|The Wonder Book of Chemistry|
|by Jean Henri Fabre|
|Starting with a mixture of iron filings and sulphur, Uncle Paul awakens in his young nephews an eagerness to learn more about the properties of the elements. Through a series of carefully-devised experiments and conversations about the experiments, he leads the boys to an understanding of some of the basic principles of chemistry. Excellent as a follow-on to 'The Story Book of Science' and 'The Secret of Everyday Things' by the same author. Ages 11-15 |
AT THE BLACKSMITH'S
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
en-  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
"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
 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-  smith, in astonishment. "No sooner does it come to the surface
than it explodes. Once more, please, so that I can see
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
"Well, that beats me!"
"I hope to make it all plain to you before long."
"Now, this very day."
"One question more, if you please, my learned neighbor.
What do you call this gas that comes from water and
 "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
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
 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
"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
"One moment, please. We will come back to that
presently. I see from my nephews' astonished
 looks that wetting coal in order to make it burn better
rather upsets their ideas. Suppose you show them how
"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
 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
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
educa-  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
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
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
"Oh, no fear of that," said Jules. "Emile will hold the
glass and I'll manage the coals. I sha'n't
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
 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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