The Chemical History of a Candle | Page 9

all, the whole
candle goes to: because, as you know very well, a candle being brought
before us and burned, disappears, if burned properly, without the least
trace of dirt in the candlestick--and this is a very curious circumstance.
In order, then, to examine this candle carefully, I have arranged certain
apparatus, the use of which you will see as I go on. Here is a candle: I
am about to put the end of this glass tube into the middle of the

flame--into that part which old Hooker has represented in the diagram
as being rather dark, and which you can see at any time, if you will
look at a candle carefully, without blowing it about. We will examine
this dark part first.
[Illustration: Fig. 7.]
Now, I take this bent glass tube, and introduce one end into that part of
the flame, and you see at once that something is coming from the flame,
out at the other end of the tube; and if I put a flask there, and leave it
for a little while, you will see that something from the middle part of
the flame is gradually drawn out, and goes through the tube and into
that flask, and there behaves very differently from what it does in the
open air. It not only escapes from the end of the tube, but falls down to
the bottom of the flask like a heavy substance, as indeed it is. We find
that this is the wax of the candle made into a vaporous fluid--not a gas.
(You must learn the difference between a gas and a vapour: a gas
remains permanent, a vapour is something that will condense.) If you
blow out a candle, you perceive a very nasty smell, resulting from the
condensation of this vapour. That is very different from what you have
outside the flame; and, in order to make that more clear to you, I am
about to produce and set fire to a larger portion of this vapour--for what
we have in the small way in a candle, to understand thoroughly, we
must, as philosophers, produce in a larger way, if needful, that we may
examine the different parts. And now Mr. Anderson will give me a
source of heat, and I am about to shew you what that vapour is. Here is
some wax in a glass flask, and I am going to make it hot, as the inside
of that candle-flame is hot, and the matter about the wick is hot. [The
Lecturer placed some wax in a glass flask, and heated it over a lamp.]
Now, I dare say that is hot enough for me. You see that the wax I put in
it has become fluid, and there is a little smoke coming from it. We shall
very soon have the vapour rising up. I will make it still hotter, and now
we get more of it, so that I can actually pour the vapour out of the flask
into that basin, and set it on fire there. This, then, is exactly the same
kind of vapour as we have in the middle of the candle; and that you
may be sure this is the case, let us try whether we have not got here, in
this flask, a real combustible vapour out of the middle of the candle.

[Taking the flask into which the tube from the candle proceeded, and
introducing a lighted taper.] See how it burns. Now, this is the vapour
from the middle of the candle, produced by its own heat; and that is one
of the first things you have to consider with respect to the progress of
the wax in the course of its combustion, and as regards the changes it
undergoes. I will arrange another tube carefully in the flame, and I
should not wonder if we were able, by a little care, to get that vapour to
pass through the tube to the other extremity, where we will light it, and
obtain absolutely the flame of the candle at a place distant from it. Now,
look at that. Is not that a very pretty experiment? Talk about laying on
gas--why, we can actually lay on a candle! And you see from this that
there are clearly two different kinds of action--one the production of
the vapour, and the other the combustion of it--both of which take place
in particular parts of the candle.
[Illustration: Fig. 8]
I shall get no vapour from that part which is already burnt. If I raise the
tube (fig. 7) to the upper part of the flame, so soon as the vapour has
been swept out, what comes away will be no longer combustible: It is
already burned. How burned? Why, burned thus:--In the middle