[AS.] The most common form of carbon. The purest form is animal charcoal, called also bone black and ivory black. It is prepared by heating bones in a vessel nearly closed ; the volatile matters are driven off, and bone black is left. It is used in purifying sugar and in the filtration of water. Wood charcoal is prepared by burning wood with a limited supply of air ; only the more volatile constituents burn away, and the greater part of the carbon is left. Charcoal so prepared is black and brittle ; it retains the form of the wood from which it is derived. Other forms of chareoal are gas carbon, coke, and lamp-black. It has a remarkable power of absorbing gases, and has therefore valuable uses in medicine and as a substance for respirators. It is used as a deodorant, and as a disinfectant in hospitals and dissecting-rooms. It is also largely employed in the manufacture of gunpowder.