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The Wonder Book of Chemistry by  Jean Henri Fabre


 

 

AT THE BLACKSMITH'S

[230]

O
NE day Uncle Paul tool his two pupils to the village blacksmith, whose smoke-stained shop was to serve as laboratory for one of the most curious experiments of their course in chemistry. He wished to prove to them that water contains a highly inflammable substance, a gas easier to burn than even phosphorus and other elements they had seen catch fire so readily. Water, which puts fires out, was now to furnish fuel for fire. Jules and Emile did not show themselves very confident of the success of what they could not but look upon as rather foolish undertaking. The blacksmith himself—farrier for half the week, locksmith on occasion, horse-doctor now and then, maker of cutlery if necessary, plumber in spare moments, tin-plater when old saucepans required his services, silver-smith and even jeweler at a pinch (for one must make a living, said he, somehow or other)—the blacksmith, we say, when told of the affair in hand, found nothing in all his varied experience to encourage hope of success in his neighbor's proposed enterprise. Nevertheless he lent a hand in the necessary preparations with a very good grace, and placed his forge, tools, and personal assistance en- [231] tirely at the other's disposal. The coal-dust that begrimed his face partly hid his mischievous smile of incredulity.

A large earthen bowl filled with water was placed on the work-bench, together with a tumbler, and a heavy iron bar was thrust into the forge to be heated red-hot. The blacksmith plied the bellows, and Uncle Paul watched the iron bar. When it was hot enough, he directed the others how to proceed.

"Fill the tumbler with water," said he to Jules, "and then with one hand hold it upside down in the bowl, the mouth always immersed. I will plunge the red-hot end of the iron bar into the water and under the inverted tumbler. Don't be afraid for your fingers; I will take care not to burn them. Without raising its mouth out of the water, tilt the glass so that the red-hot iron can be slipped under."

All this being made clear, Uncle Paul quickly plunged the end of the bar, heated to the utmost, under the mouth of the tumbler. The water boiled and bubbled violently for a moment, while globules of gas were seen to rise and collect in the inverted bottom of the glass.

"That is not enough," said Uncle Paul. "Keep hold of the tumbler while I do it three times more, always the same way, until we have several fingers' depth of gas in the glass."

Again and again the bar was returned to the forge and then plunged, glowing hot, into the water; and with each repetition the volume of gas increased. It went slowly, but still it went, and the blacksmith worked the bellows untiringly, being as [232] eager as the boys to see the result of this curious experiment. What could there be collecting in the glass? It seemed to be a sort of air, and of course it was invisible. But how did it differ from the air outside? In the course of his daily work the smith had often put red-hot iron into water, and the hissing sound that followed was familiar enough to him; but he had never gone any farther. It was only those that read books—neighbor Paul, for instance—that thought of collecting in a glass bubbles from water boiling at the touch of red-hot iron. The soot-begrimed face, streaming with sweat that looked like drops of ink, had by this time lost its incredulous smile, and in its place was an unmistakable expression of deep interest. The forge that had seemed to the worthy man to hide no secrets from him, did, after all, hold mysteries that would no doubt soon be explained.

At last Uncle Paul himself took the glass in one hand, tilted is slightly so as to let the gas escape little by little, and with the other hand held a lighted paper to the bubbles as fast as they appeared on the surface of the water. Immediately there was a pop from the bursting bubble, and a flame darted up, but so pale that one had to turn one's back to the door in order to see it. The dark shop was, in itself, well suited to the purpose of making the burning gas apparent to the eye. Pop!>  went the second bubble and pop! Pop! Pop!>  repeated the others in quick succession, each giving out a feeble flash of light. It was a sort of miniature fusillade.

"Waterproof gunpowder!" exclaimed the black- [233] smith, in astonishment. "No sooner does it come to the surface than it explodes. Once more, please, so that I can see it better."

Uncle Paul again tilted the glass. Pop! Pop! went the bubbles until the gas was all used up.

"And you say," inquired the farrier, "that this air, this gas that catches fore quicker than gun-powder, comes from water?"

"It comes from water decomposed by the red-hot iron. What else could it come from? In getting it I use only water and iron, and even the latter is not really necessary, as we shall presently see. It is, then, the water that gives us the inflammable gas."

"What a fine thing chemistry is!" said the smith, with a puzzled shake of the head. "It makes water burn. I'd like to study chemistry a little if I had time."

"You practise chemistry every day," rejoined Uncle Paul, "and very interesting chemistry, too."

"Chemistry—I? Is it chemistry when I shoe Jacques's mule or sharpen Simon's plowshare?"

"Yes, there is chemistry in those things, and you are putting chemistry into practice every day, but without knowing it."

"Well, that beats me!"

"I hope to make it all plain to you before long."

"When?"

"Now, this very day."

"One question more, if you please, my learned neighbor. What do you call this gas that comes from water and burns?"

[234] "It is called hydrogen."

"Hydrogen. All right; I'll remember that word. Some Sunday after vespers I'd like to show a few of my friends what you have just shown me. But go on. A poor ignoramus like me ought not to interrupt by asking questions when you want to be teaching your nephews. They are lucky little chaps to have you for their teacher. Oh, if I were only of their age and you would take me for a pupil! But it's too late, much too late. My old brain could n't make anything of books. Now, what else can I and my forge do for you?"

"Start up the fire again, my good friend, and make a solid bed of red-hot coals, just as hot as you can, with no flame. I am going to decompose some more water, this time with live coals instead of red-hot iron. We shall get the same inflammable gas,—a proof that it is the water that gives it, and not the iron or coal used in the process. You, Jules, hold the tumbler ready. The experiment will be just the same as with the heated iron."

They waited a few minutes to let the forge get as hot as possible; then, taking up a glowing coal with the tongs, Uncle Paul plunged it into the water and under the mouth of the glass. A bubbling followed, the gaseous globules rising in even greater number than with the iron. With a few repetitions of this procedure the glass was nearly full. The collected gas was found to burst into flame at the touch of a lighted piece of paper, thought the flame, as before, was very pale, and at each outburst of flame a slight explosion was heard. In short, the [235] live coals served exactly the same purpose as the red-hot iron, showing plainly enough that the inflammable gas, the hydrogen, as Uncle Paul had called it, came from the water; red-hot iron and live coals, things very unlike each other, served merely to set it free by decomposing the water, a little at a time.

The blacksmith seemed lost in thought over what he had just witnessed. He was reminded of an every-day occurrence in his work at the forge. His neighbor did not fail to perceive this.

"Tell me," said he to the smith; "when you want to heat a piece of iron just as hot as you can get it, so as to do a bit of welding, let us say, how do you go about it?"

"How do I go about it? I was this minute thinking of that connection with your hydrogen there, for it seemed to me to explain something that I do every day without understanding the reason. Over there in the corner is a small trough full of water, and in it I keep a sort of little rag mop with a long handle. I use it to sprinkle water on the coal in the forge, and so I get a heat such as I can't get any other way."

"You throw a little water, then, on your fire to make it hotter; you get it to burn faster by using what would seem more likely to put it out."

"That's what I do, and I'm always puzzled when I stop to think about it. Now, with your hydrogen, it might be—"

"One moment, please. We will come back to that presently. I see from my nephews' astonished [236] looks that wetting coal in order to make it burn better rather upsets their ideas. Suppose you show them how it's done."

"All right. I'm glad to do anything I can for you, to balance what I'm getting out of this lesion, now that I'm lucky enough to be one of your pupils for the day."

Plying his bellows once more, the blacksmith started up the fire, on which he had already heaped fresh coal. An iron bar was thrust into the glowing mass, and after it had been for some time subjected to the most intense heat possible under these conditions, it was withdrawn by the smith.

"See," said he, "It's red-hot, and I could n't make it any hotter by just leaving it there and pumping the bellows. It's as hot as I need it usually. But if I want to get my iron hotter still, so as to weld two pieces together on the anvil, I take my sprinkler and throw a few drops of water on to the fire; but not too much, you understand, for that would put it out."

The iron bar was then put back into the forge, and the coal was slightly sprinkled with water. The boys, like two apprentices, stood one on each side of the blacksmith, intent on seeing everything that was being done. A trivial operation that they must have witnessed many times, but without paying it the slightest attention, took on for them an intense interest now that their uncle had opened their eyes to the properties of hydrogen, the inflammable gas contained in water. To acquire an interest in anything there is nothing like having your attention [237] called to it. Knowledge adds charm to everything around us.

The effort of the water on the live coals was immediate. Behold, the tongues of flame, at first full and long, and of greatest brightness at the bottom, and reddish and smoky at the top, suddenly shrank and seemed to withdraw into the midst of the burning fuel. Then here and there, through the opening in the mass of coal, sprang up short jets of flame, giving a clear white light. These little tongues of white flame were not unlike the hydrogen flames that had been so hard to see in the daylight. Their temperature was evidently very high, for the glowing mass whence they sprang dazzled the eye. Again the bar of iron was withdrawn, this time not red-hot but of a blinding white. Snapping and crackling, it sent out a splendid shower of sparks.

"It's just as it was when we used oxygen," declared Emile, drawing back to avoid this outburst from the metal fireworks: "the iron burns."

"Yes, my little friend," replied the blacksmith, "the iron burns, and it burns so well that if I left it too long in the forge with the heat as it is now, you would see my iron bar get smaller and smaller till there was n't much left of it. Look round on the floor near the anvil, and you'll find plenty of little bits of burnt iron. We call them splinters; the hammer strikes them off from the hot iron."

"I know what you mean: they are oxid of iron."

"I don't know that word, but those little splinters are iron that has burned. They are plenty enough when I make the forge as hot as I can by sprinkling [238] on water. But let's hear now what you uncle has to tell us. How is it, neighbor, that water can start up a fire like that? Without water the iron only gets red-hot in the forge; with water it turns blinding white. That's what I don't understand."

"You will understand," replied Uncle Paul, "when I tell you that hydrogen is the fuel that gives the most heat. Neither wood, coal, charcoal, nor any other fuel makes so hot a fire as hydrogen. It is the very best of fuels, having no equal for readiness to take fire and for intensity of heat produced."

"Now I understand; at any rate I think I do," rejoined the blacksmith. "I throw a little water on the burning coal in my forge, and the water is decomposed, as you call it, just as when I saw you plunge a red-hot coal into the water under the glass. Hydrogen is produced, and it mixes with the coal and burns; and as it is the best of fuels it makes the intense heat that turns the iron white-hot so that it can be welded. With my sprinkler I give the fuel that is better than coal. Is that the way of it?"

"Precisely. Water, decomposed by the live coals, furnishes the fire with additional fuel, the very best. Did n't I tell you that you were practising chemistry every day, and very scientific chemistry, too?"

"My word, you're right! But I never suspected it. How was I to know that by wetting my coal I was making hydrogen? One has to read books to know those things, neighbor; but I am ignorant and have to give my time to may hammer and anvil, not to printed words. One thing more, now we are about it. I've heard it said by persons of educa- [239] tion that when a fire gets well to going, it's a bad plan to try to put it out with water unless you have plenty of it. If you have n't, it is better to smother the fire,—with earth, for example. Does hydrogen have anything to do with that?"

"Most assuredly it does. If a little water is sprinked on a hot fire, the water is decomposed, and so furnishes hydrogen as additional fuel for the fire, which, instead of being put out, burns all the faster, just as your forge gives more heat when you throw on a little water. But if, instead of moistening your coal with a gentle sprinkling, you watered it freely, by the bucketful, your fire would be extinguished. So fire must be fought with water that does not have to be measured out by the cupful; otherwise it is like pouring oil on to the flames, as they say."

"One need n't talk with you more than five minutes to learn something new," declared the blacksmith. "My forge is always at your service, as you know. Only too often it stands quite idle, so slack is my trade. If your chemistry calls for any more of my outfit, help yourself. My tools are yours to do what you like with."

Uncle Paul thanked his friend and took his leave. Jules carried away with him, to examine at his leisure, a handful of the iron splinters he had picked up around the anvil.

On their return home the boys asked permission to perform for themselves the fine experiment they had just seen at the blacksmith's. The inflammable gas coming out of water had so astonished them that they wished to see it again, and above all to [240] try making it themselves, with no help from their uncle; and in fact it was one of the simplest operations, nor did it require the use of any dangerous drugs. The blacksmith, it is true, had shown himself most obliging; but they did not like to make too great demands on his time or his good will. Besides, there might be some mule waiting at the door to be shod, or some tool to be mended might be heating in the forge. In busy moments of that sort chemistry would only be a bother to the good-natured smith. Home was by far the best place for it. Without disturbing any one they could perform the hydrogen experiment over and over again at their pleasure. But was the thing feasible?

"Quite feasible," their uncle assured them. "Get a brazier and light some charcoal; that will do as well as coal, and even better. Have a bowl full of water, and a tumbler, and proceed exactly as we did at the blacksmith's. When your coals are red-hot, take them up, one after another, with the tongs, and plunge them quickly into the water under the mouth of the glass. In that way you will obtain inflammable gas just as well as with the glowing coal from the forge. To be sure of the best success, see that your live coals are as hot as you can make them with the bellows; for the hotter they are, the more water they will decompose. Finally, let me caution you to look out and not burn your fingers."

"Oh, no fear of that," said Jules. "Emile will hold the glass and I'll manage the coals. I sha'n't [241] be such a blunderbuss as to burn my assistant's hand."

"I warn you that if you try to operate with hot iron, your success will be doubtful, as your brazier is hardly big enough to heat to redness an iron bar of any size. But try it if you wish, and, once more, take care not to burn yourselves."

Having given these directions, Uncle Paul left his nephews to their own devices. So well did they arrange their charcoal in the brazier, and so good a draft did their fire get, that the two young chemists soon had a bed of glowing coals at their disposal. The operation went off as well as could have been desired, the hydrogen bubbling up in fine style. Jules, whose sharp eyes nothing escaped, could even detect, when they set hydrogen on fire, a pale bluish tinge in the flame, which had not been observed in the hydrogen flame when red-hot iron was used at the blacksmith's. Emile, too, when called upon to notice the difference, did not fail to perceive it.

They then undertook the same experiment with hot iron. But they had to content themselves with something no bigger than a curtain rod, and indeed their fire could not have heated to redness a larger bar if they had had it. Consequently, they were obliged to heat and reheat their slender iron rod over and over again, at the expense of much time and patience, before they got even a small quantity of hydrogen by this method. A few little bubbles of hydrogen, which burned with an almost invisible [242] flame, were the total result of exertions that left them both in a profuse perspiration, so many times did they have to repeat the same operation. But, after all, they accomplished enough, for their uncle had warned them not to expect any great success.


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