. 
 
 REVIEW. 
 
 I. —SUMMARY OF PRINCIPLES. 
 
 223. Organic chemistry is the chemistry of the compounds 
 of carbon. 
 
 The compounds of carbon are the products of the decom- 
 position of organic bodies : with some exceptions, we have 
 no evidence that they exist ready formed in the living plant 
 or animal. 
 
 A large number of these substances contain only carbon 
 and hydrogen ; others contain oxygen in addition ; and a 
 few contain other elements, especially nitrogen. 
 
 Marsh-gas is the simplest hydrocarbon. Its molecule is 
 represented by C H4. 
 
 It is found in nature ready formed. In many places it 
 issues in large quantities from the earth : it collects in mines, 
 and it also issues from the mud of stagnant pools. 
 
 A homologous series is a series of compounds containing 
 the same elements, in which there is a common difference in 
 the molecules of successive members. 
 
 Marsh-gas is the first member of a homologous series of 
 hydrocarbons, in which the common difference is C Hj. 
 
208 CHEMISTRY. 
 
 The densities of these hydrocarbons increase regularly as 
 the molecules become more complex. 
 
 Carbon is quadrivalent, and its atoms are able to combine 
 with one another : these two assumptions furnish an explana- 
 tion of the parafHne series. 
 
 Petroleum contains several members of this series from 
 C4H10 to C9H20, inclusive, beside several hydrocarbons 
 belonging to other series. 
 
 The boiling-points of these hydrocarbons differ : hence 
 they may be separated by fractional distillation. Several 
 commercial products are obtained by the fractional distillation 
 of petroleum. 
 
 Common alcohol is obtained by distilling a fermented liquid. 
 It is a colorless liquid, lighter than water, very volatile and 
 combustible. 
 
 The molecule of alcohol is CaH^O. Its rational formula 
 isCjHjHO. According t« this formula its chemical name 
 should be ethyl hydrate. 
 
 It may be regarded as derived from ethane, Cg Hg, by the 
 substitution of H O for one atom of H. 
 
 Common alcohol is one of a large number of analogous 
 substances which constitute a series of alcohols. 
 
 An alcohol is a compound derived from a hydrocarbon 
 by substituting a molecule of hydroxyl for an atom of 
 hydrogen. 
 
 A radical is a group of atoms which passes bodily from 
 one combination to another in chemical actions. The hydro- 
 carbon combined with hydroxyl in an alcohol is called an 
 alcohol radical. 
 
 Ether is a limpid liquid, very volatile, very combustible, 
 a powerful solvent, and an anaesthetic. 
 
 It is obtained by treating ethyl or common alcohol, with 
 sulphuric acid. Its composition is represented byCiHioO, 
 or by the rational formula (C2 115)20. According to this 
 formula its chemical name should be di-ethyl oxide. 
 
 Common ether is one member of a large class of sub- 
 
CHEMISTKY. 209 
 
 stances called the ethers. An ether is a substance produced 
 by the action of a strong acid on an alcohol. 
 
 The composition of methyl ether is represented by C2H6O, 
 or by its rational formula (C 1X3)20. 
 
 But the composition of common alcohol is also represented 
 by the same formula, C2HeO. Hence these two substances 
 furnish an example of isomerism, — having the same 
 chemical composition, but different properties. 
 
 Isomerism is explained by supposing the atoms of the 
 substances to be differently arranged in the molecules. 
 
 The rational formula may show the different groupings of 
 the atoms which we suppose to exist. Thus we write for 
 alcohol C2H5OH, and for methyl ether (CHg)2 0. 
 
 The graphic form of the rational formulas shows this 
 difference stiU more clearly. Thus : — 
 
 H H H H 
 
 II II 
 
 H— C— C— O— H, H— C— O— C— H, 
 
 II II 
 
 H H H H 
 
 Alcohol. Methyl ether. 
 
 In the first we discover two groups, C2H5 and OH. In 
 the second we discover two groups, CH3 and CH3, bound 
 together by oxygen. 
 
 Isomeric substances are very numerous among the com- 
 pounds of carbon. 
 
 Olefiant gas is a colorless gas, very combustible and 
 explosive. It is represented by C2 H4. 
 
 This gas is the first member of a homologous series, — the 
 olefines. 
 
 Destructive distillation is the decomposition of an organic 
 substance by heat in the absence of air. The products are 
 solid, liquid, and gaseous. 
 
 Illuminating gas is made by the destructive distillation of 
 soft coal, sometimes of other materials. 
 
210 CHEMISTRY. 
 
 The solid residue is coke. The liquid products are col- 
 lectively called coal-tar and ammoniacal water. The gaseous 
 product contains the luminants, the diluents, and the im- 
 purities. 
 
 Carbolic acid and benzol are among the valuable products 
 obtained directly from coal-tar. From benzol comes nitro- 
 benzol, and finally aniline. From aniline many rich and 
 valuable dyes are made. 
 
 Organic matter buried in the earth undergoes a slow pro- 
 cess of destructive distillation. The varieties of mineral 
 coal, and petroleum or rock-oil, are doubtless the products of 
 such a process. 
 
 Sugar is a compound of carbon, hydrogen, and oxygen, 
 in which the last two are in the proportions to form 
 water. 
 
 There are three classes, — the sucroses, the glucoses, and 
 the amyloses. 
 
 The sucroses may be changed to glucose by dilute sulphuric 
 acid. The same is true of the amyloses. 
 
 Fermentation is a decomposition caused by ferments. The 
 vinous fermentation consists in the change of glucose into 
 carbon dioxide and alcohol. 
 
 II. —EXERCISES. 
 
 Define organic chemistry. What is an organized body? 
 What are organic substances? With which of these does 
 chemistry deal? 
 
 Define hydrocarbon. Name the simplest hydrocarbon, and 
 give its formula. Where is marsh-gas found in nature? 
 AVhat are its properties ? How may we prove that its mole- 
 cule contains four atoms of hydrogen ? 
 
 By what other names is marsh-gas known? What does 
 the name methyl hydride signify? How would its formula 
 be written ? 
 
 Give the formulas and names of the first four members of 
 
CHEMISTEY. 211 
 
 the marsh-gas series. How do chemists explain the fact 
 that hydrogen and carbon can form so many compounds? 
 Write the graphic formulas for the first four members of the 
 series. 
 
 What are the properties of this series ? 
 
 What is petroleum? What is its composition? Define 
 fractional distillation. What is kerosene? Benzine? 
 Naphtha? 
 
 How may alcohol be obtained ? What is absolute alcohol ? 
 How may it be obtained? What are the properties of 
 alcohol ? 
 
 What is the composition of alcohol? If we call it ethyl 
 hydrate, how should we write its formula? What evidence 
 is given that the molecule does contain these two groups ? 
 
 By what substitution may alcohol be derived from ethane ? 
 
 Define the term alcohol. How are the alcohols named? 
 
 Define the term radical. Show that C Hg remains unbroken 
 while methane is passing through the changes to become 
 methyl alcohol. 
 
 What is ether? What is its effect when breathed? What 
 is the effect of its evaporation? What are some of its 
 uses? 
 
 How is ether prepared ? Give the chemical change. 
 
 To what class of substances is the name ether given? 
 Which of these is the common ether? What is its formula? 
 
 What is oleflant gas ? What are some of its properties ? 
 What are its other names ? 
 
 What are the olefines? From what sources may these 
 bodies be derived ? 
 
 Define homologous series. 
 
 What is destructive distillation? 
 
 Describe the experiment showing the destructive distilla- 
 tion of wood. 
 
 What is said of pyroligneous acid ? 
 
 What is said of wood- tar? 
 
 What is said of methyl alcohol ? 
 
212 CHEMISTRY. 
 
 What is said of creosote ? "What is its most curious and 
 valuable property? 
 
 How may paraffine be obtained? What are some of its 
 properties ? 
 
 What is said of other products of destructive distillation ? 
 Do these substances exist in the plant? 
 
 Give a brief description of the manufacture of illuminating 
 gas? 
 
 What is said of mineral coal? What are two principal 
 varieties ? Which is used in making the gas ? 
 
 Describe the heating in iron retorts. 
 
 What substances are driven off? 
 
 What becomes of this mixture? What occurs in the 
 hydraulic main ? 
 
 Describe the next step in the process. 
 
 What impurities still remain ? How are they removed ? 
 
 Into what is the purified gas finally conducted ? Describe 
 the gasometer, and explain its action. 
 
 From what other substance is illuminating gas made? 
 What is water-gas ? How is it made ? How are water-gas 
 and petroleum converted into illuminating gas ? 
 
 Of what does the illuminating gas consist ? 
 
 What is the formula of carbolic acid? How is this acid 
 obtained ? What are some of its properties ? Its uses ? 
 
 What is the formula of benzol? What ai-e some of its 
 properties ? 
 
 Give the reaction by which nitro-benzol is formed ? What 
 are its uses ? 
 
 Show how nitro-benzol may be changed to aniline. 
 Describe the method adopted in the arts. What are the 
 properties of aniline? 
 
 How is aniline changed into aniline red? How are other 
 aniline dyes made ? 
 
 How have mineral coal and petroleum been formed ? 
 
 Describe the decay of vegetable matter when kept from 
 the air. Show wherein this decay differs from decay in air. 
 
CHEMISTRY. 213 
 
 Explain the formation of the varieties of coal. 
 
 In the formation of mineral coal, would these gases and 
 volatile liquids be driven off ? What would naturally become 
 of them ? Is any thing of the kind now to be found in the 
 rocks ? What name is given to them ? Describe them. 
 
 Define the term sugar. Name the three classes. 
 
 Name varieties of sucrose. How is cane-sugar obtained ? 
 What is its composition ? What are its properties ? 
 
 Name varieties of glucose. What is their composition? 
 Wherein do they differ? Give the reaction by which cane- 
 sugar is changed into grape and fruit sugar. 
 
 What are the properties of starch ? The test for its pres- 
 ence? Its composition? 
 
 What is dextrine? How is it made from starch? Give 
 the symbols, and explain the reaction. 
 
 What is a ferment? Name a familiar example. 
 
 What is fermentation? Describe the experiment, and 
 explain the reaction. What is the alcoholic fermentation ? 
 
 How are spirituous liquors obtained ? Name some com- 
 mon kinds, and tell how they are made. 
 
 What is the intoxicating principle in all kinds ? 
 
 How may alcohol be changed to acetic acid ? 
 
 Give the formula for acetic acid. 
 
 Describe the acid. 
 
 What is common vinegar composed of? What is the 
 acetous fermentation ? Is it in all respects a true fermenta- 
 tion? 
 
ai-l CHEMISTRY. 
 
 CHAPTER IV. 
 
 THE METALS. 
 
 SECTION I. 
 
 GENERAL DESCRIPTION. 
 
 224. Characteristic Properties. — The peculiarities of 
 metallic elements are more or less familiar. Their luster, as 
 of silver ; their malleability, as of gold and zinc ; their duc- 
 tility, as of iron and copper ; together with their power to 
 conduct heat and electricity, — are their most characteristic 
 properties. One or more of these properties are possessed 
 by some non-metals ; and, on the other hand, some metals 
 have them only in a slight degree. Indeed, nature seems to 
 have drawn no precise line of division between the two classes. 
 Certain elements, arsenic and antimony for example, have 
 been classed with metals, but are considered now to be non- 
 metals ; while even hydrogen, because of its chemical rela- 
 tions, is thought by some to be a metal. 
 
 Melting--Points. — ■ The metals, with the exception of 
 mercury, are solids at ordinary temperature. Some are 
 easily melted, as potassium, at 62° 5 C. (144° 5 F.) ; others 
 melt with difficulty, as iron at 1,600° C. (2,912° F.) ; while 
 others, like platinum, melt only in the intense heat of the 
 oxy hydrogen blow-pipe. 
 
 Density. — Osmium is the heaviest of metals, 22.47 times 
 heavier than water ; others, as potassium and sodinm, are 
 so light that they will float on the surface of water. Lithium 
 is the lightest of all : its specific gravity is only .594. 
 
CHEMISTRY. 
 
 21.5 
 
 Condition in Nature. — A few metals, copper and gold 
 for example, are found in nature in the metallic state : this 
 condition is commonly called Native. But in the native 
 state they are seldom pure : two or more are combined. 
 Combinations of metals are called Allots. The metals are, 
 however, usually found combined with non-metals ; and such 
 compounds are called Orbs. 
 
 225. Classification of tlie Metals. — In the following 
 table the metals are classed so as to bring together those 
 which most closely resemble each other. Many of the metals 
 are rare, and not important to the general student : others 
 are of the greatest use and interest. Of these last the 
 names are printed in capitals, and to the description of them 
 we are to pay the more particular attention. 
 
 1. -r- Metals of the Alkalies. 
 
 Li.> 
 Cs.i 
 Kb.' 
 
 Potassium 
 Sodium . 
 Littiiuin . 
 Csesium . 
 Rubidium 
 
 2. — Metals of 
 
 Earths. 
 
 Calcium . . 
 
 Strontium . 
 
 Barium . . 
 
 the Alkaline 
 
 . . Ca." 
 . . Sr." 
 . . Ba." 
 
 3. — The Aluminium Class. 
 "Aluminium. . . Al."'" 
 Indium .... In. 
 Gallium .... Ga. 
 
 — Cerium Class. 
 
 
 Cerium . . 
 
 . Ce. 
 
 Ttrium . . 
 
 . Y. 
 
 Erbium . . 
 
 . Er. 
 
 Lanthanum . 
 
 . La 
 
 Didymium . 
 
 . Di. 
 
 5. — Zinc Class. 
 
 \;iNC Zn." 
 
 ^Magnesium . . . Mg." 
 
 Cadmium . . . Cd.^' 
 
 Beryllium . . . Be. 
 
 6. — Iron Class. 
 
 *^ON Fe."." 
 
 ^JVIanganese . . . Mn."''^ 
 
 Nickel N'i."'"' 
 
 -Cobalt Co."." 
 
 7. — Tin Class. 
 
 M-IN Sn."." 
 
 Titanum .... Ti."." 
 
 Zirconium . . . Zr. 
 
 Thorium . . . . Th. 
 
 8. — Chromium Class. 
 Vjhromium . . . Cr."."^ 
 
 Molybdenum . . Mo. 
 
 Tungsten . . . W. 
 
 Uranium . . . . U. 
 
216 
 
 CHEMISTRY. 
 
 9. — Antimony Class. 
 
 N^TIMONT . . Sb.'" 
 
 NA^ksenio .... As."' 
 
 '^Bismuth .... Bi."' 
 
 Vanadium ... V. 
 
 Niobium .... Nb. 
 
 Tantalum . . . Ta. 
 
 10. — Lead Class. 
 
 "^ead Pb.n 
 
 Thallium . . . Tb. 
 
 11. — Silver Class. 
 
 ■*■ Mercury . 
 "*» Silver . . 
 
 
 
 12. — Gold Class 
 ^^Platinum 
 
 
 
 Palladium 
 
 
 
 Rhodium . 
 
 
 
 Ruthenium 
 
 
 
 Iridium . 
 
 
 
 Osmium . 
 
 
 
 Cu.n 
 Hg.» 
 Ag.' 
 
 Au."' 
 
 Pt. 
 
 PI. 
 
 Rh. 
 
 Ru. 
 
 Ir. 
 
 Os. 
 
 SECTION II. 
 
 METALS OF THE ALKALIES. 
 
 226. General Description. — The metals of the first 
 class are very soft aud light, having so violent an attraction 
 for oxygen that they can decompose water at any tempera- 
 ture. They are univalent. 
 
 Of this class only potassium and sodium are of interest to 
 the student ; and even these metals are of little use, and are 
 important only because their compounds are of great value 
 in the arts. 
 
 Illustration of these Glass Properties. — A piece of 
 potassium or of sodium may be molded in the fingers like 
 wax, and if dropped upon water it floats. 
 
 Upon a piece of ice, in a small cavity made for the pur- 
 pose, place a small fragment of potassium : a purple flame 
 springs up, as if the ice had been set on fire. A smart ex- 
 plosion usually ends the experiment ; and if we then examine 
 the water that is left in the cavity of the ice, we find it to 
 contain potassium hydrate (potash) . So strong is the attrac- 
 tion of this metal for oxygen, that it decomposes water, even 
 at the temperature of ice. This is true of the other members 
 of the group. 
 
 The Beaction. — If we study the reaction taking place 
 
CHBMISTKY. 217 
 
 in the (experiment, we shall see that the metal is univalent. 
 Thus : — 
 
 H2O + K = KHO + H. 
 
 One combining weight of potassium has simply replaced 
 one of the two combining weights of hydrogen in the mole- 
 cule of water. A similar reaction would occur with the othei 
 members of the group. The potassium hydrate formed is an 
 Alkali ; the other hydrates of the group are also alkalies. 
 The alkalies differ from most other metallic hydrates in their 
 power to withstand heat : heat alone will not decompose them. 
 
 227. Manufacture of Potassium Carbonate. — The 
 
 ashes of wood, mixed with about five per cent of lime, are 
 placed in tubs, and drenched with successive portions of fresh 
 water. As the water soaks through the ashes, it dissolves 
 out the soluble constituents, among which is the potassium 
 carbonate. This process is called leaching. The solution 
 known as Lye is put into broad and shallow pans, and evapo- 
 rated. The solid residue is called Crude Potash. By 
 strongly heating this substance, much of its impurities may 
 be driven off : the pm-er carbonate remaining is called Peakl- 
 
 ASH. 
 
 A pure salt may be obtained by dissolving the pearlash, 
 and then letting it crystallize. The salt crystallizes while 
 the impurities are still in solution : at this point the fluid is 
 drawn off, and the crystals left. The symbol of the pure 
 substance is K2 C O3. 
 
 228. Preparation of Potassium Hydrate. — Potas- 
 sium hydrate (K H O) is obtained by boiling a solution of 
 the carbonate with slaked lime (Ca(H0)2). A reaction 
 occurs, in which the potassium of the carbonate is substi- 
 tuted for the calcium of the calcium hydrate, or slaked lime, 
 and by this action potassium hydrate is formed, which 
 remains in solution, while the calcium carbonate produced 
 falls to the bottom as a heavy powder. 
 
218 CHEMISTRY. 
 
 The clear solution is afterward evaporated to dryness, and 
 the solid hydrate is then fused and run into molds. 
 
 Properties. — Potassium hydrate is very soluble in water, 
 and has a strong affinity for carbonic acid. It greedily takes 
 both these substances from the air, until at length the entire 
 mass of hydrate is changed into a sirup of the ^carbonate. 
 To indicate this property of dissolving in water absorbed 
 from the air, the term Deliquescence is used. 
 
 229. Sodium CWoride. — Sodium chloride, so well 
 known as common salt (Na CI) , is everywhere abundant. 
 In many parts of the woild it occurs in thick beds, from 
 which it may be mined. Large quantities are obtained by 
 evaporating the water of salt springs, while immense 
 quantities in solution give its characteristic saltness to the 
 sea. 
 
 The uses of this substance are important : not among 
 those least important is its use in the manufacture of the 
 other sodium compounds, especially of sodium carbonate. 
 
 230. Manufacture of Sodium Carbonate. — Eluormous 
 quantities of sodium carbonate are used in bleaching, soap- 
 making, glass-making, and other arts. The several processes 
 in its manufacture are as follows : — 
 
 Sodium Chloride changed to Sodium Sulphate. -- 
 When salt is heated with sulphuric acid in a reverberatory 
 furnace, mutual decomposition takes place. Sodium sulphate 
 and hydrochloric acid are the products of the reaction. This 
 may be understood by the equation : — 
 
 2NaCl -I- H2SO4 = NaaSO^ + 2HC1. 
 
 The sodium sulphate thus formed is valuable, aside from 
 its use in making the carbonate. It is well known under the 
 name of Glauber's Salts. In the manufacture now being 
 described, it is called Salt Cake. 
 
 The Sodium Sulphate changed to Sodium Sulphide. 
 
CHEMISTRY. 219 
 
 — "When sodium sulphate is decomposed by carbon, the 
 following reaction occurs : — 
 
 Na2S04 + 4C = Na^S + 4C0. 
 
 Sodium sulphide and carbonic oxide are produced. In the 
 manufacture of sodium carbonate, the sulphate, with small 
 coal and chalk, or limestone (calcium carbonate), are thor^ 
 oughly mixed and melted together in a furnace. The above 
 reaction takes place. 
 
 The Sodium Sulphide chang-ed to Sodium Car- 
 honate. — The sulphide formed by this reaction is at once 
 changed by the calcium carbonate according to the following 
 equation : — 
 
 Na^S + CaCOs= NajCOs + CaS. 
 
 Sodium carbonate and calcium sulphide are formed. The 
 mixture has a blackish-gray color, and is called Black Ash. 
 
 The black ash is afterward thoroughly leached ; during this 
 • process the water dissolves out the carbonate, but leaves the 
 sulphide ; and then, finally, the solution is evaporated to 
 dryness : the residue is the crude sodium carbonate of com- 
 merce, generally known as Soda Ash. 
 
 231. Acid Sodium Carbonate. — Hydrosodium car- 
 bonate (bicarbonate of soda) is obtained by exposing sodium 
 carbonate to the action of carbonic acid. Its formula is 
 HNaCOj. This is the substance familiarly known as 
 Soda, and used so commonly instead of yeast in bread- 
 making. It is used in medicine : it is also much used in 
 making effervescing drinks. 
 
 SECTION III. 
 
 METALS OF THE ALKALINE EARTHS. 
 
 232. General Description. — The metals of the second 
 class are bivalent. They form carbonates which are not 
 
220 
 
 CHEMISTKT. 
 
 soluble in water, unless it contains carbonic acid : in this 
 respect they differ from the metals of the first class. The 
 metals themselves are of little use, but some of the com- 
 pounds of calcium and barium are of considerable importance. 
 
 Illustrations of these Glass Properties The metals 
 
 of this class, like those of the first, decompose water at all 
 temperatures, but the reaction is somewhat different. If 
 calcium is used for the purpose of illustration, it will be : 
 
 H2O + Ca = CaO + H2. 
 
 Observe that one combining weight of calcium replaces 
 the two combining weights of hydrogen in water. This 
 illustrates the bivalent character of calcium : the other 
 members of the group are also bivalent. 
 
 The calcium oxide (lime) , shown in the reaction just given, 
 combuics with water, evolving much heat, actually boiling the 
 
 Pig. 94. 
 
 water (Fig. 94) to form the calcium hydrate (slaked lime), 
 which is very slightly soluble in water, forming Lime-Watek. 
 
CHEMISTRY. 221 
 
 233. Calcium Oxide. — The oxide is made on a large 
 scale, to be used in making mortar and cements, so valuable 
 in building. For this purpose fragments of limestone are 
 mixed with coal and burned in kilns. The carbonic acid of 
 the limestone is driven ofE by the heat ; and the other con- 
 stituent, lime, or, as it is often called. Quicklime, is left, 
 still in the form of hard and compact stone. In contact with 
 water the stone swells, grows intensely hot, and crumbles to 
 powder. The slaked lime thus made is mixed with sand to 
 form Mortar. 
 
 234. Calcium Carbonate. — The members of this group 
 form carbonates. Limestone and marble of every kind are 
 composed chiefly of calcium carbonate. This compound is 
 very slightly soluble in water unless it contains carbonic 
 acid, but in water charged with this gas it dissolves readily. 
 The formation of Stalactites is a beautiful illustration of 
 this action. Water, charged with carbonic acid, flowing 
 through soil and over rocks where limestone is abundant, 
 dissolves this substance. Finding its way to caverns, it 
 falls, drop by drop, from the roof. Exposed to the air, 
 carbonic acid evaporates ; the water can no longer hold the 
 carbonate in solution, but deposits it wherever it rests. 
 Drop by drop, for a moment clinging to the roof, leaves 
 its mite of carbonate behind, until pendent masses, like 
 icicles, sometimes of curious shape and beauty, are formed. 
 The carbonate forms, at the same time, on the bottom of the 
 cave, upright masses called Stalagmites. 
 
 SECTION IV. 
 
 METALS OP THE EARTHS. 
 
 235. General Description. — Aluminium is tlie most 
 important metal of the thu-d class. The others are metals 
 lately discovered by means of the spectroscope, — indium in 
 
222 • CHEMISTRY. 
 
 1863, and gallium in 1875. These metals decompose water 
 at high temperatui'es, and form sesquioxides with its oxygen. 
 
 236. Alummiiim.^This element has a combination of 
 properties which renders it one of the most interesting in the 
 whole series of metals. It has the hardness and luster of 
 silver ; and, since it does not tarnisli wlien exposed to air and 
 vegetable acids, it would seem to be fitted for the practical 
 uses to which silver is put. It melts only at a high tempera- 
 ture, and may then be cast into any desired form. This, 
 together with its malleability, ductility, and tenacity, would 
 enable it to replace iron for many purposes, while its lightness 
 (density 2.56) and beauty give it advantage over that metal. 
 
 Occurrence in Nature. — In connection with these valu- 
 able properties we find that aluminium is one of the most 
 abundant elements in nature. It is a constituent of clay and, 
 marl, of slate, and indeed of most rocks and soils. It must 
 eonstitute about one-twelfth of the solid parts of the earth. il* 
 
 But no cheap method of extracting the metal is yet known,; 
 and the expense stands in the way of its applicatiog^n thei 
 arts. It is now manufactured on a commercial scaljmi Eng- 
 gland and France, and it has been used for ornamental work 
 and in making physical apparatus where strength and light- i 
 ness are required. 
 
 237. Compounds. — The most important ^'mpounds of 
 this metal are aluminium sulphate and aKjm. The formula of 
 the first is Alj (S 04)3. It is largely ^^d in calico-printing. 
 
 Alum is a double salt : it cijfttains the metals po- 
 tassium and aluminium, both as sulphates. Its formula is 
 K2 AI2 (S 04)4 -I- 24 H2 O, and its chemical name is potassio- 
 aluminium sulphate. The water, 24 H2 0, is held.in its crys- 
 tals, and is called its "water of crystallizatio^' Heat a 
 few crystals of alum, and this water will be Expelled : the 
 alum will remain bulky, white, and opaque ; it is then called 
 " burnt alum." 
 
 Other metals beside potassium may combine with the 
 
CHEMISTRY. 223 
 
 aluminium, as sulphates, and other kinds of alum are thus 
 produced. Thus common alum is a potassium alum. So 
 also we have 
 
 NajAla (804)4 ■ • • Sodium alp*, 
 (NH4)2Al2 (864)4 • • • AmnMnium alum. 
 
 SECTION V. 
 
 METALS OF THE ZINC CLASS. 
 
 238. General Description. — The nmals of this class 
 are alike fusible at quite low temperatures, volatile at tem- 
 peratures at or below a bright red heat, and*- combustible 
 vyhen heated in the air. They are bivalent, and form, each, 
 but one oxide, chloride, and sulphide. They decompose 
 water at high temperatures, and dilute acids at low tempera- 
 tures, liberating hydrogen gas. 
 
 '' illustrations of the Class Properties. — THae melting- 
 points of these metals are comparatively low '^ot zinc at 
 423° C, of magnesium a little higher, and of cadmium a« 
 trifle lo'wer. 
 
 Heated to a bright red heat, magnesium is changed to 
 vapor ; at a low red heat cadmium vaporizes, and zinc at a 
 temperaj|«fe between these extremes. \ 
 
 At a red heat in the air these metals burn. Cadmium 
 gives the vapors of its oxide ; zinc, with a blue flame, form- 
 ing clouds of vapor; and magnesium, with a^ame of most 
 dazzling brightness, sometimes used as a source of light in 
 photography and in optical experiments. 
 
 At high temperatures they d4PBmpose water, and* form 
 oxides. In this reaction one atom of, nfetal replays |^o of 
 hydrogen, and forms an oxide with the one atom' of oxygen ; 
 and hence they are bivalent. 
 
 On contact with sulphuric or hydrochloric acid they dis- 
 place the hydrogeli', and form salts. Indeed, by this action 
 pf ziib we tove seen that hydrogen is generally prepared. 
 
224 CHEMISTRY. 
 
 239. Zinc. — Zinc blende (a sulphide) , calamine (a car- 
 bonate) , and the red oxide, are the ores of zinc found most 
 abundantly ; and from these the metal is extracted. When 
 either of the first two is used, it is first roasted, that is, 
 heated in presence of air. By this means it is changed tp 
 the form of oxide. The oxide is then mixed with coal, and 
 heated in a close vessel having an iron tube reaching ovei 
 into a cold receiver. The oxide is decomposed ; and its- 
 zinc, in the form of vapor, goes over to be condensed in the 
 receiver. 
 
 Properties of Zinc. — Zinc is a bluish- white metal, about 
 seven times (6.9) as heavy as water. 
 
 At low temperature zinc is brittle ; heated to about 200° C- 
 it is also very brittle ; but between these extremes (130° C- , 
 i: is malleable, and is rolled or hammered into thin sheets for 
 various uses. 
 
 Ziuc is not easily acted upon by air, and on this account 
 it is sometimes used as a coating to protect iron from rust. 
 Iron covered with a thin coating of zinc is said to be galvan- 
 ized. 
 
 SECTION VI. 
 
 METALS OP THE IKON CLASS. 
 
 240. Grcneral Description. — In this group we find u-on, 
 manganese, nickel, and cobalt. The last three named more 
 or less resemble iron, both in physical and chemical proper- 
 ties. It need i the intense heat of the furnace to melt iron : 
 the same is true of the others. Even at so high a tempera- 
 ture iron does not volatilize : neither do the others. Iron is 
 generally bivalent, but sometimes quadrivalent: so are the 
 rest ; and each forms several oxides, sulphides, and chlorides. 
 Like the preceding class, these metals decompose water at 
 high temperatures, and acids without the application of heat. 
 
 241. Iron. — Pm-e metallic iron is of very rare occurrencf 
 
CHEMIS^'BY. 
 
 226 
 
 'n nature. The metal is found, however, in great abundance 
 in combination with non-metals ; its oxides and its sulphides 
 being the most common ores. The magnetic oxide occurs in 
 large quantities in many parts of the United States, and is 
 used extensively in the manufacture of the metal. It is the 
 ore from which the best " Swedish iron " is also made. In 
 England an impure carbonate, called argillaceous iron-ore^ is 
 chiefly used. 
 
 The iron of commerce occurs in three forms, — cast-iron, 
 wrought-iron, and steel. 
 
 Cast-iron is a compound of iron with small and variable 
 quantities of carbon. It is obtained from the ores by heating 
 them in a blast-furnace. 
 
 Wrought-iron is nearly pure iron, but still contains a very 
 small proportion of car- 
 bon. It is obtained gen- 
 erally from cast-iron by 
 burning out its carbon 
 in a reverberatory fur- 
 nace. 
 
 Steel is also a com- 
 pound of iron and car- 
 bon, containing less car- 
 bon than cast-iron, but 
 more than wrought-iron 
 It is made from cast-iron 
 by burning out its car- 
 bon, or from wrought- 
 iron by adding carbon 
 to it. 
 
 242. Cast Iron. — In 
 
 the most ancient of his- 
 tories we read of Tubal- 
 Cain, who was the great-grandson of the son of Adam. We 
 are told that he was a cunning workman in brass and iron 
 
 Fig. 95. 
 
226 
 
 CHEMSTET. 
 
 Even in such early days this metal must have been extracted 
 from its ores. 
 
 The ores are reduced by heat in a blast-furnace. 
 The Blast-Fiirnace. — The exterior of a blast-furnace is 
 shown in Fig. 95. This, together with Fig. 96, which repre- 
 sents a section of it, 
 will enable us to explain 
 its construction. The 
 interior has the shape 
 of a double cone. It 
 is built of the most in- 
 fusible fire-brick, and 
 inclosed in solid mason- 
 ry. It is very large, 
 perhaps fifty feet high 
 by- fifteen feet in width 
 at its widest part. The 
 bottom is closed, and 
 the air needed for the 
 fire is forced by steam- 
 engines through pipes, 
 T. The fuel and the 
 ore, with broken lime- 
 Pig. 96. stone or other flux, are 
 put in at the top : the metal is drawn off at the bottom. 
 
 The Process. — The ore, if necessary, is first roasted, by 
 which it is changed to the form of oxide. The oxide mixed 
 with fuel and flux is made toflU the furnace. The fire, having 
 been started, is kept up by the blast of hot air (a cold blast 
 sometimes) driven by the engine. " Where the blast first 
 touches the burning fuel, carbon dioxide is formed : this gas, 
 with nitrogen, rising through the furnace, comes in contact 
 with white-hot carbon, and is reduced to carbon oxide. The 
 layers of solid material thrown in at the top of the furnace 
 gradually sink down ; and, as soon as a stratum of ore has 
 gone far enough to be heated by the hot mixture of nitrogen 
 
CHEMISTRY. 227 
 
 and carbon oxide, it becomes reduced to spongy metallic 
 Iron, which, mixed with flux and the earthy impurities of the 
 ore, settles down to hotter parts of the furnace, where it 
 enters into a fusible combination with carbon, while the flux 
 and earthy impurities melt together to a liquid slag. The 
 liquid carburetted iron settles to the very bottom of the 
 furnace, whence it is drawn out at intervals through a tap- 
 ping-hole, which is stopped with sand when not in use." 
 {Eliot and Storer.) 
 
 The Drawingr-off. — In front of the furnace is a large 
 level bed of sand. A channel is scooped through the middle 
 of this bed, and it reaches all the way from the bed to the 
 hearth of the furnace. From the large channel in the mid- 
 dle of the bed of sand, there are smaller ones reaching out 
 each side, and then from these there are other branches 
 about three feet long and three or four inches wide. Look 
 at the picture (Fig. 95), and you will see the arrangement of 
 this central channel with its branches. 
 
 Now, about every twelve hours the furnace is opened at the 
 bottom for the melted metal to run out. It has no choice of 
 places : it must flow down through the large channel, and off 
 into all the branches in the bed of sand. There it is allowed 
 to cool. 
 
 The iron thus obtained is the cast-iron of commerce. The 
 short bars cast in the sand are known as pigs. Indeed, the 
 crude cast-iron from the blast-furnace is often called Pig- 
 Iron. 
 
 243. Casting. — Large quantities of cast-iron are used 
 for various purposes. In order to make it into useful articles 
 it is melted, and the liquid metal is poured into molds. 
 This operation is called Casting. The melting of the iron is 
 accomplished in what is called a Cupola Furnace. 
 
 The Cupola Furnace. — This furnace is built of fire- 
 bricks, and incased in iron. It is several feet high, and 
 cylindrical, with a door at some distance above the bottom 
 
228 
 
 CHEMISTRY. 
 
 for the iron and fuel to be put in, and a hole, known as the 
 tap-hole, at the bottom, for the melted metal to run out. 
 
 In the first place, molds of the desired article are made in 
 sand. 
 
 Then, when the melted cast-iron is ready in the furnace, 
 the tap-hole is opened. A fiery stream of liquid iron pours 
 out: it is caught in ladles by the workmen, who hurry it 
 away to the molds. The fluid metal runs into every little 
 groove and corner of the mold, and there hardens into the 
 desired form. 
 
 244. Wrought-Iron. — Wrought-iron is the purest form 
 of commercial iron, and is generally obtained by treating 
 cast-iron in a reverberatory furnace. 
 
 The Keverberatory Furnace. — A section of a rever- 
 beratory furnace is shown in Fig. 97. The cast-iron is 
 
 Fig. 97. 
 
 placed at D upon the hearth. The fire, A, is separated from 
 the hearth by a wall of fire-brick. The roof is arched down- 
 ward to the chimney, which is forty or fifty feet high, to 
 cause a strong draught. 
 
 The Process. — Flame and hot gases from the fire, strik- 
 ing against the arched roof, are reflected down upon the cast- 
 
CHEMISTRY. 229 
 
 iron. In a little time the iron begins to melt. When it has 
 been all reduced to a pasty state, the furnace-man unstops 
 an opening (B), through which he puts his paddle. By 
 thoroughly stirring (puddling) the pasty mass, all parts are 
 brought in contact with the hot air, during which a part of 
 its impurities, in the form of slag or scoria, is allowed to 
 run off, while its carbon is burned, and its gas escapes to the 
 ehunney. The metal is then formed into balls, taken from 
 the furnace, pressed or hammered to remove the remaining 
 scoria, and then rolled into bars or other forms of Wrought 
 or Malleable Iron. 
 
 245. Steel. — The difference between steel and both cast- 
 iron and wrought-iron is in the quantity of carbon it contains. 
 It contains less than cast-iron and more than wrought-iron. 
 Formerly steel was made by adding carbon to wrought-iron : 
 lately it is largely made by taking a part of its carbon from 
 cast-iron. 
 
 Steel from Cast-iron. — From two to six tons of cast- 
 iron, when melted, is run into a large globular vessel, built 
 of the most infusible substance. Numerous holes in the 
 bottom of this crucible allow a strong blast of air to bubble 
 up through the melted metal. A most violent combustion 
 follows, the heat of which keeps the metal in a fluid state, 
 while its carbon and a small part of the metal itself are 
 burned to oxides. Too much carbon is, by this process, re- 
 moved, and a quantity of cast-iron is added to restore carbon 
 enough to change the whole mass into steel. The crucible is 
 then tipped upon its pivots, and the melted steel run off into 
 molds. Less than half an hour is enough to change these 
 tons of cast-iron into cast-steel. The process is known as 
 the Bessemer Process. 
 
 From Wrought-iron. — The older method of prepar- 
 ing steel is called " cementation." Bars of wrought-iron, 
 embedded in charcoal and inclosed in boxes from which air is 
 very carefully excluded, are heated to redness, and kept in 
 
230 CHEMISTRY. 
 
 this condition for several days. A curious and obscure 
 chemical action goes on, by which these two solid substances 
 unite, — the carbon penetrating and combining with all parts 
 of the iron, and thus changing it to steel. To make its 
 composition uniform, this " blistered steel, " as it is called, 
 is melted, and cast into large but short bars called ingots. 
 
 SECTION vn. 
 
 METALS OF THE TIN CLASS. 
 
 246. General Description. — Tin is the only useful 
 metal of its class. The others resemble tin in their chemical 
 properties, but they are rare and unimportant. These metals 
 are quadrivalent, and decompose water at high temperatures, 
 forming dioxides. 
 
 247. Tin. — Tin is not an abundant element in hature, 
 and yet it is one of the metals longest known to men. The 
 mineral called tinstone (stannic oxide, Sn O2) is the chief 
 source of the metal. Mixed with powdered coal and a little 
 lime, the ore is spread upon the hearth of a reverberatory 
 furnace. The carbon takes the oxygen from the ore, and 
 the melted metal is run off into iron molds. 
 
 In color tin resembles silver. It is soft, malleable, and 
 ductile. 
 
 Tin does not easily lose its luster by exposure to air, and 
 on this account it is largely' used as a covering for other 
 metals : common tin-ware is sheet-iron, which has been 
 covered with a thin coating of tin. 
 
 SECTION VIII. 
 
 METALS OF THE ANTIMONY CLASS. 
 
 248. General Description. — Of this class arsenic, anti- 
 mony, and bismuth are the most important metals. They 
 
CHEMISTRY. 231 
 
 are trivalent, and are very closely related to the trivalent 
 group of non-metals. In bismuth the metallic character is 
 very clear, in antimony it is less evident, in arsenic it is very 
 doubtful, and in phosphorus and nitrogen it is altogether 
 absent. From bismuth to nitrogen, the transition from metal 
 to non-mptal is gradual and perfect. 
 
 249. Arsenic. — ■ This element has been already described 
 as a non-metal, and its relation to nitrogen and phosphorus 
 pointed out. On the other hand, it is related to antimony and 
 bismuth, whose metallic character is more decided. It would 
 seem to be the bond which links these two divisions of the 
 elements together. 
 
 250. Antimony. — Like arsenic, antimony combines with 
 \hree atoms of hydrogen to form a combustible gas. Treated 
 m Marsh's apparatus, it also forms a stain upon white porce- 
 lain, or a metallic mirror in the tube. So great is the 
 resemblance between the stains of antimony and arsenic, 
 that care is to be used not to confound the two metals in the 
 test. The antimony stain is known by its more feeble luster, 
 its blackness, and the high heat needed to volatilize it. 
 
 Its most Useful Alloy. — Antimony, with tin and lead, 
 are melted together to make type-metal, the most useful of all 
 alloys, since the art of printing depends upon its use. It 
 has the curious property of expanding when it cools from 
 the melted liquid to the solid form. On this account, when 
 poured into the type-molds, and allowed to become cold, it 
 fills every little groove and marking of the mold, and thus 
 takes the perfect shape of the type. 
 
 251. Bismuth. — Bismuth forms oxides and chlorides 
 whose composition is analogous to those of arsenic and 
 antimony. It is trivalent, like the others. 
 
 The metal itself is of a reddish hue, and, like the other 
 two, very brittle. It melts at 264° C. (507° F.) ; and, when 
 cooling, it crystallizes and expands. 
 
232 CHEMISTRY. 
 
 With other metals bismuth forms alloys remarkable for the 
 low temperature at which they melt. Its alloy with lead and 
 tin (two parts bismuth, one of lead, and one of tin) is called 
 " fusible metal : " it melts at 93° 7 C. (200° F.). This alloy 
 is used for taking casts from medals and dies : on cooling, it 
 expands, and, filling every crevice or line of the die, makes 
 a most beautiful and faithful copy. 
 
 SECTION rx. 
 
 METALS OF THE LEAD CLASS. 
 
 252. General Description. — This class contains only 
 two metals, lead and thallium. Lead has been known from 
 the earliest times : thallium has been known only since 1861. 
 They are alike in being soft enough to yield to pressure by 
 the finger-nails ; in being fusible below red heat ; in being 
 malleable and ductile ; and in being heavy metals, lead 11.2 
 and thallium 11.8 heavier than water. 
 
 In their chemical properties these metals do not so per- 
 fectly agree. Lead is bivalent : thallium is univalent. In 
 other respects, also, thallium resembles the alkaline metals. 
 
 253. Lead.- — The ore from which the lead of commerce 
 is obtained is a sulphide (Pb S), called galena. The color 
 and luster of this ore are much like that of the metal itself, 
 but the ore is much harder. It is crystalline, and sometimes 
 occurs in cubes of the most perfect form. 
 
 To obtain metallic lead, galena is mixed with lime, and 
 roasted in a reverberatory furnace. By this means, a part of 
 the ore is changed to oxide, another part to sulphate, and 
 some remains a sulphide as it was. The air is then shut off 
 from the furnace, and the heat raised : the compounds are 
 then all decomposed, and metallic lead is produced. 
 
 Its Uses. — Metallic lead has numerous and important 
 uses. Among them we may especially notice the construc- 
 tion of water-pipes and cisterns. In cities supplied with 
 
CHEMISTRY. 233 
 
 water from reservoirs, the conduit-pipes are almost univer- 
 sally made of lead. 
 
 Action of Liead upon Water. — But, since the com- 
 pounds of lead are poisonous, the chemical action of lead 
 upon water is a matter of great importance. Together, 
 especially in the presence of air, they form an oxide which 
 is somewhat soluble in water. But this corrosive action is 
 very much modified by the presence of impurities. It is 
 increased by ammonium nitrate : it is diminished by sul- 
 phates and carbonates. 
 
 Water containing a solution of calcium carbonate scarcely 
 affects the lead, because an insoluble carbonate is formed on 
 the surface of the metal which prevents any further action ; 
 but, if it contains much free carbonic acid, this removes the 
 lead carbonate, which otherwise would protect the surface, 
 and leaves the metal of the pipes constantly exposed to cor- 
 rosion. 
 
 Whether drinking-water may be kept in lead cisterns and 
 pipes without risk to health, depends on the character of the 
 water ; and the question can be decided only by learning what 
 substances the water holds in solution, and what is their 
 chemical action on the metals. 
 
 SECTION X. 
 
 METALS OP THE SILVER CLASS. 
 
 254. General Description. — The members of this class, 
 copper, mercury, and silver, are sometimes found native, but 
 they are much more abundant in combination. Their sul- 
 phides are their most common ores. They can not decom- 
 pose water at any temperature. Copper and mercury are 
 bivalent, but silver is univalent. 
 
 255. Copper. — Free metallic copper is found in the 
 noted mines of Cornwall and Devon, in England, and in 
 many other parts of Europe. But some of the finest native 
 
234 CHEMISTRY. 
 
 copper in the world is found in the region of Lake Superior. 
 One single mass of Lake Superior copper weighed over 400 
 tons. 
 
 The native copper has very curious crystalline forms. In 
 some cases it is found in little cubes. In some eases the 
 
 small crystals are grown to- 
 gether in vast numbers, and 
 thus make large masses ; 
 and these masses often show 
 the most singular branch- 
 like shapes (Fig. 98), 
 tempting one sometimes to 
 fancy that the metal had tried to imitate the form of some 
 growing plant. 
 
 Ores of Copper. — Copper pyrites is the most abundant 
 ore of this metal. To a great deal of this ore nature has 
 given the form of beautiful cubes, having a color and luster 
 something like brass. This ore is composed of copper, iron, 
 and sulphur, Cu Fe 85. 
 
 Besides this, there are other sulphides of copper, Cua S, 
 and Cu S. The oxides also are abundant ; so also are the 
 carbonates. Malachite is one of these. 
 
 Malachite is a rich ore of copper, but much less common 
 than many others. It is a stone of most beautiful color. 
 Its rich green surface also takes a fine polish, and on 
 these accounts it is often used for purposes of ornament. 
 It is a compound of copper, represented by the formula 
 CuCOs + Cu (H0)2. 
 
 Smelting' the Ores. — To obtain the metal, the ores of 
 copper are first roasted and afterward melted. These opera- 
 tions are repeated until the mass contains only two com- 
 pounds of the metal, the oxide and the sulphide. 
 
 The mass is then again roasted ; and, during this heating, 
 the two compounds attack each other. The sulphur of one 
 and the oxygen of the other are taken away, leaving the 
 copper of both in metallic form. 
 
CHEMISTKY. 
 
 235 
 
 Refining. — This crude copper from the ore contains othei 
 metals which must be removed. The process of " refining " 
 is for tliis purpose. It consists in re-melting the metal, and 
 keeping it in the fluid form, exposed to air, for several hours. 
 By this means the impurities are oxidized or burned out. 
 The molten copper is then taken from the furnace in ladles, 
 and poured into molds, which give it the form of solid bars. 
 
 Pig. 99. 
 
 The furnace, and some of these last operations, are shown ilS 
 Fig. 99. 
 
 Properties of the Metal. — Copper is a red metal, very 
 tenacious, very ductile, and malleable. 
 
 Copper is among the very best conductors of electricity, 
 and is much used in the construction of electrical apparatus' 
 and lightning-rods. 
 
 It slowly tarnishes in the air, and is readily acted upon by 
 vegetable acids : the compounds formed are, many of them, 
 poisonous. On this account copper vessels to be used for 
 culinary purposes are usually coated with tin. 
 
236 CHEMISTRY. 
 
 Alloys of Copper. — Brass is an alloy of copper and 
 zinc : it is made by melting together two parts of copper to 
 one of zinc. 
 
 Bronze, gun-metal, and bell-metal are, for the most part, 
 mixtures of copper and tin. 
 
 German silver is an alloy of copper, zinc, and nickel. 
 
 256. Mercury. — This metal was known in very ancient 
 times ; and besides mercury, a name which the old chemists 
 gave it, this lustrous fluid was early called quicksilver, and 
 this name is still in very common use. 
 
 This metal is found in California, in China, in Austria, and 
 to some extent in other countries. Perhaps the most noted 
 among its native countries is Spain : the mines of Almaden 
 in that country have long been worked, and have yielded a 
 rich reward. 
 
 Mercury is generally found combined with sulphur. This 
 ore is called cinnabar. It is a very pretty mineral, much the 
 color of cochineal. Sometimes this ore is so pure that its 
 color is as rich and brilliant as that of vermilion. Indeed, 
 these two things have the same composition : cinnabar is the 
 sulphide which is found in the earth ; vermilion is the sul- 
 phide which is made in the chemist's laboratory. Both have 
 the composition represented by the formula HgS. 
 
 Reducing the Ore. — To obtain the metal, the cinnabar 
 is roasted in a furnace with plenty of air. The oxygen of the 
 air decomposes the ore, and combines with its sulphur, leaving 
 its mercury free. At the temperature of the furnace the 
 metal is in vapor. This vapor is carried over into cold 
 chambers, where it condenses to liquid foim. 
 
 Properties. — Mercury is a liquid metal about 13.5 times 
 heavier than water. It becomes a silver-white solid at 
 -39.6° C. (-39.4° F.). 
 
 Mercury forms two oxides, the mercurous, HgjO, and the 
 mercuric, Hg 0. The last-named substance is a red powder, 
 once known as " red precipitate," and is of historic inter- 
 
CHEMISTEY. 237 
 
 est, since by heating it Priestly discoveied oxygen in the 
 year 1774. Nevertheless mercury and oxygen have so little 
 attraction at ordinary temperature, that the surface of the 
 metal remains bright on exposure to air. 
 
 Its attraction for chlorine is stronger : the two combine at 
 ordinary temperature. Two chlorides are well known : they 
 are the mercurous chloride, HgjCL, and the mercuric chloride, 
 Hg CL. The former is calomel, so long and largely used in 
 medicine ; and the latter is corrosive sublimate, a virulent 
 poison. Both are white solids ; yet they are easily distin- 
 guished, because corrosive sublimate is soluble in water, 
 while calomel is not. 
 
 Amalgams. — The alloys of mercury are called Amal- 
 gams. The most familiar example is to be seen on the 
 backs of mirrors : this substance is an amalgam of mercury 
 and tin. 
 
 Uses. — Metallic mercury is largely used in "silvering" 
 mirrors, in the construction of thermometers and barometers, 
 and also in extracting silver and gold from their ores. 
 
 257. Silver. — Silver, like the other metals of greatest 
 use in the arts, is very widely distributed. It is found native 
 and often alloyed with mercury, copper, and gold ; but its 
 sulphide (AgjS), either alone or mixed with other metallic 
 sulphides, is its most common form. From these ores the 
 metal is usually obtained. They are found in many coun- 
 tries of Europe, but in greater abundance and richness in 
 Peru, Mexico, and the Pacific slope of the United States. 
 
 Obtaiped by Cnpellation. — Galena almost always con- 
 tains silver, and often in quantities which make it valuable for 
 the extraction of silver as well as lead. " It has been found 
 profitable to extract the silver from load that contains less 
 than one-thousandth of its weight of the precious metal." 
 From lead rich in silver this metal is obtained at once 
 by cupeUation; but, when so poor as that just described, the 
 lead is first melted, and then, while cooling slowly, it is 
 
238 CHEMISTBY. 
 
 stirred. As it cools, it crystallizes ; and the crystals may be 
 dipped out of the liquid mass iu colanders. Nojv, an alloy 
 of lead and silver will remain melted when cooled below the 
 temperature at which pure lead solidifies. Hence the crystals 
 dipped out in the colander are crystals of lead, while all 
 the silver remains in the fluid left behind. By this means the 
 proportions of lead are reduced until the metal is rich in 
 silver, after which it is cupelled. 
 
 The process of cupellaUon is based upon the fact that lead 
 is rapidly oxidized by air at high temperature, while silver is 
 not. 
 
 Tlie alloy, placed in a shallow porous vessel of bone- 
 earth, called a cupel, is melted in a furnace, and its surface 
 is at the same time exposed to a current of hot air. The 
 lead is changed to an oxide : the melted oxide is partly 
 absorbed by the cupel, while another part runs off into other 
 vessels. The silver is not affected by the air ; and, when the 
 lead has passed away, the precious metal still remains in 
 the cupel. 
 
 Obtained, by Amalgamation. — From other ores than 
 argentiferous lead, silver is extracted by a process called 
 amalgamation. It is based upon the fact that silver is very 
 soluble in mercury. 
 
 For this process, also, the ores require a preliminary treat- 
 ment. After being thoroughly ground, they are mixed with 
 common salt, and then roasted. By this means the silver is 
 changed to a chloride. The roasted substance is then mixed 
 with water and fragments of iron, and the mixture is 
 violently shaken in revolving casks. Mercury is soon added, 
 and the agitation is kept up for perhaps twenty hours. In 
 the mean time the iron decomposes the chloride, and the 
 silver thus set free is dissolved at once in the mercury. 
 The excess of mercury iu the amalgam is removed by filter- 
 ing it through leather bags under pressure, and the rest by 
 distillation. The precious metal is left behind. 
 
 Properties. — Silver is the whitest of metals. It is very 
 
CHEMISTRY. 239 
 
 malleable and ductile, much harder than gold, and ten and a 
 half times heavier than water. Its surface is not tarnished 
 on exposure to air, not even when heated in oxygen ; but 
 it quickly blackens on exposure to sulphuretted hydrogen, 
 because of the strong attraction between silver and sulphur. 
 
 Its Alloys. — Silver is too soft for most purposes in the 
 arts. Small quantities of other metals increase its hardness. 
 For coin and for articles of plate, it is alloyed with copper. 
 The English standard silver contains 7.5 per cent of copper. 
 The standard is regulated by law, and is not the same in all 
 countries. In the United States the legal silver coin is -j^ 
 silver and -^ copper. 
 
 258. Action of Light on Silver Compounds. — We 
 
 have seen that light is an active agent in many chemical 
 changes : we may add that the salts of silver are especially 
 sensitive to its influence. An easy experiment can be made 
 to Illustrate this fact. 
 
 On the Chloride.— Into a test-tube put a quantity of 
 a solution of silver nitrate, and add a few drops of hydro- 
 chloric acid. A heavy white precipitate of silver chloride 
 is at once formed, which speedily settles to the bottom. Let 
 the tube be now placed in the sunlight, and an interesting 
 change of color will be gradually produced. The snow- 
 white chloride becomes pink, violet, brown, and at last 
 dark bronze-black. The chloride, dry and pure, will not 
 show this change on exposure to light : moisture seems to 
 be necessary. Light causes a reaction between water and the 
 chloride, by which hydrochloric acid is formed, and a small 
 quantity of metallic silver is set free. To the presence of this 
 metal in a state of \'ery fine division the darkening is due. 
 
 On the Nitrate. — Silver nitrate is not changed by the 
 action of light unless in contact with organic matter : it then 
 blackens like the chloride. 
 
 On the Oxide. — When silver iodide is exposed to light 
 no visible change occurs, but still a molecular change doeg 
 
240 CHEMISTRY. 
 
 take place. This curious fact may be shown by experi- 
 ments. Let two highly polished plates of silver be held in 
 iodine vapor in the dark : by this means a thin film of iodide 
 will be made over their surfaces. Leave one plate in the 
 dark, and put the other, for a time, in the sunlight : the two 
 plates still look alike ; the light has caused no visible change. 
 But now hold both, in a box at moderate temperature, over 
 the vapor of mercury : the one which was exposed to the 
 light immediately blackens ; the other is not changed. The 
 darkening in this case is due to a combination of mercury 
 with the silver of the iodide, — the mercury decomposing the 
 iodide after exposure to the light. 
 
 The nature of the action of light in this case has been in 
 doubt. The best explanation (Amer. Jour, of Sci., vol. 42, 
 p. 198, and vol. 44, p. 71) supposes it to be a physical 
 action, by which the molecules are so disturbed as to yield 
 afterward to the attraction of mercury. That is to say, the 
 molecules of the iodide are so shaken by the impact of the 
 waves of light that their atoms are almost ready to fall 
 apart. In this condition the attraction of the mercury for 
 ihe iodine is strong enough to complete the decomposition. 
 
 t 
 
 ''"259. Photography. — Photography is the art of making 
 pictures by means of light. While there are many different 
 processes, each requiring different substances sensitive to 
 light, still the most interesting process is the one so univer- 
 sally used in portraiture ; and this is based on the sensitive- 
 ness of the compounds of silver. 
 
 The process consists of two parts ; viz., the maldng of the 
 negative, and then the making of a positive. 
 
 260. Making the NegatiA^e. — Glass is employed as the 
 substance on which the picture taken directly from the object 
 is held. But in order to use it the surface must be made 
 sensitive to light. 
 
 Preparation of the Plate. — The object is to give the 
 glass a coating which contains silver iodide. 
 
CHBMISTKY. 241 
 
 Cotton, acted on by a mixture of nitric and sulphuric 
 acids, is changed to gun-cotton, or pyroxyline ; and this, 
 when dissolved in alcohol and ether, forms the substance 
 called Collodion. A small quantity of an iodide (potassic), 
 or a mixture of two or three iodides, is put with the collodion, 
 and the solution is then rapidly poured from a wide-mouthed 
 vessel over the very clean and dry surface of the glass : the 
 alcohol and ether quickly evaporate, and leave a thin film 
 upon the glass, which is then plunged into a bath of silver 
 nitrate. While in this bath for a few minutes, the iodine in 
 the film takes silver from the nitrate, and forms silver iodide 
 (Agl). The plate being taken from the bath, thoroughly 
 washed and dried, is ready to receive the action of light. 
 
 Expo.sure in the Camera. — The plate, with the sen- 
 sitive film on its surface, is exposed in a camera for a short 
 time, during which the light from the object performs its 
 curious action upon the iodide, by which no picture is made 
 visible, but by which one is prepared to be developed. On 
 pouring over the film of iodide a solution of pyrogallic acid 
 (Cg He O3) or of ferrous sulphate (Fe S O4) , containing a few 
 drops of silver nitrate, the picture is brought out, or " devel- 
 oped " as the process is technically described. 
 
 Fixing. — ■ The next step is to dissolve away the unde- 
 composed iodide, in order to make the picture permanent ; for 
 it is evident that if any of this remains in the film the light 
 will continue to work, and thus destroy the picture. This is 
 done by washing the plate in a saturated solution of sodium 
 hyposulphite. After this the plate is thoroughly washed in 
 water, dried, and varnished on the picture side, to preserve 
 the film from injury. 
 
 Tlie Liig-Iits and Shades are Inverted. — When a pho- 
 tograph on glass is viewed by transmitted light, it will be 
 seen that the shades of the object are lights on the picture, 
 the lights and shades being reversed. Such a picture is 
 called a Negative. If the " development " be pushed far- 
 ther, more of the iodide in the film will be decomposed, and 
 
242 CHEMISTRY. 
 
 the shades will more completely intercept tlie light. From 
 such a negative a picture may be printed upon paper. This 
 picture of the negative reverses the lights and shades again, 
 and hence brings them true to the object. Such a picture, 
 in which the lights and shades are the same as those of the 
 object itself, is called a Positive. 
 
 261. Making the Positive. — The paper for this pur- 
 pose is prepared by floating it first upon a solution of salt, 
 and afterward upon one of silver nitrate. Silver chloride 
 (Ag CI) is thus formed in the paper. This paper, placed 
 under the negative, is exposed to light ; the light is stopped 
 by the shades of the negative, but passes freely through its 
 lights : upon the paper, therefore, the lights and shades cor- 
 respond with those of the object from whicli the negative 
 was taken. 
 
 The photograph is next to be thoroughly washed and then 
 "toned." The toning-bath is a solution of hydrosodium 
 carbonate (bicarbonate of soda), containing a little gold 
 chloride ( Au CI3) . The change produced by this bath is 
 beautiful to witness. From an unpleasant, dull, reddish 
 color, the picture visibly changes to a rich blue-black. The 
 picture, having next been washed in water to remove all 
 traces of the gold bath, is soaked for some minutes in sodium 
 hyposulphite, to wash out all of the undecomposed chloride, 
 and afterward for twenty-four hours in water, to remove all 
 traces of the hyposulphite. 
 
 SECTION XI. 
 
 METALS OF THE GOLD CLASS. 
 
 262. General Description. — The metals of the gold 
 class are always found in the metallic state. They are not 
 tarnished by air at any temperature short of their melting- 
 points, nor can they be dissolved by nitric acid. Only 
 
CHEMISTRY. 243 
 
 chlorine or aqua-regia can dissolve them. Gold and platinum 
 are the most familiar and important members of the class. 
 
 263. Gold. — In small quantities gold is very widely dis- 
 tributed in nature. Fine grains of it occur in the sands at 
 the bottom of many rivers, in the crystalline rocks and tlie 
 soils derived from them. Iron pyrites, found almost every- 
 where, often contains traces of gold ; and silver is never 
 found entirely free from it. Few places, however, seem to 
 possess the precious metal in quantities tliat will pay for the 
 laborious work of separating it from the sands or roclcs in 
 which it is found. 
 
 Separation of GrOld. — Except osmium, iridium, and 
 platinum, gold is the heaviest of metals. It is very much 
 heavier than sand ; so that when gold-bearing sand is vio- 
 lently shaken in water, the fine and precious grains quickly 
 sinli to the bottom, while the sand may be poured off with the 
 water. By repeating this process, called Washing, the sand 
 or other loose material is iinally all washed away. The 
 fine metallic grains left behind are seldom pure gold. The 
 baser metals — silver, copper, and others — are taken out 
 by sulphuric or nitric acid, in which they will dissolve, but 
 which can not dissolve the gold. This process of separating 
 gold from the metals with which it is alloyed is called 
 Refining. 
 
 When the native gold is scattered in fine grains through 
 solid rock, it is extracted by Amalgamation. Mercury mixed 
 with the crushed ore d' jsolves the gold : the amalgam is then 
 separated from the excess of mercury by filtration, and the 
 remainder of the mercury is afterward driven away com- 
 pletely from the gold by distillation. 
 
 Properties of Gold. — Gold is remarkable for its fine 
 yellow color and beautiful luster. Tliis metal is about nine- 
 teen times heavier than water ; its specific gravity is 19.33. 
 It is the most malleable of metals : it is said that leaves have 
 been beaten so thin that 280,000 would be needed to make 
 
244 CHEMISTRY. 
 
 an inch in tiiickness ! There is a curious fact about the color 
 of gold-leaf ; it is this : looked at in the usual way it is yel- 
 low ; but let a leaf be spread upon glass so that it may be 
 viewed in transmitted light, and it exhibits a line green color. 
 
 264. Platiimiu. — Platinum is a rare metal, not so 
 widely distributed as gold. The slopes of the Ural Moun- 
 tains, Brazil, and Peru are among the localities richest in 
 this metal. It is always found ir the metallic state, but 
 never pure. It is heavier than gold, and is obtained from 
 loose sands or soils by washing in the same way. Its com- 
 mercial value is about one-half that of gold and about eight 
 times that of siher. 
 
 Pure platinum is almost as white as silver, and can not be 
 tarnished in au- at any temperature. The most intense heat 
 of the blow-pipe is needed to melt it. On these accounts 
 platinum vessels are much used in the laboratory. Few 
 indeed are the chemicals which can affect it. Aqua-regia 
 and the caustic alkalies are among those which can. On the 
 other hand, it readily forms alloys with most other metals ; 
 and these are more easily melted than the metal itself, and 
 are soluble in acids. 
 
 REVIEW. 
 I. — SUMMARY OF PRINCIPLES. 
 
 265. Malleability, ductility, conductivity, and luster are 
 the most characteristic properties of the metals. 
 
 They occur in nature in the form of ores, in which they 
 are combined with non-metals ; as alloys, in which they are 
 combined with one another ; and as native metals, in which 
 condition they are uncombined. 
 
 The art of extracting metals from their ores is called 
 metallurgy. 
 
 Roasting and reducing are two important operations in 
 metallurgy. Roasting consists in heating the ore in the 
 presence of air : its object is to change the ore to an oxide of 
 
CHEMISTRY. 245 
 
 the metal. Reducing consists in heating the oxide with car- 
 bon, or some otlier reducing agent : its object is to decompose 
 the compound, and set the metal free. 
 
 The metals of the alkalies are lighter than water, soft as 
 wax, univalent, and have so strong attraction for oxygen 
 that they decompose water at low temperatures. Potassium 
 and sodium are the leading members of the group. 
 
 Potassium is a constituent in plants ; and when wood, for 
 example, is burned, the potassium is changed into potassium 
 carbonate. 
 
 The carbonate is obtained in solution from the wood-ashes 
 by treating them with water. This lye yields the solid potash 
 by evaporation, and the potash becomes pearlash by heat. 
 A solution of pearlash yields crystals of pure potassium 
 carbonate. 
 
 Sodium chloride is the most abundant compound of sodium. 
 It is largely used in making other useful compounds of 
 sodium. 
 
 Treated with sulphuric acid this salt yields sodium sul- 
 phate, or Glauber's salts. 
 
 The sodium sulphate is reduced by carbon to sodium 
 sulphide. 
 
 Sodium sulphide is changed by calcium carbonate into 
 sodium carbonate, or black ash. 
 
 Black ash, by leaching and evaporation, yields the sodium 
 carbonate (Na2C03) of commerce. The manufacture of 
 sodium carbonate from sodium chloride (NaCl) is an impor- 
 tant industry. 
 
 Treated with carbon dioxide, sodium carbonate becomes 
 hyclrosodium carbonate. This, is the substance known as 
 baking-soda. 
 
 The metals of the alkaline earths are bivalent, with strong 
 attraction for oxygen. They oxidize rapidly on exposure to 
 air, and decompose water at ordinary temperatures. 
 
 Calcium is the most common metal of this class. Its 
 compounds are abundant in nature and useful in the arts. 
 
246 CHEMISTRY. 
 
 Aluminium and indium are called the " metals of the 
 earths." 
 
 Aluminium is very abundant in the earth : it is a constitu- 
 ent of all clay soU and rocks, in which it exists chiefly as the 
 silicate. 
 
 The metals of the zinc class can be easily melted and 
 vaporized, and burn freely when lieated in air. They 
 decompose water at high temperatures, and evolve hydrogen 
 from dilute acids. 
 
 Zinc is the leading member of the class. It is a bluish- 
 white metal, malleable at temperatures between 100° and 
 1;)0° C. and not easily oxidized by exposure to air. 
 
 The metals of the iron class melt with difficulty, and are 
 not volatilized by the intense heat of the furnace. Iron is 
 the leading member of the class. 
 
 In commerce iron occurs in three forms; viz., cast-iron, 
 wrought-iron, and steel. 
 
 These differ in the quantity of carbon in combination with 
 iron. 
 
 Iron ore is reduced in the blast-furnace, which yields the 
 metal in form of pig-iron. 
 
 The cast-iron is changed to wrouglit-iron in the reverbera- 
 tory furnace by the action of the oxygen of the air. 
 
 (Steel is made by burning the carbon out of cast-iron in 
 the Bessemer process, or by causing carbon to combine with 
 wrought-iron in the cevientation process. 
 
 Of the tin class, tin is the only useful metal. 
 
 Tinstone, which is an oxide of the metal, is the only ore 
 from which tin is obtained. 
 
 Tin is a bluish-white, malleable metal, not easily oxidized, 
 retaining its luster on exposure to air. 
 
 Common " tin " is sheet-iron coated with a film of tin. 
 
 Of the metals of the antimony class, antimony, arsenic, 
 and bismuth are the most interesting. These metals are 
 closely related to the non-metals of the trivalent group. 
 
 The metals of the lead class are lead and thallium. 
 
CHEMISTRY. 247 
 
 Lead is a soft metal, 11.2 times heavier than water. 
 
 The principal ore of lead is galena, from which it is 
 obtained by heating with lime in a reverberatory furnace. 
 
 The compounds of lead are poisonous, and hence the risk 
 which attends the use of lead for cisterns. 
 
 The metals of the silver class, copper, mercury and 
 silver, are often found native. Theu' sulphides are their 
 most abundant ores. 
 
 Copper is a red metal, very tenacious, and very ductile. 
 It is an excellent conductor of electricity. Its surface is 
 tarnished by exposure to air, and it is readily attacked by 
 acids. 
 
 Mercury is a liquid metal, 13.5 times heavier than air. It 
 does not combine with oxygen on exposure to air. It forms 
 two oxides and two chlorides. Calomel is the mercurous 
 chloride, and corrosive sublimate is the mercuric chloride. 
 
 Alloys of mercury are called amalgams. 
 
 Silver is a white metal, very malleable and ductile, not 
 affected by air or oxygen, but blackened quickly by sulphuret- 
 ted hydrogen. 
 
 Silver is obtained from argentiferous galena by cupel- 
 lation. It is obtained from other ores by first changing them 
 to oxides, then reducing the oxides by iron, and finally sep- 
 arating the silver by amalgamation. 
 
 Silver coin of the United States is an alloy with copper, 
 containing ninety per cent of silver. 
 
 The metals of the gold class are always found native. 
 They are not affected by oxygen, and can not be dissolved 
 in strong acids. They have a strong attraction for chlorine, 
 and dissolve in aqua-regia. 
 
 Gold is a soft and heavy metal, yellow by reflected light, 
 and green by transmitted light. It is malleable in the 
 highest degree. 
 
 Platinum is almost as white as silver, not affected by 
 oxygen, but soluble in aqua-regia. 
 
248 CHEMISTEY. 
 
 II. —EXERCISES. 
 
 Name the characteristic properties of metals. "What of 
 their melting? Of their weight? In what condition are they 
 found in nature ? 
 
 Into how many classes are they grouped ? 
 
 Describe the metals of the first class. 
 
 Illustrate the class properties. How does potassium act 
 upon ice? Give the reaction. What difference between 
 alkalies and other hydrates ? 
 
 Describe the manufacture of pearlash. Of pure potassium 
 carbonate. 
 
 Describe the manufacture of potassium hydrate. What 
 are its properties? 
 
 What is the composition of sodium chloride ? How is it 
 obtained ? For what is it used ? 
 
 Show how sodium chloride is changed to sodium sulphate. 
 What are Glauber's salts? 
 
 Show how sodium sulphate is changed to sodium sulphide. 
 
 Show how sodium sulphide is changed to sodium carbonate. 
 What is the final process in this manufacture ? 
 
 Give a brief description of hydrosodium carbonate. 
 
 Give a brief description of the metals of the alkaline 
 earths. 
 
 Illustrate the bivalent character of calcium. 
 
 What is slaked lime ? For what is it used ? How is mortar 
 made ? What class of salts do the members of this group 
 form ? Are they soluble in water ? How are bicarbonates 
 formed ? Explain the production of stalactites. 
 
 What is said of the metals of the earths? 
 
 Describe aluminium. 
 
 What is said of the metals of the zinc class? 
 
 How is zinc obtained ? What are its properties ? 
 
 Illustrate the class properties, as to melting-point ; as to 
 vaporization ; as to combustion ; as to their action on water. 
 
 What is said of the metals of the iron class ? 
 
CHEMISTRY. 249 
 
 In what ores chiefly is iron found ? Name its three com- 
 mercial forms. 
 
 What is cast-iron ? How obtained ? 
 
 Describe the blast-furnace. 
 
 Describe in full the process of getting cast-iron from its 
 ores. 
 
 What is wrought-iron ? How obtained ? 
 
 Describe the reverberatory furnace. 
 
 Describe in full the process of making wrought-iron. 
 
 What is steel ? How made ? 
 
 Describe the " Bessemer process." 
 
 Describe the process of cementation. 
 
 What is said of the metals of the tin class ? 
 
 How is tin obtained ? What are some of its properties ? 
 For what is it used ? 
 
 What is said of the metals of the antimony class ? 
 
 What is said of arsenic ? 
 
 Describe antimony. 
 
 What is type-metal? 
 
 Describe bismuth. 
 
 What is said of its alloys ? 
 
 What is said of the metals of the lead class ? 
 
 What of the properties of lead and thallium ? 
 
 From what ore is lead obtained ? Describe the process. 
 
 What are the uses of lead? What is said of its use for 
 water-pipes ? 
 
 What is said of the metals of the silyer class ? 
 
 How does copper occur in nature ? 
 
 Describe the smelting of copper ores. Also, the process 
 of refining. 
 
 What are the properties of copper? 
 
 Describe its alloys, — brass, bronze, gun-metal, German 
 silver. 
 
 In what condition is mercury found? What is a peculiar 
 property of this metal ? What are its uses ? What is calo- 
 mel ? What is corrosive sublimate ? What are amalgams ? 
 
250 CHEMISTRY. 
 
 In what condition is silver found in nature? Name some 
 important localities. 
 
 By what process is silver obtained from galena rich in 
 silver? With poor galena, what process is first used? Upon 
 what principle is cupellation based ? Describe the process. 
 
 With what ores is amalgamation used to obtain the silver? 
 What preliminary treatment needed ? Describe the process 
 of amalgamation. 
 
 What is said of the alloys of silver? 
 
 What art depends upon the chemical action of light? 
 
 What are photographs ? 
 
 How is collodion made ? How is a plate of glass coated 
 with it ? What is the effect of light upon the coated plate ? 
 How is the picture developed? Describe the rest of the 
 process. 
 
 What is a " negative " ? How is the paper prepared, and 
 the ' ' positive ' ' made ? What other processes are gone 
 through with to finish the picture ? 
 
 What is said of the gold class ? 
 
 Where is gold found, and in what condition ? How is it 
 separated from sand ? From baser metals ? From rocks in 
 which fine grains are scattered ? 
 
 How does platinum occur in nature ? How is it obtained ? 
 What are some of its properties ? 
 
APPENDIX. 
 
 EASY EXPERIMENTS FOR THE CLASS-ROOM. 
 
 It is recommended that the following experiments be made, 
 in addition to those described in the text. The numbers in 
 heavy type refer to the paragraphs of the book which the 
 experiments more fully illustrate or extend. 
 
 No attempt is here made to furnish a manual of chemical 
 manipulation. Remembering the conditions which surround 
 the teachers of chemistry in a majority of our schools, it is 
 believed that no genuine service would be done by calling 
 their attention to costly apparatus, lengthy or delicate pro- 
 cesses, or even to a large number of experiments. In the 
 selections which follow, the teacher will find those which he 
 can use, and which he can use with the smallest expenditure 
 of money, time, and patience, because they combine in the 
 highest degree, — 
 
 Simplicity of details. 
 Certainty of results. 
 Cheapness of materials, 
 Adaptation to the subject. 
 
 1. Physical Changes. — Ex. 1. Provide a Bunsen's 
 burner, a piece of platinum wire about two inches long, a 
 piece of magnesium wire or ribbon about six inches long, 
 and a pair of forceps. 
 
 261 
 
252 CHEMISTKV. 
 
 With the forceps, hold the platinum wire in the flame of 
 the lamp, and notice that it glows with a bright red heat, but 
 that it suffers no change in its nature. 
 
 With the forceps, then hold the magnesium with one end in 
 the flame, and notice that it glows with a red heat, then takes 
 fire, and burns with vivid brightness, and that it is at the 
 same time changed into an entirely different kind of matter. 
 
 3. Chemical Change. — Ex. 2. Provide a test-tube, a 
 saturated solution of calcium chloride, and some dilute sul- 
 phuric acid (1 of acid to 4 of water). Fill the tube to the 
 height of two inches with the calcium chloride, and then 
 add, all at once, the dilute acid two inches more, and shake 
 quickly, or stir with a glass rod. These colorless liquids 
 combine, and produce a white solid, which will not fall out of 
 the tube, even when held bottom upward. 
 
 Ex. 3. Fill a cylinder two-thirds full of water, and add 
 about fifty cubic centimeters of a solution of lead acetate. 
 Then add, little by little, some potassium chromate. These 
 colorless liquids yield a rich yelloiv solid. 
 
 10. Mechanical and Chemical Attractions. — Ex. 4. 
 
 Take two pieces of plate-glass, very clean and smooth, and 
 slide one upon the other, gently pressing them together at 
 the same time. Notice that they cling firmly. The lower 
 one may be lifted by the upper. They are held together by 
 cohesion, or, as we are accustomed to say, by adhesion. 
 Cohesion is the generic name given to all attraction among 
 molecules. 
 
 Ex. 5. Use a magnet with small nails, and notice the effect 
 of magnetic attraction. 
 
 No permanent effect is left on bodies by the action of these 
 attractions. 
 
 Ex. 6. Take two wide-mouthed bottles of equal size. 
 Moisten the inside of one with ammonia, and the inside of 
 the other with hydrochloric acid. Invert one, and stand it 
 upon the other, mouth to mouth. Notice that, whereas the 
 
APPENDIX. • 263 
 
 contents of both were colorless, both are now filled with 
 white fumes. Two colorless gases, ammonia and hydro- 
 chloric acid, have united to form a white solid. They are 
 held in combination by chemical attraction. 
 
 11. Influence of Cohesion. — Ex. 7. Mix a little coarsely 
 powdered copper sulphate with an equal quantity of coarsely 
 powdered potassium ferrocyanide in a mortar, and notice 
 that no chemical change occurs. Grind them together : still 
 no chemical change. Sprinkle a little of the fine powder 
 into a cylinder of water, and notice the dark red- brown solid 
 produced. 
 
 Ex. 8. Mix a little ferrous sulphate, in powder, with a 
 little powdered potassium ferrocyanide : no chemical action 
 occurs. Sprinkle a very little of the mixed powder upon 
 water in a cylinder, and notice the fine blue compound 
 produced. 
 
 14. Influence of liiglit. — Ex. 9. Into a cylinder of 
 water put a small quantity of silver nitrate, and then add a 
 little hydrochloric acid. Observe the dense milk-white pre- 
 cipitate which forms. Place the cyHnder in the strong sun- 
 light, and notice the change from white to a purplish-Mack. 
 
 17. No Loss nor Gain. — Ex. 10. Provide two beakers. 
 Into one put about a hundred cubic centimeters of moderately 
 strong solution of lead nitrate, and into the other put half as 
 much solution of potassium chromate. Then put the two 
 upon one pan of the balance, and weigh them carefully. 
 Next, pour the chromate into the nitrate, and restore the 
 beaker to its place. The weight will be found unchanged, 
 notwithstanding the production of a very abundant yellow 
 solid. 
 
 24. The Law of Constant Proportions. — Ex. 11. Fill 
 a test-tube about one-third full of water, and add about a 
 quarter of an inch of silver nitrate solution. To this add a 
 few drops of hydrochloric acid, and shake it vigorously. The 
 
254 CHEMISTRY. 
 
 precipitate will soon settle. To the clear liquid above the 
 precipitate, again add drops of the acid, and repeat the opera- 
 tion until the last drops added give no precipitate at all. 
 The nitrate is then all used up by the acid to make the 
 white chloride. 
 
 Then add drops of the nitrate : a white precipitate shows 
 that the acid had been added in excess of what was needed. 
 Add nitrate as long as a precipitate is formed : it will require 
 but few drops. 
 
 The slightest quantity of either, beyond a certain definite 
 proportion, remains unchanged. 
 
 Ex. 12. Into a small beaker pour about fifty cubic centi- 
 meters of hydrochloric acid, and drop into it, little by little, 
 powdered sodium carbonate until the last small quantity pro- 
 duces no effervescence. The acid is then all neutralized. 
 Then stir in drops of the acid patiently until with the last 
 drop the last of the small quantity of solid carbonate dis- 
 appears. 
 
 Each of these substances requires a certain definite pro- 
 portion of the other : any excess remains unchanged. 
 
 Ex. 13. Evaporate the clear liquid obtained in the fore- 
 going experiment, and you will • get a good sample of com- 
 mon salt which was produced in the chemical action. 
 
 30. The Molecule. — Ex. 14. Dissolve a piece of ani- 
 line-red, no larger than the head of a small pin, in a thim- 
 ble-full of alcohol, and then pour the solution into a half- 
 gallon jar of clear water. Notice the crimson color imparted 
 to the whole. Let us estimate the half-gallon to contaiu 
 30,000 drops of water, and that to color a single drop so uni- 
 formly must require one hundred of the minute pieces into 
 which the aniline-red is di\'ided, and we must then infer that 
 the small piece of the coloring matter has been broken into 
 no less than three millions of pieces. Such an experiment 
 illustrates the exceeding great divisibility of matter. 
 
 Ex. 15. Fill a cup to the brim with hot water : sprinkle 
 
APPENDIX. 25.'} 
 
 into it slowly some finely ground loaf-sugar. Notice that 
 the sugar disappears, and further that the cup is no fuller 
 than before. Two or three tea-spoonfuls of sugar may be 
 added before the water overflows. 
 
 Ex. 16. Take a cylinder, and fill it with alcohol to a 
 height carefully marked with a rubber ring, or even a thread 
 tied around it. Take cotton, and pick it out into fine shreds, 
 and then introduce it, little by little, into the alcohol, care- 
 fully pressing it down to the bottom with a glass rod. A 
 large quantity of cotton may be introduced without raising 
 the level of the liquid. 
 
 These two experiments can be explained only by supposing 
 that the minute parts of the water or the alcohol are not in 
 actual contact, and that the minute parts of the sugar or 
 cotton enter into the spaces between them. 
 
 Such experiments as these fall far short of giving a 
 demonstration of the existence of molecules : nevertheless 
 they are useful, since they pave the way to a clearer concep- 
 tion of the molecule and of molecular spaces. 
 
 35-41. Chemical Nomenclature. — A useful exercise to 
 precede the study of the nomenclature may be conducted as 
 follows : — 
 
 Ex. 17. Place upon the table, in a promiscuous group, 
 bottles containing acids, bases, and neutral substances, two, 
 three, or more of each. Provide also two cylinders, a solu- 
 tion of blue litmus, and a pitcher of water. 
 
 Nearly fill the cylinders with water, and add litmus enough 
 to give a distinct blue color to both. 
 
 Then proceed to test the effect of each one of the sub- 
 stances by adding a few drops to the litmus. Those which 
 redden the blue color, place together in a group at one side ; 
 those which restore the blue color of reddened litmus, place 
 in a group at the other side ; and those which have no effect 
 upon either the blue or the red litmus, place together in a 
 third group. 
 
256 CHEMISTRY. 
 
 The classification of substances as acids, bases, and 
 neutral bodies, is, in this way, clearly illustrated. 
 
 If you have selected binary compounds, as, for example, 
 water, potassium iodide, mercuric chloride, to represent 
 neutral bodies, you can easily make these an introduction to 
 the study of paragraph 36, by writing their formulas on the 
 blackboard, to show the meaning of the term binary. 
 
 They will be useful again, when you reach the topic " Other 
 Binary Compounds," to illustrate the nomenclature. 
 
 39. Salts. — Ex. 18. Into a beaker put some dilute sul- 
 phuric acid, and drop into this some fragments of zinc. 
 Molent effervescence soon begins, atoms of zinc taking the 
 place of atoms of hydrogen ; and this may be kept up by 
 adding fresh pieces of the metal until the acid is exhausted. 
 
 Ex. 19. Filter the fluid just obtained, while hot, and then 
 allow it to stand quietly until cold. A mass of the white 
 crystalline salt, zinc sulpJiate, will be obtained. 
 
 Ex. 20. Repeat the experiments, using iron in the form 
 of small nails instead of zinc, and the green crystalline salt, 
 ferrous sulpJiate, will be produced. 
 
 Ex. 21. A small piece of sodium may be dropped upon 
 the surface of dilute sulphuric acid. The salt hydro-sodium 
 sidpliate will be formed. 
 
 36-41. A very useful exercise to follow the study of the 
 nomenclature may be conducted as follows : Place upon the 
 table bottles containing substances representing all classes 
 whose names have been studied. Their labels should contain 
 their names only. Let a student be given a bottle, and let 
 him, after reading the name of the substance in it, be asked 
 to state, to what class of compounds it belongs. If a binary, 
 then what are its constituents, and in what proportions, and 
 what is its formula? 
 
 If an acid, then of which class, and what are its constit- 
 uents ? 
 
 If a base, then what are its constituents? 
 
APPENDIX. 257 
 
 If a salt, then from what acid may we consider it to he 
 derived ? By what substitution ? What are its constituents ? 
 
 50. Hydrogren. — In experimenting with hydrogen the 
 greatest care should be taken to have the gas unmixed with 
 air, otherwise unexpected explosions may occur. Before 
 collecting the gas in receivers, all air should be driven out of 
 the apparatus. To know whether the gas is coming off free 
 from air, it may be tested by collecting a test-tube full, and, 
 keeping its mouth downward, apply the flame of a match. 
 If the gas continues to burn quietly after the first slight 
 explosion, it is pure enough. If the explosion is sharper, 
 and no flame at all survives it, the gas is dangerous. 
 
 51. Reaction with Iron. — Ex. 22. Put a few small 
 nails into a test-glass, and cover them with dilute sulphuric 
 acid, made by mixing one part of the acid with three parts 
 of water. Cover the glass with a glass plate. Light a 
 match after the effervescence has gone on rapidly half a 
 minute, and, removing the glass cover, bring the flame to 
 the mouth of the glass. Notice the slight explosion which 
 follows. Perhaps the flame will continue to play above the 
 foaming liquid in the glass. Hydrogen is evolved by the 
 chemical action as follows : — 
 
 Fe" + H2 S O4 = Fe S O4 + Hj. 
 
 The bivalent atom of iron takes the place of two atoms of 
 hydrogen in the molecule of acid. 
 
 52. Lightness of Hydrogen. — Ex. 23. Fill a small jar 
 with hydrogen. Lift it from the cistern of water, and turn 
 its mouth upward. Carry it two or three paces away, and 
 then bring a lighted taper into the jar : no hydrogen wiU be 
 detected. Its quick escape from the jar shows it to be 
 lighter than air. 
 
 Ex. 24. Lift another jar full of hydrogen from the 
 cistern, and keep its mouth downward while it is carried 
 
258 CHEMISTRY. 
 
 away in the same manner. Bring a lighted taper to its 
 mouth : the hydrogen takes fire, showing that the gas has 
 remained in this inverted jar, proving again that it is lighter 
 than air. 
 
 Ex. 25. Hydrogen Soap-Biibbles. — Remove the deliv- 
 ery tube of the hydrogen-generator (Fig. 23) from the cistern, 
 and attach it to the stem of a tobacco-pipe by rubber tubing. 
 Having the soap solution in a capsule, dip the bowl of the 
 pipe into it in the usual way, and let the gas, as it comes 
 over from the bottle, blow the bubble. While the bubble is 
 still small, turn the mouth of the pipe upward. The bubble, 
 having attained a diameter of three or four inches, will 
 break away, or else it may be easily detached by a sudden 
 movement of the pipe downward. It will then rise rapidly. 
 
 53. Explosive Bubbles. — Ex. 26. Cover the bottom of 
 a dinner-plate with the bubble solution. Place the mouth 
 of the pipe in the solution, slowly moving it from place to 
 place, until a number of small bubbles rest upon the surface. 
 Remove the pipe, and shortly afterward touch the bubbles 
 with the flame of a match, which for this purpose may be 
 tied upon the end of a long wire handle. 
 
 Air passes through the thin film, and mixes with the gas to 
 form the explosive mixture. 
 
 Ex. 27. The explosive character of such a mixture may 
 also be shown as follows : — 
 
 Into a wide-mouthed bottle put some fragments of zinc, and 
 just cover them with water. Select a thin cork, which fits 
 the bottle not too tightly, and make a hole through it large 
 enough to admit a match easily. Take a long wire, and bend 
 it near one end at right angles to itself. Bind a match upon 
 this short bend of the wire. All this having been arranged, 
 pour enough sulphuric acid into the bottle to liberate hydro- 
 gen with some rapidity. Insert the perforated cork, and wait 
 about half a miuute. Then fire the match, and by means of 
 its wire handle insert its flame into the perforation of the 
 
APPENDIX. 259 
 
 cork. A violent but harmless explosion instantly follows, 
 ejecting the cork from the bottle. 
 
 Ex. 28. Put a quantity of the soap-bubble solution into 
 the hand, held slightly cup-shaped to retain it. Let the gas 
 from the hydrogen bottle blow a bubble on this solution, as 
 it did on the solution in the plate, Ex. 26. Remove the pipe, 
 and touch the bubble with a match or taper flame, held in 
 readiness by an assistant. An explosion follows, while the 
 hand on which it occurs scarcely feels the slightest jar. 
 "When occurring in open air the explosion expends its 
 violence in sound ; when confined, the exploding mixture 
 shatters the vessel which holds it, as would a charge of 
 gunpowder. 
 
 57. Chlorine. — Chlorine is such a peculiarly suffocating 
 gas, that great care should be taken to prevent its escape into 
 the room. All joints in the apparatus should be perfectly 
 air-tight. The receivers should not be filled quite to the 
 brim with the gas. In changing the delivery-tube from one 
 vessel to another, the transfer should be made as quickly 
 as possible. The vessels of gas should be kept covered. 
 Bottles of white glass are very good chlorine receivers, 
 because they can be tightly closed with a cork until the gas 
 is to be used. 
 
 If a little strong sulphuric acid is put into the bottle, so 
 that the gas must bubble through it, the chlorine will be 
 dried thereby : this is a point of importance in some 
 experiments. 
 
 Ex. 29. Chlorine may be easily prepared, and in suflfl- 
 cient purity for some purposes, by covering the bottom of a 
 jar or bottle with bleaching-powder, and adding a little 
 sulphuric acid. 
 
 58. Solubility of Chlorine. — Ex. 30. Provide a bot- 
 tle with a perforated corlf, through which passes a short 
 piece of glass tube, or even a piece of pipe-stem. Fill the 
 bottle about one-third full of water, and the remaining two- 
 
260 CHEMISTRT. 
 
 thirds with chlorine from the apparatus in Fig. 29. Close 
 the bottle with its cork tightly. Cover the end of the tube 
 with the finger closely, then shake the whole violently for a 
 few moments, and afterwards insert the tube in a vessel of 
 water, and remove the finger. Water will be seen to rise into 
 the bottle to supply the place of the gas which has been 
 dissolved. 
 
 59. Chemical Properties. — Ex. 31. Tie a small tuft 
 of cotton on the end of a wire, and wet it with ether. Set it 
 on fire, and lower it into a jar of chlorine. The combustion 
 will continue, with much smoke. 
 
 The chlorine combines with the hydrogen of the ether^ 
 but not with its carbon, which is therefore set free. 
 
 Ex. 32. Bleaclilng. — • Into a bottle of chlorine pour a 
 little litmus solution : cork the bottle, and shake it ; the color 
 of the litmus is discharged. 
 
 Ex. 33. Black, or other colored ink, may be used instead 
 of litmus solution. 
 
 Ex. 34. Moisten a piece of paper containing ordinary 
 writing, such as a part of a letter, and hang it awhile in a 
 jar of chlorine. The writing will disappear. 
 
 Ex. "35. Try the experiment with a piece of newspaper 
 or other printed paper. Notice that the characters are not 
 destroyed. The coloring matter of printer's-ink is carbon, 
 for which chlorine has little attraction. 
 
 Ex. 36. Insert a rose, or other colored blossom, in a jar 
 of moist chlorine : it wiU be speedily bleached. 
 
 62. Iodine. — Ex. 37. Put a few crystals of iodine into 
 d clean and dry flask, and gently heat it : notice the fine violet 
 vapor. 
 
 Ex. 38. Solubility of Iodine. — When the flask is 
 sufficiently cool, pour water in, to fill it two-thirds full. 
 Shake it vigorously, and notice the brownish-yellow color 
 imparted to the water. Iodine is very slightly soluble in 
 water ; 1 part of iodine requires 7,000 parts of water. 
 
APPENDIX. 261 
 
 Ex. 39. Pour off this solution (iodine-water), and put 
 a little alcohol into the flask. 'Notice the deep reddish- 
 brown color which the liquid quickly assumes. Iodine is 
 very soluble in alcohol. A solution of iodine in alcohol is 
 called "tincture of iodine." It is used for medicinal pur- 
 poses. 
 
 Ex. 40. Test for Iodine. — Boil a little starch in a 
 beaker of water, and pour some of the liquid into a jar of 
 water. Then add a few drops of ' ' iodine-water, ' ' and notice 
 the fine deep-blue color produced. This result is a very 
 delicate test for the presence of free iodine. 
 
 71. Oxygen. — Certain precautions should be observed 
 in preparing oxygen (Fig. 36). The materials should be 
 dry and well powdered. The heat should be applied gently 
 at first, and afterward so regulated that a steady and not too 
 rapid stream of gas will be evolved. It will often be neces- 
 sary to withdraw the flame altogether, and restore it again 
 when the stream of gas slackens. 
 
 The end of the delivery-tube must be taken out of the 
 water before the gas whoUy ceases to issue, else, as the flask 
 cools, atmospheric pressure forces water over into the hot 
 flask, which may be then blown to pieces by the sudden evo- 
 lution of steam within. 
 
 The quantity of material needed may be estimated by 
 remembering that about two gallons of gas will be obtained 
 from an ounce of potassium chlorate. 
 
 When large quantities of oxygen are desired, metallic flasks 
 must be used instead of glass flasks, which are too frail. 
 
 Ex. 41. Fold a piece of tough paper into a narrow band. 
 Bend this band around the upper part of a hard glass test- 
 tube, and grasp both branches of it between the thumb and 
 finger. The tube is thus provided with a convenient handle. 
 
 Put about a quarter of an inch of finely powdered potas- 
 sium chlorate into the tube, and apply heat. The chlorate 
 will first melt, and afterward appear to boil. Then insert a 
 
262 CHEMISTRY. 
 
 lighted match into the mouth of the tube, and notice that the 
 vigor of its combustion is increased. Let the charred end oi 
 the match, with a spark upon it, fall upon the fused mass at 
 the bottom, and notice the brilliant deflagration which fol- 
 lows. The chlorate is decomposed by heat, yielding oxygen. 
 
 72. Ex. 42. Oxygen heavier than Air. — Having 
 two small jars of oxygen, stand one of them with its open 
 mouth upward, and leave it uncovered ; and the other with its 
 open mouth downward, and with its edges resting ou blocks to 
 support it above the table. Then test the jars by bringing a 
 lighted taper into each. It will be found that the taper burns 
 more brilliantly in that which has been standing mouth 
 upward, but is not affected by the other. Evidently the 
 oxygen has fallen out of the latter. Both jars, equally, 
 show that this gas is heavier than air. 
 
 73. Brilliant Combustion. — Ex. 43. Take a piece 
 of crayon, and provide for it a long wire handle, so that it 
 may be lowered into a jar of gas. This may be done by 
 winding one end of the wire two or three times spirally 
 around the crayon. Scoop out the upper end of the crayon, 
 making a little cup. Into this cup put a piece of camphor. 
 Set fire to the camphor, and quickly lower it into a jar of 
 oxygen : it wiU burn with intense white light. 
 
 Ex. 44. Combustion of Zinc. — Cut a long and narrow 
 strip from a sheet of zinc, and coil it by wrapping it spirally 
 around a lead-pencil. Eemove the pencil, and wind one end 
 of the strip of zinc with thread, and immerse this in melted 
 sulphur. Next set fire to this sulphur, and thrust it down 
 into a jar of oxygen. The burning sulphur will heat the 
 zinc, which will quickly take fire, and burn brilliantly. 
 
 75. Ozone. — To prepare the test-paper for ozone, take 
 two hundred cubic centimeters of water, and add one gram 
 of potassium iodide. "When solution is complete, add ten 
 grams of finely powdered starch, and heat gently until the 
 
APPENDIX. 263 
 
 fluid is thicliened by the starch. Let narrowstrips of paper 
 be drawn through this mixture. The paper may be dried, and 
 .fept for a long time in closely stoppered bottles ; but it must 
 be moistened when used. 
 
 Heat the glass rod quite too hot to be handled. 
 
 "When phosphorus is used, for the preparation of ozone, let 
 the stick be first held under water while its surface is gently 
 scraped : this cleaning of its surface is necessary if the phos- 
 phorus has been long exposed to light, and is thereby covered 
 with red coating. 
 
 80. Water as a Solvent. — Ex. 46. Fill a test-tube, 
 or small beaker, about half full of water ; sprinkle into 
 it a small quantity of finely powdered copper sulphate, and 
 shake or stir it vigorously. The blue salt will impart its own 
 color to the water ; and, if too much has not been added, the 
 solid wiU wholly disappear. A blue transparent liquid 
 remains : this is a solution of copper sulphate. 
 
 Ex. 46. To the solution just made, if it be quite trans- 
 parent, add a little more of the salt, and again agitate it. 
 Eepeat this operation, if necessary, until the last portion 
 added remains undissolved. The clear blue liquid is then a 
 saturated cold solution of copper sulphate. 
 
 Ex. 47. Apply the heat of a lamp-flame to the vessel 
 containing the saturated cold solution. It will be found that 
 the undissolved sulphate in the bottom will disappear. Then 
 add more : in a little time that too will be dissolved, showing 
 that heat increases the solubility of copper sulphate. 
 
 Ex. 48. Continue to add the powdered sulphate to the 
 hot liquid until it, at length, refuses to dissolve. The quan- 
 tity to be added may be surprising ; but finally the liquid will 
 take no more, and then it is said to be a saturated hot 
 solution. Let it stand untU cold. 
 
 82. Filtration. — Ex. 49. Into a small beaker of water 
 put enough of the copper sulphate solution, obtained above, 
 to give a slight, but distinct, blue tint ; and then add some 
 
264 CHEMISTRY. 
 
 solution of potassium ferrocyanide. as long as the precipitate 
 is increased by the addition. Notice the abundant dark- 
 brown precipitate suspended in the liquid. Treat this fluid 
 as described in paragraph 82. Fig. 44. A clear and colorless 
 liquid falls into the bottle. 
 
 Ex. 50. Distillation. — A small quantity of water may 
 be distUled in the apparatus represented in Fig. 50. Let 
 water be poured in until the retort is nearly half full, and then 
 heat it to boiling. Keep the flask, into which the beak of the 
 retort is thrust, cold by a stream of cold water, as repre- 
 sented, or by pouring cold water from a pitcher. The 
 distilled water wUl collect in the flask. 
 
 91. Eflfects of Heat on Sulphur. — The statements 
 made in the text may be very easily verified in the manner 
 described. Apply the heat carefully, and raise the tempera- 
 ture gradually. 
 
 92. Crystals by Solution. — Ex. 51. If the hot satu- 
 rated solution of copper sulphate be examined when cold, a 
 mass of blue crystals will be found. The clear blue liquid 
 which remains, is a cold saturated solution, and the crystals 
 are the excess which hot water can dissolve. If merely 
 warm water instead of boiling water be used, this excess will 
 be smaller, and the crop of crystals, on cooling, wUl be also 
 smaller. In this case they will be more distinctly defined. 
 
 Ex. 52. Make a warm saturated solution of mercuric 
 chloride. On cooling, it will deposit a crop of needle-shaped 
 crystals. 
 
 Ex. 53. Make a warm saturated solution of potassium 
 nitrate. On cooling, fine prismatic crystals will appear. 
 
 Ex. 54. Dissolve a little copper chloride in alcohol, 
 making a saturated solution. Pour this solution over a per- 
 fectly clean glass plate, and let the excess run off, leaving 
 only a film upon the surface. In a few moments a beautiful 
 crystallization will begin, and spread rapidly over the plate. 
 , Ex. 55. Use a saturated solution of ammonium chloride in 
 
APPENDIX. 265 
 
 water, to flow over the plate. Then gently warm the glass 
 over the lamp, and afterward watch the growth of crystals. 
 
 93. Sulphur and Iron. — Ex. 56. Mix very intimately 
 four grams of sulphur with seven grams of the finest iron- 
 filings, and put the mixture into an ignition-tube, that is, a 
 test-tube made of hard glass. Then apply heat to the lower 
 end of the tube. Shortly the mixture will begin to glow, on 
 account of the chemical action between the sulphur and the 
 iron. After the action has well started, withdraw the tube 
 from the flame, and the ignition will continue until the con- 
 tents have been completely changed into iron sulphide. 
 
 98. Precipitates by Sulpliiiretted. Hydi-ogen. — Ex. 
 
 57. Into one test-glass put a dilute solution of copper sul- 
 phate, into a second put a dilute solution of arsenious oxide, 
 and into a third put a dilute solution of zinc sulphate. Add 
 a few drops of hydrochloric acid to the first two solutions, 
 and some ammonia to the third. Finally, add to each some 
 of the solution of sulphuretted hydrogen, made in the way 
 represented by Fig. 47. 
 
 In the first will appear a black precipitate of copper sulphide, 
 In the second " " yellow " arsenious sulphide, 
 
 In the third " " white " zinc sulphide. 
 
 103. Nitric Acid an Oxidizing Agent. — Ex. 58. Take 
 a piece of tin-foil, about two inches square, fold it loosely, 
 and place it in a porcelain cup or small beaker. Then add a 
 small quantity of nitric acid. Very soon a violent action 
 will begin, resulting in volumes of red fumes, which escape 
 into the air, and a moist white powder in the dish. This 
 white powder is the tin oxide into which the tin has been 
 converted by the acid. 
 
 105. Sulphuric Acid and Water. — In mixing strong 
 sulphuric acid and water, always pour the acid into the 
 water, never the water into the acid. The fluid should be 
 constantly stin-ed while the acid is being added. 
 
266 CHEMISTKY. 
 
 111. Preparation of Nitrogen. — Ex. 59. Let the top 
 
 of a cork be made slightly concave with a sharp knife, and 
 then let it be thoroughly rubbed with powdered crayon or 
 chalk. Cut from the end of a stick of phosphorus under 
 water a piece as large as a small pea, and dry it completely 
 by very gently pressing it for a moment between the folds of 
 a piece of blotting or filter paper. Place the prepared cork 
 on the water over the shelf of the cistern, and lay the phos- 
 phorus upon it. Next touch the phosphorus with a hot wire, 
 and immediately invert over it a gallon jar. See Fig. 49, and 
 the text accompanying it. 
 
 It will be well to have a jar of the gas prepared before- 
 hand, with which to illustrate the properties of the gas. This 
 will obviate the necessity of waiting for the absorption of the 
 phosphoric vapors. 
 
 Ex. 60. Lightness of Nitrogen. — Fill a small jar with 
 the gas, slip a glass plate under its mouth, and lifting it from 
 the water, keeping its mouth downward, thrust a lighted 
 taper up into it. The flame will be extinguished. 
 
 The result not only shows that nitrogen will not support 
 combustion, but also that it is lighter than air. 
 
 Ex. 61. Fill the jar again, and, slipping the glass plate 
 under it as before, lift it from the water, place it mouth 
 upward on the table, and remove the plate. Leisurely light 
 a taper, and finally thrust it into the jar. The flame will not 
 be extinguished this time, which shows again that nitrogen is 
 lighter than air. 
 
 126. Nitrous Oxide. — Ex. 62. Having filled some 
 small jars with nitrous oxide, by the experiment described in 
 connection with Fig. 51, remove one to the table, on which 
 let it stand mouth upward. Slide its cover to one side, and 
 insert a lighted taper. The flame instantly enlarges, con- 
 tinues with vigor, and is surrounded by a hazy envelope. 
 
 Ex. 63. Lower into another jar of the gas a combustion- 
 spoon, containing a bit of ignited phosphorus, and notice 
 
APPENDIX. 267 
 
 that the combustion will proceed with almost as great bril- 
 liancy as in oxygen. 
 
 127. Nitric Oxide Ex. 64. Remove a small jar of 
 
 this gas to the table, and plunge a lighted taper into it : the 
 flame will be extinguished. 
 
 Ex. 65. Place a bit of phosphorus in a combustion- 
 spoon, and ignite it. When the combustion is well started, 
 plunge the phosphorus into a jar of nitric oxide : the phos- 
 phorus will continue to burn with great brilliancy. 
 
 129. Nitric Peroxide. — Ex. 66. Let a jar be about 
 half filled with nitric oxide, and place it so that its mouth 
 projects over the edge of the shelf on which it stands in the 
 cistern. Pour air from another small jar up into it, and 
 notice the cherry-red vapor which instantly appears. The 
 greater part of this red vapor is nitric peroxide. 
 
 Or the jar containing the nitric oxide may be simply lifted 
 a little to let air bubble under one edge into it. The red 
 vapors will increase with every bubble. 
 
 137. DifFiision of Liquids. — Ex. 67. Make the ex- 
 periment represented by Fig. 43, and mark the height of 
 the vial in the jar. Then leave the whole standing quietly 
 for twenty-four hours, and notice that the vial stands higher. 
 The salt water has diffused upward, lifting the vial with it. 
 
 Ex. 68. Osmose of Liquids. — Fill a wide-mouthed vial 
 with a strong solution of potassium chromate, and tie a piece 
 of bladder over it, so as to close it completely. The vial 
 should be full, and the bladder in contact with the fluid ; but 
 not the least portion of the solution should be on the outside. 
 Stand this bottle on the bottom of a large beaker, and then 
 nearly fill the beaker with water. Let the apparatus stand 
 for twenty- four hours, when it will be found that the water is 
 colored throughout, showing that the salt has passed through 
 the membrane, to diffuse through the fluid outside. 
 
 Other salts may be treated in the same way, and their dif- 
 fusion through the membrane compared. 
 
268 CHEMISTEY. 
 
 141. Phosphorus. — Phosphorus should never be handled 
 without the greatest care being taken to guard against 
 igniting it. Handle it with forceps, and cut it when under 
 water. 
 
 Ex. 69. Phosphorescence. — Place a clean stick of 
 phosphorus in a dark room : it will emit a pale, pearl-like 
 light. If the phosphorus is old, and covered with a red 
 coating, it should first be immersed in water-, and the red 
 surface removed by scraping, to expose the translucent sub- 
 stance beneath. 
 
 Ex. 70. Solubility in Ether. — Put a little ether into 
 a small vial, aud add a few small pieces of phosphorus. 
 Allow it to stand, shaking it occasionally, for several hours. 
 Much or the whole of the phosphorus will dissolve. 
 
 Ex. 71. Attraction for Oxygen. — Expose a clean 
 stick of phosphorus to the air, and notice the clouds of white 
 vapor which fall away from it. Phosphorus and oxygen 
 combine at ordinary temperature to form this phosphorus 
 oxide. 
 
 Ex. 72. Saturate a strip of filter or blotting paper with 
 the solution of phosphorus in ether, made in Ex. 70, and hang 
 it conveniently exposed to air. The ether soon evaporates ; 
 and then the phosphorus combines with oxygen of the air, 
 yielding clouds of white vaipor, and sometimes evolving heat 
 enough to set the paper on fire. 
 
 Ex. 73. Fire in Water. — Cover the bottom of an ale- 
 glass or a test-glass with potassium chlorate, and add a small 
 piece of phosphorus. Let water be introduced, enough to fill 
 the glass two-thirds full. Next fill a pipette with strong sul- 
 phuric acid ; close the top of it with the finger, and thrust the 
 lower end into the water, and down upon the chlorate. Then 
 remove the finger, and allow some of the heavy acid to flow. 
 The acid decomposes the chlorate, and liberates chlorine per- 
 oxide. This is immediately decomposed by the phosphorus, 
 which takes its oxygen, and enters into a brilliant combus- 
 tion m the water. 
 
APPENDIX. 269 
 
 153. Arsenic Compounds. — Ex. 74. Powder some 
 arsenious oxide, As^ O3, and heat it with water in a beaker. 
 It is quite soluble in hot water. Saturate the hot solution, 
 and then allow it to cool quietly. Crystals of arsenious 
 oxide will be deposited, showing that this substance is less 
 soluble in cold water. 
 
 Test the solution with litmus paper : it is an acid solution. 
 The As, O3 is therefore an anhydride. 
 
 Ex. 75. Arsenious Oxide is Volatile. — Take a piece 
 of glass tubing, about eight inches in length and three- 
 sixteenths of an inch in diameter ; hold its middle part in a 
 gas-flame, turning it constantly to heat aU sides equally, and 
 when it softens pull it apart. Two short tubes, closed at one 
 end, are thus obtained. 
 
 Into one of these tubes drop a very little arsenious oxide 
 to the bottom, and apply a gentle heat. The arsenious oxide 
 will soon leave the bottom of the tube, and afterward will be 
 found, as a ring of white crystals, in the upper cold parts ol 
 the tube. 
 
 Ex. 76. Sclieele's Green. — Put some of the arsenic 
 solution into a test-glass containing water. Next prepare 
 some ammonio-copper sulphate, as follows : To a dilute 
 solution of copper sulphate add ammonium hydrate until th<» 
 blue precipitate which is at first formed is again dissolved. 
 The rich blue solution is the ammonio-copper sulphate. Add 
 this solution, little by little, to the arsenical solution, and 
 Qotice that a fine green precipitate is produced. This is 
 Scheele's green, or copper arsenite. 
 
 Ex. 77. Reinsch's Test. — Add some of the arsenical 
 solution to a test-glass of water, and add also a drop or two 
 of hydrochloric acid. Next insert a piece of bright copper 
 wire. In a little while the copper will be found to be cov- 
 ered with a dark gray coating. The copper decomposes the 
 arsenical compound, and arsenic itself is deposited upon it. 
 
 166. Carbon Oxide. — The preparation of this gas may 
 
270 CHEMISTRY, 
 
 be accomplished with an apparatus fitted up as shown in Fig. 
 29, except that the delivery-tube should reach over to the 
 water-cistern, so that the gas may be collected over water. 
 
 Ex. 78. Put about one hundred and eighty grains of 
 finely powdered potassium ferrocyanide into the flask, and 
 add about ten times this weight of strong sulphuric acid. 
 Then cork the flask, and apply heat. The gas will be given 
 off abundantly ; and, after the air has been driven out of the 
 apparatus, several small jars or wide-mouthed bottles may be 
 filled with it. 
 
 Ex. 79. Its blue Flame. — Lift a jar from the cis- 
 tern, keeping its mouth downward, and thrust up into it the 
 flame of a taper. The taper will be extinguished on entering 
 the gas, but the gas will itself take fire, and burn with a blue 
 flame. 
 
 Ex. 80. liighter than Air. — Lift another jar of the 
 gas, and turn its mouth upward. Then introduce the flame 
 of the taper : no combustion of gas follows, showing that 
 it has escaped upward. 
 
 167. Carbon Dioxide. — There is a more simple method 
 of obtaining carbon dioxide than that described in the text, 
 which will be good enough for some purposes. Thus : — 
 
 Ex. 81. — Cover the bottom of a jar, or wide-mouthed 
 bottle, with sodium carbonate, or with small fragments of 
 marble, and pour a little hydrochloric acid upon this material. 
 Vigorous effervescence occurs : carbon dioxide is set free. 
 It lifts the air, and finally itself fills the jar. 
 
 Ex. 82. It extinguishes Flame. — Insert into the jar 
 containing the gas the flame of a taper: it is instantly 
 extinguished. 
 
 X85. Organic Substances. — Ex. 83. Take a piece of 
 common paper, and roll it into the form of a compact ball 
 the size of a small nut. Drop this to the bottom of a test- 
 tube, and heat it in the lamp-flame. The paper will give off 
 white vapors, and a brownish liquid will condense on the 
 
APPENDIX. 271 
 
 upper and cold parts of the tube ; but notice particularly that 
 the paper becomes black. When no more vapors arise, 
 remove the black mass from the tube, and notice that it is brit- 
 tle, and in all other respects shows the properties of carbon. 
 
 The experiment proves that carbon is a constituent of this 
 organic substance. 
 
 Ex. 84. Put about two inches of thick sirup of sugar 
 into a cylinder, and stir into it a nearly equal volume of 
 concentrated sulphuric acid, or " oil of vitriol." The acid 
 decomposes the sugar, removes its hydrogen and oxygen, 
 but leaves its carbon. Notice the bulky, coal-black residue. 
 Carbon is a constituent of this organic substance also. 
 
 Ex. 85. Burn a bit of camphor, and hold a white plate in 
 its flame. Notice the large deposit of carbon in the form of 
 soot. Camphor is an organic substance, and carbon is one 
 )f its constituents. 
 
 187. Marsh-Oas. — Ex. 86. Marsh-gas may be prepared 
 with the apparatus represented In Fig. 5. The ignition- tube 
 should be about eight inches long. It should be charged with 
 as much as needed of a dry powder, made by mixing two 
 grams sodium acetate, four grams caustic soda, and eight 
 grams slaked lime, and gently heating on a plate until the 
 water of crystallization of the acetate is wholly driven off. 
 The tube is then to be heated. The gas wUl be collected in 
 the first flask. 
 
 Na C2H3O2 -f- Na H O = Na^ C O3 + C H^.' 
 
 The lime is used to render the mixture porous, and prevent 
 its fusion. 
 
 Ex. 87. If a larger quantity of the gas is desired, the 
 experiment may be made with the apparatus shown in Fig. 
 48. A larger quantity of the mixture of acetate, hydrate, 
 and lime, is placed in the retort, and the gas is collected over 
 water in the cistern. 
 
 When experiments are to be made with the gas, this 
 
272 chemisj.'K1. 
 
 method of preparation is better than that given above. 
 Several small bottles may be filled for examination. 
 
 Ex. 88. Lift a bottle of marsh-gas from the cistern, 
 keeping its mouth downward, and bring a lighted taper 
 beneath it. The gas takes fire, and burns with a yellow 
 flame. 
 
 Ex. 89. Lift a bottle of the gas from the water, turn its 
 mouth upward, and, a moment or two afterward, insert a 
 lighted taper. No combustion of the gas follows. The gas 
 has escaped, showing its lightness. 
 
 Ex. 90. Lift a bottle of the gas from the cistern, and, 
 holding a lighted taper in the other hand, turn the bottle 
 mouth upward just under the flame. The gas rising out of 
 the jar comes in contact with the flame, and burns. 
 
 191. Alcohol. — Ex. 91. Dissolve ten grams of honey 
 in a liter of water,. and add a little brewer's-yeast. Fill a 
 small flask with the solution. Close the flask, and invert it 
 in a dish containing enough of the same sirup to cover the 
 mouth of it. Open it, and leave it standing in a warm place 
 for twenty- four hours. Notice then that a colorless gas has 
 collected in the upper part of the flask. 
 
 Ex. 92. Cork the flask while its mouth is still under the 
 surface of the sirup : then lift it away, and place it upright 
 on the table. The gas will now be in the neck of the flask. 
 Remove the cork carefully, and insert the flame of a match 
 or taper : it will be instantly extinguished. This, together 
 with the fact that it is heavier than air, as shown by its 
 remaining in the open flask, shows that it is carbon dioxide. 
 
 Ex. 93. Taste the fluid in the flask : it will be found to 
 have the flavor of alcohol. 
 
 Ex. 94. Close the flask with a cork provided with a 
 delivery-tube, such as may be seen represented in Fig. 59 ; 
 but instead of letting the end of the tube dip into water, as 
 there shown, let it pass into a second small flask resting on 
 the water. Then apply heat, as in the figure, and keep the 
 
APPENDIX. 273 
 
 second flask cold by means of water. At a temperature of 
 about 90° C. the dilute alcohol will distill over, and be con- 
 densed in the second flask. 
 
 194. Ether.— Ex. 95. Upon a plate first pour water 
 enough to well cover the bottom, and then carefully pour 
 ether upon one edge of the liquid, letting no drops fall out- 
 side the plate. The ether will spread over the surface of the 
 water. Next touch a match-flame to the surface at one edge, 
 and notice the instantaneous ignition. The flames will con- 
 tinue until the ether is all burned away. This shows very 
 prettily that ether is lighter than water, and very combustible. 
 
 Ex. 96. Pour two or three cubic centimeters of ether 
 into a wide-mouthed bottle or tumbler, and cover it loosely. 
 After a few moments remove the cover, and apply the flame 
 of a match. The vapors of ether will take Are, and burn 
 with a flash. Hence ether is very volatile, and its vapors are 
 heavier than air. 
 
 Ex. 97. Pour a few drops of ether on the bulb of 
 apparatus (Fig. 1), and notice the rise of the liquid in the 
 tube below. The rapid evaporation of the ether absorbs 
 heat, and cools the bulb and the air within. 
 
 196. Oleflant Gas. — Ex. 98. For the preparation of 
 this gas, the apparatus shown in Fig. 36 may be used. The 
 flask should be large : one holding a liter may be used with 
 the following quantity of materials, but in any case it should 
 not be more than one-third full. Into the flask put fifty 
 cubic centimeters of alcohol, and add two hundred cubic cen- 
 tuneters of strong sulphuric acid. Shake the mixture well, 
 and then place the cork in the neck of the flask, and apply a 
 gentle heat. The chemical action quickly begins. Ether is 
 set free at first, but ethylene soon takes its place. Hence the 
 first portions of gas may be allowed to escape before the 
 receiver is brought over the end of the delivery-tube to catch 
 the ethylene. 
 
 Watch and regulate the beat, so that the liquid may not 
 
274 CHEMISTRY. 
 
 froth up too much in the flask, and do not keep the operation 
 going too long, since sulphurous acid is produced in the last 
 stages of the reaction. 
 
 Ex. 99. Lift a jar of the gas from the cistern, mouth 
 downward, and thrust a lighted taper up into it: the gas 
 takes fire at the mouth of the jar, and burns with a bright 
 flame. Turn the jar mouth upward while the gas is burn- 
 ing, and the flame will be fed by the gas escaping upward. 
 It is a little lighter than air (.978). 
 
 227. Flame Tests for Potassium and Sodium. — Ex. 
 
 100. Bend the end of a platinum wire into a loop, moisten 
 it, and gather some powdered potassium compound, as potas- 
 sium chloride, upon it, and then thrust it into the edge of a 
 colorless gas-flame, or even of an alcohol-flame. Notice the 
 fine violet color imparted. 
 
 Ex. 101. Clean the platinum wire, and use it again in the 
 same .way, with some compound of sodium, — sodium chloride 
 for example, — and notice the rich yellow color imparted to 
 the flame. 
 
 Ex. 102. Make a strong solution of sodium chloride in 
 alcohol. Fix a small tuft of cotton on the end of a wire, 
 and wet it with this solution. By touching a match-flame to 
 the tuft, a fine, large flame will be produced, which shows the 
 yellow color to good advantage. 
 
 233. Lime- Water. — Ex. 103. Into a bottle of clear 
 water put a small quantity of lime, and shake it thoroughly. 
 A little of the lime will dissolve. Pour the milky liquid upon 
 a filter : the clear and colorless filtrate is lime-water. 
 
 235. Calcium Carbonate. — Ex. 104. Fill a test-glass 
 one-fourth full of lime-water, and dilute it with an equal 
 quantity of water. Pass carbon dioxide through this solu- 
 tion, by means of the apparatus. Fig. 69, by putting the end 
 of the delivery-tube into the test-glass. Notice that the fluid 
 soon becomes milky : this is owing to the production of cal- 
 
APPENDIX. 275 
 
 cium carbonate, which is insoluble in water, and appears as a 
 white precipitate. 
 
 Ca (H 0)2 + 002 = CaCOs + HjO. 
 
 Ex. 105. Solubility of the CaCO^ Continue the 
 
 stream of carbon dioxide, and after a time notice that the 
 whiteness of the liquid is diminished. Indeed, after a while 
 the solution may become again quite clear. The carbonate 
 which formed at first is dissolved. 
 
 Ex. 106. To restore the Carbonate. — Put this clear 
 solution of the carbonate in a flask, and boil it for some time. 
 Notice that it becomes turbid again. The carbon dioxide is 
 driven away by the heat, and the water can no longer hold 
 the carbonate in solution. Hence it re-appears. 
 
 Ex. 107. A Class-Test for the Group. — Prepare 
 three test-glasses, one with a solution of calcium chloride, 
 another with strontium chloride, and the third with barium 
 chloride. Into each pour a little ammonium carbonate. 
 Notice that a white precipitate at once forms. The com- 
 pounds of these metals behave alike toward ammonium 
 carbonate : they are converted into carbonates, which are 
 precipitated. 
 
 Ex. 108. The Flame-Tests. — Prepare a strong solu- 
 tion of each, barium chloride, strontium chloride, and cal- 
 cium chloride. Soak a piece of pumice in each, and then 
 with a pair of forceps hold them, successively, in the color- 
 less gas-flame. The barium compound yields a delicate 
 green flame ; the calcium compound, a pale rose-red ; and 
 the strontium compound, a fine crimson. 
 
 237. To precipitate Aluminium Hydrate. — Ex. 109. 
 Prepare a solution of aluminium sulphate or of alum in a 
 test-glass, and add ammonia, little by little. A gelatinous 
 white precipitate falls: this is the aluminium hydrate, 
 Alj (H 0)6. 
 
 Ex. 110. Canmine Lake. — Boil a little cochineal in 
 
276 CHEMISTRY. 
 
 a small flask of vpater until the coloring matter is extracted. 
 Filter this solution into a test-glass, or beaker. Add to this 
 colored water about an equal volume of aluminium sulphate 
 or alum. Finally add ammonia. A colored precipitate is at 
 once produced, which, on settling, leaves the solution quite 
 or nearly colorless. 
 
 The ammonia precipitates the aluminium hydrate as in the 
 preceding experiment. But this hydrate has a strong attrac- 
 tion for the coloring matter of the cochineal, and carries it 
 along with itself. The colored precipitate is called Carjiine 
 Lake. 
 
 Ex. 111. Other Lakes. — Almost any other organic 
 coloring matter may be used instead of the cochineal. A 
 colored precipitate will be produced: all such are called 
 Lakes. 
 
 It is this power of aluminium hydrate to precipitate color- 
 ing matter, that renders aluminium sulphate and alum useful 
 in the arts of dyeing and calico-printing. 
 
 240. Compounds of Iron. — Iron forms two large and 
 important classes of compounds, called respectively the 
 Ferrous compounds and the Ferric compounds. 
 
 Ex. 112. The Ferrous Hydrate. — Boil a little water 
 in a beaker, to expel its dissolved air, and then dissolve in 
 it a few small crystals of ferrous sulphate (green vitriol). 
 Select those which are green, without white spots. Into 
 another beaker put a little solution of potassium hydrate, 
 and boil it also, to expel the air which it holds in solution. 
 Finally pour the two solutions together, and notice the pro- 
 duction of a copious white or greenish- white precipitate : this 
 is ferrous hydrate^ Fe (H 0)2. When pure, it is white : in 
 presence of air, it becomes green. 
 
 Ex. 113. The Ferric Hydrate. — Malfe a solution of 
 ferrous sulphate in water, add a few drops of strong nitric 
 acid, and then heat to the boiling-point. Finally add 
 potassium hydrate. Instead of the whitish-green precipitate 
 
APPENDIX. 277 
 
 obtained before, a copious red-brown precipitate is produced : 
 this is the ferric hydrate, Fej (H 0)6. 
 
 The nitric acid changed the ferrous into the ferric sulphate. 
 
 Ex. 114. Test for Ferrous Compounds. — Select a per- 
 fect blue-green crystal of ferrous sulphate, and dissolve it in 
 recently boiled water. Divide the solution into two parts. 
 To one part add a little potassium ferrocyanide, and notice 
 the pale-hlue precipitate which appears. 
 
 To the other part add a little potassium ferricyanide, and 
 notice the fine dark-blue precipitate of ferrous ferricyanide. 
 
 Pale-blue precipitates with ferrocyanide, and dark-blue 
 precipitates with ferricyanide, are given by the ferrous com- 
 pounds, 
 
 Ex. 115. Test for Ferric Compounds. — Add a few 
 drops of nitric acid to a solution of ferrous sulphate, and 
 heat it to boiling, in order to change it into ferric sulphate, 
 and divide the solution into two parts. 
 
 Add to one part a little potassium ferrocyanide, and notice 
 the rich blue precipitate of " Prussian blue " which instantly 
 appears. 
 
 Add to the other part a little ferricyanide, and notice, that 
 while the liquid becomes colored, yet no precipitate is pro- 
 duced. 
 
 Deep-blue precipitates with ferrocyanide, and no precipi- 
 tates with ferricyanide, are given by the ferric compounds. 
 
 Ex. 116. To dye Cloth Blue. — Make a solution of 
 . ferric sulphate by adding a little nitric acid to ferrous sul- 
 phate, and heating the mixture to the boiling-point. In 
 another beaker make a solution of potassium ferrocyanide. 
 Dip a piece of white cotton cloth into the ferric sulphate, and 
 afterward immerse it in the ferrocyanide. Prussian blue will 
 be precipitated upon every fiber of the cloth, and color it 
 permanently blue. 
 
 Prussian blue is largely used in the arts of dyeing and 
 
 calico-printing. 
 Ex. 117. To dye Clotli Black. — Make a weak solution 
 
278 CHEMISTRY. 
 
 of tannic acid in water, in one beaker, and a solution of 
 ferrous sulphate in another. Bring a little of the two 
 together in a test-glass, and notice the dark-colored precipi- 
 tate formed. This precipitate becomes black on exposure to 
 air. It is the ferric tannate. 
 
 Ex. 118. Saturate a piece of cotton cloth in the solution 
 of tannic acid, and let it dry. Immerse the dried cloth in 
 the ferrous sulphate, and hang it up exposed to air. Ferric 
 tannate will be precipitated upon the fibers of the cloth, and 
 dye them black. 
 
 Ex. 119. Tannic Acid in Tea. — Let a few tearleaves 
 be boiled in a small quantity of water. Pour the clear solu- 
 tion into a test-glass, and add a few drops of ferrous sul- 
 phate. The liquid blackens, and on standing it will deposit 
 a precipitate of ferric tannate. 
 
 In the same way one may detect the existence of tannic 
 acid (tannin) in coffee, in the husk of the horse-chestnut, in 
 oak-bark, or in sumach. 
 
 253. Compounds of Lead. — Ex. 120. Into a test-glass, 
 containing strong nitric acid, put some clippings of metallic 
 lead. A violent chemical action soon sets in, with the evolu- 
 tion of volumes of red vapors. The lead is converted into 
 lead nitrate, which remains dissolved in the liquid. 
 
 Ex. 121. Add a considerable quantity of the lead, enough 
 to use up all the acid, and put the test-glass outside the 
 window, so that the fumes may not fill the room, and let the 
 action go on as long as it will. 
 
 The liquid which may be poured off clear, or filtered if 
 necessary, contains the nitrate, which may be used in other 
 experiments. It will be well to make this experiment before- 
 hand, so that the nitrate may be ready for use when wanted. 
 
 Ex. 122. liCad Chloride. — Into a beaker put a tea- 
 spoonful of the nitrate solution, and add one hundred cubic 
 centimeters of water. Then add a little hydrochloric acid, 
 as long as a precipitate forms. This white precipitate is the 
 lead chloride. 
 
APPENDIX. 279 
 
 Ex. 123. Obtained in Crystals. — Heat the beaker until 
 its contents boil, and notice that the chloride dissolves to a 
 clear solution. Then place the beaker aside, where it will be 
 undisturbed, and let it cool. By and by examine it, and 
 notice the needle-shaped crystals of chloride which have been 
 deposited. 
 
 This compound is very soluble in hot water, slightly in cold 
 water, and the excess crystallizes. 
 
 Ex. 124. Lead Iodide. — Into a beaker containing water 
 put another small portion of the lead nitrate solution, and 
 add to this, drop after drop of potassium iodide. Each drop 
 produces an additional quantity of the rich yellow precipitate 
 of Lead Iodide. 
 
 Ex. 125. Obtained in Crystals. — Add a few drops of 
 hydrochloric acid to the contents of the beaker, and heat to 
 boiling. The iodide dissolves. Stand the beaker in cold 
 water, or let a stream of cold water run upon it to hasten its 
 cooling, and watch the result. The iodide separates from 
 the liquid ; and, on holding the beaker up to the light, multi- 
 tudes of brilliant crystalline 'scales will be seen reflecting all 
 the colors of the rainbow. 
 
 Ex. 126. Lead Chromate. — Fill a tall cylinder three- 
 fourths full of water, and add fifty cubic centimeters of lead 
 nitrate. Add a solution of potassium chromate, little by little, 
 and notice the fine yellow cloud-like masses of Lead Chro- 
 mate which roll downward towards the bottom of the jar. 
 
 Ex. 127. Action of Lead on Water. —Two days be- 
 fore this subject is reached, prepare the experiment as 
 follows : — 
 
 Into each of two bottles put some clippings of lead : the 
 surfaces should be bright. Fill one, two-thirds full of rain- 
 water, and the other with spring-water. It is likely that the 
 rain-water will be found to be turbid, and that the spring- 
 water will remain clear. 
 
 Or a little ammonium nitrate may be purposely added to 
 the rain-water, and a little potassium carbonate to the spring- 
 water, by which these results are facilitated. 
 
280 CHEMISTRY. 
 
 255. Compounds of Copper. — Ex. 128. Fill a dinner- 
 plate nearly full of water, and in the middle of it stand a 
 test-glass. Put some clippings of copper into the glass, and 
 pour upon them moderately dilute nitric acid, a little more 
 than enough to cover them. At once invert over the glass a 
 large receiver (shown in Fig. 20) . A violent action quickly 
 begins. The air in the receiver becomes cherry-red. The 
 fluid in the test-glass becomes intensely blue. The red fumes 
 will, for the most part, be dissolved in the water, and thus be 
 prevented from escaping into the room ; and, if a little blue 
 litmus is put into the water, another change of color wUl be 
 witnessed, from blue to red. 
 
 The blue liquid in the test-glass is a solution of copper 
 nitrate. Pour it off from the residue of copper into a small 
 beaker. 
 
 Ex. 129. Copper Hydrate. — Add a few drops of this 
 nitrate solution to a test-glass of water, and then, drop by 
 drop, ammonia, and observe the pale-blue precipitate : it is 
 copper hydrate. 
 
 But continue to add the ammonia, and the pale-blue pre- 
 cipitate will begin to disappear. It dissolves, a fine rich blue 
 liquid being obtained. 
 
 Ex. 130. To a test-glass of water, first add some drops 
 of solution of copper sulphate, often called " blue vitriol," 
 and then carefully add ammonia. The same pale-blue hydrate 
 is precipitated. Continue the addition of the ammonia, and 
 the hydrate dissolves in the excess as before, yielding a 
 transparent liquid with beautiful azure-blue color. The rich- 
 ness of this color may appear to better advantage by diluting 
 the liquid. For this purpose pour it into a beaker, and add 
 water until the light can be seen through the solution. 
 
 This is a very sensitive test for copper salts. A very 
 minute quantity can be detected by this ammoaJo-copper 
 sulphate solution. 
 
APPENDIX. 
 
 281 
 
 No. 1 SET OF APPARATUS. 
 
 JNCLtrDIIirG EVERY ARTICLE NEEDED FOR THE ONE HUNDRED AND 
 THIRTY "EXPERIMENTS FOR THE CLASS-ROOM." 
 
 1 Bunsen's burner. 
 
 1 forceps (steel). 
 
 ^ dozen test-tubes (6-inch) . 
 
 1 test-tube stand. 
 
 1 pair adhesive plates (glass) . 
 
 1 small horseshoe-magnet. 
 
 ^ dozen bottles, saltmouth (1- 
 
 pint) . 
 ^ dozen bottles, saltmouth (^- 
 
 pint) . 
 1 mortar (Wedgwood, 4- 
 
 in.). 
 ^ dozen glass cylinders (12 X 
 
 1^ inch) . 
 ^ dozen beakers (16-ounce). 
 ^ dozen beakers (6-ounce) . 
 1 evaporating-disk (porcelain, 
 
 8-ounce) . 
 1 glass jar, tin cap (^-gallon). 
 1 glass funnel (4-inch). 
 J dozen test-glasses (4-ounce) . 
 ^ dozen bell- jars (1-pint). 
 1 bell- jar (1 -quart). 
 1 beU-jar (^gallon). 
 
 1 ignition side-neck test-tube 
 (8-inch). 
 
 1 tubulated retort (16-ounce). 
 
 1 battery-jar (6 X ^ inch). 
 
 1 combustion-spoon. 
 
 1 pipette. 
 
 1 air-thermometer. 
 
 1 hydrogen apparatus (gas 
 bottle, 1-pint, fitted thistle- 
 tube and delivery- tube) . 
 
 1 oxygen apparatus (flask 8- 
 ounce, fitted delivery-tube). 
 
 1 chlorine apparatus (flask 8- 
 ounee, fitted thistle-tube and 
 delivery-tube) . 
 
 1 Woulf's bottle (3-neck, 4- 
 ounce) . 
 
 1 retort-stand. 
 
 1 pneumatic cistern. 
 
 ^ pound glass tubing (^-inch 
 OMiside) . 
 
 4 feet rubber tubing (|^-inch 
 inside) . 
 
 1 three-cornered file. 
 
 CHEMICALS 
 
 NEEDED FOR THE ONE HUNDRED AND THIRTY "EXPERIMENTS 
 FOR THE CLASS-ROOM." 
 
 Platinum wire, 3 inches. 
 Magnesium ribbon, 1 foot. 
 Calcium chloride, 4 ounces. 
 
 Lead acetate, 1 ounce. 
 Potassium chromate, 1 ounce. 
 Copper sulphate, 4 ounces. 
 
282 
 
 CHEMISTEY. 
 
 Potassium ferrocyanide, ^ oz. 
 Ferrous sulphate, 4 ounces. 
 Silver nitrate solution, 4 oz. 
 Lead nitrate, ^ ounce. 
 Sodium carbonate, 4 ounces. 
 Aniline red, ^ ounce. 
 Manganese dioxide, ^ pound. 
 Bleaching powder, ^ pound.. 
 Litmus, 2 ounces. 
 Potassium chlorate, 4 ounces. 
 Potassium iodide, ^ ounce. 
 Mercuric chloride, 1 ounce. 
 Potassium nitrate, 4 ounces. 
 Ammonium chloride, ^ ounce. 
 Ammonium nitrate, 4 ounces. 
 Ammonia, aqua, 4 ounces. 
 Arsenious acid, J ounce. 
 Sodium acetate, 4 ounces. 
 Sodium hydrate, 4 ounces. 
 Potassium chloride, 2 ounces. 
 
 Strontium chloride, 2 ounces 
 Barium chloride, 2 ounces. 
 Potassium ferrocyanide, -1^ oz. 
 Ammonium carbonate, 2 oz. 
 Sulphuric acid, 1 pound. 
 Hydrochloric acid, 1 pound. 
 Nitric acid, 1 pound. 
 Alum, 4 ounces. 
 Tannin, ^ ounce. 
 Alcohol, 1 quart. 
 Ether, 4 ounces. 
 Cochineal, ^ ounce. 
 Copper foil, ^ pound. 
 Tin foil, J pound. 
 Sulphur, 4 ounces. 
 Phosphorus, 2 ounces. 
 Iodine, J ounce. 
 Sodium, ^ ounce. 
 Zinc, granulated, 1 pound. 
 
 No. 2 SET OF APPARATUS. 
 
 ESrCLUDING AI.L THAT IS NEEDED FOR THE FULL ILLUSTRATION 
 OF THE TEXT. 
 
 1 No. 1 set complete. 
 
 2 flasks (round bottom, 8-oz.). 
 2 flasks (flat bottom, 6-oz.). 
 
 1 flask (round bottom, very light, 1500 cc). 
 
 1 beaker (selected, very light, such size that the 1500-cc. 
 flask when inverted in it will reach nearly to the bottom, 
 and close the mouth of the beaker neatly at the same time) . 
 
 1 bell-jar (1-gallon). 
 
 1 glass crystallizing-basin (6 inches diameter). 
 
 1 alcohol lamp. 
 
APPENDIX. 283 
 
 1 decomposing cell for water. 
 
 1 battery (2 or 4 cells, Bunsen's or Grenet). 
 
 1 electroscope (pith-ball). 
 
 1 glass tube for friction. 
 
 2 cylinders (glass, 6 X IJ in.)' 
 1 eudiometer (50 cc). 
 
 1 induction-coil (^ in. spark). 
 1 balance (Robervall's). 
 
 1 set of weights (I kilo down) . 
 
 2 graduated glass tubes (^-inch diameter, graduated to cc, 
 12 inches long). 
 
 1 retort-holder (Shelbaek's) . 
 
 1 foot magnesium ribbon. 
 
 1 deflagrating stand. 
 
 1 wire-gauze spoon. 
 
 1 Woulf's bottle (2-necked, 16-ounce). 
 
 1 rubber bag (1 -gallon). 
 
 1 chloride-calcium jar (9-in.). 
 
 2 pinch-cocks. 
 
 1 tripod (1-ring). 
 1 aspirator-bottle (1-gallon). 
 1 reduction- tube (1-bulb). 
 ^ dozen U-tubes (side-neck and corks) . 
 1 chloride-calcium tube. 
 
 1 diffusion-of-gases apparatus, i.e., glass tube 12 inches 
 long, with porous cup at one end. 
 
 1 Hofmann's apparatus for combustion of oxygen. 
 
 2 dozen corks, assorted. 
 
 4 feet copper wire for battery connections. 
 
284 CHEMISTKY. 
 
 GENERAL REVIEW. 
 
 [The following exercises cover the most important facts and princi- 
 ples which have been presented in the foregoing course of chemistry, 
 and may prove to be useful as a guide in conducting a general review 
 or a final examination. It will be seen that they divide the subject into 
 five nearly equal parts, but that each exercise may be easily divided 
 into two when it is desirable to extend the review over two weeks 
 instead of one.] 
 
 I. 
 
 What is an experiment ? 
 
 Describe two experiments which show the difference be- 
 tween mechanical and chemical action. 
 
 Having two solid substances, how will you proceed in 
 order to bring them into chemical action ? 
 
 Describe the influence of heat, of light, and of electricity, 
 on chemical action. 
 
 Prove that matter is indestructible. 
 
 Give some account of the process of weighing. 
 
 Give some account of the process of measuring. 
 
 What is analysis ? What is synthesis ? 
 
 Describe an .analysis of water, and state the results. 
 
 Describe the synthesis of water, and state the results. 
 
 What law of combination is illustrated by these constant 
 results ? 
 
 State the law of multiple proportions. 
 
 State Gay Lussac's law of volumes. 
 
 State Avogadro's law. 
 
 Define the following tei-ms : molecule, atom, combining 
 weight, combining volume, specific gravity. 
 
 Give the value of each of the foregoing terms for oxygen, 
 hydrogen, and nitrogen. 
 
 If there be fifteen grains of oxygen, how much hydrogen 
 is needed to convert it into water, and how much water will 
 be produced by their union? 
 
 Show by example the difference between a symbol and a 
 formula. 
 
APPENDIX. 285 
 
 What are oxides? acids? hydrates? salts? How is each 
 of these classes of compounds named ? 
 
 What experiment will decide whether a soluble substance 
 is acid or basic ? 
 
 Let phosphorus be burned in dry air : give the formula 
 and the name of the product. 
 
 Let phosphorus be burned in the presence of water : give 
 the formula and the name of the product. 
 
 In the last case, state all the facts which the formula 
 teaches about the substance. 
 
 Name the constituents of hydrosodium sulphate, and give 
 its formula. 
 
 Name the substances whose formulas are K N O3, Naa CO3, 
 H Na CO3, Ca(H0)2, Fe^ O3. 
 
 II. 
 
 Define element. What may be said as to the number of 
 the element^F 
 
 On what principle are the non-metals classified? Name 
 and define the groups. 
 
 Define quantivalence. 
 
 Write the graphic symbol of chlorine, oxygen, nitrogen, 
 and carbon. 
 
 Write the graphic formula for hydrochloric acid ; for 
 water ; for ammonia ; for marsh-gas. 
 
 What are such graphic formulas intended to show ? What 
 are they not intended to show ? 
 
 What are all the different kinds of formula which have 
 been defined in this book ? 
 
 Describe two ways of getting the hydrogen from water. 
 Is there any other way ? 
 
 What are the physical properties of hydrogen? What are 
 its chemical properties? How does it occur in nature? 
 
 For what numerical values does hydrogen furnish the 
 unit? 
 
•286 CHEMISTRY. 
 
 Define re-action. How are chemical changes represented 
 to the eye ? 
 
 "Write the re-actions which occur in the different experi- 
 ments for preparing hydrogen. 
 
 Why does one atom of zinc require two molecules of 
 hydrochloric acid in chemical re-action, while an atom of 
 potassium requires only one ? 
 
 Suppose we have ten thousand grains of water at 0° C, 
 and wish to heat it to the boiling-point by a flame of hydro- 
 gen, and that we must .make our hydrogen by means of zinc 
 and sulphuric acid : how much of these materials must we 
 use? 
 
 Name the members of the univalent group of non-metals. 
 In what forms are these elements found in nature ? 
 
 Compare the physical properties of these elements. 
 
 Compare their chemical properties. 
 
 For what pm-poses are the compounds of these elements 
 used in the arts ? ^ 
 
 Describe the preparation of chlorine. 
 
 Describe hydrochloric acid, stating how it is prepared, its 
 properties and its uses. 
 
 What is aqua-regia, and for what is it useful ? 
 
 From the formula of hydrochloric acid, calculate its per- 
 centage composition. 
 
 Name the members of the bivalent group of non-metals. 
 Which are of most practical importance ? Are these impor- 
 tant ones found abundantly in nature ? In what forms ? 
 
 Describe the preparation of oxygen. 
 
 Ten liters of oxygen are needed for experiment : how much 
 potassium chlorate must be used to furnish it? 
 
 What is the combining weight of oxygen ? its molecular 
 weight? its density? 
 
 What are the relations of oxygen to combustion and to the 
 life of animals? 
 
 Define allotropism, and describe ozone. 
 
 How is the sulphur of commerce obtained? What is " plas- 
 tic sulphur"? 
 
APPENDIX. 287 
 
 Why is sulphur said to be dimorphous ? 
 
 By what two general methods may crystals be obtained? 
 
 III. 
 
 What important compounds do oxygen and sulphur form 
 with hydrogen ? 
 
 What are the names and the formulas for the compounds 
 of oxygen with chlorine ? 
 
 What are the names and the formulas for the compounds 
 of sulphur with oxygen? 
 
 Give a complete description of the electrolysis of water and 
 its results. 
 
 Give the freezing-point, the boiling-point, and point of 
 maximum density, of water, in both Fahrenheit and centigrade 
 degrees. 
 
 Define the terms solution, solvent, soluble, and saturated. 
 
 How may water be iDurifled from solid impurities ? From 
 volatile impu|«ties ? Effect of freezing ? 
 
 What is the difference between hard and soft water ? and 
 how may hard water be softened ? 
 
 What is hydrogen dioxide ? What is hydroxyl ? 
 
 Give the preparation and properties of H, S, and illustrate 
 its re-action with metallic compounds by an example. 
 
 Describe the process of bleaching with sulphurous oxide. 
 What is another substance used in bleaching? 
 
 State what you can about sulphuric acid. 
 
 Define oxidizing agent ; reducing agent. 
 
 What is a monobasic acid ? A dibasic acid ? A normal 
 salt? An acid salt? 
 
 Name and give the symbols of the members of the triva- 
 lent group of non-metals. 
 
 Where is nitrogen found in nature ? 
 
 Describe the occurrence of phosphorus in nature. Of ar- 
 senic. * 
 
 Describe each of these elements. 
 
288 CHEMISTEY. 
 
 Give the formulas and names of the compounds of these 
 elements with hydrogen. Are these compounds of practical 
 value ? 
 
 Say what you can about the preparation, properties, and 
 uses of ammonia. 
 
 Give the names and formulas of the several oxides of ni- 
 trogen. Which of these have corresponding acids ? Describe 
 nitric acid. 
 
 Give the composition of the atmosphere as completely as 
 you can. Why is the atmosphere a mixture rather than a 
 compound ? 
 
 Define and illustrate diffusion and osmose. 
 
 Describe "Marsh's Test" for arsenic, and point out all 
 the chemical re-actions which occur in it. 
 
 Name and describe some of the most common compounds 
 of arsenic. 
 
 What is an anaesthetic? Which of the compounds of ni- 
 trogen with oxygen are anaesthetic ? and how is it prepared ? 
 
 What substance is an antidote to arsenical poison ? and how 
 may it be prepared? Name other antidotes which may be 
 used instead if need be. 
 
 What non-metals constitute the quadrivalent group? and 
 what are their symbols ? 
 
 What can you say of silicon ? 
 
 What is glass ? and from what materials is it made ? W hat 
 are the most important varieties ? 
 
 Give an outline of the process of making glass. 
 
 Name and describe the three allotropic forms of cai-bon. 
 
 IV. 
 
 Give the names of the compounds of carbon and oxygen, 
 and their formulas, and describe the effect of each when 
 breathed. 
 
 Define combustion, and show what chemical action it rep- 
 resents. 
 
APPENDIX. 289 
 
 Why is it necessary to touch a match to a combustible 
 before it will burn ? 
 
 What are the usual products of combustion? and why? 
 
 Why does wood burn with flame, while anthracite burns 
 only with a glow ? How do you account for the blue flame 
 which is often seen over a coal fire ? 
 
 How do we explain the production of the light in a lumi- 
 nous flame ? Describe the oxyhydrogen light. 
 
 What is the proper supply of air needed to give the full 
 heating effect of a fuel? How would you calculate the 
 amount ? 
 
 What chemical changes take place in the air and in the 
 blood during respiration? 
 
 Explain the need of ventilating rooms. 
 
 What are the chemical changes which occur' in the process 
 of decay? 
 
 Show that combustion, respiration, and decay are much 
 alike in chemical character. 
 
 Define organic chemistry. 
 
 Distinguish between organized bodies and organic sub- 
 stances. Which do we study in chemistry ? 
 
 Define hydrocarbon. Define homologous series. 
 
 Give the formulas and names of several members of the 
 marsh-gas series. 
 
 What explanation of the large number of hydrocarbons is 
 given ? 
 
 Give the properties of marsh-gas ; also of the marsh-gas 
 series. 
 
 How are the various commercial fluids obtained from 
 petroleum ? 
 
 How is common alcohol obtained? What are its proper- 
 ties ? Its composition ? What is its relation to ethane ? 
 
 Describe the alcohol series. 
 
 Define and illustrate the term radical. 
 
 How is common ether obtained ? What are its properties ? 
 Give the general definition of an ether. 
 
290 CHEMISTRY. 
 
 What are the defines ? Name some of them. 
 
 Define and illustrate destructive distillation. 
 
 Name and describe some of the products of the distillation 
 of wood. 
 
 To what large industrial pmpose is destructive distillation 
 applied ? What can you say of the two principal varieties of 
 mineral coal? 
 
 Trace the successive stages in the manufacture of illumi- 
 nating gas. 
 
 What is benzol? Nitro-benzol ? Aniline? Aniline red? 
 Aniline dyes? 
 
 V. 
 
 Give the chemical meaning of the term sugar. 
 
 Into what three classes are the sugars chiefly grouped? 
 Give examples of each. 
 
 Give the composition of cane-sugar ; of starch ; of grape- 
 sugar ; of dextrine. 
 
 Define the terms ferment, fermentation. 
 
 Give the chemical changes which occur first in converting 
 sucrose to glucose, and second in the fermentation of the 
 latter. 
 
 Define the terms ore, aUoy, native metal. 
 
 What are the characteristic properties of the metals of the 
 alkalies ? What is an alkali ? 
 
 Describe the manufacture of sodium carbonate. 
 
 What are the general properties of the metals of the alka- 
 line earths ? 
 
 What can you say of calcium oxide and its uses ? 
 
 Explain the formation of stalactites and stalagmites. 
 
 What are alums ? Give the composition and properties of 
 common alum. 
 
 From what ores, and in what way, is zinc obtained? 
 
 What can you say of the occurrence of iron in nature? 
 Name, and state the difference between, the forms of iron in 
 commerce. 
 
APPENDIX. 291 
 
 Describe the blast-furnace. Describe the process of re- 
 ducing iron ore in the blast-furnace. 
 How are iron " castings " made? 
 Describe the manufacture of wrought-iron. 
 Describe the "Bessemer process" of making steel from 
 cast-iron. 
 
 Describe the method of making steel from wrought-iron. 
 Say what you can of the occurrence, extraction, and prop- 
 erties of tin. 
 
 Name the metals of the antimony class. To what non- 
 metals are they closely related ? 
 
 What is type-metal? and on what property does its useful- 
 ness depend? 
 
 What is the composition, and what are the properties, of 
 " fusible metal " ? 
 From what ore, and in what way, is lead obtained ? 
 What can you say of the chemical action of water in lead 
 pipes ? 
 
 How does copper occur in nature ? 
 What are the chief ores of copper ? 
 How is copper obtained from its ores ? 
 Name and describe the most important alloys of copper. 
 From what ore, and how, is mercury obtained ? 
 What are calomel and corrosive sublimate? How can 
 these be distinguished? 
 
 How is silver extracted from argentiferous galena ? 
 How is silver obtained from other ores than argentiferous 
 galena ? 
 
 What is the composition of American silver coin ? 
 What is the action of light on the compounds of silver ? 
 Define photography. 
 
 What is the difference between a negative and a positive 
 picture ? 
 
 How is the negative made ? How is the positive made ? 
 In what condition does gold occur in nature ? How is gold 
 
292 CHEMISTRY. 
 
 separated from gold-bearing sand? How is it separated 
 from gold-bearing quartz ? 
 
 Where, and in what form, is platinum found? What are 
 some of its properties ? 
 
 Write out the re-action which occurs when hydrochloric 
 acid is added to silver nitrate. 
 
 Write the re-action which takes place when a silver plate is 
 held in the vapor of iodine. 
 
 Write the re-action which occurs when the plate covered 
 with collodion is in the bath of silver nitrate. 
 
 Write the re-action which occurs when paper for the " posi- 
 tive " is floated on the two liquids needed for its preparation. 
 
 Write the re-actions which would occur if a silver coin 
 should be placed in nitric acid. 
 
 What compound is formed when gold is dissolved in aqua- 
 regia ? 
 
INDEX. 
 
 (The numbers refer to pages.) 
 
 Acids 43 
 
 composition of • . M 
 
 dibasic HO 
 
 hydrogen 45 
 
 oxygen 44 
 
 Acetic acid 206 
 
 Alcohol 186 
 
 radicals 189 
 
 Alcohols, series of 188 
 
 Alkalies 217 
 
 AUotropism 87 
 
 Alloys 215 
 
 of antimony 231 
 
 of bismuth . . . , 232 
 
 of copper 236 
 
 of mercury 237 
 
 of silver 239 
 
 Alum/ 222 
 
 AluminiuEj 221 
 
 Amalgams 237 
 
 Amalgamation 238 
 
 Amethyst 143 
 
 Ammonia 117 
 
 Ammonia alum 223 
 
 Amylose 204 
 
 Analysis 23 
 
 Anhydrides 106 
 
 Aniline 200 
 
 dyes 201 
 
 red '. ... 201 
 
 Animal charcoal 149 
 
 Annealing 146 
 
 Antimony 231 
 
 Argand burner 167 
 
 Arsenic 134,231 
 
 compounds with hydrogen 134 
 
 compounds with oxygen 136 
 
 293 
 
294 INDEX. 
 
 Arsenic, Marsh's test for 135 
 
 Reinsch's test for 269 
 
 Artiads 58 
 
 Asphalt 199 
 
 Atmosphere 124 
 
 percentage composition of 140 
 
 Atom 33 
 
 Atomic theory 33 
 
 Atomic weight 35 
 
 of the elements 53 
 
 Attraction 10 
 
 Avogadro's Law 35 
 
 Balance, the chemical 20 
 
 Bases 47 
 
 Bell-metal 236 
 
 Benzine 186 
 
 Benzol 199 
 
 Bessemer process 229 
 
 Binary compounds 36 
 
 names of 42 
 
 Bismuth 231 
 
 Blastfurnace 226 
 
 Bleaching with chlorine 73 
 
 with sulphur . . . , 107 
 
 illustrated 260 
 
 powder 98 
 
 Bone-black 149 
 
 Boracic acid 137 
 
 Borates .... 138 
 
 Borax 137 
 
 Boron 137 
 
 Brass 23fi 
 
 Brimstone 102 
 
 Bromine 75 
 
 Bronze 236 
 
 Bunsen's burner 167 
 
 Cadmium 223 
 
 Calcium 220 
 
 carbonate 221 
 
 oxide 221 
 
 Carbolic acid 199 
 
 Carbon 147 
 
 amorphous 149 
 
 allotropic forms of 152 
 
 combustion of, in oxygen 84 
 
 compounds with hydrogen 180 
 
 compounds with oxygen 84 
 
INDEX. 295 
 
 Carbon, crystallized 160 
 
 dioxide 153 
 
 monoxide 153 
 
 occurrence in nature 152 
 
 Carbon dioxide 153 
 
 a product of combustion 162 
 
 Carbonic acid 15g 
 
 Carboys 109 
 
 Changes, chemical 2 
 
 physical 1 
 
 Charcoal 148 
 
 Chemical action 3 
 
 attraction 10 
 
 combination 4 
 
 decomposition 5 
 
 no loss nor gain in 17 
 
 Chemistry defined 6 
 
 an experimental science 7 
 
 Chloric acid 98 
 
 Chlorine 70 
 
 attraction of, for hydrogen 72 
 
 attraction of, for metals 73 
 
 chemical character of ■ 72 
 
 compound of, with hydrogen 76 
 
 compounds of, with oxygen 97 
 
 liquefaction of 72 
 
 occurrence of, in nature 73 
 
 preparation of 70 
 
 properties of 72 
 
 Choke-damp 152 
 
 Classification of acids 44 
 
 of elements 54 
 
 of metals 215 
 
 of non-metals 54 
 
 Coal 195 
 
 varieties of 202 
 
 Coal naphtha 199 
 
 Coal tar 199 
 
 Dalton's theory 33 
 
 Decay "4 
 
 Deliquescence 218 
 
 Destructive distillation . 192 
 
 application of 194 
 
 slow 201 
 
 Dextrine 204 
 
 Diamond 150 
 
 Diastase 204 
 
290 INDEX. 
 
 Diffusion 127 
 
 Dimorphism 103 
 
 Distillation 9* 
 
 destmctive 192 
 
 fractional . 185 
 
 Electrical attraction 10 
 
 Electricity affecting chemical action 14 
 
 Electrolysis 14, 16 
 
 Element defined 8 
 
 Elements, atomic weight o£ 53 
 
 classification of 54, 215 
 
 Ustof 63 
 
 metallic 44 
 
 non-metallic 52 
 
 . number of 52 
 
 symbols of 53 
 
 Empirical formulas 59 
 
 Ethane 183 
 
 Ethene 191 
 
 Ether 189 
 
 Ethers, series of 190 
 
 Ethyline 191 
 
 Eudiometer 26 
 
 Experiment defined. 7 
 
 Experimental method 7 
 
 Ferment 205 
 
 Fermentation 205 
 
 Filtration 93 
 
 Fire-damp 182 
 
 Flame . 163 
 
 of the argand burner 167 
 
 of the Bunsen's burner 167 
 
 of the candle 164 
 
 of the gas-burner 167 
 
 of hydrogen 66 
 
 tests for barium, strontium, and calcium .... 275 
 
 tests for potassium and sodium 274 
 
 Flowers of sulphur 102 
 
 Fluorine 75 
 
 Formulas, of compounds 40 
 
 constitutional 56 
 
 empirical 59 
 
 graphic 56 
 
 rational 59 
 
 Fractional distillation 185 
 
 French system of measures 21 
 
 Fuel 162 
 
INDEX. 297 
 
 Purnace, the blast 226 
 
 the cupola 227 
 
 the reverberatory 228 
 
 Fusible alloy 232 
 
 Fusion affecting chemical action . 12 
 
 Galena ^ 203 
 
 Gallium 222 
 
 Gas, illuminating 193 
 
 from petroleum 198 
 
 Gases, diffusion of 128 
 
 osmose of 129 
 
 liquefaction of 64,72,84,155 
 
 solubility of 91 
 
 Gasoline 186 
 
 Gay Lussac's Law 34 
 
 German silver 236 
 
 Glass 144 
 
 Glauber's salts 81, 218 
 
 Glucose 203 
 
 Gold 243 
 
 Graphic formulas 56 
 
 symbols 55 
 
 Graphite 152 
 
 Gravitation 10 
 
 Gun-metal 236 
 
 Heat affecting chemical action 12 
 
 Hydrates 47 
 
 Hydrochloric acid 76 
 
 chemical character of 79 
 
 composition of - 29 
 
 molecular weight of 79 
 
 preparation of 77 
 
 solubility of 78 
 
 uses of 80 
 
 Hypochlorous.acid 98 
 
 Hydrogeii 60 
 
 as a standard 67 
 
 chemical properties of 65 
 
 combustibility of 66 
 
 combustion of 88 
 
 explosibility of 67 
 
 liquefaction of 64 
 
 molecular formula of 67 
 
 occlusion of 64 
 
 occurrence of 67 
 
 physical properties of 63 
 
 preparation of 60, 61, 63 
 
298 INDEX. 
 
 Hydrogen, aalts 46 
 
 solubility of 64 
 
 units 67 
 
 weight ol one liter of 67 
 
 Hydrogen arsenide 134 
 
 Hydrogen dioxide . . . . 96 
 
 Hydrogen nitride 117 
 
 Hydrogen phosphide 132 
 
 Hydrogen siilphide 103 
 
 Ice 89 
 
 Illuminating gas 195 
 
 Indestructibility of matter 17 
 
 Indium 221 
 
 Iodine 75 
 
 Iron ..224 
 
 cast 225 
 
 casting 227 
 
 compounds of 276 
 
 galvanized 224 
 
 malleable 229 
 
 ores of 225 
 
 pig 227 
 
 puddling . 229 
 
 reduction of the ores of 226 
 
 wrought . . 229 
 
 Isomeric substances 205 
 
 Isomerism 209 
 
 Kerosene 186 
 
 Law, of Avogadro 35 
 
 of constant proportions 31 
 
 of Gay Lussac 34 
 
 of multiple proportions 31 
 
 of the diffusion of gases 129 
 
 Laws of combination 29 
 
 Lamp-black 144 
 
 Laughing-gas 121 
 
 Lead 232 
 
 action of, on water 279 
 
 compounds of 278 
 
 Light 165 
 
 oxyhydrogen • 168 
 
 source of 168 
 
 Lime 221 
 
 Lime-water 220 
 
 Liquids, diffusion of 127 
 
 osmose of 128 
 
 Liquefaction of gases 64, 72, 84, 155 
 
INDEX. 299 
 
 Lake, caimlne 275 
 
 Lakes 270 
 
 Magnesium 223 
 
 combustion ol 41 
 
 Malachite 234 
 
 Manganese .... . .— . — "; ; ." ."2^4 
 
 Manufacture of illuminating gas 195 
 
 of potassium carbonate 217 
 
 of sodium carbonate 218 
 
 of sulphuric acid 108 
 
 Maish-gas 182 
 
 series 183 
 
 Marsh's test 135 
 
 Measuring 21 
 
 Mercuric oxide 4 
 
 decomposition of 6 
 
 Mercury 236 
 
 Metallurgy 244 
 
 Metals 54 
 
 characteristic properties ot 214 
 
 classification of 215 
 
 density of 214 
 
 melting-points of 214 
 
 symbols of the 215 
 
 of the Alkalies 216 
 
 of the Alkaline earths 219 
 
 of the Antimony class 230 
 
 of the Earths 221 
 
 of the Gold class 242 
 
 of the Iron class 224 
 
 of the Lead class 232 
 
 of the Silver class 233 
 
 of the Tin class 230 
 
 of the Zinc class 223 
 
 Methane 183 
 
 Methyl 183 
 
 Methyl alcohol 193 
 
 Methyl hydride 183 
 
 Metric system 21 
 
 Mineral springs 92 
 
 Mixture defined 9 
 
 Molecular weights 35 
 
 volumes ^ 
 
 Molecule defined 34 
 
 Molecules, unsaturated ^ 
 
 Mortar 221 
 
 Muriatic acid • ^ 
 
300 INDEX. 
 
 Naphtha 186,199 
 
 Nascent state 117 
 
 Nickel 224 
 
 Nitric acid 119 
 
 an oxidizing agent 108, 120 
 
 Nitric anhydride 124 
 
 Nitric oxide 122 
 
 Nitric peroxide 123 
 
 Nitro-benzol 200 
 
 Nitrogen 115 
 
 compound with hydrogen 117 
 
 compounds with oxygen 31, 119 
 
 group of non-metals 138 
 
 in the atmosphere 124 
 
 occurrence in nature 117 
 
 preparation of 115 
 
 properties of 115 
 
 Nitrous anhydride 123 
 
 Nitrous oxide . . . 121 
 
 Nomenclature 41 
 
 of acids 44 
 
 of hinary compounds 41 
 
 of hydrates 47 
 
 of oxides 42 
 
 of salts 46 
 
 Non-metals 54 
 
 classification of 54 
 
 The Bivalent group 83, 112 
 
 The Trivalent group 115, 138 
 
 The Univalent group 70, 75 
 
 The Quadrivalent group 143, 146 
 
 Notation 39 
 
 Observation 6 
 
 Occlusion 64 
 
 Oil of vitriol ... 109 
 
 Olefiant gas 191 
 
 Olefines 191 
 
 Opal 143 
 
 Ores 215 
 
 Organic chemistry 180 
 
 Organic substances 181 
 
 Organized bodies 180 
 
 Osmose of gases 129 
 
 of liquids 128 
 
 Oxidation in combustion 160 
 
 Oxides 42 
 
 Oxidizing agent 108 
 
INDEX. 801 
 
 Oxygen 83 
 
 allotropic form of 87 
 
 properties of 84 
 
 compounds with carbon 152 
 
 compounds with chlorine 97 
 
 compounds with hydrogen 88, 96, 99 
 
 compounds with nitrogen 119 
 
 compounds with sulphur ... .... 105 
 
 compound with silicon 143 
 
 compounds with phosphorus 133 
 
 group of non-metals 112 
 
 In the atmosphere 123 
 
 liquefaction of 84 
 
 occurrence of 88 
 
 preparation of 83 
 
 Oxyhydrogen blow-pipe 170 
 
 heat 168 
 
 light 168 
 
 Oxysalts 46 
 
 Ozone 86 
 
 test-paper for 262 
 
 Paraffine 194 
 
 ParafBnes 184 
 
 Pearlash 217 
 
 Ferissads 68 
 
 Petroleum 185 
 
 decomposition of 198 
 
 origin of 202 
 
 Phosphorus .... 130 
 
 compounds with hydrogen 132 
 
 compounds with oxygen 133 
 
 phosphorescence of 268 
 
 uses of 131 
 
 Photography 240 
 
 Photophone 112 
 
 Pig-iron 227 
 
 Platinum , . . 244 
 
 Potash 217 
 
 Potassium 216 
 
 Precipitate 26,28 
 
 Quantivalence 
 
 Quicklime ^ 
 
 Safety-lamp ^^ 
 
 Salt in sea-water 
 
 Salt-cake 
 
 s^"« -.^ :;.■;.■ no 
 
 acid 
 
302 INBEX. 
 
 Salts, haloid 4B 
 
 hydrogen 46 
 
 names of 46 
 
 normal 110 
 
 oxygen 46 
 
 Scheele's Green 269 
 
 Selenium Ill 
 
 Series, the alcohol 188 
 
 the ether 190 
 
 the marsh-gas 183 
 
 homologous 191 
 
 Silica 14? ^ 
 
 Silicon 143 
 
 Silver 237 
 
 alloys of 239 
 
 compounds of affected by light 239 
 
 Snowflakes 90 
 
 Solution 11, 89 
 
 Soda 219 
 
 Soda-ash 219 
 
 Soda-water 155 
 
 Sodium 216 
 
 acid carbonate 219 
 
 alum 223 
 
 carbonate 218 
 
 chloride 218 
 
 sulphate 218 
 
 sulphide 218 
 
 Specific gravity 38 
 
 Spectrum analysis 25 
 
 Spirituous liquors 205 
 
 Starch 209 
 
 Stalactites and stalagmites 221 
 
 Steel 229 
 
 Sucrose 203 
 
 Sugar 203 
 
 varieties of 203 
 
 Sulphates HO 
 
 Sulphur 101 
 
 compound with hydrogen 103 
 
 compounds with oxygen 105 
 
 crystalline forms 102 
 
 occurrence in nature 103 
 
 plastic 102 
 
 uses of 103 
 
 Sulphurets 103 
 
 Sulphuretted hydrogen 103 
 
INDEX. 303 
 
 Sulphuric acid 108 
 
 Sulphuric ether ! ! ! ! 190 
 
 Sulphurous acid 106 
 
 Sulphurous oxide 106 
 
 Symbols 39 
 
 Synthesis 23 
 
 Tannic acid, test for 278 
 
 Tar 193,199 
 
 Tellurium 112 
 
 Thallium 232 
 
 Tin 230 
 
 Type-metal 231 
 
 Unit, of combining weights 31, 36 
 
 of quantivalence 55 
 
 Units, hydrogen 67 
 
 Ventilation, need of 174 
 
 Vinegar 206 
 
 Water 88 
 
 action of, on lead 233 
 
 chalybeate 92 
 
 combining weight of 32 
 
 composition of 99 
 
 decomposition of 5, 7 
 
 electrolysis 24 
 
 freezing-point of 89 
 
 graphic formula of 99 
 
 hard and soft 96 
 
 in the atmosphere 125 
 
 natural 92 
 
 of crystallization 138 
 
 percentage composition of 25 
 
 purification of 93 
 
 of the sea 92 
 
 solvent powers of 89 
 
 synthesis of 26 
 
 "Water-gas ^^^ 
 
 "Weighing 20 
 
 Weight, a measure of matter ^' 
 
 Weights, the metric system of 21 
 
 Wood, constituents of ^ 
 
 decay of "* 
 
 destructive distillation of '■^^ 
 
 tar 1^3 
 
 193 
 
 _. ^°«sar : ; ; 206 
 
 3^'°« 223 
 
 Zinc 2^ 
 
 malleability of 
 
Physics 
 
 Cooley's Student's Manual of Physics 
 
 For the Study Room and Laboratory. By L. C. CooLEY, 
 Ph.D., Professor of Mathematics in Vassar College. 
 
 Cloth, 1 2mo, 448 pages. Illustrated $1.00 
 
 A new text-book in Physics for high schools, academies, and colleges. 
 It embodies a full and thorough treatment of the laws of physics, the 
 best methods in science teaching, the latest discoveries and appUcations 
 in physics, and a full course in laboratory practice. Special care has 
 been taken to select experiments which will not overtax the capacities of 
 beginners nor require expensive apparatus, but which at the same time 
 will call for systematic and original work and lead to accurate results. 
 
 Harrington's Physics for Grannmar Schools 
 
 By C. L. Harrington, M.A. Cloth, i2mo, 123 pages. 50 cents 
 A practical text-book based on the natural or experimental method, 
 
 elementary enough for pupils in grammar schools, and afiording a 
 
 thorough preparation for advanced study. 
 
 Appletons' School Physics 
 
 Cloth, i2mo, 552 pages $1.20 
 
 A thoroughly nK>dern text-book on Natural Philosophy, which 
 
 reflects the most advanced pedagogical methods and the latest laboratory 
 
 practice. 
 
 Steele's Popular Physics 
 
 By J. DORMAN Steele, Ph.D. Cloth, i2mo, 392 pages . $1.00 
 A popular text-book, in which the principles of the science are 
 
 presented in such an attractive manner as to awaken and fix the attention 
 
 of every pupil. 
 
 Trowbridge's New Physics 
 
 By John Trowbridge, S.D. Cloth, i2mo, 387 pages . $1.20 
 A thoroughly modern work, intended as a class manual of Physics 
 
 for colleges and advanced preparatory schools. 
 
 Hammel's Observation Blanks in Physics 
 By William C. A. Hammel. 
 
 Flexible, quarto, 42 pages. Illustrated . . . .30 cents 
 A pupil's laboratory manual and notebook for the first term's work. 
 
 Blanks are left in which the pupil writes his observations and the 
 
 principles illustrated. 
 
 Copies of any of these books will he sent^ prepaid^ to any address on receipt 
 of the price by the Publishers: 
 
 American Book Company 
 
 NEW YORK . CINCINNATI . CHICAGO 
 
 (go) 
 
Zoology and Natural History 
 
 Apgar's Birds of the United States 
 
 By Austin C. Apgar. Clotli, i2mo, 41s pages . . $2.00 
 Designed to encourage the study of birds by making It a pleasant 
 and easy taslc. The boob is attractive and popular in style and at the 
 same time thoroughly scientific and accurate in its descriptions and 
 classifications. The illustrations were drawn especially for this work 
 and include full figures of over 300 different American species. 
 
 Burnet's School Zoology 
 
 By Margaretta Burnet. Cloth, i2mo, 216 pages . 75 cents 
 A new text-book for high schools and academies, by a practical 
 
 teacher; suiBciently elementary for beginners and full enough for the 
 
 usual course in Natural History. 
 
 Needham's Elementary Lessons in Zoology 
 
 By James G. Needham, M.S. Cloth, i2mo, 302 pages 90 cents 
 A text-book for high schools, academies, normal schools and prepar- 
 atory college classes. Special attention is given to the study by scientific 
 methods, laboratory practice, microscopic study, and practical zootomy. 
 
 Holders' Elementary Zoology 
 
 By C. F. Holder and J. B. Holder, M.D. 
 
 Cloth, i2mo, 401 pages $1.20 
 
 A text-book for high school classes and other schools of secondary 
 
 grade. 
 
 Morse's First Book in Zoology 
 
 By Edward S. Morse, Ph.D. Boards, t2mo, 204 pages 87 cents 
 For the study of the lower and plainer forms of animal life. The 
 
 examples presented are such as are common and familiar. 
 
 Steele's Popular Zoology 
 
 By J. DORMAN Steele, Ph.D., and J. W. P. Jenks. 
 
 Cloth, i2mo, 369 pages $1 .20 
 
 For academies, preparatory schools, and general reading. The 
 treatment is marked by the same clearness and interest that characterize 
 all Professor Steele's text-books in the Natural Sciences. 
 
 Tenneys' Natural History of Animals 
 
 By Sanborn Tenney and Abbey A. Tenney. 
 
 Revised Edition. Cloth, l2mo, 281 pages . . . $1.20 
 
 This new edition has been thoroughly revised, the recent changes in 
 
 classification introduced, and the book in all respects brought up to date. 
 
 Copies of any of the above booh will be sent prepaid to any address, on 
 receipt of the price, by the Publishers : 
 
 American Book Company 
 
 New York ♦ Cincinnati ♦ Chicago 
 
Text-Books in Geology 
 
 Dana's Geological Story Briefly Told 
 
 By James D. Dana. Cloth, i2mo, 302 pages . . . $1.15 
 A new edition of this popular work for beginners in the 
 study and for the general reader. The book has been en- 
 tirely rewritten, and improved by the addition of many 
 new illustrations and interesting descriptions of the latest 
 phases and discoveries of the science. In contents and dress 
 it is an attractive volume either for the reader or student. 
 
 Dana's Revised Text-Book of Geology 
 
 Edited by William North Rice, Ph.D., LL.D., Professor 
 
 of Geology, Wesleyan University. Cloth, i2mo, 482 pages. $1.40 
 
 This is the standard text-book for high school and 
 elementary college work. The book has been thoroughly 
 revised, enlarged, and improved, while the general and 
 distinctive features of the former work have been preserved. 
 As now published, it combines the results of the life ex- 
 perience and observation of its distinguished author with 
 the latest discoveries and researches in the science. 
 
 Dana's Manual of Geology 
 
 By James D. Dana. 
 
 Cloth, 8vo, 1087 pages. 1575 illustrations .... $5.00 
 
 This great work was thoroughly revised and entirely 
 rewritten under the direct supervision of its author, just 
 before his death. It is recognized as a standard authority, 
 and is used as a manual of instruction in all higher insti- 
 tutions of learning. 
 
 Le Conte's Compend of Geology 
 
 By Joseph Le CoNTE, LL.D. Cloth, i2mo, 399 pages . $1.20 
 Designed for high schools, academies, and all sec- 
 ondary schools. In the revised edition of this well-known 
 and popular text-book, the general plan and arrangement 
 remain the same, but such modifications and additions 
 have been made as were necessary to bring the work up to 
 the present condition of the science. 
 
 Copies of any of the above books will be sent prepaid to any address, on 
 receipt of the price, by the Publishers : 
 
 American Book Company 
 
 New York ♦ Cincinnati ♦ Chicago 
 
 (93) 
 
Text-Books in Astronomy 
 
 Todd's New Astronomy 
 
 By David P. Todd, A.A., Ph.D., Professor of Astronomy 
 
 and Director of the Observatory, Amherst College. 
 
 Cloth, i2mo, 480 pages. With colored plates and illustrations $1 .30 
 
 A new text-book, deigned for high schools, academies, and other 
 preparatory schools. Its muminative treatment and striking illustrations 
 make it an ideal text-book for students, and deeply dnteresting for the 
 general reader. The noteworthy feature which distinguishes this from 
 other text-books on Astronomy is the practical way in which the subjects 
 treated are enforced by laboratory experiments and methods. In this 
 the author follows the principle that Astronomy is preeminently a science 
 of observation and should be so taught. 
 
 The treatment of the planets and other heavenly bodies and of the 
 law of universal gravitation is unusually full and clear. The marvelous 
 discoveries of Astronomy in recent years, and the latest advances in 
 methods of teaching the science, are all represented in this book. 
 
 Steele's New Descriptive Astronomy 
 
 By J. DORMAN Steele, Ph.D. Cloth, i2mo, 338 pages . $1.00 
 
 A popular text-book, calculated to attract the attention and awaken 
 the enthusiasm of students. It supplies an adequate course in the study 
 for high schools and college preparatory classes. 
 
 Lockyer's Astronomies 
 
 By J. N. LocKYER, F.R.S. 
 
 Astronomy. (Science Primer Series.) 136 pages . . 35 cents 
 
 Elementary Lessons in Astronomy. 312 pages . . $1.22 
 
 Bowen's Astronomy by Observation 
 By Eliza A. Bowen. 
 
 Boards, quarto, 94 pages. Colored maps and illustrations . $1 .00 
 Especially adapted for use as an atlas to accompany any text-book 
 
 in Astronomy. Careful directions are given when, how, and where to 
 
 find the heavenly bodies. 
 
 C<>/>ies of any of the above books will be sent prepaid to any address, on 
 receipt of the price, by the Publishers . 
 
 American Book Company 
 
 New York ♦ Cincinr,ati ♦ Chicago 
 
 (94) 
 
Physical Geography 
 
 Appletons' Physical Geography 
 
 By John D. Quackenbos, John S. Newberry, Charles H. 
 Hitchcock, W. Le Conte Stevens, Wm. H. Dall, Henry 
 Gannett, C. Hart Merriam, Nathaniel L. Britton, 
 George F. Kunz and Lieut. Geo. M. Stoney. 
 
 Cloth, quarto, 140 pages $1 .60 
 
 Prepared on a new and original plan. Richly illustrated with engrav- 
 ings, diagrams and maps in color, and including a separate chapter on 
 the geologi6al history and the physical features of the United States. 
 The aim has been to popularize the study of Physical Geography by 
 furnishing a complete, attractive, carefully condensed text-book. 
 
 Cornell's Physical Geography 
 
 Boards, quarto, 104 pages $1.12 
 
 Revised edition, with such alterations and additions as were found 
 necessary to bring the work in all respects up to date. 
 
 Hinman's Eclectic Physical Geography 
 
 Cloth, i2mo, 382 pages $1.00 
 
 By Russell Hinman. A model text-book of the subject in a new 
 and convenient form. It embodies a strictly scientific and accurate 
 treatment of Physiography and other branches of Physical Geography. 
 Adapted for classes in high schools, academies and colleges, and for 
 private students. The text is fully illustrated by numerous maps, 
 charts, cuts and diagrams. 
 
 Guyot's Physical Geography 
 
 Cloth, quarto, 124 pages $1 .60 
 
 By Arnold Guyot. Thoroughly revised and supplied with newly 
 engraved maps, illustrations, etc. A standard work by one of the ablest 
 of modern geographers. All parts of the subject are presented in their 
 true relations and in their proper subordination. 
 
 Monteith's New Physical Geography 
 
 Cloth, quarto, 144 pages $1.00 
 
 An elementary work adapted for use in common and grammar schools, 
 as well as in high schools. 
 
 Copies of any of the above books will be sent prepaid to any address^ on 
 receipt of the price, by the Publishers: 
 
 American Book Company 
 
 New York ♦ Cincinnati • Chicago 
 
 (98) 
 
Laboratory Physics 
 
 Hammel's Observation Blanks in Physics 
 
 By William C. A. Hammel, Professor of Physics in 
 Maryland State School. Boards, Quarto, 42 pages. 
 Illustrated 30 cents 
 
 These Observation Blanks are designed for use as a 
 Pupil's Laboratory Manual and Note Book for the first 
 term's work in the study of Physics. They combine in 
 convenient form descriptions and illustrations of the appa- 
 ratus required for making experiments in Physics, with 
 special reference to the elements of Air, Liquids, and Heat; 
 directions for making the required apparatus from simple 
 inexpensive materials, and for performing the experiments, 
 etc. The book is supplied with blanks for making drawings 
 of the apparatus and for the pupil to record what he has 
 observed and inferred concerning the experiment and the 
 principle illustrated. 
 
 The experiments are carefully selected in the light of 
 experience and arranged in logical order. The treatment 
 throughout is in accordance with the best laboratory practice 
 of the day. 
 
 Hon. W. T. Harris, U. S. Commissioner of Education, 
 says of these Blanks: 
 
 "I have seen several attempts to assist the work of 
 pupils engaged in the study of Physics, but I have never 
 seen anything which promises to be of such practical assist- 
 ance as Hammel's Observation Blanks." 
 
 Specimen copies of the above book will be sent prepaid to any address, 
 on receipt of the price, by the Publishers; 
 
 American Book Company 
 
 New York ♦ Cincinnati ♦ Chicago 
 
 (103) 
 
Gray's Series of Botanies 
 
 By the late Asa Gray, LL.D., of Harvard University 
 
 FOR ELEMENTARY AND GRAMMAR SCHOOLS 
 
 Gray's How Plants Grow. With a Popular Flora . . $0.80 
 A simple introduction to the study of Botany. 
 
 Gray's How Plants Behave. A Botany for Young People . .54 
 A primary book showing how plants move, climb, act, etc. 
 
 FOR SECONDARY SCHOOLS 
 
 Gray's Lessons in Botany. Revised edition ... .94 
 
 Gray's Field, Forest, and Garden Botany. New edition, 
 
 containing Flora only 1.44 
 
 Gray's School and Field Book of Botany. Comprising the 
 
 "Lessons" and "Field, Forest, and Garden Botany,'' 1.80 
 A complete book for school use. 
 
 FOR COLLEGES AND ADVANCED STUDENTS 
 
 Gray's Manual of Botany. Revised, containing Flora only. 
 
 For the Northern United States, east of the Missisippi, 1 .62 
 The Same. Tourist's edition. Thin paper, flexible leather, 2.00 
 Gray's Lessons and Manual of Botany. One volume. Revised, 
 
 comprising the "Lessons in Botany" and the "Manual," 2.16 
 Gray's Botanical Text-Book 
 
 I. Gray's Structural Botany 2.00 
 
 II. Goodale's Physiological Botany .... 2.00 
 
 FOR WESTERN STUDENTS 
 
 Coulter's Manual of the Botany of the Rocky Mountains . 1.62 
 Gray and Coulter's Text-Book of Western Botany. Com- 
 prising Gray's "Lessons" and Coulter's " Manual of 
 the Rocky Mountains " 2.16 
 
 Copies of any of the above books will be sent, prepaid, to any address 
 on receipt of the price by the Publishers ; 
 
 American Book Company 
 
 NEW YORK - CINCINNATI . CHICAGO 
 
 (io6) 
 
Aids to Field and Laboratory Work 
 in Botany 
 
 Apgars' Plant Analysis. By E. A. and A. C. Apgar. 
 
 Cloth, small 410, 124 pages 55 cents 
 
 A book of blank schedules, adapted to Gray's Botanies, for pupils' 
 use in writing and preserving brief systematic descriptions of the plants 
 analyzed.by them in field or class work. Space is allowed for descrip- 
 tions of about one hundred and twenty-four plants with an alphabetical 
 . index. 
 
 An analytical arrangement of botanical terms is provided, in which 
 the words defined are illustrated by small wood cuts, which show at a 
 glance the characteristics named in the definition. 
 
 By using the Plant Analysis, pupils will become familiar with the 
 meaning of botanical terms, and will learn how to apply these terms in 
 botanical descriptions. 
 
 Apgar's Trees of the Northern United States 
 
 Their Study, Description, and Determination. For the use of 
 
 Schools and Private Students. By Austin C. Apgar. 
 
 Cloth, i2mo, 224 pages. Copiously Illustrated . . . $T.OO 
 
 This work has been prepared as an accessory to the study of Botany, 
 and to assist and encourage teachers in introducing into their classes 
 instruction in Nature Study. The trees of our forests, lawns, yards, 
 orchards, streets, borders and parks afford a most favorable and fruitful 
 field for the purposes of such study. They are real objects of nature, 
 easily accessible, and of such a character as to admit of being studied at 
 all seasons and in all localities. Besides, the subject is one of general 
 and increasing interest, and one that can be taught successfully by those 
 who have had no regular scientific training. 
 
 Copies of either of the above books will be sent, prepaid, to any address on 
 receipt of the price by the Publishers; 
 
 American Book Company 
 
 NEW YORK ♦ CINCINNATI ♦ CHICAGO 
 
 (107) 
 
Text-Books in Natural History 
 
 Clark's Laboratory Manual in Practical Botany. For secondary 
 
 schools and elementary work in colleges .... $0.96 
 
 Gray's How Plants Grow. An elementary Text-Book with a pop- 
 ular Flora 80 
 
 Gray's Lessons in Botany. Revised. The elements of Botany 
 
 for high schools, academies, etc 94 
 
 Gray's Field, Forest, and Garden Botany. Revised. A practical 
 Flora to the common plants of the United States, east of the 
 looth meridian 1 .44 
 
 Gray's School and Field Book of Botany. Including the " Les- 
 sons" and the " Field, Forest, and Garden Botany,'' making 
 a complete text-book for high schools, academies, etc. . . 1 80 
 
 Apgar's Trees of the Northern United ■ States, Their study, 
 
 description, and determination ...... 1 .00 
 
 Apgar's Birds of the United States. A manual for the study and 
 identification of all birds east of the Rocky Mountains. 
 Beautifully illustrated 2.00 
 
 Burnet's School Zoology. For use in schools where time is 
 
 limited and where no laboratory is provided . . . .75 
 
 Needham's Elementary Lessons in Zoology. A text-book for the 
 study of animal life and structure in schools equipped, more 
 or less, with laboratory facilities 90 
 
 Dana's Geological Story Briefly Told. A new edition of this pop- 
 ular work for beginners 1.15 
 
 Dana's Text-Book of Geology. Fifth edition, revised and en- 
 larged. Edited by William North Rice . . . . 1 .40 
 
 Dana's Manual of Geology. Fourth revised edition. Entirely 
 rewritten and revised by the author. The standard Manual 
 of Geology in colleges and universities .... 5.00 
 
 Copies of the above hooks will be sent prepaid to any address^ on receipt 
 of the price, by the Publishers : 
 
 American Book Company 
 
 New York • Cincinnati . Chicago 
 
 (109)