Carbon

Carbon (atomic weight 11.97) is a non-metallic elementary substance, which occurs very abundantly and is widely distributed. It occurs free in three different modifications, viz. as diamond, graphite, and charcoal. All organic matter contains carbon combined with other elements. It occurs combined with hydrogen in many mineral oils or petroleum, etc. Combined with oxygen it is found in the atmosphere and volcanic gases. In combination with oxygen and magnesia, or lime (dolomite and limestone), it forms a large portion of the earth's crust. The diamond is the purest form, of carbon. It is found chiefly in South Africa, India, and Brazil. It was proved to consist solely of carbon by Lavoisier, who showed that when burnt, carbon dioxide, C02, was the only product. It is generally colourless, has a fine lustre, and is the hardest substance known. It crystallises in the regular system, and has a specific gravity 3.5. Graphite occurs in the United States, Siberia, etc., and in England in Cornwall and Cumberland. It has a specific gravity 2.2, is of a glistening grey-black colour, and leaves a streak on paper. It is hence used for the manufacture of pencils and is known as black lead or plumbago. Besides its use for this purpose it is largely employed as a lubricant, and for the manufacture of crucibles. It crystallises in hexagonal plates. Charcoal or amorphous carbon is obtained by heating many organic substances in the absence of air. From wood by such a process wood charcoal is obtained. It is very porous, and can absorb many gases. Animal charcoal or bone black (q.v.) is obtainedl similarly from bones. Lamp black, an impure carbon obtained by the imperfect combustion of oil, etc., is largely used as a pigment. Gas carbon, is a very hard variety left in gas retorts after heating coal for the production of illuminating gas. All these latter forms are more or less impure, containing variable quantities of ash, etc. The different varieties of coal all consist chiefly of carbon, the quantity varying from about 70 per cent. in brown coal to about 97 per cent. in anthracite. Carbon burns in air forming carbon dioxide. Another oxide also exists - carbonic or monoxide (q.v.), CO. With hydrogen and oxygen, etc., it forms a very large number of compounds of every variety of chemical and physical character. The chemistry of the carbon compounds on this account is regarded by itself as a branch of the science, and commonly called organic chemistry.