At length Guyton resolved to examine this subject, and his experiments afforded very important results. The diamond on which he experimented was burnt in a vessel of oxygen gas, by directing the so lar rays upon it through a very powerful lens. It assumed at first a leaden colour ; by the farther continuance of the heat its surface appeared charred. At length it appeared sensibly to diminish, and in lit tle more than an hour and a half was en tirely consumed. The product of the combustion was then examined, and was found to be pure carbonic acid, the same as that formed in the burning of charcoal; but what surprised Guyton was, the quan tity produced was much greater than what would have been produced by the combustion of the same weight of charcoal in oxygen gas : 28 parts of charcoal form by combustion 100 parts of carbonic acid; that is, combined with 72 of oxygen ; but from only 17.8 of diamond, the same quantity of carbonic acid is produced, that quantity having combined with 82.1 of oxygen. In other words, one part of charcoal combines with 2 of oxygen, forming 3i of carbonic acid, while one part of diamond requires 4 of oxygen, and produces 5 of acid. As the term car bon in the new nomenclature is under stood to be applied to the simple base of carbonic acid, it is evident that it can no longer be applied to the inflammable mat ter of charcoal ; for in that matter it must be combined with some other principle.
Guyton supposes that this principle is oxy gen, or that that inflammable body is an oxide of carbon, standing in the same re lation to carbon and carbonic acid that ni trous oxide does to nitrogen and nitric acid. Berthollet, on the contrary, has supposed that charcoal contains hydrogen as a constituent part. Whichever of these opinions is adopted, the name car bon, it is obvious, must now be applied to the simple base, and will therefore be the chemical or systematic term appropriated to the diamond. See DIAMOND.
Besides charcoal and carbonic acid, other substances have been discovered to be binary compounds of carbon. The one knewn by the name of black-lead, or plumbago, approaches nearer to the dia mond, or combines with more oxygen in forming carbonic acid, than charcoal does ; and between charcoal and carbonic acid is a gaseous compound, into the com position of which oxygen enters, though it is still of the nature of an oxide. Car bon too combines with hydrogen and oxy gen, forming various elastic compounds.
See GAS.