|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 |
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 suphur. 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 mountains in search of
more stones like this one. So successful 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 conditions take regular shapes in which
smooth facets arrange themselves according to
geometrical laws. Such substances are then said to be
"We will return to this subject later if opportunity
occurs," said he; "but to-day other things
de-  mand our attention. So far we have been merely
discussing, talking together, supporting our assertions
by sundry facts picked up here and there. Your minds
had to be prepared, had to become accustomed 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
"Shall we have lots of them?" was the eager inquiry.
"As many as you please, my lads. Along that line,
chemistry never comes to an end."
"Oh, that'll 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 yourselves. 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
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 outset, if you do
not already know it, that air forms around the earth an
envelop known as the
atmos-  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 invisible
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 compared
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,
invisible. 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 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)
 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 quantity
of it, isolate it form 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
conditions,—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 inestimable
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
 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 substances
having a tenuity or thiness similar to that gas; 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
"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 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 moment and explain the
cause; but just now let us proceed 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,
 and the air from my lungs makes the water bubble.
Because of its superior lightness it makes it 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
"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
 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
"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 disappeared."
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?"
 "You may, my boy. If you enjoy the experiment of
bottling up your breath, I for my part enjoy your
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
"We must practise a little ingenuity, my child; for if
we didn'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
 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 surprise, is all
that at present propose.
"Air, I told you, can be weighed just the same as any
other substance; and its weight, as I said before, has
been found to be one gram and three decigrams a liter.
That is very little, but the atmosphere 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 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 inverted bottle. It is the
atmosphere pushing in every
 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, which
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
"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 doesn'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."
 "But 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 restrains it."
"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 upside 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. Without 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 lit. 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
 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 projected
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 containers 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 quantity of gas
from vessel to another, or to transfuse 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
container, or it may be I wish to transfer only half
of it. I fill this second glass with water and invert
ilt 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 side-wise under the other, whereupon 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,
 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 corrosive
liquids, is of glass, a very resistant substance. As
long as only gas is to be transfused, it will suffice
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. Furthermore, 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
"A funnel of some sort is indispensable for transfusing
a gas from a container of any kind to a bottle with a
narrow neck such as bottles commonly have. 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 yourselves as
often as you like, collecting your breath in a glass,
transfusing it into another, or into a bottle turned
upside down, thus getting your hand into practice. I
shall soon need your assistance."
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