AN'ILINE (From anil, Ar. an-nil, for al, the + nil, from Skr. pill, indigo), A M TDO-BEN ZENE, or PHENYL-A MI NE, A liquid organic substance extensively used in the manu facture of dyes. Pure aniline is colorless, has a faint, somewhat disagreeable odor. and boils at 183° C. When exposed to the action of air and light, it gradually turns dark red. It combines with acids to form salts, such as aniline hydro chloride, It may be readily pre pared by the reducing action of nascent hydro gen on nitrobenzene, according to the following chemical equation: = C,1-,NH, • + 211,0 Nitrobenzene Aniline On a small scale the reduction is most conveni ently effected by slowly adding strong hydro chloric acid to nitrobenzene placed in a flask with granulated tin; the product of the reaction. a compound of aniline and chloride of tin, is decomposed with soda, and the aniline thus set free is separated Iron) the mixture by distilling with a current of steam. On a large industrial scale aniline is made as follows. A small quan tity of ground scrapings of soft iron castings. technically called strarf, is introduced• together with some water, into a large cast-iron still furnished with powerful agitators. Crude by drochlorie acid is then added, and nitrobenzene is allowed slowly to flow into the still ; at the same time, through another opening, the rest of the swarf to be employed in the operation is allowed to flow into the still in a steady stream. After the first energetic action has subsided. the reacting mixture is heated with a current of steam introduced into the apparatus through several pipes. Six to eight hours suffice to trans form all the nitrobenzene employed in one opera tion. The process may be called continuous, since the acid employed serves merely to start the reaction. and might. theoretically, he used in reducing all indefinite quantity of nitrobenzene, the reduction being effected by the iron and water. In reality, however, a portion of the
acid remains combined as ferrous chloride, most of the iron being transformed into its magnetic oxide, Fe,0,, technically called black stuff. All the aniline brought into commerce is made in this manner. Aniline was first discovered in 1826 by Unverdorben, among the products ob tained in the destructive distillation of indigo. In 1834 Runge found it in coal-tar; in 1841 Zinin obtained it by reducing nitrohenzene with sulphurctted hydrogen. and in 1843 Hofmann effeeted the same reduction with nascent hydro g,en, by the reaction of dilute acid and metals. The manufacture of aniline has been an impor tant branch of industry since 1856, when the discovery of mauve was perfeeted by Perkin.
The qualities of commercial aniline adapted to certain purpose, often contain, besides ani line. large quantities of other substanees. Thus. crude "aniline for red" contains only about 25 per emit. of aniline. the rest being ortho-toluidine and para-tolnidine. compounds chemically allied to aniline. The presence of aniline in a sub stance submitted for analysis may be readily detected by dissolving some of the substance in water and adding a solution of bleaching-powder: in the presence of aniline an intense purple col oration is produced. .\nother test for aniline is afforded by the so-called carbylamine reaction: a drop of aniline added to a mixture of chloro form and a solution of caustic potash in ordinary alcohol produces an intensely nauseous smell, due to the formation of phenyl-carbylamine (phenyl iso-cyanide), CANC. For bibliography, see COAL-TAR Counts.