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The Wonder Book of Chemistry by  Jean Henri Fabre

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COMPOUND SUBSTANCES

[54]

"W
ITH the materials of his handicraft—with stones, bricks, mortar, and plaster—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, will the threescore elements at her disposal, nature fashions all the things that come from her hand, in the animal, the vegetable, and the mineral kingdoms. An artisan of sublime achievements, 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, absolutely nothing is known to us that, when decomposed (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 substance. Consider for a moment the element that [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, to, 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 combinations 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 is an oak fagot—why should it not have gone to the making of a pear, an apple, or a chestnut? Is there not carbon in those?"

"Yes, there is," replied Jules. "When you leave chestnuts on the coals too long they turn to charcoal, and if you forget apples or pears put to bake [56] 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 collects 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 [57] a complete list. I will mention finally the muttonchops 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!" 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 carbon 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] 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 bow?


" '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 sumptuous palace, the bowl of a fountain for a princely garden, or a modest slab, a commonplace bureau-top or mantelpiece. He decided 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 mankind falls prostate. Out of one and the same material 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 whatever she chooses out of the chemicals at her disposal. [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 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 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 metalloids."

"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] sword-swallowers like the jugglers we see at the fair; but we haven'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 indispensable t us that without it 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 elements 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 something considerable, and strength is none to 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 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 [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 introduced into the body, would endanger life, for they are poisons. I keep 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 [62] 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 appreciable difference in the grand total of the world's material riches. Among these minor elements I will mention gold. Confining ourselves to the fundamentals, we can see that, at most, only about a dozen simple substances contribute to form the immense majority of the products of nature."

"But there's one difficulty, it seems to me," objected 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 couldn'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 [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, Hindustani, 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 alphabet. 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 of the moment, my boy, that these letters represent our simple substances, while words represent the compound substances. The comparison is not so very far-fetched, for just as words having 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 element which, according to their properties, their [64] number, and the manner of their grouping, determine 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 they alphabet 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 alphabet would represent all the various vocal sounds. What difference is there, I ask you, in the pronunciation 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 that there are simple substances forming the great majority of compounds. In their modes of grouping, however, the elements enjoy a great advantage 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 [65] for example, that long and cumbrous word, intercommunicability. 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 combination 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 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 that there can be an almost infinite variety of compounds? To aid us in explaining this, take the word rain, for example. For the initial letter r  substitute another, and then another, and so on, and we have the common words, gain, lain, wain, pain, and others, all belonging to our language. In the [66] same way pin  becomes tin  and din  and sin. By a simple change of one letter, the rest of the word of a wholly different meaning. So it is with chemical compounds: 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 compounds. 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 substances, 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 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 entirely 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 tht the number of compounds must be very great,—that it must be enormous, even with only the dozen simple substances that play the chief [67] part. One element changed and another repeated must produce an almost endless variety of different groups."

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

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

"You would like to have an example of a compound 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 saying 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 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 ignorant, and they take it for something precious, whereas it is really of small value. You can find as many of these stones as you please among the rocks in 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] 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 wouldn't imagine 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 bba?"

"Exactly. To indicate this repetition of the sulphur, they say in chemistry that iron pyrites is the bisulphid  of iron, and you know that they first syllable 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 [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."


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