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THE WONDER BOOK OF CHEMISTRY

THE WONDER BOOK OF CHEMISTRY

BY JEAN-HENRI FABRE

Author of "THE STORY-BOOK OF SCIENCE," "OuR HUMBLE

HELPERS," "FIELD, FOREST AND FARM," "THE SECRET

OF EVERY DAY THINGS," "ANIMAL LIFE

IN FIELD AND GARDEN," etc.

TRANSLATED FROM THE FRENCH BY FLORENCE CONSTABLE BICKNELL

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NEW YORK

THE CENTURY CO.

1922

Copyright, 1922, by THE CENTURY Co.

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PRINTED IN TT. S. A.

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TEANSLATOE'S PEEFACE

"What is the use of a book without pictures or conversations ?" asks Alice, disgustedly, just before taking her departure for Wonderland, where she finds no lack of animated discourse.

This book, like its predecessors in the series, is conversational in form and has as many pictures as the subject-matter calls for.

All boys and some girls, as well as their elders, take more or less interest in the marvels of chem- istry. To give an elementary but useful knowledge of these marvels, chiefly by means of simple experi- ments clearly described by the writer and easily per- formed at home by any wide -awake young reader, is the object of tlie, foil owing talks by "Uncle Paul."

The personal, biographical interest of the book is not to be overlooked. The boys Jules and Emile are the author's own children^ faithfully portrayed even to the names they bear. In his captivating fashion the man of vast learning makes himself at once teacher and comrade to his young hearers, and we learn that "his chemistry lessons especially had a great success. With apparatus of his own devising and of the simplest kind he could perform a host of elementary experiments, the apparatus as a rule consisting of the most ordinary materials, such as a common flask or bottle, an old mustard-pot, a

TRANSLATOR'S PREFACE

tumbler, a goose-quill or a pipe-stem. A series of astonishing phenomena amazed their wondering eyes. He made them see, touch, taste, handle, and smell, and always 'the hand assisted the word/ al- ways 'the example accompanied the precept,' for no one more fully valued the profound maxim, so neg- lected and misunderstood, that 'to see is to know.' " Though living creatures necessarily claimed the nat- uralist's first affections, he none the less "animates even the simple elementary bodies, celebrating the marvelous activities of the air, the violence of chlo- rin, the metamorphoses of carbon, the miraculous bridals of phosphorus, and the ' splendors which ac- company the birth of a drop cf water.' "

Concerning the eager young pupils, Jules and Emile, by this time well known to all readers of the series, a still further word may not be out of place. Emile, the younger, the "giddy-pate" of the nar- rative, impulsive and f nil of v boyish '.curiosity and vigorous young life, is-drawr^ '.for us with fidelity and a delightful touch of humor by the loving father. Jules is shown to us as more 'secla te and gifted with finer qualities, and with his grief-stricken par- ent we mourn his early death. "He was a youth of great promise, 'all fire, all flame'; of a serious na- ture ; an exquisite being, of a precocious intelligence, whose rare aptitudes both for science and literature were truly extraordinary. Such too was the sub- tlety of his senses that by handling no matter what plant, with his eyes closed, he could recognize and define it merely by the sense of touch. This de-

TRANSLATOR'S PREFACE

lightful companion of his father's studies had scarcely passed his fifteenth year when death re- moved him. A terrible void was left in his heart, which was never filled. Thirty years later the least allusion to this child, however tactful, which recalled this dear memory to his mind, would wring his heart, and his whole body would be shaken by his sobs.' In a memorial foreword to the second volume of his "Souvenirs Entomologiques " the bereaved father pays loving tribute to this lost son and fellow- worker.

Thus it is that the following chapters will be found to have a human and personal appeal to supplement their scientific interest. May they yield both pleas- ure and profit to their readers !

* The quoted passages are from Dr. C. V. Legros's "La Vie de J.-H. Fabre, Naturaliste," translated by Mr. Bernard Miall under the title, "Fabre, Poet of Science," and published by The Century Co.

CONTENTS

CHAPTER PAGE

I INTRODUCTION 3

II MIXING AND COMBINING 6

III THE SLICE OF TOAST . . . ... 26

IV SIMPLE SUBSTANCES 42

V COMPOUND SUBSTANCES ........ 54

VI EXPERIMENTS WITH THE BREATH . .• . .70

VII EXPERIMENTS WITH AIR ....... 83

VIII FURTHER EXPERIMENTS WITH AIR . . . 96

IX THE Two SPARROWS L. . . 109

X BURNING PHOSPHORUS . > R > t. . . 124

XI BURNING METALS .... ^ ..... 139

XII SALTS 154

XIII A TALK ON TOOLS ..... L.: .. 171

XIV OXYGEN ._ 187

XV AIR AND COMBUSTION 211

XVI RUST 224

XVII AT THE BLACKSMITH'S 230

XVIII HYDROGEN 243

XIX A DROP OF WATER 264

XX A PIECE OF CHALK 284

XXI CARBONIC-ACID GAS 300

CONTENTS

CHAPTER PAGE

XXII DIFFERENT KINDS OF WATER . . . -L. . 311

XXIII PLANTS AT WORK .323

XXIV SULPHUR . . 345

XXV CHLORIN 360

XXVI NITROGEN COMPOUNDS 375

THE WONDER BOOK OF CHEMISTRY

THE WONDER BOOK OF CHEMISTRY

CHAPTER I

INTRODUCTION

UNCLE PAUL is a man of some learning who waters his lettuce-plants and weeds his cabbages and turnips in the quiet of a humble little village. Staying with him are his nephews, Emile and Jules, young scholars already grappling with the intricacies of the rule of three and the pit- falls of the past participle, and both of them very eager to learn. Jules, the elder, is even now be- ginning to suspect that school will not have taught him everything when he has mastered his grammar and arithmetic. Their uncle does his best to en- courage the boys' desire for knowledge, convinced as he is that in the stern battle of life our best weapon is a trained intellect.

For some time past his family had noticed in him an unusual preoccupation. There was ripening in his mind a plan for teaching his nephews the rudi- ments of chemistry, that science so fruitful in its practical applications.

"What are these dear children going to be, some day?' he asked himself. "Will they be manu- facturers, artisans, mechanics, farm laborers, or

3

4 THE WONDER BOOK OF CHEMISTRY

what? Who knows? One thing, at any rate, is certain, and that is, whatever direction their activ- ity takes it will be to their advantage to be able to give an account of the things they have accom- plished. A little science is something that they must have. I should like my nephews to know what air is, and water; why we breathe, and why wood burns ; the nutritive elements essential to plant life, and the constituents of the soil. And it is no vague and imperfect knowledge from hearsay I would have them gain of these fundamental truths, on which depend agriculture and the industrial arts and our health itself; I would have them know these things thoroughly from their own observation and experi- ence. Books here are insufficient, and can serve merely as aids to scientific experiment. But how shall we manage it?'

In this wise did Uncle Paul ponder over his pro- ject, a project involving grave difficulties, such as the want of a laboratory and of all those ingenious devices without which it would at first seem im- possible to undertake any serious experiments in chemistry, the only appliances at hand being the commonest of household utensils, — bottles and phials, jars and pitchers, plates and cups and earthen bowls, drinking-glasses and old mustard- pots. It is true the distance to town was not great. For special occasions, but within the very modest limits set by an imperative economy, a few drugs and glass implements might be bought. Ten francs must be made to cover these extraordinary pur- chases. How, then, to impart some useful knowl-

INTRODUCTION 5

edge of chemistry with the help of little more than such simple appliances as the village could furnish -that was the problem.

But in the end it came about that one day Uncle Paul announced to his nephews that he proposed to enliven the monotony of their regular studies by in- troducing a little diversion. Without using the word " chemistry, " which would have meant nothing to them, he spoke of certain interesting things he had to show them, of various wonderful experiments to be performed. Lively and curious, as are all children, Emile and Jules greeted this announce- ment with enthusiasm.

"When shall we begin !" they asked. "To- morrow— to-day ? ' '

* ' To-day, very soon. Give me five minutes for my preparations.''

CHAPTER II

MIXING AND COMBINING

NO sooner said than done. Uncle Paul went to his neighbor the locksmith and from among the files on the artisan 's work-bench selected something and wrapped it up in a piece of paper. Then he visited the apothecary and for a few cents bought a drug which he also wrapped in a bit of old newspaper, after which he returned home with his two packages.

"What is this?" he asked, opening one of the par- cels before the children.

"It is a yellow powder that makes a little crack- ling sound when you rub it between your fingers/ replied Emile. "I think it must be sulphur.'

"And I," added Jules, "am sure it is sulphur. But we '11 soon see."

So saying he took a pinch of the yellow powder and dropped it on some live coals from the kitchen fire, whereupon it began to burn with the blue flame

•

and the suffocating odor of a sulphur match.

"That proves it, I hope,' cried the lad, much pleased with himself at having found a quick way to demonstrate the nature of the substance offered by his uncle. "It is sulphur and nothing else, for that

6

MIXING AND COMBINING 7

is the only thing that burns with that blue flame and that smell that makes you cough.'

"Yes, mv bovs." assented their uncle, "it is sul-

* •>

phur powdered very fine and called flowers of sulphur. And now what is this .' '

He opened the second package and displayed its contents, consisting of a powdered metal, the fact of its being a metal showing clearly in its glittering particles.

"That looks very much like iron filing-. ' ' declared the younger of the two observers.

"It does more than look like them/' asserted the other; "it really is iron filings. Uncle Paul, you must have got them from the locksmith's.'

"Though I must congratulate Jules on his clever- ness and quickness/' rejoined Uncle Paul, "I ought at the same time to warn him against jumping to conclusions. In the studies we are about to take up together it is best to exercise careful scrutiny be- fore venturing on any assertions, as otherwise one would run the risk of making frequent mistakes. You say these metallic particles are iron filings ; but lead filings, tin filings, zinc filings, iron filings — all are of very much the same appearance, being all light in color and having a bright luster. You de- clared the yellow powder to be sulphur after you had proved it by dropping a pinch on burning coals. Xow find an equally decisive proof that these filings are of iron.'

The boys put on their thinking-caps and looked at each other in mutual questioning, but no happy

8 THE WONDER BOOK OF CHEMISTRY

thought came at their bidding. To what test could they put those filings to prove that they were indeed of iron? It was a puzzling problem, that was cer- tain. But at last Uncle Paul started the boys on the right track.

"How about the magnet, " said he, "that horse- shoe shaped piece of iron bought by Jules at the last fair and added to his little cabinet of apparatus for making experiments in physics? Wouldn't it be just the thing to help you out in your present per- plexity f Many a time I Ve seen you amusing your- selves with that magnet by making it draw to itself bits of iron, nails, needles. Does it have the same effect on lead?"

"No," replied Jules; "I have never been able to make it take up the least little bit of lead, though it will lift much heavier weights of iron, — a key, for example. ' '

"Does it attract tin?"

"No; no more than lead."

"And zinc and copper — does it have any effect on them?"

"No more than on lead or tin. Ah ! Now I have it. The magnet attracts only iron. That 's the test we 're after. Now we '11 see."

Thereupon Jules ran upstairs, two steps at a time, and hastened to his cupboard where, on a pine shelf, were arranged his books and his little pieces of apparatus, — simple appliances and mostly of his own make. Eagerly catching up his magnet, he ran downstairs and brought it almost in contact with the filings. Immediately there were clusters of them

MIXING AND COMBINING 9

clinging to the two ends of the magnet, forming long beards of bristling appearance.

"See there," cried the lad, "how it makes the fil- ings come to it ! I am sure now they are iron, noth- ing but iron. '

"Yes, my boy, they are iron," assented his uncle; "and it was the locksmith's work-bench that fur- nished me with the filings. Now, with this iron and this sulphur, which we have just proved to be iron and sulphur beyond any doubt, we will enter upon our study of chemistry. Give your attention to what I am about to do."

So saying, he emptied on a large sheet of paper both the flowers of sulphur and the iron filings, after which he mixed them thoroughly together by shak- ing the paper like a sieve and stirring its contents with his fingers.

"Look, now," said he; "what have we on the paper?"

"Oh, that 's easy enough," Jules made answer; "it 's just a mixture of sulphur and iron filings/'

"Yes, a mixture; and could you still tell the one substance from the other, all mixed together as they are?"

"Nothing easier," answered Emile, examining closely what was on the paper. ' ' Here, for instance, are some grains of sulphur; I know them by their yellow color; and here are some of the iron filings, as you can tell by their shiny look."

"And would you undertake to separate the par- ticles of one kind from those of the other, — to sort them all out ? "

10 THE WONDER BOOK OF CHEMISTRY

"Why not, if it really had to be done? I have good eyes, and with the help of a pin I could gather all the sulphur together on one side and all the iron on the other. Only, I doubt whether my patience would hold out to the end. '

"Yes, it certainly would be a rather longer job than picking over a plate of beans; and Emile's patience, however great it may be, would be hardly equal to the task. Still, the thing is not impossible. In that little heap, which has now neither the yellow color of pure sulphur nor the lustrous gray of pure iron, but which has at once something of the two colors and is consequently of a greenish appearance — in that little heap of matter, I say, an eye of sufficient patience and a hand of sufficient dexterity could, between them, see and separate what is sul- phur from the iron. But there are other ways of making the separation. Who will find one ? Come, now, set your wits to work. > '

"I have it!" cried Jules, passing the ends or poles of his magnet back and forth through the mixture.

"Just what I was going to propose, " said Emile, "if Jules had given me a moment to think about it. Xow that Uncle has reminded us of the magnet, the rest comes of itself."

"To hit on the way out of a difficulty after a mo- ment 's reflection is all very well, my young friend, ' rejoined his uncle; "but to hit on it immediately is still better. However, you will get even with Jules very soon, I am sure. Now let us see how his method of sorting the two substances succeeds.'

Jules went on passing his magnet through the mix-

MIXING AND COMBINING 11

ture of iron filings and sulphur, with the result that the metallic particles were attracted to the two poles of the magnet and clung to them, while the sulphur was left behind. Again and again the magnet was plunged into the heap, and each time it was with- drawn loaded at its two extremities with long and thick beards of filings which the young operator de- tached with his finger-tips, and placed at one side. Not a particle of the sulphur clung to the magnet, or at least not by the force of attraction, the magnet ex- erting no such force on sulphur ; and if any scatter- ing particles were found among the iron filings set aside by themselves, it was simply because they had become enmeshed among the grains of metal. A second, similar sorting very easily separated them.

"That 's the way to do it!" exclaimed Jules, de- lighted with the success of his operations. ' ' That 's the way, see! The magnet comes out each time loaded with filings, and the sulphur is left behind. If I went on, it would n 't take me more than ten min- utes to separate all the iron on the paper from the sulphur. ' '

"It is unnecessary to continue, my dear child," said Uncle Paul. "Your method is perfect, being both expeditious and unfailing in its results. Now put the iron filings back with the sulphur and mix the two well together. Your magnet, so serviceable to us in this process of sorting the two substances, is not at the disposal of every one. Would n't it be possible to get along without it, to make the desired separation in some other way? It is well, it is even indispensable, especially for us with our meager

12 THE WONDER BOOK OF CHEMISTRY

outfit, to learn how to do without what we do not possess, and nevertheless to attain results. Let us, then, dispense with our magnet and find some other way to separate the iron filings and the sulphur. Think a moment. I will help you. Which is the heavier of the two substances, the sulphur or the iron?"

"The iron," replied the two young chemists.

"And what would the iron do if we threw it into water?"

"It would sink to the bottom."

"And the sulphur — what would that do? I mean finely powdered sulphur, flowers of sulphur, not sul- phur in the lump, for that too would sink in water. ' '

"I see!" Emile made haste to answer, lest he should again be outstripped in this race of wits by his elder brother. "I see! I will throw the whole mixture into a glass of water and the iron will sink to the bottom, but the sulphur — wait a minute — the sulphur — "

"Hush, Jules!" cautioned his uncle, as the lad showed signs of breaking in. "Let your brother finish. ' '

"The sulphur," repeated Emile, his cheeks flushed with animation, "will stay on the surface; or perhaps it will sink, but not so fast as the iron, which is much heavier. "Let 's try it."

"I was confident, my good Emile," said his uncle, approvingly, "that you would soon get even with Jules. Yes, your idea is excellent, and if you hesi- tate a little in putting it into words, that is only be- cause you are in some doubt as to how the sulphur

MIXING AND COMBINING 13

will behave. I will put the thing to the test for you. ' ' Uncle Paul thereupon took a large glass and filled it with water, into which he dropped a handful of the mixture, stirring the liquid at the same time with a small wooden stick. Having thus started a brisk movement in the glass, he paused and awaited re- sults. Very soon the iron filings, because of their weight, had settled to the bottom, while the flowers of sulphur continued to circle about in the liquid. This liquid was next poured off into another glass, and when it came to rest the sulphur held in sus- pension gradually settled. Thus the two substances were collected, each by itself, the iron in the first glass, the sulphur in the second.

"You see, my young friends," said Uncle Paul, "it is accomplished quite as expeditiously as with the magnet, and the process calls for nothing that any one would not have at hand. Let us learn, I repeat, to do without what we lack and still to attain the end in view. It would be easy, you understand, for us to separate the two substances in the whole mixture by treating it a handful at a time in the manner just shown to you; but that is quite un- necessary for my present purpose. Let us sum up briefly what we have just learned. Two or more substances of different kinds form a mixture when their union does not prevent their being separated by the simple process of sorting, effected in one way or another. The heap there before you is a mix- ture of sulphur and iron, and these can be separated either with the help of a magnet or with water or, given sufficient time and patience, a grain at a time

14 THE WONDER BOOK OF CHEMISTRY

by hand. So much for that. Now let us pass on to something else."

So saying, he put the mixture of iron filings and sulphur into a bowl, added a little water, and kneaded the mass with his fingers until it formed a thick paste. Then he took a bottle of clear glass, an old discarded bottle that had once contained some sort of syrup or medicine, and filled it with the paste. Finally, in order to heat the mass somewhat, the bottle thus filled was set in the sun, and as it was a summer day the result purposed by Uncle Paul was not long in being attained, thanks to the temper- ature.

"Now pay close attention/ he admonished his pupils, "and you will see something curious. "

The boys were all eyes, all attention, in their eagerness to lose nothing of this their first experi- ment in chemistry. What was going to happen in the bottle? They did not have very long to wait. A quarter of an hour had not passed before some- thing remarkable took place: the contents of the bottle, at first greenish in color from the yellow of the sulphur and the gray of the iron, began grad- ually to turn black and present the appearance of soot, while at the same time jets of vapor accom- panied by hissing sounds escaped from the mouth of the bottle and small quantities of the black sub- stance were ejected as if by the force of an explosion.

"Jules," said his uncle, "take the bottle in your hand a moment and, no matter what happens, don't loose your hold."

MIXING AND COMBINING 15

Unsuspectingly the boy approached and grasped the bottle firmly in his hand.

"Oh, wow!" he cried, with a start of pain and sur- prise ; "it 's hot, hot !" And all his self-control was needed to prevent his dropping the burning bottle. Replacing it on the ground more quickly than he had taken it up, he turned to his uncle, shaking his fingers like one who has inadvertently touched hot iron. "How it scorches, Uncle!" he continued. "You can't hold it more than a second, it 's so hot. If the bottle had been over a fire I should have expected to find it hot ; but there is no fire here to heat it, and yet it gets hot like that, all by itself! Who would have thought it?"

Emile in his turn had to handle the wonderful bottle that of its own accord grew so hot as almost to burn any one touching it. First feeling of it cautiously with his finger-tips, then grasping it boldly in his hand, he set it down again not less quickly than Jules had done, while his looks showed the profound astonishment, the utter bewilderment, caused by this generation of heat from no apparent source.

"Water was poured on the mixture of iron filings and sulphur," said he to himself; "it was all wet with water, which is not exactly the right sort of fuel for a fire, and then the whole was set in the sunshine, which isn't what you could call hot, and pretty soon, for no reason that I can see, the mixture grew scorching hot. I can't understand it."

Ah, my little lad, Uncle Paul's chemical experi-

16 THE WONDER BOOK OF CHEMISTRY

ments will give you many another surprise before they are finished! He who enters on the study of chemistry finds himself transported to a new world, where marvel follows marvel in endless succession. But don't be too bewildered; keep your eyes open, remember what you see, and gradually light will dawn on these perplexing operations which now seem rather to partake of magic than of veritable science.

"We have now learned," resumed Uncle Paul, "at the cost of some little pain to you, that the con- tents of the bottle become heated, apparently of their own accord, and that this heat is not slight, but very considerable, even sufficient to give a burning sensation. All the rest that happened we must re- gard as merely resulting from this development of heat. The water with which I moistened the mix- ture was turned to steam, and hence produced the jets of white vapor that escaped from the bottle. From this vaporized water came also the hissing sounds, the little explosions, and the throwing out of solid matter. If I had had at my disposal a larger quantity of iron filings and sulphur, — if my mixture, instead of being limited to a handful or two, had amounted to a full decaliter or more, — I could have produced some far more remarkable results. But I will content myself with describing to you a curious experiment that used to afford no little entertain- ment to the onlookers.

"A generous allowance of mingled iron filings and sulphur was placed at the bottom of a large hole in the ground, water was sprinkled over the mass, and

MIXING AND COMBINING 17

a mound of damp earth was then heaped upon it. Soon this little mound would begin to behave exactly like a volcano in eruption: the ground would tremble all about the base of the mound, the heaped- up mass would crack open here and there, and through the cracks would spurt jets of steam accom- panied by hissing sounds, explosions, and even tongues of flame. This was called an artificial vol- cano ; but I must not omit to add that real volcanoes are set in action by something quite different from what was going on in that buried mixture of iron filings and sulphur, though this is not the time or the place to explain the difference. However, there is nothing to prevent your employing some of your leisure moments in constructing a miniature volcano of your own with a small quantity of iron filings and an equal amount of powdered sulphur. Your mole- hill of moistened earth, small though it must be, will not lack interest for you : it will at least break open in cracks and send out hot steam. '

Emile and Jules resolved to gather up all the iron filings they could at the locksmith's and to buy a few sous' worth of flowers of sulphur, with which they would, at the earliest opportunity, perform the experiment of the artificial volcano. Meanwhile, as they were discussing this project, the agitation inside the bottle was gradually subsiding and the temperature rapidly falling, until finally the bottle became cool enough to be handled without inconven- ience. Uncle Paul took it up and emptied its con- tents on a sheet of paper. What came out was a very black powder resembling soot.

18 THE WONDER BOOK OF CHEMISTRY

"Now use your eyes," said he, "and see if you can find any of the sulphur; try to discover even one little grain of it if no more."

The boys rummaged through the heap, stirring it with a pin and scrutinizing it very closely, but could not point to a single particle of sulphur after all their pains.

"Where can it be now?" queried the searchers. "What has become of all that sulphur? It must be there somehow, for we saw it put into the bottle, saw it plainly enough. It is somewhere in that black heap; nothing could be more certain. It hasn't been lost during the experiment, for it did n't come out of the bottle ; nothing much except a little steam came out. It must be here, and yet we can't find the tiniest grain of it."

"Perhaps," suggested Jules, "we can't see it even if it is there because it has turned black ; but we '11 try it with fire, and that will settle the question."

And convinced that he now had the solution of the mystery, Jules ra-n into the kitchen and fetched some live coals, on which he dropped a pinch of the black powder. But what was his disappointment when, after waiting a while and then blowing on the coals to make them burn more brightly, and after trying another pinch of the powder and then still another, each time from a different part of the heap, no igni- tion took place, no blue sulphurous flame showed itself !

"Well, I declare," exclaimed the bewildered lad, "that beats me! With all that sulphur somewhere in the powder, it still won't burn."

MIXING AND COMBINING 19

"And the iron," said Emile, "I can't see that, either. There *s nothing there but a sort of black soot, nothing at all that shines like iron. Let 's try the magnet and see if it will separate any of the filings from the re-s*t."

But the magnet produced as little effect as had the live coals; no more bristling beards, no more strings of iron filings clinging to the poles of the magnet, after these had been passed to and fro through the black powder. Nothing was attracted, nothing showed any tendency to -adhere to the piece of magnetized iron.

"Well, that 's strange, " declared Emile, still push- ing the magnet into the inert heap, now here, now there. "There 's plenty of iron there, that *s cer- tain, and yet not a particle of it will stick to the magnet. If I had n 't seen the iron put there I should say there was n't any in the whole heap."

"And I," chimed in Jules, "should say there was n't a particle of sulphur there, if I had n't seen it mixed with the iron. Yet of the two substances that certainly went into the heap, it now seems to contain not an atom; not a speck of sulphur, not a speck of iron can be found in what was made out of sulphur and iron."

Uncle Paul let his two nephews have their say, convinced that ideas thus born of personal obser- vation are worth far more than those adopted on the authority of another. To see is to know. But after the boys had become thoroughly persuaded of their powerlessness to find and separate either the sulphur or the iron, then at last he intervened.

20 TH'E WONDER BOOK OF CHEMISTRY

"Well," said he, "would you now undertake to sort the two substances, particle by particle!"

"It 's no use," was the reply; "we can't find the least trace of either of them."

"How about using the magnet?"

"That 's no good, either; it won't attract any- thing. ' '

"Well, then, try water."

' 1 1 have n 't much hope it will help us, ' ' answered Jules, "for the whole heap seems to be all of a kind, nothing heavy and nothing light. Still, it may be worth trying."

A pinch of the black stuff was dropped into water and stirred into the liquid, but it all sank very soon to the bottom of the glass, without the slightest tendency to any separation.

"So, then," resumed Uncle Paul, "sorting is no longer possible by any of the methods that at first succeeded so well. And that is not all: the ap- pearance and the properties of the mass before us have undergone siich a change that, if you did not know beforehand what was there, you would never suspect the presence of the two ingredients."

"But who in the world would ever imagine this black stuff was made of sulphur and iron f ' ' the boys exclaimed.

"The appearance of the mass is changed, as I say," their uncle admitted. "The sulphur had a beautiful yellow color, the iron a lustrous gray, whereas the substance resulting from their com- bination is neither yellow nor gray nor lustrous ; it is, on the contrary, of a deep, dull blabk. And the

MIXING AND COMBINING 21

properties are likewise altered: the sulphur was found to take fire readily and to burn with a blue flame accompanied by stifling fumes, but this black substance refuses to ignite when it is placed on glow- ing coals ; and the iron filing's were attracted by the magnet, which has no effect on the black powder here. Hence we must conclude that this powder is neither sulphur nor iron, but some third substance of a wholly different nature. Shall we call it a mixture of sulphur and iron? Certainly not, for it is no longer possible to divide the mass into those two ingredients by any process of sorting, the properties of sulphur and of iron having given place to others showing nothing in common with the first two. We have, then, to do with an association far more intimate than that known as ' mixture,' — with one that is known in chemistry as ' combination.' Mixture leaves to the mingling substances their distinctive qualities intact ; combination causes them to disappear, and substitutes others in their place. After mixture it is always possible to separate the ingredients by some simple process of sorting ap- plicable to the given case; after combination this is never possible. Hence we may say that two or more substances are combined when they can no longer be separated by the process of sorting, in the customary sense of that word; when, in short, their characteristic properties have disappeared and given place to others.

"Observe, also, my young friends, that these new properties resulting from combination can by no means be predicted from the nature of the com-

22 THE WONDER BOOK OF CHEMISTRY

bining substances. Who would ever imagine, with no previous study of these curious things, that sulphur, yellow and readily combustible, could en- ter into the formation of a black and incombustible powder? And who would think that iron, with its metallic luster and its quick response to the magnet, could be capable of entering into the composition of a substance having a dull black color and no ten- dency whatever to be attracted by the magnet? Such things are impossible of prediction without previous knowledge. Combination, as you will have occasion to note again and again, works a funda- mental change in matter, turning white to black and black to white, sweet to bitter and bitter to sweet, harmless substances to deadly poison and deadly poison to something entirely harmless. Watch well the result when two or more substances combine.

"Still another point demands serious attention. In the process of combining, our mixture of iron filings and sulphur became much heated by spon- taneous action; in fact, it grew so burning hot that it was impossible to hold the bottle in one's hands. Jules will long remember the surprise caused him by this unexpected heat. In this connection I must tell you that this rise in temperature is nothing ex- ceptional, nothing peculiar to the combining of iron and sulphur. Every time two or more substances enter into combination there is heat generated, sometimes &o slight as to be detected only by the most delicate instruments; sometimes, and more often, of a degree unbearable to the touch; and

MIXING AND COMBINING 23

sometimes, again, of such intensity as to be appar- ent to the eye in glowing redness or even blinding incandescence. In short, whenever combination takes place there is more or less heat; and, con- versely, whenever heat or light Is manifested it is almost always a sign that combination is going on. "

1 'I should like to ask a question, Uncle Paul," Jules interposed. ""When coal burns in a furnace, is there a combination going on between different substances?"

"•Certainly there is."

"One of the substances, then, must be the coal, mustn't it?"

"Yes, one is the coal."

"And the other?"

"The other is contained in the air. It is in- visible, but none the less it is there. We shall con- sider it at length in its proper place/

"And the wood that burns in the fireplace and gives out heat and light?'

"There too we have a combination that includes the substance of the wood and that other substance contained in the air."

"And lamps and candles that we use for light?"

"Combination there also.'

"Then every time I set fire to anything I start a combination?"

"Precisely; you cause two different substances to combine."

"What a funny thing it is, combination!"

"More than funny, my boy; it is useful beyond

24 THE WONDER BOOK OF CHEMISTRY

your power to imagine, and that is why I wish you not to remain ignorant of the marvelous trans- formations it brings about."

"And will you tell us all about these wonderful things V9

"So far as I am able I will tell you about them, if you will both pay close attention. "

"Oh, there 'a no danger of our not doing that. We won't lose a word, and we '11 remember it all, too. I like this kind of lessons ever so much better than long division and conjugation of verbs. Don't you, Emile?"

"I should say so!" was the emphatic reply. "I wish I could have lessons like this all day and every day. I 'd leave my grammar any time to help make an artificial volcano."

"My dear young friends.," their uncle admonished them, "don't let your enthusiasm for chemistry cause you to slight your grammar, if you wish to keep on good terms with me. Chemistry has its place, but so has language, and no small place, either. Don't neglect your conjugations, hard though they may seem to you. But now let us re- turn to our subject of combination.

"It is, as I have said, always accompanied by heat, sometimes by light. Explosions, detonations, flashes of light, luminous outbursts, and brilliant sparks — all the dazzling display of an exhibition of fireworks, in short — are by no means exceptional when two substances come together in chemical com- bination. In the act of thus coming together the two substances unite in the closest of bonds; they

MIXING AND COMBINING 25

marry, as we might say, and heat and light make ha,ste to celebrate the nuptials just as pinwheels and Roman candles celebrate weddings with us. Do not laugh at my comparison ; it is apter than you think. Chemical combination is like marriage: it makes one out of two.

"Now I have to tell you what this substance is that has resulted from the marriage of sulphur and iron. We cannot call it sulphur, as it is no longer sulphur; nor can we call it iron, as it is no longer iron. Neither would it do to call it a mixture of sulphur and iron, for what was a mixture in the beginning has ceased to be one now. Its name in chemistry is sulphid of iron, a name that enables us to remember the two substances united in the bonds of chemical matrimony, — iron, which we here write out unchanged, and sulphur, which appears somewhat disguised in the word 'sulphid.' "

CHAPTER III

THE SLICE OF TOAST

THE boys bad made tbeir little artificial vol- cano, and it had proved to be a success, the mole-hill of moist earth becoming much heated, cracking open, and giving vent to spurts of steam accompanied by sharp hissings. All had turned out to the complete satisfaction of the young ex- perimenters, and the resulting sulphid of iron, on being examined at leisure and subjected to every test their imagination could suggest, was declared to be the same substance as that produced by their uncle. At this point he joined them.

"In the black powder now remaining at the heart of your artificial volcano/' said he, "there is iron and there is sulphur. No possible doubt as to that can lurk in your minds after you have seen this substance prepared and, what is more, have pre- pared it yourselves with your own hands. Never- theless, there is no sign of either any iron or any sulphur in this black powder, so utterly different is it in color and general appearance from both those substances. Had I begun by showing you this powder already made, without telling you of what it was composed, you would most certainly never have suspected it to contain any sulphur or any

26

THE SLICE OF TOAST 27

iron; and had I told you its ingredients without letting you witness the combining process, you would, I am sure, have taken your uncle's word for it, but at the same time you would have been no little astonished. 'What,' you would have ex- claimed, 'sulphur in that stuff, there, which is not in the least yellow and will not burn? And iron, too, where there isn't the faintest shine of iron and nothing sticks to the magnet?' In short, you would have believed me because of vour trust in mv word,

*/ */

but you would not have had the certainty that conies from seeing the thing done.

"This certainty I have given you by means of the experiment performed before your very eyes, and you have further strengthened that certainty by performing the experiment yourselves. We are, then, all three of us, firmly convinced that in this black substance before us there are both sulphur and iron. And now another question arises: Is it possible to make the iron and the sulphur here com- bined resume each its original form? Can the com- bination be undone ;and the two ingredients re- covered as they were in the beginning? Yes, my young friends, the thing is possible, but no simple process of sorting will suffice to disunite the two substances. You remember how all your attempts to accomplish this were so much wasted effort. What combination has joined together, no sorting can put asunder. To effect the separation, it is necessary to resort to scientific methods belonging to the domain of chemistry; and as your acquire- ments in that domain are still of the slightest, I

28 THE WONDER BOOK OF CHEMISTRY

will not invoke the aid of those methods. Besides, for our present purposes the actual separation of the sulphur and the iron is of very little impor- tance. Inasmuch as the black powder does really contain them, it is incontestable that they can, by the requisite means, be obtained from that powder ; 'and that is all I wish to impress upon you at present."

' ' There can't be any doubt," Jules assented, 1 'that a substance made of iron and sulphur must furnish iron and sulphur when properly treated. No one could dispute that. All the same, I should like to see the iron filings come back as iron and the flowers of sulphur come back as sulphur."

"I repeat, my dear child, that the operation would not be difficult, but it would call for drugs quite unknown to you and would be a mysterious and perplexing performance in your eyes. Let us see but little at a time and see that little plainly; that is the way to acquire substantial and lasting knowl- edge.

"But, now that we are on the subject, I will say to you that what is done by combination is not always the easiest thing in the world to be undone. These chemical marriages, signalized by manifesta- tions of heat and light, unite substances in bonds so close that to sever them it is necessary to employ methods known only to advanced science. However easy the act of union, the disunion is difficult. Com- bination takes place of itself; separation is a more arduous undertaking. We have lately seen the iron and the sulphur combine in a short time with no aid

THE SLICE OF TOAST 29

from us ; but if now we should try to separate them, we should meet with enormous resistance, which only the most skilful methods could overcome.

" There are instances, however, in which quite the* opposite is to be noted, combination being so difficult and delicate a process as to defy our utmost en- deavors, but separation offering so little of resist- ance that a mere nothing, almost, will accomplish it. There are substances that dissolve their part- nership with peculiar ease : a shock, a jar, a breath, an imperceptible trifle, will suffice to effect the severance. You touch them, you merely move them a little, and, piff ! there is an explosion before you can snatch your hand away, with a flying of par- ticles in this direction and that as if no such thing as union had ever existed. These are chemical mar- riages between incompatible natures that sigh only for divorce. "

"And are there really, " asked Emile, "sub- stances that fly apart, that go piff! just from being touched!"

"Yes, my child, there certainly are. You your- self are familiar with some of them. Those New- Year's bonbons done up in particolored paper and known to you as snappers — don't they recall any- thing to your mind?"

"Why, yes; each bonbon has a rebus to be guessed, and then there 's a little strip of parch- ment that gives a pop when you pull it by both ends at once. What is it that makes the little ex- plosion !M

"It is a substance made by combining different

30 THE WONDER BOOK OF CHEMISTRY

ingredients which fly asunder as soon as they are disturbed by the parting of the two pieces of parch- ment forming the strip. You see how easy the act of separation is in this case : just disturb the slum- bers of the explosive material by pulling at the two ends of the strip, and that is enough to cause a dis- ruption accompanied by a sharp report. In like manner a house of cards collapses at a mere touch.

"A similar substance causes the explosion of the toy torpedoes that give a pop when you throw them on the ground, and to this substance is due also the explosive quality in the percussion-caps of guns, the cap being ignited by the fall of the hammer when the trigger is pulled. A quick spurt of flame is produced, and this penetrates the touch-hole and discharges the powder in the gun-barrel. Consider for a moment the construction of these percussion- caps. At the bottom of the little cup-shaped bit of copper forming the cap you can see a white sub- stance deposited in a thin coating on the metal. It is the fulminating-powder, made of several in- gredients carefully combined in accordance with chemical science and ready to fly apart with violence at the mere shock imparted by the hammer. But this is enough about these touchy and noisily dan- gerous substances, so prone to separate into their elements with a loud report as soon as we have joined those elements together. Let us proceed to something harmless. What should you say there is in a slice of bread V

"I should say — I should say/' Emile hastened to

THE SLICE OF TOAST 31

answer, "that there is flour.' And with that he

thought he had said the last word on the subject. "True,' assented his uncle, "but what is there

in flour?"

' * In flour ? What can there be in it except flour ? ' "But what if I told you there was carbon, or what

amounts to the same thing, charcoal, in flour?' "What, charcoal in flour?' "Yes, my boy, charcoal, — a lot of it.' "Oh, Uncle, you are only in fun! We don't eat

charcoal."

"Ah, my young sir, you don't believe it? But

did n't I tell vou that chemical combination can turn

•

black to white, sour to sweet, the uneatable +o nourishing food? Furthermore, I will show you some of this charcoal that is found in bread; or, rather, I don't need to do that, as you have seen it hundreds of times and it will be enough now to jog vour memorv. Tell me: don't vou often toast vour

w _ m » w

bread a little over the fire before crumbling it into milk for your breakfast?'

"Why, yes, I let it get crisp and brown. It 's ever so much better that way; it goes better with milk when it is toasted just enough to make a crunching sound when you break it. In the winter, when the stove is hot, you can do it just right.'

"But what if you forget your slice of bread on the stove! What if vou let it toast too Ions:? What

«/

happens to it then? Come, now, tell me, from your own remembrance of the thing, for I would n 't on any account influence your opinion in this serious

32 THE WONDER BOOK OF CHEMISTRY

matter. What would happen if your bread stayed on the hot stove a whole hour?'

"That 's easy enough to answer : it would all turn to charcoal. I 've seen it happen lots of times.'

"Well, then, tell me, where did the charcoal come from?— out of the stove?"

"Oh, no, not at all!"

"Then from the bread itself?"

"Yes, it must have come from the bread."

"But from no substance can there come anything that was not there before ; nothing can furnish what it does not already have. Consequently, bread, which yields charcoal after being exposed some time to the action of fire, must itself contain charcoal, or carbon if we choose to use that word. '

"Why, that 's so! I hadn't thought of it be- fore. ' '

"There are many other things, my little lad, that you have seen again and again without grasp- ing their significance, because no one has set you on the right road. I shall often turn these common occurrences to account by showing you to what im- portant truths they open the wray when you reflect on them a little. Reflection now makes you aware that bread contains quantities of carbon."

"I admit that bread contains carbon,' assented Jules. "The proof is there before your eyes, plain enough. But, as Emile says, we don't eat charcoal, and we do eat bread ; charcoal is black, and bread is white."

"If the charcoal, or the carbon, were alone," re-

THE SLICE OF TOAST 33

plied his uncle, "it would be black and uneatable, as you have described it, and it would remain so in- definitely. But it is not alone and by itself in bread ; it is associated or combined with other things, and the combination has none of the qualities you have named as belonging to charcoal, just as sulphid of iron has none of the qualities belonging to sulphur and iron. These other qualities found in bread are driven out by excessive heat, and the charcoal re- mains, with all the characteristics peculiar to it, — blackness, hardness, brittleness, unpalatability, — in short, unmistakable charcoaliness. The heat of the stove undoes the work of combination, sundering what was joined together in the bread. That is the whole secret of the transformation of a slice of bread into a slice of charcoal when the toasting process has gone too far. Now let us inquire into the other things that accompany the carbon in white bread. They are known to you; you have seen them, and you have smelt their disagreeable odor when heat drives them out.'

"I don't quite understand you,' said Jules, "unless you mean that bad-smelling smoke that comes from bread when it is turning to charcoal."

"Exactly; you have my meaning. That smoke was a part of the bread it came from. The char- coal and the offensive fumes you know so well would, if recombined as they were at first, consti- tute precisely the slice of bread as it was before being subjected to the action of heat. Heat wrought the separation, dissipating some of the constituent

THE WONDER BOOK OF CHEMISTRY

elements in the air and leaving behind, stripped of its previous disguise, the black and uneatable substance so well known to you as charcoal. "

"Then those bad-smelling fumes and the charcoal, with nothing else, make bread, and two things that couldn't be eaten separately form by their union our chief food?'

"You have put it quite correctly: substances that by themselves, far from yielding nourishment, would be positively harmful if eaten, become by combina- tion transformed into excellent food."

"I must believe you, Uncle Paul, because you say it is so; but — but — "

"I understand, my young friend, your hesitation and your 'buts.' On first hearing these things one can hardly believe them, so at variance are they with accepted notions. Therefore I do not ask you to take my bare word; you must be convinced by something other than my authority. Did I not at the very beginning prepare the way for these start- ling developments by means of a perfectly con- clusive experiment! Eecall the black substance that we obtained in the medicine-bottle. Eecall that sulphur now no longer sulphur and that iron now no longer iron. Why should there be anything more surprising in the fact that charcoal and some bad-smelling fumes can cease to be what they now are, and can become bread?'

"You are right, Uncle, and the best thing to do is to take your word for it."

"To take my word for it sometimes may be neces- sary, as when the proof of an assertion would entail

THE SLICE OF TOAST 35

explanations too difficult for you to follow; but as far as possible I shall impose nothing on you as an article of faith, choosing rather to let you see, touch, and conclude for yourselves. I wish you to see the light and to witness the evidence, not to retain a mere mass of truths accepted on the authority of my word. In bread decomposed by heat I show you charcoal and call your attention to certain peculiar odors or fumes. What, now, is the natural inference ?"

"That bread consists of that charcoal and those fumes united. It is too plain to be doubted. "

"Yes, when facts speak we must accept what they say without heeding the counter-suggestions of long habit. These facts tell us that bread may be re- solved by the action of heat into charcoal and certain vapors. Let us grasp that truth and acknowledge ourselves convinced.

"One other thing puzzles me," said Jules, "and it is the hardest puzzle yet. You say that the char- coal and the vapors separated by heat would, if recombined, make the bread again as it was before. Then, does n't fire destroy any of the bread?"

"The word ' destroy' has more than one meaning, m7 boy. If in using it you mean that a slice of bread, after being subjected to intense heat, no longer exists as bread, you are quite right: the resultant charcoal and vapors are in no sense bread, but merely the substances of which bread is formed. If, on the other hand, you mean that the bread is reduced to nothing, you are greatly mistaken, for there is not a particle of matter in existence that

36 THE WONDER BOOK OF CHEMISTRY

can by any force or device at our command be put out of existence. "

"But that was just what I meant, — reduced to nothing, put out of existence. We speak of fire as destroying or annihilating everything."

"Then, in the literal sense of those words, we talk foolishly, for again I assure you that nothing in the whole universe, not even the tiniest grain of sand, is ever annihilated. Neither fire nor any other agency can annihilate even the finest thread of a spider's web.

"Listen, now, with close attention, for the sub- ject is worth it. We will suppose a fine house is built, with spacious halls, splendid apartments, chambers, kitchen, vestibule, piazza, doors, win- dows,— in short, everything belonging to a comfort- able and attractive abode. In building it the work- men had to place in their proper positions count- less materials, such as cut stone, brick, rubble-stone, mortar, tiles, beams, boards, laths, plaster, metal fixtures, and so on. The house stands there, stanch and proud and suited to the requirements of the most exacting. Can it be destroyed! All too easily. Call back the masons with their picks and crowbars and hammers, and if necessary they will tear down the building much more quickly than they put it up. The fine mansion will soon be nothing but a shape- less pile of ruins, of rubbish ; it will be destroyed as a house.

"But will it be annihilated, reduced to nothing? Evidently not. Does there not remain an enormous heap of materials, — of stone, brick, wood, iron, —

THE SLICE OF TOAST 37

of everything, in fact, that went to the building of the house? The house, then, is not annihilated, and, what is more, not a particle that entered into its construction has been reduced to nothing. Even the last grain of sand used in mixing the mortar is sure to be in existence somewhere. The wind may have blown away some of the plaster-dust as the house was being torn down; but that dust, of a fineness hardly visible, is nevertheless undestroyed, however widely dispersed by the wind; and if it cannot now be gathered up, we can at least see it in our mind's eye, scattered in this direction and that. Of the entire building, therefore, that has been demolished not a particle of dust has been an- nihilated.

"Well, now, fire in its turn is a demolisher, but nothing more. It demolishes buildings made of many materials combined, but it never reduces to nothing the smallest particle, the minutest grain of dust, in those materials. We subject to its destruc- tive power a mouthful of bread, and destruction follows, but never anything like annihilation; for what is left, after the fire has played its part, is just as truly matter as was the bread itself. That residue is in the form of charcoal and certain fumes or vapors, the charcoal remaining in a little mass by itself, the vapors being dissipated and no longer traceable, even as the plaster-dust was lost to view. Bid yourselves, then, forever, of the foolish notion of annihilation. "

"There goes Jules again with another of his

38 THE WONDER BOOK OF CHEMISTRY

'buts'! "What is your difficulty this time, my lad?'

"When you burn a stick of wood in the fireplace, isn't it reduced to nothing, or almost nothing?. There 's only a pinch of ashes left at the end. I see how the ashes come from what was once wood, but they amount to so little they can't represent all that has been demolished by the fire. The greater part of the wood, then, must have been reduced to nothing. ' '

"Your observation shows a thoughtful mind, and is of the kind I like. Accordingly, I hasten to answer you. I just spoke of the plaster-dust blown away by the wind in the demolition of our supposed house. Is it not plain that, the walls being built largely of powdery materials capable of being caught up by a passing breeze, a considerable part would be thus borne away in various directions, leaving behind a proportionately diminished heap of refuse?"

"Certainly; I admit that."

"If, now, it were possible in a work of masonry for the whole structure to be swept away as im- palpable dust, what would remain?'

"Nothing, of course."

"But would the building on that account have been reduced to nothing?'

"Why, no; it would have been turned into fine dust scattered all about.'

1 ' Just so with your stick of wood, my little friend : fire resolves it into its constituent elements, some of which are far more impalpable than the finest dust. These are lost to view, being dissipated here and

THE SLICE OF TOAST 39

there in the boundless atmosphere, and as we find nothing left but a handful of ashes we are prone to believe the rest has been annihilated, whereas it still exists, indestructible, floating in the atmosphere and having a limpidity, a colorlessness, as complete as that of the air itself."

''Then a stick of wood that has just been burnt up in the fireplace is mostly scattered in the air in a sort of fine dust that we can't see?"

"Yes, my boy; and the same is to be said of all fuel that we burn to obtain either heat or light."

"Now I see why wood, when it is burned, seems to be reduced to nothing. What was the wood has, as you say, been mostly carried away without our seeing it, somewhat as the plaster-dust of a house that is being torn down is blown away by the wind."

"Note also, my boys, that out of the materials left when a house is torn down, another house can be built, different in form and on another site if de- sired. The heap of ruins will thus become once more a finished structure. But, further, there is no reason why these same materials could not be used for making other things, the stones for one purpose, the bricks for another, the wood for still another, so that the ruins of our demolished house would enter into various constructions having each its own form and purpose and character.

"Somewhat thus is it with matter in general. Let us suppose two, three, or four substances, each of a different nature from the others, to enter into combination. They function all together in a certain manner; they dispose themselves so as to form what

40 THE WONDER BOOK OF CHEMISTRY

I will call a kind of building; and by thus associat- ing they produce a substance quite different from any of the constituent substances, just as our fin- ished house is neither sand nor lime, nor plaster, nor brick, nor, in fine, any of the materials used by the builders.

" After a while, for some reason or other, these combined substances separate, and the chemical structure is demolished. The ruins are left; there has been no loss of matter. What will nature do with these ruins? Perhaps any one of a thousand things; perhaps use a little of this ingredient for one purpose, a little of that for another, and so on until the last particle of matter has been utilized and the result is a great variety of productions, all very different from the original substance. What went to make something black, will, it may be, now enter into the formation of a white substance ; what was a part of something sour, may contribute to the making of something sweet ; and what helped to con- stitute a poison, is likely enough to be found again in an article of food, just as the bricks of a former conduit may by a totally different application serve in the construction of a chimney and thus make a passage for smoke and flames instead of for water.

"Thus it is that nothing is ever annihilated, des- pite all appearances to the contrary, appearances that so often deceive us because we do not observe accurately. Let us pay closer attention, and we shall perceive that all matter persists, indestructi- ble. It enters into an infinite variety of combina- tions, forever uniting and separating and uniting

THE SLICE OF TOAST

again, some of its manifold forms being every moment destroyed and every moment renewed, in an endless series of transformations, without the loss or gain of a single particle in the whole universe. "

CHAPTER IV

SIMPLE SUBSTANCES

"T ET us return now to the black powder, 1 ^ the sulphid of iron, that served as our starting-point in this discussion. By a process far less simple than ordinary sorting, a process known to chemical science, this substance can be decom- posed and the sulphur and iron separated. Sub- jected to the easy decomposition wrought by fire, bread furnishes, as its most notable constituent, carbon. Now of what, in their turn, are carbon and sulphur and iron each composed! Let me give you the answer made to this question by scientific investigation as conducted ever since these sub- stances became the objects of man's interest and study. No matter with what thoroughness, with what elaborate and painstaking experiments, they are examined, no matter how powerful the forces brought to bear on them, carbon and sulphur and iron never give us anything but carbon and sulphur and iron."

"But it seems to me," objected Jules, "that sulphur does give something that isn't sulphur. When you set fire to a little of it, there is a blue flame and some sort of vapor that makes you cough. That vapor must come from the sulphur, but it is

42

SIMPLE SUBSTANCES 43

something very different from sulphur, for it makes us cough worse than if we had the whooping-cough, and sulphur doesn't do that even if you hold it right under your nose."

"Let us understand each other, my boy. When I say that sulphur never gives us anything but sulphur, I mean that it cannot be decomposed into other substances ; but I do not by any means assert that it cannot by combination with other substances produce not only the vapor that makes us cough, but also many other things, notably the black powder you now know so well, the sulphid of iron. I told you that every substance, in burning, combines with another which we cannot see, and which is contained in the atmosphere about us. If sulphur becomes enveloped in blue flames, it is a sign that it is com- bining with that atmospheric substance. The re- sult of this combination is the vapor that makes us cough. "

"Then that vapor is more complicated than sul- phur?"

"Yes."

"It must be made of two things, sulphur and that stuff in the air you told us about, while sulphur is made of only one thing, sulphur itself."

"Quite right. I repeat, then, that sulphur, even when put to every sort of test, has never been de- composed, never been divided into different sub- stances, as, for example, the black powder in our medicine-bottle could be divided into iron and sul- phur, and as bread could be resolved into several ingredients, carbon among them. Sulphur goes to

44 THE WONDER BOOK OF CHEMISTRY

the making of a great many things more complicated than itself, but can never yield anything simpler. When we come to sulphur, decomposition stops; by no means at our command have we yet succeeded in dividing sulphur into two or more other sub- stances. Hence we call sulphur a simple substance, meaning that its further simplification is impossible. Water, air, a pebble, a piece of wood, a plant, an animal — all these may be regarded as substances, but they are not simple substances. Bear that in mind.

"Carbon and iron are also simple substances, for the same reason that sulphur is a simple substance : they cannot be made to yield anything except carbon and iron unless they are combined with other things ; but this would not be a simplifying., it would be a complicating process. 'Chemists have carefully ex- amined all substances to be found in nature, whether on the earth's surface or beneath, whether in the depths of the sea or in the air about and above us, and whether belonging to the animal or the vege- table or the mineral kingdom; they have examined all, studied all, analyzed all, and the fruit of this immense task, prosecuted with all possible learn- ing and patience, is the conclusion that the number of undecomposable or simple substances amounts to sixty l or thereabout, including iron, sulphur, and carbon, which we have just been considering. "

"And will you tell us about all these simple sub- stances ?" asked Emile.

i Since thia was written twenty or more have been added to the 1 ist . — Trans lator.

SIMPLE SUBSTANCES 45

1 i Not all ; far from it, for the greater part would not interest us; but you shall hear about some of the more important ones. Moreover, you already know a number of simple substances besides the three — iron, sulphur, and carbon — which we have just examined."

"I know other simple substances? " the boy ex- claimed in surprise. "I did not know I was so wise!"

"You knew carbon without suspecting it of ob- stinately resisting all attempts to decompose it. There are more things in your good little head than you are aware of; my part is to put some sort of order into your jumbled ideas. But I shall refrain as far as possible from teaching you outright, pre- ferring to make you recall what you already know. I will tell you at this point, however, that all metals are simple substances."

"I see. Then copper, lead, tin, silver, gold, and others that I forget, are simple substances, just the same as iron."

"An expert chemist could not have put it better. They are so many substances on which decomposi- tion has no hold; they are simple substances. But there is one metal in common use that Emile has omitted. Think! It begins with £."

"With £? Wait — it is zinc, the same as our watering-cans are made of."

"Right. These are not nearly all the metals, though; there are many others, and among them some extremely curious ones, but they are not in gen- eral use. I will acquaint you with them as fast as we

46 THE WONDER BOOK OF CHEMISTRY

have occasion to handle them. One, however, might be mentioned here. This metal runs like melted tin, but at the same time it is cold. It has the color of silver, and it goes up and down in a thread-like column in the thermometer to show us the tempera- ture of the atmosphere."

"Oh, that is mercury, or quicksilver!"

4 Exactly. Its common name of quicksilver might deceive you. It has the shiny appearance of silver, but none of that metal's other qualities. It is a distinct metal, as different from silver as are lead and copper. The term 'quick' indicates that it runs all about, flowing in little globules and always elud- ing the fingers that try to grasp it."

"Then quicksilver is a metal, the same as iron, copper, lead, or gold?"

'It is a metal, no more and no less, but different from others in that the mere warmth of our climate, even in winter, is sufficient to keep it in a molten state, whereas to melt lead the heat of burning coal is necessary, and for copper and especially iron it takes the hottest kind of furnace. But were it cooled sufficiently, it would become hard and not unlike a piece of silver in appearance. " "Money could be made of it, then?" "There would be nothing to prevent; but it would be a strange kind of money, for a few minutes after putting it in your pocket you would find it melted and running all about.

'The color of inctals does not vary much: silver and mercury are white, tin a little less so, and lead still less, while gold is yellow, copper red, and the

SIMPLE SUBSTANCES 47

others, notably iron and zinc, grayish white. All shine brightly, at least when recently cleaned; or, in other words, they all have a metallic luster. But you know the proverb, 'All that glisters is not gold.' In the same way, all that shines is not metal. You would not have to hunt long in the garden to find some insect — some beetle, for instance — whose rich wing-sheaths have the luster of polished metal, though in reality they are nothing but scales of horn. Certain stones, judged by their deceptive luster, might be mistaken, some for gold, others for silver ; and yet they contain not the slightest particle of these two metals. The glittering yellow spangles 1 mixed with the blue sand used for drying ink after writing have nothing in common with gold except the glitter, and are not even made of metal. So it is that all metals, without exception, have the peculiar luster called metallic; but this luster may be found, just as bright, in a great many other things that are not metals.

"The other simple substances, sulphur and car- bon among them, are without metallic luster; some there are, too, and very important ones, that are colorless, invisible, of the same subtle quality as air. These non-metallic simple substances are called by the general name of metalloids. Carbon is a metalloid, sulphur is another. The number of metalloids is not great, about a dozen perhaps, but the part they play is highly important. One might say of them what is, alas, only too true of human

i Particles of mica. Before blotting-paper came into use, fine sand was sprinkled over fresh \vriting to absorb the ink. — Translator.

48 THE WONDER BOOK OF CHEMISTRY

beings: those that make the greatest noise are not the ones that are the most useful. Indeed, though the metalloids are of primary importance in the construction of the things about us, being no less necessary in the countless works of nature than stone and bricks and mortar in our buildings, there are some that many of us do not even know by name. One must at least have read some book on chemistry to be aware of their existence. If we were not told of them by those more learned than ourselves, we should remain ignorant of them to the end of our days. One of these important substances — and it is one without which we should speedily die — has a name that is probably unfamiliar to your young ears; you may, in fact, never have heard it mentioned. It is oxygen. "

"Oh, what a funny name!" cried Emile. "I Ve never heard it before."

"And these: hydrogen, nitrogen — do you know them?"

"No more than the other."

"I suspected as much. They are the names of two good and useful metalloids that quietly perform their appointed tasks without soliciting public notice, just as a generous giver is willing to remain unknown, provided only his gift reaches its destina- tion. All three — oxygen, hydrogen, and nitrogen — are the less likely to attract popular attention, despite the importance of their services, because they have the invisibility, the thinness, of air. Very often, too, they are concealed in combinations in which only the higher science can detect their pres-

SIMPLE SUBSTANCES 49

ence. Beason enough, then, for our remaining in ignorance about these substances that play the lead- ing parts in nature's never-ending drama."

"Are they, then, so very important?'

"Yes, my boy, they are extremely important.'

"More so than gold?"

"You are all astray, my dear Emile, on this sub- ject of importance. Gold is unquestionably a very useful metal to man; it is the sign of riches, of the savings amassed by labor. Coined into money, it passes from hand to hand and is good in all ex- changes, in all commercial transactions. It is a splendid part to play, I admit; but if gold were to disappear entirely from the earth, what would happen? Nothing very serious. Banks might be inconvenienced, commerce upset for a little while, but that is all. The world would soon move on again as before. Suppose, on the other hand, one of these three metalloids whose names you have just learned — oxygen, for example — should disap- pear. Immediately everything on earth would die, from the biggest animal to the tiniest worm; all plant life would perish, from the giant of the forest to the smallest thread of moss. Life would hence- forth be impossible and this inhabited globe become a gloomy solitude, with man, animal, and plant for- ever banished. That, as you see, would be a far more serious disaster than the inconvenience of a banker or the vexation of a merchant.

"In the general scheme of things, gold plays only an insignificant part, almost a negligible part. If it were lacking altogether, the order of nature would

50 THE WONDER BOOK OF CHEMISTRY

not be affected. Oxygen, hydrogen, and nitrogen, on the contrary, fulfil in this world of ours func- tions so important that if any one of these three were taken away, everything would be turned topsy- turvy and life would be rendered impossible. To these three carbon must be added, for its part is riot less important ; and thus we have four substances in- dispensable to all life, vegetable as well as animal. Now compare with them, if you like, this gold that everybody talks about, is familiar with, longs for, and that many wear themselves out in trying to get. Was I not right when I said that making the most noise in the world is a very different thing from rendering the highest service? Believe me, my young friends, gold is but a poor thing when looked at from the proper point of view.'

"And you will tell us about this oxygen, this hydrogen and nitrogen, that the world cannot do without?" asked Jules.

" Certainly. I shall begin with them. Honor to whom honor is due. To tell you what they are and what they do will take up more time than all the rest. To complete the list of metalloids that you need henceforth to know, at least by name, I will mention one other. It is the substance you see at the tip end of a match, overlying a layer of sulphur, and taking fire with friction. It will give a mild glow, too, when rubbed between the fingers in a darkened room."

"That must be phosphorus."

"Yes, phosphorus. It also is a metalloid. Let

SIMPLE SUBSTANCES 51

us sum up at this point. There are about sixty simple substances, divided into metals and metal- loids. Metals have a peculiar sheen called metallic luster. Those known to you are iron, copper, lead, tin, zinc, mercury, silver, and gold. Some of the others deserve our attention as well, and I will speak of them as occasion arises. There are, all told, about fifty * metals. The metalloids, which are much fewer in number, or about a dozen in all, have not the so-called metallic luster. The most important ones are oxygen, hydrogen, nitrogen, car- bon, sulphur, and phosphorus. The first three in the list are, like air, invisible.

"Simple substances, metals as well as metalloids, are also called elements. By this is meant that they are the undecomposable or prime substances used by nature in all her works. "

"But, Uncle Paul,*' Jules here interposed, "I read in a book that there are only four elements in nature, not sixty, and that they are earth, air, fire and water. ' '

"That book repeated the false notions of ancient times, notions preserved to our day in popular speech, in which long habit is slow to give place to the progress of science. It was, indeed, formerly believed that everything in nature could be traced back to earth, air, fire, and water, which were thought to be the four undecomposable substances, the four elements, of which all things were made.

i The recognized number is now nearer seventy than fifty. — Translator.

52 THE WONDER BOOK OF CHEMISTRY

But it has been found after more careful study that not one of the elements as understood by the ancients is really a simple substance.

"In the first place, fire — or, rather, heat — is not a material thing at all, and consequently has no place in the list of simple substances, which are matter even when they are invisible. All matter can be weighed and measured. We speak of a cubic foot of oxygen, a pound of sulphur ; but it would be the height of absurdity to speak of a cubic foot of heat or a pound of warmth. You might just as well pretend to weigh by the pound and measure by the quart the notes that come from the strings of a violin.7'

"A pound of F sharp or a quart of E flat would certainly sound funny," Jules agreed, smiling at the odd association of words.

"You smile, naturally enough, for a musical note cannot be weighed in the scales or measured by the quart or the bushel. And why is this impossible? Because sound is not matter, but a movement trans- mitted in successive waves from the sonorous body to our ears. The same with heat: it is a peculiar mode of motion. To my regret, I can but touch on this interesting subject at this time, since to ex- plain it properly would take so long that chemistry would in the meantime be forgotten. I will simply say, then, that heat cannot be classed as an element, because it is not matter.

"When we come to air, however, we have quite another thing. It can be measured by the quart, weighed by the pound. It is probably new to you

SIMPLE SUBSTANCES 53

to hear air spoken of as being weighed and meas- ured; but nothing could be more correct. Physics could teach us much about this if we had the time just now to give to it. Air is matter, though, un- fortunately for the credit of the ancient theory, this matter is not a simple substance. Instead of being made of one thing, air is made of two very different things. I will tell you their names before I under- take to prove to you by experiment the truth of this assertion. Air is composed of oxygen and nitrogen.

"Nor is water any more truly a simple substance, an element, than air. At the proper time I will show you that it is a compound of oxygen and hydrogen.

"As to earth, what is meant by that word! Evi- dently the mixture of mineral substances — sand, clay, gravel, pebbles, rocks, stones — that form the solid part of the globe. Thus, instead of being an element, one simple substance, it contains all the elements, from the first to the last. From the earth are obtained all the metals and various metalloids; in fact, all simple substances could be derived from' this source if we cared to decompose those combina- tions in which many of them are at present tied up. We may, then, say of the four elements, com- monly so called after the ancient conception of the matter, that not one of them will bear critical ex- amination, not one will prove to be a simple sub- stance, an element, as the word is understood to- day. "

"W

CHAPTER V

COMPOUND SUBSTANCES

ITH the materials of his handicraft -with stones, bricks, mortar, and plas- ter— a mason can build, at his will, vault, bridge, wall, reservoir, shed, coach-house, factory, cellar, terrace, hut, castle, or palace; and each of these constructions, although of like materials, will differ in form, purpose, and other qualities. In similar manner, with the threescore elements at her dis- posal, nature fashions all the things that come from her hand, in the animal, the vegetable, and the mineral kingdoms. An artisan of sublime achieve- ments, she demands but a few materials; and not even all of these does she often use at once, in order to obtain results of infinite variety. Combined in countless ways, these elements or simple substances form everything on and in the earth. Nothing, ab- solutely nothing is known to us that, when decom- posed (if it be not simple to begin with), fails to resolve itself into a certain number of metals or metalloids or both."

"Then everything comes from these same simple substances ?" asked the children.

"Everything that is not already a simple sub- stance. Consider for a moment the element that

64

COMPOUND SUBSTANCES 55

you see most often under one or another of its various disguises, — carbon. I have shown it to you as forming a part of bread. You know, too, that wood contains it, as can be seen from the charred fagots in the open fire. Now, the carbon in bread and that in the trunks and branches of trees are exactly the same, so that in the ever-changing com- binations of nature the carbon in the loaf of bread might reappear in an oak fagot, and that in the oak fagot might turn up again in the loaf of bread. "

"And so," observed Emile, more in jest than in earnest, "when we eat a slice of bread and butter, we are eating what might have made a knotty stump. ' '

"Who knows, then, my little lad," his uncle took him up, "how many knotty stumps you have eaten in your lifetime! I hope soon to show you that your jesting remark comes nearer the truth than you thought."

"Uncle Paul, I won't say anything more! Your simple substances are too much for me.'

"Too much for you? Not at all. But perhaps you feel yourself, for the moment, a little dazzled by the blinding light of a new truth, just as a strong ray of sunshine dazzles the eyes. Let us continue, and gradually everything will appear clear to you. The carbon in an oak fagot — why should it not have gone to the making of a pear, an apple, or a chest- nut? Is there not carbon in those?"

"Yes, there is," replied Jules. "When you leave chestnuts on the coals too long they turn to char- coal, and if you forget apples or pears put to bake

56 THE WONDER BOOK OF CHEMISTRY

in the oven you find them nothing but lumps of charcoal. "

" Again, this charred chestnut, apple, or pear is of the same substance as that in firewood and in bread. Do you now begin to glimpse the fact that it is possible to eat what, by a change of destination, might have become a stump or a stick for the fire ! ' '

"I can more than glimpse it,' Emile answered; "I see it."

"And you will soon see it clearer. If instead of using olive-oil on our salad or for frying fish, we put it into a lamp, it will burn and give light. Now let us hold a piece of window-glass or a plate over the flame. Instantly a coating of black dust col- lects on it."

"I know, that is lampblack. I make my glasses dark with it when I want to look at the sun in an eclipse."

"And what is this lampblack?"

"It looks very much like charcoal-dust."

"It really is charcoal, or carbon. And where does this carbon come from, if you please?'

"I don't see where it could come from, unless from the oil burned in the lamp.'

"It does come from the oil, that is plain; from the oil decomposed by the heat of the flame. So there is carbon in oil. Needless to add, this carbon differs not at all from other carbon. It is found in grease, in tallow, for candles and tapers give lampblack just as does the oil-burning lamp. It is also in resin, which burns with a thick black smoke; it is in — But I should never get to the end if I tried to give

COMPOUND SUBSTANCES 57

a complete list. I will mention finally the mutton- chops you have seen so often on the dinner-table. If the cook is not careful, what becomes of them on the gridiron? "

"Why, that 's so!'7 Emile exclaimed. "I hadn't thought of it. If you let them cook too long, the chops all turn to charcoal.'

"What, then, do we infer from that?" asked, Uncle Paul.

"We infer that there is carbon in meat. It must be everywhere!"

"Everywhere? Oh, no! Far from it. But car- bon occurs very often. You will find it especially in all animal and vegetable products. All these substances, when decomposed by fire, leave carbon in their ashes. So you can easily make out as long a list as you choose of substances containing this element. ' '

"Paper, white as it is, must have some, for it turns black when you burn it. But, tell me, does paper come from plants?"

"Yes, my child, it comes from vegetable matter, being made out of old rags, and these old rags are the remnants of fabrics woven of linen or cotton."

"Milk," asked Jules, "which is still whiter than paper — does that too have carbon in it? I have seen the foam turn black at the edge of the saucepan when the fire was too hot.'

"Yes, milk too contains carbon, I can assure you. But let that do for the present. Further examples are not needed to show you what varied uses carbon can serve at the hands of Mother Nature. Now will

58 THE WONDER BOOK OF CHEMISTRY

Emile recite the fable he has been learning by heart the last few days?"

"Which one?"

"The one about the sculptor and the statue of Jupiter."

"Oh, yes, I know:

"A block of marble, fair to see,

Filled with delight a sculptor's soul. He bought it. 'Now what shall it be, A god, a table, or a bowl .?

" 'A god were best, an awful god,

With thunderbolt in lifted hand. Mankind shall tremble at his nod, His name be feared in every land.'

Here Uncle Paul stopped the reciter: "That is enough, my boy. You have a good memory. What does the good La Fontaine tell us? He tells us that •a sculptor, viewing the superb block of marble he had just bought, asked himself what he should do with his purchase. His chisel could make of it at will a bath for a sumptuous palace, the bowl of a fountain for a princely garden, or a modest slab, a commonplace bureau-top or mantelpiece. He de- cided on a god. The block of marble which could become a bowl in which to wash face and hands, shall be Jove the Thunderer, before whom all man- kind falls prostrate. Out of one and the same ma- terial the chisel is to bring forth, not a trivial piece of furniture, but a noble statue. In like manner does Nature proceed, able as she is to make what- ever she chooses out of the chemicals at her disposal.

COMPOUND SUBSTANCES 59

A little carbon, let us say, is at hand. 'What shall my art make of it?' she asks. ' Shall it be a flower, turnip, flesh, or hair of an animal! It shall be a flower; more than that, it shall by its coloring and perfume be the queen of the flower garden.' And the splendid rose comes forth from the carbon that might have become sheep's tallow or a part of a donkey's horny hoof."

"But there 's something else in the rose besides this carbon that makes so many things, isn't there?" asked Emile.

"Certainly; otherwise the carbon would remain carbon and nothing more. It is combined with other simple substances. The same must be said of it in all the other things we have just named as containing carbon. ' '

' * Then, ' said Jules, summing up what his uncle had told them, "bread, milk, grease, oil, fruit, flowers, linen, cotton, paper, and lots of other things, all contain carbon and also various other elements that never change their nature, whether they are in a flower or in a lump of tallow, in a piece of paper or in a stick of wood. They are always the same metals and the same metalloids. And are our bodies too made of these things?"

"As far as matter is concerned, man does not differ from the rest of creation. His body has for its constituents exactly the same metals and metal- loids."

"What!" cried Emile, surprised at this human chemistry. "Are there metals in us? Are our bodies mines? I could believe it if we were all

60 THE WONDER BOOK OF CHEMISTRY

sword-swallowers like the jugglers we see at the fair; but we have n't quite come to that yet.'

"Agreed. Nevertheless, there is iron in us, — - precisely the same metal as is swallowed by the jugglers you speak of. And iron is so indispens- able to us that without it we should lead a languish- ing life; or, rather, we should find it impossible to live at all. It is iron, let me add in this connection, that gives to our blood its red color. ' '

"I know that our blood is colored red somehow or other ; but, all the same, I know that nobody can eat metals, not even the juggler who fools us with his cleverness. Where does this coloring matter come from, then?"

"Like carbon, sulphur, and whatever other ele- ments the body needs, it comes from our food, which contains it, a little here and a little there, without our knowing it. And are you quite sure that we never take iron, real iron without any disguise? At your age, when the mere work of growing is some- thing considerable, and strength is none too great, the doctor often orders iron, which is taken in the form of a very fine powder, or is given to us to drink in water that has had old iron in it for some time, and has thus become slightly charged with the rust. That is not exactly the same as swallowing swords, but it is eating iron nevertheless/

"I am ready now to believe we eat as many metals as you please," Emile assented.

"Not so fast! Don't let us make the human body a mine, as you called it just now. I am speaking only of iron, to which might be added three or four

COMPOUND SUBSTANCES 61

other metals that, unfortunately, you know nothing about as yet. There are metals familiar to us all, such as lead, copper, zinc, gold, and silver, that have no place in the human body or in animals or in plants. Certain metals, indeed, if they were intro- duced into the body, would endanger life, for they are poisons. I keep to iron, then, and will add that very little of it is enough to give color and other peculiar properties to the blood, — so little, in fact, that the body of an animal the size of an ox would furnish hardly enough iron to make a nail. I will add that this nail would cost a fabulous sum, so much labor and pains would have to be expended in the mining of this animal ore. If necessary, the thing could be done, which is all I wish to make you understand.

"We have now reached the point where you ought to begin to perceive that simple substances, by combining in many ways, produce a vast variety of other substances endowed with widely varying properties. These substances are called compound because they are each composed of a number of elements. Water is a compound substance; so are flour, wood, and paper, oil and grease, pine resin, animal flesh and horn, the essence of the rose, and, in short, such a multitude of things that the list would never come to an end. Water is composed of oxygen and 'hydrogen, two metalloids that we shall take an early opportunity to become acquainted with. The other things I have just named contain carbon among their elements.

So vast is the number of compound substances

i .

62 THE WONDER BOOK OF CHEMISTRY

that we might almost call it infinite. At any rate, no limit is known. And yet all these compounds come from the mixing together of two or more of those simple substances that do not number so very many, some threescore in all. Furthermore, many of these simple substances play so unimportant a part that their entire omission would make no ap- preciable difference in the grand total of the world's material riches. Among these minor elements I will mention gold. Confining ourselves to the fun- damentals, we can see that, at most, only about a dozen simple substances contribute to form the im- mense majority of the products of nature.'

1 'But there 's one difficulty, it seems to me,' ob- jected Jules; "and it strikes me all the more after what you have just said. I was wondering how such a lot of different things — so many that perhaps they could n 't be counted — can all come from sixty elements. And now I wonder still more how the great majority of these countless things can come from only a dozen elements.'

"I was expecting this objection to be raised, and was about to answer it in advance when you got ahead of me; for which, in truth, I am very glad, as thus I receive a fresh proof of the reflective quality of your mind. I have proposed a puzzle to you, and now I will use an illustration that will help you to solve it. Our alphabet has twenty-six letters. How many words can be formed with these characters?'

"Why — I — I don't know what to say. I have never counted them, for a dictionary, even a small

COMPOUND SUBSTANCES 63

one, has lots and lots of words. Let us say ten thousand. ' '

* ' We will let it go at that — ten thousand, in round numbers. It is not necessary to be very exact in this matter. You will notice that we are speaking only of our own language ; but the same characters could be used for writing all the languages of the world that have been spoken in the past, that are spoken to-day, or that may be spoken in the future. I omit certain instances of peculiar pronunciation, which are negligible in this connection. With our twenty-six letters, then, Latin, French, English, Italian, Spanish, German, Danish, Swedish, and many other languages are written. The same letters, too, could be used for Greek, Chinese, Hin- dustani, Arabic, and all other tongues with written characters differing from ours only in form. There is no language, even to the lowest negro dialect, that could not be represented in some sort by our alpha- bet. In this grand total of languages and dialects what multitudes of words there must be!"

"We should have to count them," said Jules, "not by tens of thousands, but by millions and millions."

"Now, imagine for the moment, my boy, that these letters represent our simple substances, while words represent the compound substances. The compar- ison is not so very far-fetched, for just as words hav- ing each its own value, its peculiar meaning, are formed by combining letters in groups of two, three, four, or more, and in such and such an order, so compound substances are made by combining certain elements which, according to their properties, their

64 THE WONDER BOOK OF CHEMISTRY

number, and the manner of their grouping-, deter- mine the nature of the compound. "

" Simple substances, then," put in Jules, "are the elements of material things just as letters are the elements of words. "

"Yes, my boy."

"Then the number of compound substances must be as immense as the number of words in all the languages of the world. Still, I should say the al- phabet would give the greater variety. It has twenty-six letters, and you have just told us that most compound substances are made from a dozen elements at most. Twenty-six ought to give more combinations than twelve."

"I will ask you to note that the number of letters might be considerably reduced and still the alpha- bet would represent all the various vocal sounds. What difference is there, I ask you, in the pronun- ciation of k, q, and hard c? None. One of these characters is necessary, the others are superfluous. In like manner soft c is the same as the hissing s, and x is simply ks, nor does y as a vowel differ from i. Rid of its duplicating characters, the alphabet could, as you see, be reduced a good deal and still be rich enough to furnish the elements of innumerable words. But I admit that even so there remain more letters than there are simple substances forming the great majority of compounds. In their modes of grouping, however, the elements enjoy a great ad- vantage over the letters of the alphabet.

"To make a word, we usually group two, three, four, often five or six, and even more letters. Take

COMPOUND SUBSTANCES 65

for example, that long and cumbrous word, inter- communic 'ability. One must draw a good breath in order to pronounce it all. There -are twenty letters in the word, or almost as many as there are in the whole alphabet, though it is true that some of these letters are repeated, which reduces the number of separate characters to thirteen. Chemical com- bination scorns such cumbrous piling up of elements, and imposes upon itself a rigid rule never to resort to it, holding that complicated mixtures are none of its business. To form compound substances it groups only two simple ones, or sometimes three, very rarely four. Imagine a language with words of only two, three, or at most four letters, and you will get a notion of the compound substances resulting from the union of chemical elements. Sulphid of iron is a compound of two elements, — a word of two letters, if you choose, continuing our comparison. Water is another. Oil has three, and animal flesh four. Compounds of two elements are called ' binary compounds'; those of three, ' ternary,' and those of four ' quaternary.' These terms come from the Latin words meaning respectively two, three, and four.

"Now, if four elements at the most, and commonly only two or three, are united in combination, how is it that there can be an almost infinite variety of com- pounds ? To aid us in explaining this, take the word rain, for example. For the initial letter r substi- tute another, and then another, and so on, and we have the common words, gain, lain, vain, wain, pain, and others, all belonging to our language. In the

66 THE WONDER BOOK OF CHEMISTRY

same way pin becomes tin and din and sin. By a simple change of one letter, the rest of the word remaining unaltered, we have a word of a wholly different meaning. So it is with chemical com- pounds : let one element be replaced by another, the rest remaining unchanged, and behold, at once we have new properties, a substance very different from the first.

"But, further than this, there is still another change that gives an even greater variety of com- pounds. Just as in a single word the same letter may be repeated several times (note the letter i occurring four times in the long word just cited as an example), so the same element is, in many sub- stances, repeated in chemical combination. It is taken two, three, four, five, and even more times, producing each time a compound having its own peculiar properties. We should hunt in vain in the dictionary for words suitable as illustrations of this

V

principle, for our language refuses to repeat the same letter over and over again in one short word. But let us imagine a series of words such as ba, bba, bbba, bbbba, and so on, and let us suppose that each of these, although containing only the letters b and a, one of which is repeated, has a meaning en- tirely different from that of any of the others. We can thus gain a fairly good idea of what takes place in compound substances."

"If that 's the way of it," said Jules, "I can see well enough that the number of compounds must be very great, — that it must be enormous, even with only the dozen simple substances that play the chief

COMPOUND SUBSTANCES 67

part. One element changed and another repeated must produce an almost endless variety of different groups.'

1 'And what does Emile think about it?" asked his uncle.

"I rather agree with Jules: there 's much more variety than I had thought. But I should see it better if I could understand how bba is really differ- ent from ba.'

"You would like to have an example of a com- pound substance whose nature changes completely when one of its elements is doubled ?"

"Oh, Uncle, that 's just what I should like to see; and Jules would too, I 'm sure.'

"I can easily gratify you, my little lads.'

And so savins: Uncle Paul took from one of his

•

drawers something that he showed to his listeners. It was a rather heavy object, of a beautiful shiny yellow, and when exposed to the sun it gave out flashes of light. From its brilliance it might have passed for a metal.

"But that is gold!" cried Emile in astonishment at sight of the splendid stone; "a lump of gold as big as your two fists!'

"It is asses' gold, my boy,' replied his uncle, "named thus by miners because it deceives the ig- norant, and they take it for something precious, whereas it is reallv of small value. You can find

•

as many of these stones as you please among the rocks in the mountains; but it wouldn't profit you a penny to pick them up. This substance is also called, in more learned language, iron pyrites, the

68 THE WONDER BOOK OF CHEMISTRY

last part of the term being taken from the Greek word for fire ; for the stone will, in fact, emit sparks when struck with a piece of steel, — as, for example, with the back of a knife, — and these sparks are brighter than those obtained with flint and steel. "

Here, by way of illustration, Uncle Paul made the stone that looked like gold give out brilliant sparks by striking it with a knife. Then he continued his talk:

"Iron pyrites or asses' gold has nothing about it of real gold but its luster and its yellow color. It is not a simple substance, but a compound of two elements that are familiar to you, though you would n't ima>gine them to be here, disguised as they are by the act of combination. One is iron, the other sulphur."

"That shiny yellow stuff that you would take for gold is made of iron and sulphur, like the ugly black powder in the artificial volcano?" was Emile's incredulous exclamation.

"It is made of iron and sulphur, and nothing else."

"But how different it is from either of them!"

"This difference comes from the sulphur's being repeated in asses' gold.'

"The word, instead of making ba, makes bbaf-

"Exactly. To indicate this repetition of the sul- phur, they say in chemistry that iron pyrites is the bisulphid of iron, and you know that the first syl- lable of that term means twice."

' ' Then it 's the same as if they said ' twice sulphur and once iron.' The black powder in the artificial

COMPOUND SUBSTANCES 69

volcano is sulphid of iron, and this asses ' gold is

bisulphid of iron."

"Precisely. It couldn't have been put better." "I thank you, Uncle Paul, for showing us this

splendid stone. It will make me remember that in

chemistry ba and bba are not at all the same thing."

CHAPTER VI

EXPERIMENTS WITH THE BREATH

IMPRESSED by its glitter, the boys often talked to each other about the asses ' gold which, despite its rich appearance, is made of just such sulphur and iron as go to make the black powder of the artificial volcano, but with a double quantity of sulphur. The magnificent stone left with them by their uncle they took delight in striking with steel, in some dark place, so as to produce bright flashes of sparks. Furthermore, directed by Uncle Paul, they resolved to visit some of the neighboring moun- tains in search of more stones like this one. So suc- cessful was their quest that Jules 's cabinet became filled with pieces of iron pyrites of all sizes and of varying degrees of brilliancy. There were some golden yellow, cut in facets as if a lapidary had taken it into his head to polish them, while others were shapeless and more of an iron gray. Uncle Paul told them that the former were crystals, and that the majority of substances can under favorable condi- tions take regular shapes in which smooth facets arrange themselves according to geometrical laws. Such substances are then said to be crvstallized.

V

"We will return to this subject later if opportun- ity occurs," said he; "but to-day other things de-

70

EXPERIMENTS WITH THE BREATH 71

mand our attention. So far we have been merely discussing, talking together, supporting our asser- tions by sundry facts picked up here and there. Your minds had to be prepared, had to become accus- tomed to certain ideas and expressions. But, now that you are ripe for it, we are going to have a little real chemistry; that is, we are going to perform some experiments. To see, touch, taste, handle, and smell for oneself, and to observe at leisure, — that is the only way to learn quickly and well. So, then, we will proceed with our experiments. "

" Shall we have lots of them?" was the eager in- quiry.

"As many as you please, my lads. Along that line, chemistry never comes to an end. "

"Oh, that '11 be splendid! We shall never get tired of experiments. And may we repeat them by ourselves just as we did with the artificial volcano? That will make twice as much fun.'

"If they are not dangerous there is no reason why you should not perform the experiments your- selves. When there is any danger I will tell you beforehand what precautions are necessary. I count on Jules to take the lead, for I know how careful and how skilful he is.'

At this word of praise a slight color flushed the older boy's pale cheeks.

"Now, what shall we begin with?" said Uncle Paul. "It shall be with a substance that plays a most important part, air. Let me tell you at the out- set, if you do not already know it, that air forms around the earth an envelop known as the atmos-

72 THE WONDER BOOK OF CHEMISTRY

phere and having a thickness of about fifteen leagues at the most moderate estimate. It is a substance of an extremely subtle nature, so intangible and invis- ible that one is at first surprised to hear it spoken of as matter. 'What!' we exclaim; 'air is matter? Air has weight?' Yes, my boys, air is matter and can be weighed. With its delicate instruments physics can weigh air, and it teaches us that a liter of this invisible matter weighs one and three tenths grams. That is very little when compared with the weight of lead, it is true; but it is a good deal when com- pared with other substances that we shall soon learn about. ' '

"Are there things lighter than air!" asked Jules in surprise. "Yet people say, 'as light as air,' as if there were nothing else of so little weight."

"Let them say it, but rest assured there are other things that in respect to weight are to air what wood is to lead. Air is colorless and, for that reason, in- visible. Understand me correctly, however: when I say 'colorless' and 'invisible' I am speaking of air in small quantities ; in large volumes that would no longer be true. Water will help us to understand this. Seen in a drinking-glass or in a bottle, it is colorless; seen in a deep body, as in a lake or the sea, it shows its blue color according to the depth of the water. Likewise with air: it is of a blue tinge, but so pale that to become perceptible the body of air must have enormous thickness. That explains why the sky is blue : the thickness of the atmospheric envelop (some fifteen leagues, as I said before)

EXPERIMENTS WITH THE BREATH 73

brings out its true color, which is imperceptible to the eye in a layer of moderate depth.

"Invisible, subtle, intangible, escaping the clutch of the fingers, air seems to present insurmountable difficulties to any one wishing to study it closely. If we desire to submit it to tests that will reveal its nature and properties, we must take a certain quan- tity of it, isolate it from the rest of the atmosphere, shut it up in some sort of container, make it flow out in this direction or that as we may choose, carry it from place to place, expose it to such and such con- ditions,— in short, make it obedient to our control as we should a piece of stone or a pebble. But how can we see the invisible, grasp the elusive, handle the intangible! The difficulty, you see, is no small one. ' '

"It seems to me so great, " replied Jules, "that I can't begin to guess how it is overcome. But I have too much confidence in you, Uncle, to doubt that we shall manage it somehow. "

"We must; otherwise we should be held up at the very start. And that would be a pity, for air would not be the only thing to get the better of us. There are many other substances just as invisible, just as subtle, just as intangible as air, and of inestim- able importance. They would all remain unknown to us if our present difficulty could not be overcome ; and the great science of our day, chemistry, the mother of industrial wonders, would remain to be discovered in some ever-retreating future when the art of handling the intangible should have been mastered. All these substances, having the subtle

74 THE WONDER BOOK OF CHEMISTRY

and elusive quality of air, are known by the general name of gases. Air itself is a gas."

"And there is the gas they use for lighting, too," said Emile. "I thought that was the only thing called gas."

"What is burned in chandeliers in our cities is a gas, but not the only one. There are many others, each with its own peculiar qualities. The word gas, then, is a general term by which we designate all sub- stances having a tenuity or thinness similar to that of air ; and if we commonly restrict it to illuminating gas, it is because the latter is much better known to us all than any of the others except air. In ordinary language a general term is thus monopolized by one particular substance.

"But to return to our problem, how can we handle air, how subject any gas whatever to observation? I will show you. Suppose we wish to collect the air that comes from our lungs, — our breath, in short. I dip a tumbler into a bowl of water and fill it, after which I invert it in the bowl and raise it. As long as the brim remains completely submerged the water does not run out, but is held suspended above the general level of the liquid in the bowl. I see by your looks that this lifting of water and holding it motionless above the level of the surrounding liquid excites some surprise. I will return to this in a mo- ment and explain the cause ; but just now let us pro- ceed with our experiment. Here is the glass, full of water and held up by one hand, with the brim immersed. Now with a glass tube — or, if necessary, with a reed or a big straw — I blow under the glass,

EXPERIMENTS WITH THE BREATH 75

and the air from my lungs makes the water bubble. Because of its superior lightness it makes its way upward in big globules through the contents of the glass until it reaches the inverted tumbler's bottom. As the breath — or, to express it better, the exhaled air — collects in the upper part of the glass, the water thus displaced descends and reenters the bowl. The thing is done : I have collected my breath ; there it

is in the glass ready to undergo any tests we choose to apply."

"How easy it is, after all!" exclaimed Emile, much impressed by what he had just seen.

"It is nearly always so, my child, — very easy when we know how, very difficult when we do not. '

"Then this glass holds what we send out of our mouth when we blow out a candle ; I mean, it is filled with breath. It certainly is a curious thing to collect like this what can't be seen or felt. When I let out my breath after puffing up my cheeks, I don't see anything at all ; and yet I just now saw your breath

76 THE WONDER BOOK OF CHEMISTRY

going up through the water and making it bubble."

"The commotion in the water made it seem to you as if you saw what is by its very nature invisible. ' '

"Now that the water is still again, I see nothing, though I am sure the part of the glass that looks empty really has something in it; for I saw that something come and take the place of the water, which went down slowly in the glass. All the same, it seems to me very funny to have that glass full of Uncle Paul's breath. May I try filling it with mine?"

"Certainly; but first you must empty out what is now in the glass."

"Empty it out? But how?"

"In this way."

So saying, Uncle Paul took the glass and inclined it just enough to let a part of the brim come to the surface of the water, whereupon something escaped with a bubbling sound.

"It 's gone," cried Emile. "Let who wants to, run after it and catch it in the air where it has dis- appeared."

The glass being refilled with water, Emile took the straw and blew as his uncle had done, controlling the muscles of his cheeks so that he might watch the bubbles as they rose one by one ; and great was his delight to see so easily, and to shut up in a glass so securely, what he had thought must always remain invisible and unmanageable.

"That was soon done," said he, when the glass was full. "I could fill a big bottle with my breath just as easily as a tumbler. May I, Uncle Paul?"

EXPERIMENTS WITH THE BREATH 77

"You may, my boy. If you enjoy the experiment of bottling up your breath, I for my part enjoy your enthusiasm.7

A large bottle of clear glass with a wide neck was standing on the table, having been placed there by Uncle Paul for later experiments. Emile took it up and went to the bowl, but soon saw that the latter was not deep enough to dip the bottle into so as to fill it and then admit of its being lifted up with the mouth under water as had just been done with the glass. "Look," said he, after a few vain attempts; "the way you did it with the tumbler won't work. What shall I do?"

"Since the difficulty does not yield to a frontal attack, let us turn its flank. Watch me. ' '

Therewith Uncle Paul placed the bottle on the table and filled it from the carafe. Then, clapping the palm of his left hand over the mouth as a stopper, he took the bottle in his other hand, turned it upside down, and plunged it while stopped in this manner into the bowl of water. Then he removed his left hand, and the bottle with its neck immersed retained its liquid contents suspended above the exterior level, without losing a drop.

"You always find a way out, Uncle Paul,' said Emile, delighted at this easy way of overcoming the difficulty.

"We must practise a little ingenuity, my child; for if we did n 't, what could we accomplish with the poor apparatus our small village provides? Skill must make up for the defects of our appliances.'

Emile blew, filling the bottle with his breath in a

78 THE WONDER BOOK OF CHEMISTRY

few minutes. Then, after Jules also had performed the operation, so as to accustom himself a little to handling gas, their uncle continued thus :

"Why does the water in the glass and in the bottle remain above the level of that in the bowl? This is what we must now find out, though not in all its details, for to do so would take us out of chemistry into physics. A brief explanation, just enough to show you the cause of what now excites your sur- prise, is all that I at present propose.

"Air, I told you, can be weighed just the same as any other substance; and its weight, as I said be- fore, has been found to be one gram and three deci- grams a liter. That is very little, but the atmos- phere is at least fifteen leagues thick, which must make an enormous number of liters piled one on top of another. Since, then, the atmosphere has weight it must press with all its force on objects immersed in it ; it must press on them from above, from below, from the right, from the left, from every direction. It presses, for instance, on the water in our bowl; and the pressure, being transmitted by the liquid to the mouth of the bottle, keeps the water in the latter suspended above the exterior level.

"A striking experiment will convince you of this thrust exerted by the atmosphere. Over the mouth of a bottle filled with water we place a piece of damp paper, and while this is held in position with one hand the bottle is turned upside down with the other. Then the hand holding the paper can be withdrawn without the escape of a drop of water from the in- verted bottle. It is the atmosphere pushing in every

EXPERIMENTS WITH THE BREATH 79

direction, upward as well as downward, that holds the water in. The office of the paper is to keep the air from entering the liquid mass and breaking it up, wrhich would immediately cause the escape of the water.'

"And shall we try this wonderful experiment?" asked the boys, in eager curiosity.

"Shall we try it? you say. Do you think I should have told you about it if we were not going to try it? Up and at it then! Here is our bottle, and here are paper and water; nothing further is needed."

The bottle was filled to the brim and a piece of damp paper placed over its mouth. With his right hand Uncle Paul raised the bottle by its bottom, holding the fingers of his left hand meanwhile on the paper. Then he carefully turned the bottle upside down, let go of the paper, and the thing was done: not a drop of water escaped from the bottle, even though its neck pointed downward. Emile, more excited than ever, could not contain himself.

"That 's fine!' he declared, "not a drop comes out of the bottle, and it 's turned upside down, too. If it had a cork in it, the thing would be natural enough ; but the paper does n 't cork the bottle ; if you blew on it, it would come away. How long will the water stay in like that ? ' '

"As long as you please; as long as one has patience to hold the bottle as I am holding it now."

80 THE WONDER BOOK OF CHEMISTRY

the water is trying all "the time to get out? It presses down and would fall if it could!'

"Yes, it keeps pressing down, and tends to fall, but the stronger pressure of the atmosphere re- strains it.'7

"And what if we took away the piece of paper?'

"Immediately the water would run out, just as we have so often seen it do from a bottle or carafe tipped sidewise, or, still more, from one turned up- side down. This piece of paper closes the bottle's mouth so that water and air are placed in a position where one pushes squarely against the other. With- out it the water would slip through the air, the air through the water, and in this mutual evasion the bottle would speedily empty itself. Put two iron rods together, end to end, and exert pressure ; there will be mutual resistance. That is what happens when we put the piece of paper between the air and the water. But if the iron rods were made into two bundles of very fine needles pushing against each other, end to end, these same rods would slip into and through each other just as happens with the air and water when there is no paper to separate them.

"To return to the bottle that Emile used to hold the breath he blew into it: as long as its mouth is immersed in the bowl the water it contains does not run out, but is held above the surrounding level by the force of the air pushing against it. Now, what would happen if instead of this bottle we used a very tall container, — a tube, for example, closed at its upper end? Would this tube, whatever its length, still remain full when raised out of the water except

EXPERIMENTS WITH THE BREATH 81

its lower end? No. If the tube were raised so as to project only ten meters above the surface of the water, it would indeed remain full; but if it pro- jected beyond this height the part of the tube above ten meters would be empty. The pressure of the atmosphere can hold up a column of water only ten meters high; that is the extreme limit. Our con- tainers here, as you see, are well within this limit in their height. However big or tall our bottles may be, there is no danger of their being so tall that the pressure of the atmosphere cannot hold back the water that fills them.

"Finally, suppose we wish ^ to transfer a quantityof gas from one vessel to another, or to tranfuse it as they say. This gas shall, again, be our breath, which will perfectly well serve the purpose of the demonstration I have in view. I fill a glass with it by blowing through a tube in the manner just shown ; and now I propose to make this volume of gas pass into another con- tainer, or it may be I wish to transfer only half of it. I fill this second glass with water and invert it in the bowl so as to keep only the brim immersed. The first glass, with only its brim still in the water, is then tilted sidewise under the other, where- upon the air it contains escapes in bubbles and passes into the second glass, wholly or in part, as I choose.

"To decant a liquid — to pour wine, for example,

82 THE WONDER BOOK OF CHEMISTRY

from one bottle into another — a funnel is used, as you know. The same utensil is often very useful for decanting gases; but a chemist's funnel, which is likely to come into contact with all sorts of cor- rosive liquids, is of glass, a very resistant substance. As long as only gas is to be transfused, it will suf- fice to add a modest tin funnel to our simple outfit ; but if we had a glass funnel it would be better and more in keeping with chemical practice. Further- more, glass has one inestimable advantage over tin : it is transparent, and thus allows us to see all that takes place within it. But with nothing beyond a common tin funnel we are not necessarily brought to a halt in our operations.

"A funnel of some sort is indispensable for trans- fusing a gas from a container of any kind to a bottle with a narrow neck such as bottles commonly have.

i'

Of course the transfusion is effected under water. The bottle, filled with water and held with its mouth immersed, has the funnel inserted into it by one hand operating under water. That done, the jar or whatever it may be that contains the gas is brought under the funnel and inclined little by little until

•*/

bubbles of the gas escape into the flaring mouth of the funnel and pass thence into the bottle.

' ' That will do for to-day, my boys. You are now in a position to repeat these experiments by your- selves as often as you like, collecting your breath in a glass, tranf using it into another, or into a bottle turned upside down, thus getting your hand into practice. I shall soon need your assistance."

CHAPTER VII

EXPERIMENTS WITH AIR

UNCLE PAUL took a rather deep dish and in the center he fixed a candle with a few drops of melted wax. Then he lighted the candle and covered it with a large, wide-mouthed bottle of clear glass. After this he poured water into the dish until it was quite full.

Meanwhile the children looked on, chattering between themselves and wondering what their uncle was up to with his lighted candle all surrounded with water and burning in a bottle upside down in the middle of a dish. What curious experiment was he about to perform? They were not left long in doubt. Every- thing being ready, Uncle Paul began thus : "What is there in the bottle?" "A lighted candle,' Emile hastened to answer. "Is there nothing else there!' "No, nothing. I don't see anything but the candle."

"You forget that there are some things we cannot

S3

84 THE WONDER BOOK OF CHEMISTRY

see. You must use here the eyes of the mind, not those of the body."

Emile scratched behind his ear with the tip of his finger and winked hard, as was his wont when puz- zled. He was trying to think what the invisible thing could be that his uncle referred to. Jules came to his aid.

"It is air," declared the older boy. "There is air in the bottle where the candle is burning."

"But Uncle Paul didn't put any there," Emile rejoined.

"Is it necessary to put any there, little giddy- pate?" his uncle demanded. "Is not the bottle full of it without any help from us? All the vessels we use, all our flasks, jars, bottles, glasses, containers of whatever kind, being immersed in the atmosphere, in the very depths of this ocean of air, are filled with this gas as they would be with water if they were plunged uncorked into that liquid. If it does not contain anything else, every bottle, whether right side up or wrong side up, is full of air, which gets in of itself, usually without our paying any heed to it. ,When a bottle of wine is drained to the last drop, we say it is empty. Should we really call it empty if we chose our words with extreme care? Certainly not, for the so-called empty bottle is as full as ever, full to the top ; it is filled with the air that has taken the wine's place. And so it is with all vessels when we empty them of their contents : if they were full be- fore, they remain full afterward, though the nature of their contents has changed. Nothing is abso-

EXPERIMENTS WITH AIR 85

lutely empty, nothing can be empty, when air is free to enter it. We can, it is true, empty a vessel in the literal sense ; we can create a void or vacuum, as the learned men say ; but that is an elaborate operation, and its success demands proper appliances."

"You mean an air-pump ?" asked Jules.

"Yes, my boy, an air-pump, a special kind of pump that sucks the air from a tightly closed vessel and discharges it into the outer -atmosphere. But as nothing of the sort has been used here, my bottle is full of air exactly like the air around us. Conse- quently the candle is burning in the midst of the air contained in the bottle. Now, why did I fill the dish with water? For this reason : The air in the bottle is the substance I propose to study with you by sub- jecting it to certain experiments, particularly this experiment with the lighted candle. And so we must separate this air from the rest of the atmosphere, isolating it in a closed container, as otherwise our experiment could not be carried through; and, fur- thermore, we should be unable to tell what portion of the atmosphere we had been experimenting with. The bottle alone does not furnish complete isola- tion, for, between its mouth and the bottom of the dish, air could easily slip in and mix with that already in the bottle. A barrier must be interposed to separate the inner from the outer air, and this barrier is furnished by the bed of water in the dish. Thus we obtain perfect isolation; and you will also see that the water serves a second purpose, being an indicator of what takes place in the bottle,

86 THE WONDER BOOK OF CHEMISTRY

But I must not distract your attention by too much explanation. Now watch closely what is going on in the bottle.'7

Behold, in a few minutes the candle-flame, which at first was full and bright like that of a candle burning in the open air instead of in a bottle, began to get dimmer little by little, becoming shorter, shrinking in width, and looking dull and smoky. Soon it had diminished to a mere point, and finally to nothing at all. The flame was quite extinguished.

"Look!" cried Emile. "The candle has gone out without any one's blowing it out.'

"Wait a moment, Emile, and we will presently talk the thing over. Just now keep your eyes open and watch what is happening in the water, the in- dicator I spoke about.'

Emile and Jules watched attentively and saw the water gradually rise in the neck of the bottle, com- pletely fill it, and go still farther, so that an appreci- able part of the bottle, at first filled with air, was occupied by the liquid coming from the dish and slipping in from beneath. Its ascent was slow, and when at last it was finished Uncle Paul broke the silence.

"Now," said he, "you may ask all the questions you please."

"I should like to have one thing explained," said Emile. "When a candle is burning and you want to put it out, you have to blow on it. But here no one blew out the candle, and if we had wanted to we couldn't have done it on account of the bottle

EXPERIMENTS WITH AIR 87

over it. Not a breath of air came, that is certain; no puff of wind. Under cover of the bottle no breath of air or puff of wind could get at it. The flame was perfectly still; it stood up straight and calm; and yet, without any reason that I can see, it got dim and dwindled to nothing but a point, and then at last went out altogether. "

"I should like to ask something, too," put in the older boy. "The bottle was at first filled full of air ; now, besides the air that is left, it has several fingers of water from the dish. I saw this water rise little by little as the flame dwindled. So some- thing has been taken from what was in the bottle at first, for the water rose and took its place. But how did that something disappear, and where has it gone to? If you had not told us and made us un- derstand that nothing is ever annihilated, I should say that a part of the air was being annihilated while the candle burned."

1 ' Jules 's point shall have our attention first, as it will furnish us the explanation of Emile's difficulty. A part of the bottle's gaseous contents has disap- peared, apparently; the water's rising above its level in the dish to fill the vacancy would seem to prove it in a way to convince the most incredulous. Something, I repeat, has disappeared, so far as we can see; but we must not for a moment suppose it has been annihilated. Let us investigate further, and we shall discover what has become of this something that seems to be lacking.

"I have already told you that heat and light are

88 THE WONDER BOOK OF CHEMISTRY

nearly always sure signs of the mingling of sub- stances of different natures, — of chemical combina- tion, in short. "

"I remember," said Jules. "You called it the fireworks that celebrate chemical weddings. Can such weddings take place in a bottle I"

"Yes. The flame was hot and it gave out light; hence a chemical combination was going on, pro- ducing this heat and light. And what substances were they that were thus combining? One of them, beyond a doubt, was supplied by the fatty material of the candle as it melted under the heat from the lighted wick; the other could have come only from the air, since the bottle contained nothing else. From this combination sprang something new, some- thing that was no longer either candle grease or air, something with properties that neither air nor candle possesses. The compound thus formed is an invisible substance, a gas just as air is a gas, and for that reason invisible.'

"But if a gas is made out of air and candle grease," Jules objected, "this gas takes the place of the air that disappeared, and the bottle ought to be just as full as it was before. I don't see why the water rises.'

"Wait; we are coming to that. The compound we are speaking of is readily soluble in water, somewhat as sugar and salt easily dissolve in that liquid. Once dissolved in this way, sugar and salt disappear, become invisible, and the only evidence we have of their presence is the sweet or the salt

EXPERIMENTS WITH AIR 89

taste of the water. In like manner, what is pro- duced by the flame disappears : it enters the water and becomes incorporated with it. Similar but much richer gaseous solutions are familiar to you. I hardly need to remind you of beer, cider, spar- kling wine, and soda-water, drinks that make the cork pop and that foam when poured into the glass. All these liquids hold quantities of gas in solution, — so much of it, in fact, that they cannot retain it when escape is possible ; and therefore it thrusts out the cork and covers the drink with foam. Now, curiously enough, the gas that makes these bever- ages foam is precisely the gas that the candle- flame manufactures. Some day I will take this in- teresting subject up again. I mention it here in passing, but have not time to dwell on it.

" Since the compound produced by the candle grease and the air disappears from sight, being dissolved in the water, a vacant space must be left; and this it is that the water in the dish, under pressure of the atmosphere, rises in the bottle to occupy, showing us by the height to which it rises the amount of air that has disappeared. '

"It has n't risen far," said Emile. "See! It 's only just above the neck. '

"That shows that the candle burned up only a small part of the air in the bottle, — a tenth part, let us say, if the water that has made its way in fills a tenth part of the bottle's total capacity.'

"But as there is still so much air in the bottle, why didn't the candle use that up just as it did the

90 THE WONDER BOOK OF CHEMISTRY

other part? I don't see that it is any different from what that was. It is still transparent, invisible, and hasn't a particle of smoke.'

"Here is where we come to your question, my boy, the question why the candle went out without being blown out. The candle-flame is caused by the combination of the material of the candle with certain other material contained in the air. Air and candle are equally necessary in feeding the flame. If either be lacking, the flame is extin- guished. As to the candle's being necessary, that is plain enough: no fuel, no flame. But in regard to the air you don't feel quite so sure. And yet what you have just witnessed ought to give you food for reflection. If the candle went out of its own accord, there was certainly something want-

ing. '

"I 'in ready enough to admit that. Yes, that must have been the trouble ; something was want- ing, as no one blew out the candle and there was n 't a breath of wind. Now, what was it?'

"What was lacking must have been air, as the bottle contained nothing else to begin with. Air is indispensable for keeping a flame burning.'

"But there is still air in the bottle, — lots of it, almost the whole bottleful."

"I do not deny it; but listen a moment. Is it not possible that air, instead of being made of only one substance, is made of two of different kinds, equally colorless, equally subtle and invisible, and very thoroughly mixed together? Is it not possible, too, that one of these gaseous substances can keep a

EXPERIMENTS WITH AIR 91

flame going, whereas the other cannot, and that the first-named forms but a small part of the atmos- phere as compared with the second? If so, when this first part is used up in the bottle, the candle goes out of itself, as we say, the candle grease no longer finding what it needs for burning, and there will be left in the bottle, colorless and invisible, as it was in the first place, the other gaseous element, of no use for keeping a flame alive. '

"How clear that makes everything, Uncle,' said Jules. "Now I see it all perfectly. The candle went out of itself when there was no more of this gas material to keep it burning. By combining with a little burnt grease, this matter turned into some- thing else, a gas that in dissolving disappeared in the water while the water in the dish rose and took its place. Now the bottle holds only the kind of gas of no use to a flame, and that is why the candle stopped burning.'

"Yes, that 's the way of it, with one slight correc- tion. A candle-flame is not by any means a fire strong enough to use up all the gaseous element needed for the act of burning; there is still some of it left over, but too little to keep the candle alight. The air has become impoverished, but not deprived of all it contained of the element in question. An- other day we will try to find a way to remove the last trace of this flame-supporting gas. At present let us rest content with our partial result. The con- tents of the bottle will no longer keep a candle burn- ing, and a lighted candle put into the bottle would immediately be extinguished. "

92 THE WONDER BOOK OF CHEMISTRY

"A candle would go out if put into that bottle V asked Emile, still rather inclined to doubt.

"Certainly it would, and almost as quickly as if you plunged it into water. How can you expect it to burn? If the one that was there could not burn, why should another do any better? They are all made alike. "

"All the same, I 'd like to see it tried. "

"Your curiosity shall be gratified.'

With this Uncle Paul took a short candle-end and tied it to a wire bent up at the bottom. Then, raising the bottle a little with one hand, he slipped the palm of the other over the mouth, which was still under water, thus stopping it up. After this he set the bottle upright on the table without let- ting it lose any of its contents, liquid or gase- ous, and withdrew the hand he had used as a stop- per.

"But the air in the bottle will get out," objected Emile, "if you leave the bottle open."

"There is no danger of that," his uncle reassured him. "The invisible gas there, being as heavy as air, will not escape. However, to make sure of it, here is a stopper we can use.'

It was a little piece of glass from a broken win- dow-pane. Uncle Paul placed it over the bottle's mouth.

"Now," said he, "let us proceed to our experi- ment."

The candle fastened to the wire was lighted and allowed to burn until the flame was bright and full, after which Uncle Paul removed the piece of glass

EXPERIMENTS WITH AIR

and gently let down into the bottle the lighted candle, which almost immediately became dim and went out. A second attempt met with the same speedy result. If violently blown upon or plunged into water, the candle could not have gone out more promptly.

4 'Well, are you convinced now, Master Unbe- liever? Here, try it for yourself, so as to be quite satisfied/'

Emile took the candle and began the experiment over again, lowering the flame little by little, very gently, very cautiously, so as to keep it away from the sides of the bottle, thinking that careful management might accustom the flame to this unsuit- able atmosphere. But it was of no use. Though several times repeated, the attempt invariably failed : a little higher or a little lower in the bottle, the flame always went out.

"It 's no good, the candle won't burn there," de- clared the boy, tired of attempting the impossible. "I should be perfectly sure of it if I were certain the bottle had nothing to do with it. Could n 't the t nearness of the glass and the want of space make the candle go out?"

"That is a very natural question, but it is soon answered. Here is a bottle like the first, of the same size and with the same wide neck. It is filled with air that has not been impoverished by anything

94 THE WONDER BOOK OF CHEMISTRY

burning in it, the same kind of air as that all around us. Repeat your experiment with that.'7

Emile lowered the candle into the bottle, and it burned very well, exactly as if in the open air. Whether put in abruptly or gently, near to or away from the enclosing glass, it remained alight and burned as it had outside. His constant failure with the first bottle and his repeated success with the second dispelled Emile 's last lingering doubt.

1 1 1 have nothing more to say, ' ' he declared. i i The stuff in the bottle where the first candle burned doesn't suit it now at all."

"You are convinced, then?"

"Yes."

"Completely?"

"Yes."

"Then I will continue. What we conclude from our experiment is that air is composed of two differ- ent gases, equally invisible but of so unlike a nature, each to the other, as to prevent our confusing them. One, the less abundant, suits the candle- flame and combustion in general; the other, more plentiful, does not. The first is called oxygen, the second nitrogen. They are two simple substances, two metalloids. As to air, which is a mixture of these two gases, we can no longer properly call it an element as did the anicients. It is a compound of two substances of very different natures. This has been known only a comparatively short time."

"I wonder why it took so long to find out about air," said Jules. "It would have been such a simple

EXPERIMENTS WITH AIR 95

thing to burn a candle in a bottle turned upside down in a dish of water. '

"Very simple, undoubtedly ; but it had to be thought of, and there was the difficulty."

CHAPTER VIII

FUBTHZB EXPERIMENTS WITH ATE

R experiment with the candle burn- ing in a bottle turned upside down in water, is one of the easiest to perform, calling for nothing that is not readily procurable. But, un- fortunately, it is an incomplete experiment, for the reason I have alreadv indicated. It shows us that

*

air is composed of two different gases, one that will keep a flame burning and is called oxygen, and an- other of a contrary nature in this respect and known as nitrogen: but it does not tell us how much there is of each, because what is left after the candle goes out, still retains a good proportion of oxygen instead of being reduced to pure nitrogen.

"A candle-flame is delicate: a moderate puff of wind will blow it out. In the bottle, I admit, it is sheltered from anv current of air, but its weak-

•

ness prevents its using up all the gas on which it could feed. It turns dim and then goes out alto- gether when this gas begins to get scarce. If the comparison is not too far-fetched, one might call the candle-flame a guest at table with a poor appetite, leaving on his plate the greater part of the food served to him. Let us, then, call in a guest with a stronger stomach and able to eat his food to the

96

FURTHER EXPERIMENTS WITH AIR 97

last morsel, leaving nothing but the uneatable, the bare bones. I mean, let us find a kind of fuel that burns with enough energv to consume all the oxvgren

*-> V % t.

to the last trace and leave only the useless gas, the nitrogen.

' ' What shall this fuel be ? Shall it be coal ? Xo ; that would not do any better than candle-grease, burning less freely, in fact, because needing the heat of a glowing furnace to keep it going, and that is out of the question in our experiment, which owes more than half of its value to its very simplic- ity. Shall it be sulphur? There, assuredly, we have a strong stomach needing no second invita- tion when oxygen is offered. Once set fire to. it burns vigorously. But it has its faults, — its suffo- cating fumes. Nevertheless. I should be glad to avail myself of it if there were not something better at hand. You are familiar enough with the common match, the little stick of wood tipped with sulphur, and lightly coating the sulphur we find — See who can tell me first.'

"Phosphorus!1 cried the two listeners at the same time.

"Yes, phosphorus, which is inflammable to a degree not attained by any other substance in com- mon use: phosphorus, which takes fire by being merely rubbed against the sandpaper cover of the match-box or against a rough wall. Xothing equals it in the vigor and persistence with which it burns. Here, truly, we have the greedy guest who will leave nothing on his plate. But first let us get a little better acquainted with him. Phosphorus

98 THE WONDER BOOK OF CHEMISTRY

is not very well known to you, as hitherto you have seen it only on the tips of matches/

"Sometimes," said Emile, "the tips are red, and sometimes blue, or yellow, or almost black. Does phosphorus have all those colors T

"No; of itself phosphorus has only one color, which is nearly that of yellow wax. But the match- manufacturer adds colored powder, sometimes of one hue, sometimes of another, according to Kis fancy, for the sake of giving a little variety to his wares and thus pleasing the purchaser's eye. Glue is also mixed with the phosphorus to make it stick to the sulphur. So what you are used to seeing is not pure phosphorus; but I will show you some that is perfectly pure.

"A few days ago, being called to town on bus- iness, I bought a number of things that our labora- tory was much in need of. A laboratory, let me explain to you, is a place devoted to scientific re- search; it is the scientist's workshop. Modest though our workshop is, it must have some equip- ment, certain implements and supplies ; otherwise we should have nothing but our ten fingers for an outfit, and what could we do with them? We should simply have to content ourselves with talking and nothing else. But that I will not have, for I do not think much of chemistry carried on in words only. I wish to give you facts, things that you can see over and over again, substances that you can feel of, taste, examine, handle for yourselves, as that is the only true way to learn.

FURTHER EXPERIMENTS WITH AIR 99

"What could the blacksmith do without his anvil and hammer? Nothing. Equally helpless is the chemist without the various appliances and drugs of his laboratory. We will furnish ours, then, little by little, but in a very modest way, I assure you beforehand, as your uncle's resources do not permit luxury. We will have the indispensable, but noth- ing more. Nor is it altogether a misfortune to be thus forced to use one's wits a little, in devising ways and means to make what one has suffice, and in getting along without what one does not have. Our earthen dish borrowed from the kitchen, our old medicine-bottles and preserve-jars — did they not play their part well! I assure you in all sincerity, we could not have done better if we had had the outfit of a costly laboratory. Why shouldn't we continue our studies in this way, as far as may be? If you ever chance to have access to a real labora- tory, and to work in it, my little lads, you will take pleasure in recalling your uncle's poor outfit and in reflecting how little it took to lay the solid foundations of useful knowledge in your minds, and how little it would need to do so for others even in our smallest villages.

"It may well happen that we shall be halted now and then by difficulties impossible for us to over- come; then, and only then, we shall be forced to appeal to the expert chemist for aid. Such is our position to-day. We had need of phosphorus, and here it is, bought recently at the druggist's in town."

100 THE WONDER BOOK OF CHEMISTRY

Uncle Paul here set before his nephews a bottle holding in water a yellow substance in the form of a stick as long and as thick as one's little finger.

"That,' said he, "is pure phosphorus. It is semi-transparent, which, with its color, makes it look like a pretty piece of wax such as we have in the honeycomb. It is like wax before being bleached at the taper factory by long exposure to the sun."

"Why do you keep it in water ?" asked Jules.

"I keep it in water because if exposed to the air it would soon catch fire. So inflammable is it that the slightest heat is enough to ignite it."

"But the phosphorus on matches doesn't catch fire like that ; you have to scratch it. '

"I told you that in matches it is not used in a pure state. It is mixed with certain other substances with glue and colored powder, which lessen its in- flammability. But even so it sometimes occurs in summer that matches take fire of their own accord. This is a serious fault which, added to others, will perhaps some day induce us to give up the use of phosphorus, when science has discovered something better to take its place."

"And why," asked Emile, "doesn't it catch fire in the water, if it is so eager to burn?"

"Has Emile forgotten what I told him yester- day? In order to have fire, two things are neces- sary, each as indispensable as the other, — the thing that burns and the thing that makes it burn, this latter being a gas called oxygen, contained in the air. Combustion is brought about when the two combine. Where there is no air— or ? rather, where

FURTHER EXPERIMENTS WITH AIR 101

there is no oxygen — combustion is impossible, how- ever inflammable the fuel may be. So I guard the phosphorus from risk of taking fire by keeping it in water, which protects it from the air. This being excluded, we are sure the phosphorus will not catch fire.

"•Still another precaution is not out of place with this dangerous substance. The bottle holding the phosphorus in water might get broken, which would expose the phosphorus to the air. Therefore we must guard against any chance shock or fall, and to this end the bottle is enclosed in a tin box which serves as a shock-absorber. In this double en- closure and immersed in water, phosphorus is kept indefinitely on the druggist's shelf without any danger.

"It remains for me to add that a burn from phosphorus is a serious accident, a most painful accident. There is nothing tha| smarts more than a wound made by this terrible stuff. Neither live coals nor red-hot iron can cause so acute and last- ing a pain. I will leave you to imagine the fate of the thoughtless person who, wrapping a piece of phosphorus in paper, should put it into his pocket, proposing to amuse himself with it later and make it shine in the dark. The heat of his body would set fire to his perilous possession, and the impru- dent one would be burned to his very entrails, while he filled the air with his shrieks of agony. Be care- ful then, my boys, not to play with this terrible substance. If the thirst for knowledge should tempt you to handle it at all, do so with the utmost caution.

102 THE WONDER BOOK OF CHEMISTRY

I appeal here to Emile's obedience and Jules 's pru- dence. Had I not perfect confidence in you, did I not know you to be incapable of reckless folly, I should double-lock and triple-lock my arsenal of drugs and banish phosphorus from our lessons for- ever.

"I should be all the more impelled to this course because the risk of fire and serious burns is not the only danger to be considered ; there is another peril, which you must be still more careful to guard against. Phosphorus is a deadly poison, a few particles of it being enough to cause death with frightful sufferings. I will say no more; you are warned. Look on phosphorus as one of the most formidable of foes, and let no carelessness on your part lay you open to its assaults.

" After these warnings, dictated by prudence, I will now explain how phosphorus may be used to show what air is made of. We must burn a little in a certain volume of air properly separated from the rest of the atmosphere. Our container in this operation should be of considerable size, so that the glass may be far enough from the flame to escape the risk of being cracked or broken by the heat. A common glass preserve-jar holding two liters or more, and as large at the top as at the bottom, would do very well if I had not something better. This something better is a chemist's bell- glass, a recent purchase of mine, which we shall find to be one of the most useful appliances in our laboratory. I will ask you to be especially careful of it. It is, as you see, a simple container of color-

FURTHER EXPERIMENTS WITH AIR 103

less glass, cylindrical in form, with a dome-shaped top surmounted by a little knob for taking hold of. Some are made with flaring mouth, reminding one of the shape of our bronze church bells, whence comes the name of bell-glass. For certain delicate plants requiring shelter and warmth gardeners use similar glass covers, but they are commonly too large and cumbrous for laboratory use. If one could find a medium-sized one, it would do perfectly.

"A large bottle, a gardener's glass plant-pro- tector of suitable size, or the ordinary chemist's bell-glass — any one of these that should chance to fall into our hands would serve as a container for burn- ing phosphorus; but Uncle Paul's purse has procured for us a real laboratory bell-glass, so let us be grateful for it and proceed with our experiment.

"The combustion, the burning of our bit of phos- phorus, must take place on water, to prevent any communication between the air in the glass and that outside. Consequently, the phosphorus has to be placed on a tiny raft that will keep it dry, and for this purpose we can use any small object that will float, as a piece of cork or a bit of wood. But this float of ours would catch fire if unprotected from the burning phosphorus. Accordingly, we will put the latter in a tiny earthenware cup resting on the float; and for our cup we will simply take a con- cave fragment of some old broken pot. Now all is ready and we will proceed to business.

104 THE WONDER BOOK OF CHEMISTRY

"First we must cut off a piece of our stick of phosphorus. It is soft enough to cut with a knife, being of about the hardness of rather firm wax : but it is not a thing to be cut as carelessly as one might whittle a stick of pine wood, the mere friction of the knife being likely to prove sufficient to set fire to the phosphorus if it were exposed to the air, with consequent serious injury to the clumsy operator. The inflammable stuff should not be held in the air except by the finger-tips and for as short a time as possible, and the cutting should take place under water. "\Vatch me. '

Uncle Paul put his fingers into the bottle and drew out the phosphorus stick, which gave out a rather strong smell of garlic, with some slight wisps of white smoke. The children were told that this smell of garlic is the natural odor of phosphorus, and that the white smoke would be found to give out light if looked at in the dark. Matches emit, to a lesser extent, these same odorous fumes. The phosphorus was immediately plunged into the bowl of water, and there, both hands under water, Uncle Paul with a knife cut off a piece about as large as two peas. This fragment was placed on a bit of broken crockery, and that on a little wooden raft of sufficient buoyancy to float its load; then the whole' thing was set on the surface of the water in the middle of the bowl. A lighted match quickly started the phosphorus to burning, and Uncle Paul hastened to cover it with the bell-glass, which was, of course, full of air.

Behold, then, the phosphorus blazing away with

FURTHER EXPERIMENTS WITH AIR 105

a violence quite new to the boys, who up to this time had seen no more of the inflammable stuff than the minute quantity at the tip of a match. The flame crackled, the light was brilliant, almost blind- ing. A dense cloud of white smoke formed, giving the appearance of milk to the contents of the bell- glass. At the same time the water in the bowl rose so rapidly in the glass that Uncle Paul was obliged to add more, in order not to leave the bottom of the bowl dry, for that would have let air into the bell-glass. So thick was the milky-looking cloud that the phosphorus flame could no longer be seen ; or, if seen, it was only at intervals, like lightning in a mass of clouds. But the jets of light became more and more infrequent and feeble, and finallv ceased altogether.

•

"It is over,' Uncle Paul an- nounced. "The phosphorus has used up all the oxygen in the air contained in the bell-glass, and there is nothing left but nitrogen, which will not support combustion, although there is still some combustible matter left on the bit of crockery. We shall see it when the white smoke has cleared away. Mean- while let us talk a little about this smoke, which seems to attract your attention by reason of its beautiful milky appearance. It comes from burned phosphorus — that is to say, from the phosphorus combined with the oxygen of the atmosphere. A brilliant light, of such intensity as to try our eyes,

106 THE WONDER BOOK OF CHEMISTRY

accompanied this act of combining, as it always does. I say nothing of the heat, to which the bit of broken crockery could testify if it could speak. These fumes are easily dissolved in water, and thus there is left a vacant space which the water from the dish rises to fill, little bv little, in this way showing how

v tf CD

much oxygen has disappeared. We should have to wait only about twenty minutes, more or less, for

V »'

the contents of the glass to become as clear and transparent as at the start. But to hasten the proc- ess and not to put your patience to such a test, let us see what this will do: we shake the bell-glass gently so that the moving water washes the interior and takes up the smoke. By this operation the con- tents will soon be made clear."

With a little careful management in shaking the glass, the gas within was soon made to resume its original transparency, and then there was revealed, on the bit of broken earthenware, the residue of what had been placed there, but now of a reddish color and, indeed, so changed in appearance that the boys would not have recognized it as phos- phorus. Melted by the heat so that it was spread out on the piece of earthenware, it had quite an altered look. But to convince his hearers that it was still phosphorus, their uncle tilted the bell-glass slightly, so as to bring the little raft near its edge, when it became an easy matter to withdraw the raft and its load.

"What we have here," said he, "is really phos- phorus despite the reddish tinge that heat and melt- ing have given it. There is even more left over

FURTHER EXPERIMENTS WITH AIR 107

than there was burned. You shall judge for your- selves. ' '

The potsherd was taken out into the garden so as not to mingle the disagreeable phosphorus fumes with the air of the workroom, then with a match the reddish substance was set fire to, and it burned with the bright light and dense white smoke attend- ing the combustion under glass. Thus it was proved that there remained some phosphorus, even a good deal, as it burned for a considerable time; and in this instance every particle of it was consumed, the last trace being dissipated in the air as white smoke.

"If combustion stopped under the bell-glass, " Uncle Paul continued, "it was not for lack of some- thing to burn, for there was a good deal of it left at the end, but for lack of the gas necessary to sup- port combustion — oxygen, in a word. It stopped when the last trace of this gas was used up, phos- phorus being able to burn as long as there is any oxygen left, however little it may be. Consequently, the bell-glass now contains nothing but pure nitro- gen, a gas in which no substance whatever can burn.

"The phosphorus experiment tells us once again, but more positively and more distinctly, w7hat the candle experiment told us : the atmosphere contains two gases, oxygen, which supports combustion, and nitrogen, in which neither candle nor phosphorus nor anything else can burn. It tells us, also, in what proportions the two gases, both simple sub- stances, both metalloids, are combined in the atmos- phere. Our bell-glass is cylindrical. If we divide

108 THE WONDER BDOK OF CHEMISTRY

its height into five equal parts, these will represent equal capacities, equal volumes. Now we see that the water that rose in the glass and took the place of the departed oxygen has mounted to a fifth of the total height, nitrogen occupying the other four- fifths. Thus the air about us has four times as much nitrogen as oxygen; or, to express it differ- ently, in five liters of air there are four of nitrogen and one of oxygen.

"We will stop here for to-day. To-morrow, let me notify you in advance, our chemical experiments will call for two live and uninjured sparrows. Set your snares and catch them. I must ask you also to be careful not to molest any of the various species of garden birds, industrious hunters of insects and worms that are the scourge of agriculture; but I gladly give you a free rein in regard to those pil- laging sparrows that, eager to find some tender foliage to tickle their palates in the spring, fly down from the neighboring roofs and nip my peas as fast as they sprout. I must have two of these birds for our instruction and to serve as a lesson to their brother marauders. "

CHAPTEE IX

THE TWO SPARROWS

THE two sparrows had been caught. Spring- traps, hidden under a thin layer of earth amid the rows of sprouting peas, and each baited with a piece of bread, had soon accomplished their purpose. Extricated from their entanglement in time to prevent strangling, the two captives were now moving about, full of life, in a cage. The boys were impatient to know what their uncle proposed to do with them, eagerly looking forward to some highly interesting and important experiment. A course of study having for them the keenest inter- est, and carrying with it the fun of catching spar- rows, was real play in their eyes, — a circumstance highly pleasing to their uncle, who was convinced that in order to learn well one must enjoy learning. "Ever since yesterday, " said he to them, "the bell-glass full of gas, in which the phosphorus would no longer burn, has been standing in the bowl of water. The white smoke left after the experiment, and of which a little might have continued to linger all the afternoon, has now had ample time to dis- appear, to become absorbed in the water, so that at present there is nothing in the glass but perfectly pure nitrogen. Notice the transparency, the com-

109

110 THE WONDER BOOK OF CHEMISTRY

plete invisibility, of this gas. Would n't you take it for ordinary air, air such as filled the bell-glass in the beginning? It looks just the same, and yet how different are its properties! In this gas nothing will burn, no matter what we try. After what has occurred, this is plain enough without further demonstration. Some phosphorus — a good deal of it, in fact — was left inside the bell-glass, as was proved when we burned this residue out in the garden. If this remnant of phosphorus could not burn under the glass, but did burn very readily in the open air, the reason must be that it no longer had around it the gas needed to support combus- tion, having consumed what was originally con- tained in the bell-glass. In the open air is found an unlimited supply of what it had lacked under the glass, and that is why it began to burn again more brightly than ever and continued to do so until the last particle of the phosphorus was used up.

' ' Hence it is plain enough that as phosphorus could not go on burning in the gas now remaining in the bell-glass, no other substance whatever can burn there. Where the most inflammable of sub- stances stops burning how could one less inflam- mable remain on fire?'

"That is very clear," admitted Jules; "what the strongest cannot do, certainly the weakest cannot. Then this gas — this nitrogen, as you call it — would immediately quench any fire that could be plunged into it?"

"Certainly. No burning substance plunged into it could go on burning for a single moment."

THE TWO SPARROWS 111

"It would be the same as when the candle stopped burning in the bottle? Emile, with all his care, couldn't make it stay alight.'

"Yes, that 's it, except that it falls short of the truth. I told you a candle-flame has n 't energy enough to use all the oxygen in the air. A con- siderable part is left over in any such experiment as we performed at first; that is to say, in the experiment with the candle burning inside the bottle turned upside down, what is left of the gas is not pure nitrogen; there is still a little oxygen mixed with it, but not enough to keep a second candle alight where the first one ceased to burn. We found, in fact, that we couldn't put a lighted candle in there without its going out immediately. But a more in- flammable substance, such as phosphorus, would find what it needed in the residue of oxygen there, and would go on burning for some time where the candle could not"

"One might, then, put it this way," suggested Jules: "phosphorus is so hungry for oxygen that it licks up the leavings of the candle, which has a more delicate appetite.'

"Yes, that would express it admirably. If there are any remnants of oxygen, phosphorus, with its robust appetite, will be sure to devour them; but if there are no such leavings, it must go without, and in that case it ceases to burn just as any other combustible material would have to do.'

"That seems clear enough," said Emile, in his turn; "but, all the same, I should like to see it proved by experiment."

THE WONDER BOOK OF CHEMISTRY

"What you desire is exactly what I propose to do,' ' replied his uncle; "only we must first transfer a little of the gas from the bell-glass to a wide- mouthed bottle, in which our tests can be made more conveniently. So now is the time for us to put into practice the little I have told you about the trans- fusion of gases. As our bowl is too small and too shallow for this purpose, we will use this large tub filled with water."

So saying, Uncle Paul lowered the bowl with the bell-glass into the tub without disarranging them, and as soon as the rim of the glass was immersed he withdrew the bowl. A wide-mouthed bottle full of water, inverted and with only its mouth im- mersed, was held in position by Jules. His uncle tilted the bell-glass a little, and made some of the gas pass into the bottle and fill it. Then the bowl was again slipped under the bell-glass, and the whole thing was replaced on the table. Finally, the bottle, filled with nitrogen and stopped with the palm of the hand, was set upright on the table and a piece of glass laid over its mouth. In these various op- erations, harder to describe than to execute, care was taken never to leave the containers of nitrogen open to the outer air, an indispensable precaution and one easy to observe by keeping their mouths immersed and operating under water.

"Here we have our bottle full of nitrogen, " said Uncle Paul. "Now what shall we try first, — sul- phur, phosphorus, or candle?"

"Let 's begin with the weakest," was Emile's suggestion, "and try the candle first."

THE TWO SPARROWS 113

The candle, tied to a wire, was lighted and slowly let down into the bottle. Scarcely had it passed the mouth when it suddenly went completely out, not retaining even for an instant that red glow on the wick which is wont to linger for some time after the candle-flame has been blown out. A plunge into water could not have caused a more instantaneous and complete extinction.

' ' Ha ! ' ' cried Emile, ' ' that goes much better than when we tried it before. Yesterday the flame seemed to hesitate, sometimes, about going out; it had to be let down well into the bottle, and the wick appeared to want to keep its red spot; but to-day we see nothing of the sort. As soon as the candle was lowered into the neck of the bottle, flame and red spot both vanished at the same time. And now let 's try phosphorus."

"Phosphorus will not burn there any better; you shall see."

The fragment of broken crockery again served as a cup the size of a five-franc piece. An iron wire was bent at one end into a ring for holding this cup, which in turn was to hold the piece of phos- phorus. These arrangements completed, the phos- phorus was first lighted, and then lowered by means of the iron wire into the bottle of nitrogen. It went out abruptly, as had been expected. What burned so furiously outside the bottle immediately refused to burn when put inside.

A similar test was made with sulphur, which Emile seemed to think might burn in the bottle be- cause of its high inflammability; but it went out

114 THE WONDER BOOK OF CHEMISTRY

as quickly as the candle and the phosphorus.

"Further tests are needless, " declared Uncle Paul; "they would only lead to the same result. Nothing can burn in nitrogen; or, in other words, that gas will not support combustion.

"So now we will proceed to make use of your two sparrows, whose part in our study of chemistry is still a puzzle to you. They will teach us some very interesting things, to atone in part for our loss in the peas they have destroyed. 'In the first place, we must fill our bottle once more with nitrogen. What is still there has come into contact with phos- phorus, sulphur, and candle-grease; therefore we are not certain that it is perfectly pure, as it should be for the purpose of our experiment. Accordingly, we will obtain a fresh supply from the bell-glass, first emptying out what is already in the bottle. But how shall we proceed to accomplish this!"

"To empty a bottle, all you have to do is to turn it upside down," Emile made haste to explain, with- out stopping to think.

"Yes, if the bottle contained water or some other liquid," replied his uncle; "but it contains a gas of about the same weight as air. If you should try to empty a bottle of air by turning it upside down, you would never succeed.'

"That 's so. Then let 's blow as hard as we can into the bottle, and we shall drive out what is in it."

"Agreed; but first tell me how we are to know when we have driven it all out, there being nothing to show what goes out and what comes in. Further-

THE TWO SPARROWS 115

more, you will only replace the first gas with an- other, your breath, which will be just as hard to drive out ; and so the thing will have to be done all over again, and after that still again, and so on without end."

"Keally, the more I think of it, the harder it looks to me. I was a little too hasty when I said it was so easy to do. Jules says never a word, and I '11 bet he doesn't know any better than I how to manage it."

"I own I am puzzled, " said Jules. "This little matter, which seemed a mere nothing, brings me up short."

"It will not stop you very long. Here is how it is done.'

His uncle took the bottle and plunged it into the tub, where it quickly filled with water.

"There you have the gas driven out completely."

"Yes," agreed the boys, "but now the bottle is full of water. ' '

"And what is to prevent our replacing it with nitrogen from the bell-glass just as we did before?"

"Why, that 's so! It 's as easy as can be. The only hard part was to think of it in the first place, just as you said yesterday."

"I am reminded at this point," said Uncle Paul, "of something that may appropriately be mentioned here. In order to ascertain whether the composition of the air is everywhere the same, aeronauts and travelers sometimes bring back air taken at the height they have reached. Now, how can a sample of air be taken at the summit of Mont Blanc, for in-

116 THE WONDER BOOK OF CHEMISTRY

stance, or in the lofty altitudes attained by balloon- ists? How make sure that the air really comes from precisely such and such a place, from a given mountain-top, for example, or from a certain height in the heavens above? Imagine a series of bottles labeled: 'This is from the top of Mount Perdu/ 'This was taken at a height of eight thousand meters, by an aeronaut/ 'This was brought by vessel from such and such a latitude and longitude at sea/ How are specimens to be obtained from vari- ous distant points when they are desired for the purpose of chemical examination? Nothing easier. A bottle filled with water is emptied at the exact spot where it is proposed to take a sample of the air, and the air at this spot rushes in to take the place of the liquid poured out. Then the bottle, carefully corked, will hold henceforth, with no further precautions, the invisible substance that at first seemed so hard to collect in perfect purity. "We now come to the sparrows, whose part in all this I see you are impatient to learn. From the contents of the bell-glass I once more fill our bottle with nitrogen in the manner already shown. A second bottle of the same size and shape, but full of air, is placed on the table beside the first. There they both are, with pieces of glass over their mouths as stoppers. In the appearance of their contents there is no difference, each bottle showing the same clearness, the same invisibility, as to what is inside. Now I will put these two sparrows into our bottles, which are large enough to hold them for the short time required by the experiment. But

THE TWO SPARROWS

117

first I will ask Emile which bottle, if he were a bird, he would prefer to go into, the one with air or the one with nitrogen.'

"A week ago," replied the boy, "I should have said it didn't matter which I chose, for there is nothing to be seen in the one any more than in the other; but now, to tell the truth, I 'm beginning to be afraid of these invisible things. That rascally nitrogen that puts out a candle is not to be trusted. I don't know much about it, and I do know a little more about air, and so I 'd rather trust air than nitrogen. If I were a sparrow, then, I 'd choose the bottle filled with air."

"And you would choose very wisely, as you shall soon see. '

Taken from the temporary cage, the sparrows were put, one into the bottle full of air, the other into the bottle of nitrogen. The piece of glass laid over the mouth of each bottle shut in its occupant completely. The young observers looked on, deeply interested in what was to come next. In the bottle of air nothing unusual occurred. The captive fluttered about, pecking at its prison-wall of glass, that mysterious obstruction which it could not see and yet could not pass through. It tried to take flight, fell back, rose again, and recommenced its vain attempts. All this was simply the agitation of a bird seeking to regain its lost liberty, a desperate attempt to escape from the prison, and nothing more. Vigorously alive, struggling with beak, claw, and wing, the bird

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evidently had no other feeling than one of extreme fright.

Quite otherwise did the sparrow in the bottle filled with nitrogen behave. No sooner was it placed in its glass cage than it was overcome as if with stupor. Staggering, beak open, breast heaving, it appeared almost at its last gasp. Seized with convulsions, it fell sidewise, struggled aimlessly, opened its beak again and again as it panted for breath, and then ceased to move. The bird was dead. The other, on the contrary, was still comporting itself in a very lively fashion.

' ' This experiment, ' ' Uncle Paul confessed, "is one that I have no liking for; nor does it please you any better, my dear children. The sight of a creature in pain, suffer- ing as the victim of our curiosity, like this sparrow dying to afford us instruction, is as repugnant to your kindly nature as it is to mine. It is a thing to see once, the pursuit of knowledge having its cruel necessities; but it is not to be repeated. Let us hasten to liberate the survivor. For the sake of its fellow, dead in the cause of chemistry, I forgive it for pilfering my peas. '

The two sparrows were taken out of the bottles, the one from that containing air being as lively as a cricket. Emile held it in his hand a moment, bade it good^by, took it to the open window, and let it go, whereupon it flew away like an arrow, with a cry of supreme joy. The other, its poor little claws

THE TWO SPARROWS 119

stiff in death, remained on the table, breast upward. Emile and Jules gave it occasional side glances, puzzled to understand the cause of so sudden a death, and perhaps hoping to see it come back to life. Their uncle perceived what was in their minds.

"Do not hope for the sparrow 's revival," said he. "It is dead — poor little thing! — dead for good and all. "

"Is this nitrogen, then, such a terrible poison?" asked Jules.

"No, my young friend. Far from being a poison, nitrogen is perfectly harmless. It must be harm- less or we could not live in an atmosphere of which it constitutes four fifths. We all breathe it inces- santly, and not one of us ever has any reason to complain of it. Nitrogen is quite harmless; that is not what killed the bird."

' ' Then why did it die I "

"The candle which burns in the air goes out in nitrogen. Is it because of this gas? No, for if that were so, the candle could not burn in an atmos- phere abounding in nitrogen. Where this gas is present all by itself the candle goes out, not on account of the nitrogen, but because it lacks the element essential to combustion, and that is oxygen. It is not the presence of the one gas, but the absence of the other, that makes combustion impossible.

"We ourselves perish quickly in water. Why? Can it be that water is a poison? Certainly not; such an idea would never occur to us. We die in the water for want of air, water itself having noth- ing to do with the death of the person drowned,

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which is due solely to the lack of breathable air. In like manner we may say the sparrow met its death by drowning in nitrogen. It cannot truly be said that air was wholly lacking, for the bird had a plenty of one of the two gases composing the atmos- phere; it was merely deprived of that part which alone is breathable, which alone promotes in the animal, for the purpose of sustaining life, an action comparable in every way to that set up in the candle-flame to cause it to burn.

"It is the lack of oxygen, then, that caused the sparrow's death and the going out of the candle. Where there is no oxygen, neither life nor combus- tion is possible. No animal can live where a candle cannot burn, for life and combustion are closely akin, as I will show you at the proper time. But first we must study carefully this partner of nitro- gen in our atmosphere, this gas called oxygen; and then you will be in a position to see the close re- semblance between life and fire."

The boys exchanged glances of surprise at hear- ing their uncle thus associate these two things.

"I am saying nothing," he continued, "that does not agree with the most careful scientific observa- tions ; that has not, indeed, to some extent, become a part of our every-day thinking, so obvious is it to every one. We say of a fire that has gone out, that it is dead. The famous song that Harlequin sings under his friend Pierrot's window tells us that the candle is dead. In order to die it must first have lived. The dead fire, the dead candle, had, while they burned, I will not say life, for that would be

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going too far, but at least a state not unlike life in respect to the chemical action concerned. A lighted candle and a live animal consume oxygen in order to continue burning in the one case and living in the other. Both candle-flame and animal die in nitrogen because this oxygen is lacking there. That is the whole secret of the end of the poor sparrow. ' '

"And other animals?" asked Emile. " Would they die in the nitrogen as the sparrow did?'

"All would die there, some sooner, some later, according to their different kinds — absolutely all, since no creature, however small, can live without oxygen, for which nitrogen will not in the least serve as a substitute. If it were not a cruelty as repug- nant as it would be useless, we might repeat our experiment with all the inhabitants of our garden,- with its birds, field-mice, moles, insects, snails, and so on, — and we should see them all succumb in nitro- gen, some quickly, others after a long enough time to try our patience ; for I must tell you that though all animals without exception need oxygen if they are to live, they do not all feel its need with equal urgency. There are some that are overpowered instantly in nitrogen: such was the case with our sparrow ; others can live in it for hours or even for days, but are sure to die at last. The rule is uni- versal; the length of the victim's resistance alone varies. First to succumb are the birds, their breathing being very rapid. Then follow the fur- bearing animals, — the cat, the dog, the rabbit, etc., — in short, the mammals, as naturalists call them. Reptiles have a much greater power of resistance:

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a lizard, a snake, or a frog would perhaps not be quite dead even at the end of an hour. Finally, insects, snails, and other small forms of animal life are the last to perish.

"This is something so important that I must not refuse to illustrate it by experiment, despite our pity for suffering. Besides, I have in mind a poor victim that would otherwise perish miserably under the cat's claws. Better that it should meet with a gentle death in nitrogen than endure the cruel suffering the cat's claws would inflict. We shall be doing it a kindness to spare it that torture. It is a mouse caught in the mouse-trap. I saw it this morning on one of the pantry shelves. Emile, go and get it.'

Emile came back with the mouse-trap and its captive. From the nitrogen left in the bell-glass, the bottle in which the sparrow had died was re- filled. Opening the trap a little, Uncle Paul dropped the mouse into the bottle. Finding itself in this glass prison, the animal first circled around several times, hugging the wall and seeking an outlet, with no further appearance of discomfort than fright. Then it crouched down, began to tremble, and seemed to go to sleep. Finally, a sudden convul- sion announced that it was dead. Only a few minutes had passed, but it was clear that the animal had taken longer to die than the bird.

"Give the mouse to the cat," said Uncle Paul, "and that shall end our experiments with animals. Now let us sum up what we have just learned. Nitrogen forms four fifths of our atmosphere. It

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is a colorless, odorless, invisible gas in which noth- ing can burn. A lighted candle goes out the mo- ment it is lowered into this gas. Nor can animal life sustain itself in nitrogen: any animal that breathes it unmixed with oxygen dies sooner or later, not on account of the nitrogen itself, which has no harmful properties, but for lack of oxygen, the only part of the atmosphere that will sustain life."

CHAPTER X

BURNING PHOSPHORUS

PREPARATIONS had been made for some new experiments, which pupils always like. On the table stood the tin box containing the bottle with the phosphorus; also there was the famous bell-glass resting on a plate, in the middle of which was a saucer full of lime.

' ' What is Uncle going to show us with all these fixings!'7 queried the boys.

"The air we breathe," he began, "is still very imperfectly known to you. Of the two elements composing it, only one, nitrogen, has been shown you; the other, oxygen, less abundant but much more important, is hardly known to you except by name. You recall what the experiment with burn- ing phosphorus showed us, — that oxygen forms the fifth part of our atmosphere, — and you also know, rather from my telling you than from the evidence of actual facts, that it is the gas needed when any- thing is to be burned. Without oxygen the flame goes out, and without it the life of an animal also comes to an end. But what is this gas? What will it do alone, by itself, and not mixed with nitrogen as it is in the atmosphere? That, my little friends,

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BURNING PHOSPHORUS 125

is the important question. I am going to try to answer it for you.

"In five liters of atmospheric air there are four liters of nitrogen and one of oxygen ; so that is the source we must go to when we wish to obtain in a pure state either one of these two elements. Now, in the atmosphere the two gases are not chemically combined, but simply mixed, as I shall have occasion to prove to you later. As they are only mixed, a simple separation of the two is all that is needed, though even this is a difficult matter; for how can we separate two substances that cannot be handled or even seen! A little while ago when we mixed powdered sulphur and iron filings, Emile thought it not impossible to separate the two, grain by grain, at a great cost of time and patience. And he was right: the task is not too much for nimble fingers and sharp eyes. With this mixture called air, however, it is a very different thing. The two substances forming the mixture can be neither seen nor felt, and if they could be seen it would still be hardly any easier to separate them, so subtle is their nature. What, then, are we to do!"

"It was easy enough to separate iron and sul- phur/' said Jules, after a moment's reflection, "by using a magnet, even though the two substances were both of them powdered very fine. Couldn't we use some means for sorting the two gases that air is made of?'

"Yes," chimed in Emile, "I 'd like to find some- thing that we could hold in the air and make it attract one of the gases and leave the other behind,

126 THE WONDER BOOK OF CHEMISTRY

just as the magnet attracted the iron filings and left the sulphur. "

" Do you know, my lads, that what you say shows more understanding of the matter than I had ex- pected V rejoined Uncle Paul. "Your answers de- light me, anticipating as they do what I was about to propose as the only practicable means to be em- ployed. What Emile says he would like to find is already known to you ; you have seen it in operation, and no longer ago than day before yesterday. "

"Phosphorus?" queried the boys.

"Yes, phosphorus. When it was burned under the bell-glass, did it not take to itself the oxygen and leave its companion, nitrogen, in the glass?"

"Yes, that 's just what it did."

"Did n't it behave very much like the magnet you thrust into the mixture of iron filings and sulphur so that it drew the iron filings to itself and left the sulphur on the paper?"

"To be sure it did!"

"The magnet attracts iron, but has no effect on sulphur, which is thus left by itself. In the same way burning phosphorus attracts and retains the oxygen in the air, but leaves the nitrogen, for which it has no liking."

"Now we have it, I think," said Jules. "The magnet, covered with iron filings, was drawn out of the mixture, and then we rubbed off the filings on to another piece of paper away from the sulphur. Let 's make the phosphorus take all the oxygen it wants, and then we '11 take it away again."

"A capital suggestion," applauded Uncle Paul;

BURNING PHOSPHORUS 127

"but, unfortunately, it won't quite work. The magnet readily gives up its load of filings, but not so with phosphorus and its load of oxygen. I have told you of its voracious appetite. Once having got its fill of oxygen, it is impossible to make it disgorge except by forcible means not at our command in our humble laboratory. What it gets it keeps a good hold of, so that with our modest resources we should never succeed in making it let go.'

"Let it keep its oxygen, then!" cried Jules in vexation at seeing his project fail just as he thought it about to succeed. "I '11 try another way. Isn't there something that will work just the opposite of phosphorus, — something that will take the nitro- gen from the air and leave the oxygen alone by it- self? That would be much simpler."

"No doubt that would be much simpler, but — '

"Is there a but!"

"Alas, yes, and a most serious one! You must know that nitrogen is a most unsociable element, decidedly hostile to the notion of alliances. No ele- ment will have anything to do with it, as a rule, and it has no use for a partner of any sort. Chemical combination it abhors, and only when coaxed by the most skilful and delicate devices will it consent to any such union. Let us not, then, for a moment think of withdrawing nitrogen from the air by com- bining it with another substance ; all attempts in that direction would be sure to result in failure.

"Must we, then, give up in despair? Not at all. The first method is excellent if we only use it with discretion. Phosphorus, it is true, keeps a most

128 THE WONDER BOOK OF CHEMISTRY

obstinate hold on the gas it has united with in the act of burning, and it is useless to expect it to «Let go of the oxygen it has taken from the air. But, fortunately, not all simple substances are like it. We shall find some more accommodating, willing to surrender their plunder without too much coaxing. For to-day we will content ourselves with learning how this gas is accumulated and, as we might say, stored up in a burnt substance; and for the pur^ poses of this demonstration phosphorus will serve. "You have not forgotten how smoke formed in the bell-glass when phosphorus was burned there, in our experiment of day before yesterday. That thick cloud of milk-white appearance made too deep an impression on you to be soon forgotten. And you remember how, little by little, it dispersed, be- ing taken up by the water in the bowl. If I had not called your attention to this point, perhaps that dis- appearance would have seemed to you a real instance of annihilation, and you would have retained the notion, so generally held, that fire reduces to nothing the material that it burns. I instructed you to the

J

contrary, but that is not enough; I wish to add to ' my mere assertion the more convincing testimony of fact. Accordingly, I propose to show you that fire does not annihilate, but only transforms; that it changes the appearance and the properties of matter without affecting its existence. Phosphorus will furnish us a fine example of this, and at the same time give us some knowledge of the chief topic of our to-day's lesson. The experiment I am pro- posing will show us, on the one hand, the indestructi-

BURNING PHOSPHORUS 129

bility of matter by fire, and, on the other, the stor- ing up of oxygen by combustion.

"The white fumes given out by burning phos- phorus are very easily dissolved in water, which ac- counts for their prompt disappearance in our recent experiment. To preserve them, to let them take on the state natural to them when cold, and then to examine them at leisure, it is absolutely necessary to do the burning where there is no water. Nor is even this precaution sufficient, so great is the liking for water of this compound formed by burning phos- phorus. The atmosphere is always moist, whence come rain and dew. However dry it may seem to us, it is sure to contain more or less of the invisible vapor of water, which the burned phosphorus would greedily pounce upon, dissolving itself therein just as sugar dissolves in water. Consequently, we must have perfectly dry air in the bell-glass where the burning is to take place.

"This dry air I obtain by means of quicklime, — that is to say, lime before it is slaked by the mason, or, in other words, lime just as it comes from the lime-kiln where it has been prepared. You don't need to be told what happens to a piece of lime left in the air for some time.'

* ' I know what you mean, ' ' said Jules. ' ' The piece of lime gradually cracks open, and then crumbles to dust, just as it does when you sprinkle it with water; only then it crumbles a good deal faster.'

"That is it. Sprinkled with water, a piece of lime cracks, splits, crumbles to dust. Exposed to the air for some time, it acts in the same way, but

130 THE WONDER BOOK OF CHEMISTRY

more slowly. Why? Because it absorbs the mois- ture in the surrounding air, until, little by little, this moisture has had the same effect on it as a fine spray of water would have had. Thus it is that lime has the habit of attracting moisture, however little there may be within its reach. It wrenches it by force, we might say, from the surrounding atmosphere, and takes every bit of it. Here we have, then, a very easy and convenient way to obtain perfectly dry air.

"A few hours ago I took care to place a saucer of quicklime in the middle of a large plate, and covered it with the bell-glass, the latter resting on the plate and being, of course, full of air. With this precaution the fumes of the burning phosphorus cannot escape, and not only the imprisoned air, but also the surface of the plate under the glass and the inside of the glass itself, will be rendered very dry. Now for the burning of our phosphorus.'*

Uncle Paul cut off a piece of this substance under water and dried it carefully with blotting-paper. Then, placing it on a bit of broken crockery, he with- drew the saucer full of lime and substituted the phosphorus, which he set fire to, whereupon the bell- glass with its contents of dry air was immediately replaced on the plate. The burning did not at first differ in any way from that already seen by the boys ; there was the same bright light, with the same eddies of dense white smoke. But at this point there occurred something new: on the inside of the cold glass the smoke condensed and became a beau- tiful, white, flaky substance that detached itself and

BURNING PHOSPHORUS 131

fell here and there with all the appearance of falling snow. Soon the plate was covered with a layer of this strange snow-like substance that had come from the very heart of the flames.

"Well, Emile," said his uncle, "what do you think of this snow! "

"I think it is very wonderful. Who would ever have expected fire to make a snow-storm! But I know well enough it isn't real snow, though one might be fooled by its looks. Those flakes, all so white and beautiful, must come from the burning phosphorus, for they couldn't come from anything else."

"Yes, that is quite clear. The substance we see forming here has nothing of snow about it except its appearance. In reality it is quite another thing, as we shall soon see. But first let us make it snow a little more. The fire is dying down ; we will feed it."

Uncle Paul raised the bell-glass a little, and the burning, which had begun to languish, started up again with all its former vigor.

"Air was beginning to fail," said he; "the phos- phorus had nearly exhausted its supply of gas, and was about to die down, but, by raising the bell-glass a little, I have let in more air, and the fire revives. Let us give it a little more air still, so that we may be sure to have enough of this strange snow."

When, after three or four renewals of air, the layer of snow on the plate was deemed thick enough, Uncle Paul took a pair of pincers and drew out the piece of crockery with the phosphorus on it and

132 THE WONDER BOOK OF CHEMISTRY

carried it into the garden, that the still unconsumed material might there burn itself out with no incon- venience to lungs or sense of smell.

"Now, my young friends," he resumed, "I invite you to examine what there is in the plate. It is, as you see, a white, flaky substance looking much like snow. That is what phosphorus turns to when burned. Fire has not destroyed it, but has changed it into something else, and the change is so complete that if you did not know where this false snow came from you could never guess its nature. I repeat, fire does not destroy anything; what it devours, what it consumes, is not reduced to nothing, but changed into something else, which sometimes van- ishes from before our eyes as an invisible gas, and at other times arrests even the least heedful attention as a much grosser substance. What you see here in the plate — this stuff that we can feel, smell, and taste — is phosphorus consumed by fire, phosphorus still in existence though it has been burnt up. Thus is illustrated before your eyes the first point I had in view in this experiment, — namely, that nothing is ever annihilated even by the action of fire.

"Suppose we had here a fine pair of scales for weighing, exactly balanced as are scales used by chemists, and capable of telling us with precision the weight of a fly's wing. The weighing of even so minute a bit of matter is very often called for in the delicate operations of chemistry. With a pair of scales of such sensitiveness, we could have ascer- tained the weight of the piece of phosphorus in milli- grams. Nothing then would have stood in the way

BURNING PHOSPHORUS 133

of our burning the whole of that piece under the bell-glass by renewing the air as often as was neces- sary; and at the end we could have taken a feather and swept up the snowy deposit even to the last flake, after which we could have weighed it on our scales. Let us suppose these two weighings to have been carried out, one before the phosphorus was burned and the other after. Now, which will weigh the more, the unburnt substance or the burnt?

"Misled by that false notion of fire as a destroyer, the novice would answer at once that the burnt sub- stance would weigh less than the other, arguing that if fire does not entirely destroy, it at least destroys in part. But you, my boys, forewarned against this error in our earlier talks, and having had your eyes opened by a number of experiments, will not, I be- lieve, make this foolish answer.'

"I should think not," was the