substances, and to make them tell us what we want to know. And now, first
of all, I take iron. It is a common thing in all chemical reactions, where
we get any result of this kind, to find that it is increased by the action
of heat; and if we want to examine minutely and carefully the action of
bodies one upon another, we often have to refer to the action of heat. You
are aware, I believe, that iron-filings burn beautifully in the air; but I
am about to shew you an experiment of this kind, because it will impress
upon you what I am going to say about iron in its action on water. If I
take a flame and make it hollow;—you know why, because I want to get air
to it and into it, and therefore I make it hollow—and then take a few
iron-filings and drop them into the flame, you see how well they burn.
That combustion results from the chemical action which is going on when we
ignite those particles. And so we proceed to consider these different
effects, and ascertain what iron will do when it meets with water. It will
tell us the story so beautifully, so gradually and regularly, that I think
it will please you very much.
I have here a furnace with a pipe going through it like an iron
gun barrel, and I have stuffed that barrel full of bright iron-turnings,
and placed it across the fire, to be made red-hot. We can either send air
through the barrel to come in contact with the iron, or we can send steam
from this little boiler at the end of the barrel. Here is a stop-cock
which shuts off the steam from the barrel until we wish to admit it. There
is some water in these glass jars, which I have coloured blue, so that you
may see what happens. Now, you know very well that any steam I might send
through that barrel, if it went through into the water, would be
condensed; for you have seen that steam cannot retain its gaseous form if
it be cooled down.
[Illustration: Fig. 14.]
You saw it here [pointing to the tin flask] crushing itself into a small
bulk, and causing the flask holding it to collapse; so that if I were to
send steam through that barrel, it would be condensed—supposing the
barrel were cold: it is, therefore, heated to perform the experiment I am
now about to shew you. I am going to send the steam through the barrel in
small quantities; and you shall judge for yourselves, when you see it
issue from the other end, whether it still remains steam. Steam is
condensable into water, and when you lower the temperature of steam, you
convert it back into fluid water; but I have lowered the temperature of
the gas which I have collected in this jar, by passing it through water
after it has traversed the iron barrel, and still it does not change back
into water. I will take another test and apply to this gas. (I hold the
jar in an inverted position, or my substance would escape.) If I now apply
a light to the mouth of the jar, 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 that jar burnt. We may obtain this
substance equally from water produced from the candle-flame as from any
other source. When it is obtained by the action of the iron upon the
aqueous vapour, it leaves the iron in a state very similar to that in
which these filings were after they were burnt. It makes the iron heavier
than it was before. So long as the iron remains in the tube and is heated,
and is cooled again without the access of air or water, it does not change
in its weight; but after having had this current of steam passed over it,
it then comes out heavier that it was before, having taken something out
of the steam, and having allowed something else to pass forth, which we
see here. And now, as we have another jar full, I will shew you something
most interesting. It is a combustible gas; and I might at once take this
jar and set fire to the contents, and shew you that it is combustible; but
I intend to shew you more if I can. It is also a very light substance.
Steam will condense: this body will rise in the air, and not condense.
[Illustration: Fig. 15]
Suppose I take another glass jar, empty of all but air: if I examine it
with a taper, I shall find that it contains nothing but air. I will now
take this jar 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 that which did contain the gas procured from
the steam, what does it contain now? You will find it now only contains
air. But look! Here is the combustible substance [taking the other jar]
which I have poured out of the one jar 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.
Now, this substance which we have just prepared by the action of iron on
the steam or water, we can also get by means of those other things which
you have already seen act so well upon the water. If I take a piece of
potassium, and make the necessary arrangements, it will produce this gas;
and if, instead, a piece of zinc, I find, when I come to examine it very
carefully, that the main reason why this zinc cannot act upon the water
continuously as the other metal does, is because the result of the action
of the water envelopes the zinc in a kind of protecting coat. We have
learned in consequence, that if we put into our vessel only the zinc and
water, they by themselves do not give rise to much action, and we get no
result. But suppose I proceed to dissolve off this varnish—this
encumbering substance—which I can do by a little acid; the moment I do
this, I find the zinc acting upon the water exactly as the iron did, but
at the common temperature. The acid in no way is altered, except in its
combination with the oxide of zinc, which is produced. I have now poured
the acid into the glass, and the effect is as though I were applying heat
to cause this boiling up. There is something coming off from the zinc very
abundantly, which is not steam. There is a jar full of it; and you will
find that I have exactly the same combustible substance remaining in the
vessel, when I hold it upside-down, that I produced during the experiment
with the iron barrel. This is what we get from water—the same substance
which is contained in the candle.
[Illustration: Fig. 16.]
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, generates water. [Footnote: [greek: hudos],
“water,” and [greek: gennao], “I generate.”] Mr. Anderson having now been
able to get two or three jars of gas, we shall have a few experiments to
make, and I want to shew you the best way of making these experiments. I
am not afraid to shew you, for I wish you to make experiments, if you will
only make them with care and attention, and the assent of those around
you. As we advance in Chemistry, we are obliged to deal with substances
which are rather injurious, if in their wrong places—the acids, and heat,
and combustible things we use, might do harm if carelessly employed. If
you want to make hydrogen, you can make it easily from bits of zinc, and
sulphuric or muriatic acid. Here is what in former times was called the
“philosopher’s candle.” It is a little phial with a cork, and a tube or
pipe passing through it.
[Illustration: Fig. 17.]
And I am now putting a few little pieces of zinc into it. This little
instrument I am going to apply to a useful purpose in our
demonstrations—for I want to shew you that you can prepare hydrogen, and
make some experiments with it as you please at your own homes. Let me here
tell you why I am so careful to fill this phial nearly, and yet not quite
full. I do it because the evolved gas, which, as you have seen, is very
combustible, is explosive to a considerable extent when mixed with air,
and might lead to harm, if you were to apply a light to the end of that
pipe before all the air had been swept out of the space above the water. I
am now about to pour in the sulphuric acid. I have used very little zinc,
and more sulphuric acid and water, because I want to keep it at work for
some time. I therefore take care in this way to modify the proportions of
the ingredients, so that I may have a regular supply—not too quick, and
not too slow. Supposing I now take a glass and put it upside-down over the
end of the tube, because the hydrogen is light I expect that it will
remain in that vessel a little while. We will now test the contents of our
glass to see if there be hydrogen in it. I think I am safe in saying we
have caught some [applying a light]. There it is, you see. I will now
apply a light to the top of the tube. There is the hydrogen burning. There
is our philosophical candle. It is a foolish feeble sort of a flame, you
may say; but it is so hot that scarcely any common flame gives out so much
heat. It goes on burning regularly, and I am now about to put that flame
to burn under a certain arrangement, in order that we may examine its
results and make use of the information which we may thereby acquire.
Inasmuch as the candle produces water, and this gas comes out of the
water, let us see what this gives us by the same process of combustion
that the candle went through when it burnt in the atmosphere; and for that
purpose I am going to put the lamp under this apparatus, in order to
condense whatever may arise from the combustion within it In the course of
a short time you will see moisture appearing in the cylinder, and you will
get the water running down the side; and the water from this hydrogen
flame will have absolutely the same effect upon all our tests, being
obtained by the same general process as in the former case. 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 shew you this
by an experiment which, if you are very clever, some of you may even have
skill enough to repeat. Here is our generator of hydrogen, and here are
some soap-suds. I have an india-rubber tube connected with the hydrogen
generator, and at the end of the tube is a tobacco-pipe.
[Illustration: Fig. 18.]
I can thus put the pipe into the suds, and blow bubbles by means of the
hydrogen. You observe how the bubbles fall downwards when I blow them with
my warm breath; but notice the difference when I blow them with hydrogen.
[The Lecturer here blew bubbles with hydrogen, which rose to the roof of
the theatre.] It shews 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 shew 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. Mr. Anderson will
fasten this tube on to our generator, and we shall have a stream of
hydrogen here with which we can charge this balloon made of collodion. I
need not even be very careful to get all the air out, for I know the power
of this gas to carry it up. [Two collodion balloons were inflated, and
sent up, one being held by a string.] Here is another larger one made of
thin membrane, which we will fill and allow to ascend. You will see they
will all remain floating about until the gas escapes.
What, then, are the comparative weights of these substances? I have a
table here which will shew you the proportion which their weights bear to
each other. I have taken a pint and a cubic foot as the measures, and have
placed opposite to them the respective figures. A pint measure of this
hydrogen weighs three-quarters of our smallest weight (a grain), and a
cubic foot weighs one-twelfth of an ounce; whereas a pint of water weighs
8,750 grains, and a cubic foot of water weighs almost 1,000 ounces. You
see, therefore, what a vast difference there is between the weight of a
cubic foot of water and a cubic foot of hydrogen.
Hydrogen gives rise to no substance that can become solid, either during
combustion or afterwards as a product of its combustion. But when it
burns, it produces water only; and if we take a cold glass and put it over
the flame, it becomes damp, and you have water, produced immediately in
appreciable quantity; and nothing is produced by its combustion but the
same water which you have seen the flame of the candle produce. It is
important to remember that this hydrogen is the only thing in nature which
furnishes water as the sole product of combustion.
And now we must endeavour to find some additional proof of the general
character and composition of water; and for this purpose I will keep you a
little longer, so that at our next meeting we may be better prepared for
the subject. We have the power of arranging the zinc which you have seen
acting upon the water by the assistance of an acid, in such a manner as to
cause all the power to be evolved in the place where we require it I have
behind me a voltaic pile, and I am just about to shew you, at the end of
this lecture, its character and power, that you may see what we shall have
to deal with when next we meet. I hold here the extremities of the wires
which transport the power from behind me, and which I shall cause to act
on the water.
We have previously seen what a power of combustion is possessed by the
potassium, or the zinc, or the iron-filings; but none of them shew such
energy as this. [The Lecturer here made contact between the two terminal
wires of the battery, when a brilliant flash of light was produced.] This
light is, in fact, produced by a forty-zinc power of burning: it is a
power that I can carry about in my hands, through these wires, at
pleasure—although, if I applied it wrongly to myself, it would destroy me
in an instant, for it is a most intense thing, and the power you see here
put forth while you count five [bringing the poles in contact, and
exhibiting the electric light] is equivalent to the power of several
thunder-storms, so great is its force[14]. And that you may see what
intense energy it has, I will take the ends of the wires which convey the
power from the battery, and with it I dare say I can burn this iron file.
Now, this is a chemical power, and one which, when we next meet, I shall
apply to water, and shew you what results we are able to produce.
LECTURE IV.
HYDROGEN IN THE CANDLE—BURNS INTO WATER—THE OTHER PART OF WATER—OXYGEN.
I see you are not tired of the candle yet, or I am sure you would not be
interested in the subject in the way you are. When our candle was burning,
we found it produced water exactly like the water we have around us; and
by further examination of this water we found in it that curious body,
hydrogen—that light substance of which there is some in this jar. We
afterwards saw the burning powers of that hydrogen, and that it produced
water. And I think I introduced to your notice an apparatus which I very
briefly said was an arrangement of chemical force, or power, or energy, so
adjusted as to convey its power to us in these wires; and I said I should
use that force to pull the water to pieces, to see what else there was in
the water besides hydrogen; because, you remember, when we passed the
water through the iron tube, we by no means got the weight of water back
which we put in, in the form of steam, though we had a very large quantity
of gas evolved. We have now to see what is the other substance present.
That you may understand the character and use of this instrument, let us
make an experiment or two. Let us put together, first of all, some
substances, knowing what they are, and then see what that instrument does
to them. There is some copper (observe the various changes which it can
undergo), and here is some nitric acid, and you will find that this, being
a strong chemical agent, will act very powerfully when I add it to the
copper. It is now sending forth a beautiful red vapour; but as we do not
want that vapour, Mr. Anderson will hold it near the chimney for a short
time, that we may have the use and beauty of the experiment without the
annoyance. The copper which I have put into the flask will dissolve: it
will change the acid and the water into a blue fluid, containing copper
and other things; and I propose then shewing you how this voltaic battery
deals with it; and in the mean time we will arrange another kind of
experiment for you to see what power it has. This is a substance which is
to us like water—that is to say, it contains bodies which we do not know
of as yet, as water contains a body which we do not know as yet. Now, this
solution of a salt[15] I will put upon paper, and spread about, and apply
the power of the battery to it, and observe what will happen. Three or
four important things will happen which we shall take advantage of. I
place this wetted paper upon a sheet of tinfoil, which is convenient for
keeping all clean, and also for the advantageous application of the power;
and this solution, you see, is not at all affected by being put upon the
paper or tinfoil, nor by anything else I have brought in contact with it
yet, and which, therefore, is free to us to use as regards that
instrument. But first let us see that our instrument is in order. Here are
our wires. Let us see whether it is in the state in which it was last
time. We can soon tell. As yet, when I bring them together, we have no
power, because the conveyers—what we call the electrodes—the passages or
ways for the electricity—are stopped; but now Mr. Anderson by that
[referring to a sudden flash at the ends of the wires] has given me a
telegram to say that it is ready. Before I begin our experiment I will get
Mr. Anderson to break contact again at the battery behind me, and we will
put a platinum-wire across to connect the poles, and then if I find I can
ignite a pretty good length of this wire, we shall be safe in our
experiment. Now you will see the power. [The connection was established,
and the intermediate wire became red-hot.] There is the power running
beautifully through the wire, which I have made thin on purpose to shew
you that we have those powerful forces; and now, having that power, we
will proceed with it to the examination of water.
I have here two pieces of platinum, and if I lay them down upon this piece
of paper [the moistened paper on the tinfoil], you will see no action; and
if I take them up, there is no change that you can see, but the
arrangement remains just as it was before. But, now, see what happens: if
I take these two poles and put either one or the other of them down
separately on the platinum-plates, they do nothing for me, both are
perfectly without action; but if I let them both be in contact at the same
moment, see what happens [a brown spot appeared under each pole of the
battery]. Look here at the effect that takes place, and see how I have
pulled something apart from the white—something brown; and I have no
doubt, if I were to arrange it thus, and were to put one of the poles to
the tinfoil on the other side of the paper—why, I get such a beautiful
action upon the paper, that I am going to see whether I cannot write with
it—a telegram, if you please. [The Lecturer here traced the word
“juvenile” on the paper with one of the terminal wires.] See there how
beautifully we can get our results!
You see we have here drawn something, which we have not known about
before, out of this solution. Let us now take that flask from Mr.
Andersen’s hands, and see what we can draw out of that. This, you know, is
a liquid which we have just made up from copper and nitric acid, whilst
our other experiments were in hand; and though I am making this experiment
very hastily, and may bungle a little, yet I prefer to let you see what I
do rather than prepare it beforehand.
Now, see what happens. These two platinum-plates are the two ends (or I
will make them so immediately) of this apparatus; and I am about to put
them in contact with that solution just as we did a moment ago on the
paper. It does not matter to us whether the solution be on the paper or
whether it be in the jar, so long as we bring the ends of the apparatus to
it. If I put the two platinums in by themselves, they come out as clean
and as white as they go in [inserting them into the fluid without
connecting them with the battery]; but when we take the power and lay that
on [the platinums were connected with the battery and again dipped into
the solution], this, you see [exhibiting one of the platinums], is at once
turned into copper, as it were: it has become like a plate of copper; and
that [exhibiting the other piece of platinum] has come out quite clean. If
I take this coppered piece and change sides, the copper will leave the
right-hand side and come over to the left side; what was before the
coppered plate comes out clean, and the plate which was clean comes out
coated with copper; and thus you see that the same copper we put into this
solution we can also take out of it by means of this instrument.
Putting that solution aside, let us now see what effect this instrument
will have upon water. Here are two little platinum-plates which I intend
to make the ends of the battery, and this (C) is a little vessel so shaped
as to enable me to take it to pieces, and shew you its construction. In
these two cups (A and B) I pour mercury, which touches the ends of the
wires connected with the platinum-plates. In the vessel (C) I pour some
water containing a little acid (but which is put only for the purpose of
facilitating the action; it undergoes no change in the process), and
connected with the top of the vessel is a bent glass tube (D), which may
remind you of the pipe which was connected with the gun barrel in our
furnace experiment, and which now passes under the jar (F). I have now
adjusted this apparatus, and we will proceed to affect the water in some
way or other. In the other case, I sent the water through a tube which was
made red-hot; I am now going to pass the electricity through the contents
of this vessel. Perhaps I may boil the water; if I do boil the water, I
shall get steam; and you know that steam condenses when it gets cold, and
you will therefore see by that whether I do boil the water or not.
Perhaps, however, I shall not boil the water, but produce some other
effect. You shall have the experiment and see. There is one wire which I
will put to this side (A), and here is the other wire which I will put to
the other side (B), and you will soon see whether any disturbance takes
place. Here it is seeming to boil up famously; but does it boil? Let us
see whether that which goes out is steam or not. I think you will soon see
the jar (F) will be filled with vapour, if that which rises from the water
is steam. But can it be steam? Why, certainly not; because there it
remains, you see, unchanged. There it is standing over the water, and it
cannot therefore be steam, but must be a permanent gas of some sort What
is it? Is it hydrogen? Is it anything else? Well, we will examine it. If
it is hydrogen, it will burn. [The Lecturer then ignited a portion of the
gas collected, which burnt with an explosion.]
[Illustration: Fig. 19]