W‌hen we parted we had just mentioned the word “products” from the candle. For when
a candle burns we found we were able to get various products from it. There was one substance
which was not obtained when the candle was burning properly, which was charcoal or smoke;
and there was some other substance that went upwards from the flame which did not appear
as smoke, but took some other form, and made part of that general current which, ascending
from the candle upwards, becomes invisible, and escapes. There were also other products
to mention. You remember that in that rising current having its origin at the candle, we
found that one part was condensable against a cold spoon and another part was incondensable.
We will first take the condensable part, and examine it; and, strange to say, we find that
that part of the product is just water—nothing but water. On the last occasion I spoke of
it incidentally, merely saying that water was produced among the condensable products
of the candle; but today I wish to draw your attention to water, that we may examine it
carefully, especially in relation to this subject, and also with respect to its general
existence on the surface of the globe. Now, having previously arranged an experiment for
the purpose of condensing water from the products of the candle, my next point will be to show
you this water; and perhaps one of the best means that I can adopt for showing its presence
is to exhibit a very visible action of water, and then to apply that test to what is collected
as a drop at the bottom of the vessel. A small piece of potassium shows the presence of water
by lighting up and floating about, burning with a violent flame.
You see a drop of water—a condensed product of the candle—
hanging from under the surface of the dish. I will
show you that the potassium has the same action upon it as upon the water in the dish in the
experiment we have just tried. I will take a drop upon a glass slide, and when I put
the potassium to it, you will see at once, from it taking fire, that there is water present.
Now, that water was produced by the candle. Water is one individual thing—it never changes.
We can add to it by careful adjustment, for a little while, or we can take it apart, and
get other things from it; but water, as water, remains always the same, either in a solid,
liquid, or fluid state. And now—to go into the history of this wonderful production of
water from combustibles, and by combustion—I must first of all tell you that this water
may exist in different conditions; and although you may now be acquainted with all its forms,
they still require us to give a little attention to them for the present, so that we may perceive
how the water, while it goes through its protean changes, is entirely and absolutely the same
thing, whether it is produced from a candle, by combustion, or from the rivers or ocean.
First of all, water, when at the coldest, is ice. Now, we scientists speak of water
as water, whether it be in its liquid, or solid, or gaseous state—we speak of it chemically
as water. Water is a thing compounded of two substances, one of which we have derived from
the candle, and the other which we shall find elsewhere. Water may occur as ice. Ice changes
back into water when the temperature is raised: water also changes into steam when it is warmed
enough. The water which I have before me is in its densest state, and although it changes
in condition, in form, and in many other qualities, it still is water; and whether we change it
into steam by heat, or whether we alter it into ice by cooling, it increases in volume—in
the first case very largely and wonderfully, and in the second very strangely and powerfully.
For instance, I will have this metal bottle, into which I’ve poured a little water. I’m
converting the water into steam, for the purpose of showing to you the different volumes which
water occupies in its different states of liquid water and water vapor or steam. See
what a stream of vapor is issuing from this bottle! You observe that we must have made
it quite full of steam to have it sent out in that great quantity. And now, as we can
convert the water into steam by heat, we convert it back into liquid water by the application
of cold. And if we take a watch glass . . .
. . . and hold it over this steam, see how soon it gets
damp with water; it will condense until the glass is warm—it condenses the water which
is now running down the sides of it. I have here another experiment to show the
condensation of water from a vaporous state back into a liquid state, in the same way
as the vapor, one of the products of the candle, was condensed against the bottom of the dish,
and obtained in the form of water; and to show you how truly and thoroughly these changes
take place, I will take this bottle, which is now full of steam, and close the top.
We shall see what takes place when we cause this water or steam to return back to the fluid
state by cooling it in water.
You see what has happened. If I had closed the lid, and
still kept the heat applied to it, it would have burst the vessel; yet, when the steam
returns to the state of liquid water, the bottle collapses, there being a vacuum produced
inside by the condensation of the steam. I show you these experiments for the purpose
of pointing out that in all these occurrences there is nothing that changes the water into
any other thing—it still remains water; and so the vessel is obliged to give way,
and is crushed inwards, as in the other case, by the further application of heat, it would
have been blown outwards. And what do you think the bulk of that water is when it assumes
the vaporous condition? A cubic inch of water will expand to a cubic foot of steam; and,
on the contrary, the application of cold will contract that large amount of steam into this
small quantity of water.
Let us now take the case of water changing into ice: we can effect
that by cooling the water in a dry ice/acetone bath; and I shall do so to show you that when
water becomes ice, it changes in volume in an extraordinary way. These bottles are made
of cast iron; they are very strong and very thick—I suppose they are each a third of
an inch in thickness. I’ve filled this one with water, to exclude all air, and I’ll
screw the plug in tightly.
We shall see that when we freeze the water in the vessel,
it will not be able to hold the ice, and the expansion within will break it into pieces.
No communication will take place, you observe, between the water in the bottle and the ice
in the outer bowl. But there will be a conveyance of heat from one to the other.
The cold has taken possession of the bottle and its contents.
Although the iron was thick, the ice has burst it asunder.
You see some ice, partly enclosed by the covering of iron which is too small
for them, because the ice is larger in bulk than the water. You know very well that ice
floats on water. Why? Because the ice is larger than the quantity of water which can produce
it; and therefore the ice weighs the lighter, and the water is the heavier.
To return to our quiet philosophy. We shall not in future be deceived, therefore, by any changes that
are produced in water. Water is the same everywhere, whether produced from the ocean or from the
flame of the candle. Where, then, is the water which we get from a candle? I must anticipate
a little, and tell you. It evidently comes, as to part of it, from the candle; but is
it within the candle beforehand? No. It is not in the candle; and it is not in the air
round about the candle which is necessary for its combustion. It is neither in one nor
the other, but it comes from their combined action, a part from the candle, a part from
the air; and this we have now to trace, so that we may understand thoroughly what is
the chemical history of a candle when we have it burning on our table. How shall we get
at this? I myself know plenty of ways, but I want you to get at it from the association
in your minds of what I have already told you. I think you can see a little in this
way. I’ll use electricity to pull water to pieces. This power supply makes it as though
I were applying heat to cause the water to appear to boil. When we separate or electrolyze
water into its parts we get two volumes of one gas, and one of another. The gases produced
are not steam. Steam is condensible into water, and when you lower the temperature of steam,
you convert it back into fluid water. As you know water is liquid at room temperature.
Notice that this gas, which I have collected, does not become a liquid. I will take another
test and apply it to this gas.
If I now apply a light to the mouth of the test tube, it ignites with a slight noise.
That tells you that it is not steam. Steam puts out a fire—it does not burn;
but you saw that what I had in this test tube burnt. We may obtain this
substance equally from water produced from the candle-flame as from any other source.
Here is a vial full of the same gas. I will show you something most interesting. It is
a combustible gas; but it is also less dense than air. Steam will condense: this body will
rise in the air, and not condense. Suppose I take another vial, empty of all but air:
if I examine it with a flame, I shall find that it contains nothing but air.
I will now take this vial full of the gas that I am speaking of, and deal with it as though it were a light
body. I will hold both upside-down, and turn the one up under the other.
And now what does
the vial contain that had the gas procured from the steam? You will find it only contains air.
But look!
Here is the combustible substance which I have poured out of the one vial into
the other. It still preserves its quality, and condition, and independence, and therefore
is the more worthy of our consideration, as belonging to the products of a candle.
This is what we get from water—the same substance which is contained in the candle.
Let us now trace distinctly the connection between these two points. This is hydrogen—a
body classed among those things which in chemistry we call elements, because we can get nothing
else out of them. A candle is not an elementary body, because we can get carbon out of it;
we can get this hydrogen out of it, or at least out of the water which it supplies.
And this gas has been so named hydrogen, because it is that element which, in association with
another element, generates water. This hydrogen is a very beautiful substance. It is so light
that it carries things up: it is far lighter than the atmosphere; and I dare say I can
show you this by an experiment.
Here is our tank of hydrogen, and here are some soap-suds.
I have a rubber tube connected with the hydrogen tank, and at the end of it is a plastic pipe.
Now, I could blow bubbles with my breath . . .
. . . or, blow bubbles by means of the hydrogen.
You observe how the bubbles fell downwards when I blew them with my warm breath; but
notice the difference when I blow them with hydrogen.
It shows you how light this gas must be in order to carry with it
not merely the ordinary soap-bubble, but the larger portion
of a drop hanging to the bottom of it. I can show its lightness in a better way than this:
larger bubbles than these may be so lifted up—indeed, in former times balloons used
to be filled with this gas. Water also contains oxygen. Oxygen, as you will immediately imagine,
exists in the atmosphere; for how should the candle burn to produce water without it?
Such a thing would be absolutely impossible, and chemically impossible, without oxygen.
Now, as regards this very property of oxygen supporting combustion, which we may compare to air,
I will take a piece of candle to show it to you in a rough way, and the result will be
rough. You see the combustion in air. How will it burn in oxygen? I have here a jar
of oxygen for you to compare the action of this gas with that of air.
See how brightly and how beautifully it burns! Is it wonderful how great the supporting powers of oxygen
are as regards combustion? But it does not affect merely the combustion of hydrogen,
or carbon, or the candle; but it exalts all combustions of the common kind. We must now,
for a little while longer, look at it with respect to hydrogen.
I am now about to set fire to oxygen and hydrogen, mixed in the proportion in which they occur
in water. Here is a vessel of soap bubbles made with one volume of oxygen and two volumes
of hydrogen exactly of the same nature as the gas we obtained from electrolysis.
I will take a bubble in my hand and you will perhaps think I am acting oddly in this experiment;
but it is to show you that we must not always trust to noise and sound, but rather to real facts.
This oxygen united with the hydrogen, as you saw by the phenomena, and heard by
the sound, with the utmost readiness of action, and all its powers were taken up in its neutralization
of the qualities of the hydrogen. So now I think you will perceive the whole history
of water with reference to oxygen and the air, from what we have said before. Why does
a piece of potassium decompose water? Because it finds oxygen in the water. What is set
free when I put it in the water? It sets free hydrogen, and the hydrogen burns; but the
potassium itself combines with oxygen; and this piece of potassium, in taking the water
apart—the water, you may say, derived from the combustion of the candle—takes away
the oxygen which the candle took from the air, and so sets the hydrogen free; and even
if I take a piece of ice, and put a piece of potassium upon it, the beautiful affinities
by which the oxygen and the hydrogen are related are such, that the ice will absolutely set
fire to the potassium. It produces a sort of volcanic action.
It will be my place, when next we meet, having pointed out these anomalous actions, to show
you that none of these extra and strange effects are met with by us—that none of these strange
and injurious actions take place when we are burning, not merely a candle, but gas in our
homes, or fuel in our fireplaces, so long as we confine ourselves within the laws that
Nature has made for our guidance.