Charcoal

(char'kōl.) (Chem.) A name given to several varieties of carbon, the most important of which are, wood charcoal, animal charcoal, and lamp-black. Wood C. is obtained by charring wood, and the principal object of its preparation, now by far le important than formerly, is the greater caloric effect it affords than wood; a given weight of C. producing twice as much available heat as an equal weight of wood, since the former contains more actual fuel and le oxygen, and much of the heat evolved by the wood is absorbed or rendered latent by the action of heat upon it. The vapor of burning C., which is carbonic acid, is highly noxious. C. is black, brittle, light, and inodorous, and resists decay for an indefinite period. That made from a dense wood has the curious property of condensing gases and vapors in its pores. Liquid and solid substances are also capable of being removed by that agent from their solution in water. This is more readily traced in the case of substances which impart a color to the solution, such color being often removed by the C.; the coloring matter, however, seeming merely to adhere to the C., for it may be extracted from it by treatment with a weak alkaline liquid. The de coloring power of wood C. is very feeble in comparison with that po e ed by animal C., Ivory-black, or BONE-BLACK, q. v. Lamp-black approaches more nearly in composition to pure carbon than either of the others, and is the soot obtained from the imperfect combustion of resinous and tarry matters (or of highly bituminous coal), from which source it | derives the small quantities of resin, of nitrogen, and sulphur which it contains. The uses of this substance, as an ingredient of pigments, of printing-ink, and of blacking, depend evidently more upon its black color than upon its chemical properties. [s. 165]