ANILINE, PHENYLADIINE, or AMINOBENZENE, (C6H5NH2)  , an organic base first obtained from the destructive distillation of indigo in 1826 by O . Unverdorben (Pogg . Ann., 1826, 8, p . 397), who named it crystalline . In 1834, F . Runge (Pogg . Ann., 1834, 31, P . 65; 32, p . 331) isolated from coal-tar a substance which produced a beautiful blue colour on treatment with chloride of lime; this he named kyanol or cyanol . In 1841, C . J . Fritzsche showed that by treating indigo with caustic potash it yielded an oil, which he named aniline, from the specific name of one of the indigo-yielding plants, Indigofera anil, anil being derived from the Sanskrit nila, dark-blue, and nil¢, the indigo plant .

About the same

time N . N . Zinin found that on reducing nitrobenzene, a base was formed which he named benzidam . A . W. von Hofmann investigated these variously prepared substances, and proved them to be identical, and thenceforth they took their place as one body, under the name aniline or phenylamine . Pure aniline is a basic substance of an oily consistence, colourless, melting at -8° and boiling at 184° C . On exposure to air it absorbs oxygen and resinifies, becoming deep brown in colour; it ignites readily, burning with a large smoky flame . It possesses a somewhat pleasant vinous odour and a burning aromatic taste; it is a highly acrid poison . Aniline is a weak base and forms salts with the mineral acids . Aniline hydrochloride forms large colourless tables, which become greenish on exposure; it is the " aniline salt " of commerce . The sulphate forms beautiful white plates . Although aniline is but feebly basic, it precipitates zinc, aluminium and ferric salts, and on warming expels ammonia from its salts .

Aniline combines directly with alkyl iodides to

form secondary and tertiary amines; boiled with carbon disulphide it gives sulphocarbanilide (diphenyl thio-urea), CS(NHC6H5)2, which may be decomposed into phenyl mustard-oil, C6H5CNS, and triphenyl guanidine, C6H5N: C(NHC6H5)2 . Sulphuric acid at 18o° gives sulphanilic acid, NH2 C6H4•SO3H . Anilides, compounds in which the amino group is substituted by an acid radical, are prepared by heating aniline with certain acids; antifebrin or acetanilide is thus obtained from acetic acid and aniline . The oxidation of aniline has been carefully investigated . In alkaline solution azobenzene results, while arsenic acid produces the violet-colouring matter violaniline . Chromic acid converts it into quinone, while chlorates, in the presence of certain metallic salts (especially of vanadium), give aniline black . Hydrochloric acid and potassium chlorate give chloranil . Potassium permanganate in neutral solution oxidizes it to nitro-benzene, in alkaline solution to azobenzene, ammonia and oxalic acid, in acid solution to aniline black . Hypochlorous acid gives para-amino phenol and para-amino diphenylamine (E . Bambergex, Ber., 1898, 31, p . 1522) . The great commercial value of aniline is due to the readiness with which it yields, directly or indirectly, valuable dyestuffs .

The

discovery of mauve in 1858 by Sir W . H . Perkin was the first of a series of dyestuffs which are now to be numbered by hundreds . Reference should be made to the articles DYEING, FUCHSINE, SAFRANINE, INDULINES, for more details on this subject . In addition to dyestuffs, it is a starting-product for the manufacture of many drugs, such as antipyrine, antifebrin, &c . Aniline is manufactured by reducing nitrobenzene with iron and hydrochloric acid and steam-distilling the product . The purity of the product depends upon the quality of the benzene from which the nitrobenzene was prepared . In commerce three brands of aniline are distinguished—aniline oil for blue, which is pure aniline; aniline oil for red, a mixture of equimolecular quantities of aniline and ortho- and para-toluidines; and aniline oil for safranine, which contains aniline and ortho-toluidine, and is obtained from the distillate (echappes) of the fuchsine fusion . Monomethyl and dimethyl aniline are colourless liquids prepared by heating aniline, aniline hydro-chloride and methyl alcohol in an autoclave at 220° . They are of great importance in the colour industry . Monomethyl aniline boils at 193—195°; dimethyl aniline at 192° .