All
the carbon which is burned in oxygen, or air, comes out as carbonic acid,
whilst those particles which are not so burned shew you the second
substance in the carbonic acid--namely, the carbon--that body which made
the flame so bright whilst there was plenty of air, but which was thrown
off in excess when there was not oxygen enough to burn it.
I have also to shew you a little more distinctly the history of carbon and
oxygen, in their union to make carbonic acid. You are now better able to
understand this than before, and I have prepared three or four experiments
by way of illustration. This jar is filled with oxygen, and here is some
carbon which has been placed in a crucible, for the purpose of being made
red-hot. I keep my jar dry, and venture to give you a result imperfect in
some degree, in order that I may make the experiment brighter. I am about
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.
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