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 .