Plumbago, or “black-lead,” as it is very improperly called, is also nearly pure carbon, a very small quantity of iron being united with it.
By far the greater part of all vegetable, and a very large portion of animal bodies consists of carbon; and in the state of carbonic acid in combination with lime and some other earths, it forms nearly the half of all the chalk, marble, and limestone of our hills; so that it is, in one shape or other, one of the most widely diffused bodies in nature.
Carbon forms two gaseous compounds with oxygen; the first, called carbonic oxide, is easily obtained by boiling oxalic acid with its own bulk of sulphuric acid, in a flask to which a cork and bent tube is attached. The gas comes over in large quantities, and must be collected in a gas jar, or the pneumatic trough. It is inflammable, and burns with a lambent blue flame.
The other compound, carbonic acid, is transparent, colourless, much heavier than atmospheric air, has an agreeable taste, has the power of irritating the mucous membrane of the nose, (as any one can tell who has drunk soda-water), without possessing any particular odour, is absorbed by water, does not support respiration, and extinguishes flame.
Carbonic acid gas may be obtained with the greatest facility by pouring some muriatic or sulphuric acid, diluted with about six parts of water, upon some pieces of marble or limestone in a bottle with a tube attached, when the gas comes over in torrents. It may be collected over water.
EXPERIMENTS.
STOPPERED BOTTLE FOR HOLDING GAS.
1. To show the great comparative weight of this gas, place a lighted taper at the bottom of a tall glass jar, then take a jar full of carbonic acid gas, and pour it as you would pour water into the jar containing the lighted taper; you will soon find the taper will be extinguished as effectually as if you had poured water on it, and the smoke of the taper will float on the surface of the gas in very beautiful wavy forms.