purified piece of carbon, there is no ash left. The carbon burns as a
solid dense body, that heat alone cannot change as to its solidity, and
yet it passes away into vapour that never condenses into solid or liquid
under ordinary circumstances; and what is more curious still, is the fact
that the oxygen does not change in its bulk by the solution of the carbon
in it. Just as the bulk is at first, so it is at last, only it has become
carbonic acid.

There is another experiment which I must give you before you are fully
acquainted with the general nature of carbonic acid. Being a compound
body, consisting of carbon and oxygen, carbonic acid is a body that we
ought to be able to take asunder. And so we can. As we did with water, so
we can with carbonic acid--take the two parts asunder. The simplest and
quickest way is to act upon the carbonic acid by a substance that can
attract the oxygen from it, and leave the carbon behind. You recollect
that I took potassium and put it upon water or ice, and you saw that it
could take the oxygen from the hydrogen. Now, suppose we do something of
the same kind here with this carbonic acid. You know carbonic acid to be a
heavy gas. I will not test it with lime-water, as that will interfere with
our subsequent experiments; but I think the heaviness of the gas and the
power of extinguishing flame will be sufficient for our purpose. I
introduce a flame into the gas, and you will see whether it will be put
out. You see the light is extinguished. Indeed, the gas may, perhaps, put
out phosphorus, which, you know, has a pretty strong combustion. Here is a
piece of phosphorus heated to a high degree. I introduce it into gas, and
you observe the light is put out; but it will take fire again in the air,
because there it re-enters into combustion. Now, let me take a piece of
potassium, a substance which, even at common temperatures, can act upon
carbonic acid, though not sufficiently for our present purpose, because it
soon gets covered with a protecting coat; but if we warm it up to the