Online Encyclopedia


Online Encyclopedia
Originally appearing in Volume V05, Page 304 of the 1911 Encyclopedia Britannica.
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CARBOLIC ACID or PHENOL (hydroxy-benzene), C6H5OH, an acid found in the urine of the herbivorae, and in small quantity in castoreum (F. Wohler, Ann., 1848, 67, p. 36o). Its principal commercial source is the fraction of coal-tar which distils between 150 and 200° C., in which it was discovered in 1834 by F. Runge. In order to obtain the phenol from this distillate, it is treated with caustic soda, which dissolves the phenol and its homologues together with a certain quantity of naphthalene and other hydrocarbons. The solution is diluted with water, and the hydrocarbons are thereby precipitated and separated. The solution is then acidified, and the phenols are;liberated and form an oily layer on the surface of the acid. This layer is separated, and the phenol recovered by a process of fractional distillation. It may be synthetically prepared by fusing potassium benzene sulphonate with caustic alkalis (A. Kekule, A. Wurtz); by the action of nitrous acid on aniline; by passing oxygen into boiling benzene containing aluminium chloride (C. Friedel and J. M. Crafts, Ann. Chim. Phys., 1888 (6) 14, p. 435); by heating phenol carboxylic acids with baryta; and, in small quantities by the oxidation of benzene with hydrogen peroxide or nascent ozone (A. R. Leeds, Ber., 1881, 14, p. 976). It crystallizes in rhombic needles, which melt at 42.5-43° C., and boil at 182-183° C.; its specific gravity is I•o906 (o° C.). It has a characteristic smell, and a biting taste; it is poisonous, and acts as a powerful antiseptic. It dissolves in water, 15 parts of water dissolving about one part of phenol at 16-17° C., but it is miscible in all proportions at about 7o° C.; it is volatile in steam, and is readily soluble in alcohol, ether, benzene, carbon bisulphide, chloroform and glacial acetic acid. It is also readily soluble in solutions of the caustic alkalis, slightly soluble in aqueous ammonia solution, and almost insoluble in sodium carbonate solution. When exposed in the moist condition to the air it gradually acquires a red colour. With ferric chloride it gives a violet coloration, and with bromine water a white precipitate of tribromphenol. chemistry was followed by the preparation of many metallic carbides previously unknown, some of which, especially calcium carbide, are now of great commercial importance. Carbides of the following general formulae have been obtained by H. Moissan (M denotes an atom of metal and C of carbon):
End of Article: CARBOLIC ACID
CARBON (symbol C, atomic weight 12)

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