to put the oxygen and the carbon together. That this is carbon (common
charcoal pulverised), you will see by the way in which it burns in the air
[letting some of the red-hot charcoal fall out of the crucible]. I am now
about to burn it in oxygen gas, and look at the difference. It may appear
to you at a distance as if it were burning with a flame; but it is not so.
Every little piece of charcoal is burning as a spark, and whilst it so
burns it is producing carbonic acid. I specially want these two or three
experiments to point out what I shall dwell upon more distinctly
by-and-by that carbon burns in this way, and not as a flame.
Instead of taking many particles of carbon to burn, I will take a rather
large piece, which will enable you to see the form and size; and to trace
the effects very decidedly. Here is the jar of oxygen, and here is the
piece of charcoal, to which I have fastened a little piece of wood, which
I can set fire to, and so commence the combustion, which I could not
conveniently do without. You now see the charcoal burning, but not as a
flame (or if there be a flame, it is the smallest possible one, which I
know the cause of namely, the formation of a little carbonic oxide close
upon the surface of the carbon). It goes on burning, you see, slowly
producing carbonic acid by the union of this carbon or charcoal (they are
equivalent terms) with the oxygen. I have here another piece of charcoal,
a piece of bark, which has the quality of being blown to pieces exploding
as it burns. By the effect of the heat, we shall reduce the lump of carbon
into particles that will fly off; still every particle, equally with the
whole mass, burns in this peculiar way: it burns as a coal, and not like a
flame. You observe a multitude of little combustions going on, but no
flame. I do not know a finer experiment than this, to shew that carbon
burns with a spark.
Here, then, is carbonic acid formed from its elements. It is produced at
once; and if we examined it by lime-water, you will see that we have the
same substance which I have previously described to you. By putting
together 6 parts of carbon by weight (whether it comes from the flame of a
candle or from powdered charcoal) and 16 parts of oxygen by weight, we
have 22 parts of carbonic acid; and, as we saw last time, the 22 parts of
carbonic acid, combined with 28 parts of lime, produced common carbonate
of lime. If you were to examine an oyster-shell, and weigh the component
parts, you would find that every 50 parts would give 6 of carbon and 16 of
oxygen, combined with 28 of lime. However, I do not want to trouble you
with these minuti it is only the general philosophy of the matter that
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