ANILINE, PHENYLADIINE, or AMINOBENZENE, (C6H5NH2)

This article appears in Volume V02, Page 48 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: ANC-APO

ANILINE, PHENYLADIINE, or AMINOBENZENE, (C6H5NH2) , an organic base first obtained from the destructive

distillation

DISTILLATION (from the Lat. distillare, more correctly destillare, to drop or trickle down)

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

CAUSTIC (Gr. rcavvraubs, burning)

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

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

TASTE (from Lat. taxare, to touch sharply; tangere, to touch)

; it is a highly acrid poison.
Aniline is a weak base and forms salts with the

mineral

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

DIPHENYL (phenyl benzene), C6H5

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 C6H4SO3H. Anilides, compounds in which the amino group is substituted by an acid radical, are prepared by

heating

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

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

SERIES (a Latin word from serere, to join)

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 distinguishedaniline 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

HEATING

aniline, aniline hydro-chloride and methyl alcohol in an autoclave at 220. They are of

great

GREAT

importance in the colour industry. Monomethyl aniline boils at 193195; dimethyl aniline at 192.

End of Article: ANILINE, PHENYLADIINE, or AMINOBENZENE, (C6H5NH2)

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