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The Wonder Book of Chemistry by  Jean Henri Fabre


 

 

SIMPLE SUBSTANCES

[42]

"L
ET us return now to the black powder, 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 decomposed and the sulphur and iron separated. Subjected 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 substances 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 [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 combining with that atmospheric substance. The result of this combination is the vapor that makes us cough."

"Then that vapor is more complicated than sulphur?"

"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 decomposed, never been divided into different substances, as, for example, the black powder in our medicine-bottle could be divided into iron and sulphur, and as bread could be resolved into several ingredients, carbon among them. Sulphur goes to [44] 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 substances. 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 ainmal—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 examined 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 mineral kingdom; they have examined all, studied all, analyzed all, and the fruit of this immense task, prosecuted with all possible learning and patience, is the conclusion that the number of undecomposable or simple substances amounts to sixty or thereabout, including iron, sulphur, and carbon, which we have just been considering."

"And will you tell us about all these simple substances?" asked Emile.

45 "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 exclaimed in surprise. "I did not know I was so wise!"

"You knew carbon without suspecting it of obstinately 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, preferring you to 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 decomposition has no hold; they are simple substances. But there is one metal in common use that Emile has omitted. Think! It begins with a z."

"With z?  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 general use. I will acquaint you with them as fast as we [46] 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 temperature of the atmosphere."

"Oh, that is mercury, or quicksilver!"

"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 eluding 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 metals 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 [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 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 carbon 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 [48] 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 destination. 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- [49] ence. Reason enough, then, for our remaining in ignorance about these substances that play the leading 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 subject 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 exchanges, in all commercial transactions. It is a spendid 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 disappear. 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 henceforth be impossible and this inhabited globe become a gloomy solitude, with man, animal, and plant forever 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] not be affected. Oxygen, hydrogen, and nitrogen, on the contrary, fulfil in this world of ours functions 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 not less important; and thus we have our four substances indispensable 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 will 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 [51] us sum up at this point. There are about sixty simple substances, divided into metals and metalloids. 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 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, hygrogen, nitrogen, carbon, 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. [52] 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."

"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 transmitted 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 explain 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 [53] to hear air spoken of as being weighed and measured; 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, unfortunately 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 undertake 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? Evidently 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 combinations in which many of them are at present tied up. We may, then, say of the four elements, commonly so called after the ancient conception of the matter, that not one of them will bear critical examination, not one will prove to be a simple substance, an element, as the word is understood today."


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