Amido-azo-benzol, 0214. N2. C6114.NH2.—This is produced by passing nitrogen trioxide into a warm solution of aniline, and by reducing mono-nitro-azo-benzol with ammonium sulphide. It crystallizes from alcohol in yellow needles, which sublime at a high temperature ; it is a weak base, forming salts of a red or violet colour. It is the commercial source of " aniline yellow " (q. v.).
Tri-amido-azo-benzol. N,{0713 4(2242)2.—The hydrochloride of this base forms the principal portion of " phenylene-brown," or " Manchester-brown," which is manufactured by adding a solution of sodium nitrate to a cold solution of para-amido-azo-benzol hydrochloride. See pheny leue-brown.
C211, Diphenylamine, or Phenylaniline. C2H, N.—This is formed when a mixture of aniline and aniline hydrochloride is heated under pressure. It is a crystalline solid, melting at 45° (113° F.), and boiling at 310° (590° F.); possessing a peculiar and agreeable smell; and forming salts, which are decomposed by water. With nitric acid, it yields an intensely blue liquid. Hofmann obtained it by the dry distillation of triphenyl-rosaniline. It is found in the distillate at 280°- 300° (536°-572° F.), and, when mixed with hydrochloric acid, forms the solid chloride of diphenylamine, which is not soluble readily in this acid ; it is purified by washing in alcohol, and crystallizing in needles from its solution in petroleum spirit ; on exposure to the air, these crystals turn blue. By treatment with ammonia, it separates as a colourless, oily liquid, passing quickly into a crystalline mass.
Ditoluyl-amine, Phenyl-toluyl-amine, and Diphenylamine .—These substances are prepared in a wrought iron spherical digester, supplied with safety valve, pressure gauge, thermometer tube, and a screw plug, or large stop-cock connected with a condenser. The capacity of the vessel is about twice the bulk of liquids to be operated upon; small pantities should be dealt with. About 70 kilo. anhydrous aniline hydrochloride, and 50 kilo. aniline are heated together for two hours at 200° (392° F.), while the condemier is connected. The heat is gradually raised to 215°-220° (412°-428° F.); the outlet is then closed, and the heat is raised to 250° (489°F.), this preasure being 10-15i atmos. The operation lasta twelve hours ; during six hours, the heat is gradually raised froin 240° to 260° (464°-500° F.), and the pressure from 3 to 5 or 6 atmos. The yield should be 60-73 per cent. on the weight of aniline employed. The liquids which pass over consist principally of water and hydrochloric acid, aniline, &c., and are not returned to the digester. After cooling, the crude mass is dissolved in 70 kilo. cold hydrochloric) acid, and the aolution, filtered if necessary, is poured into 300-400 lit. water,
and left to settle for twelve hours. The hydrochlorate of diphenylamine is decomposed ; the liberated base falls to the bottom, and the hydrochlorate of aniline, remaining in solution, is recovered by evaporation. The dipbenylamine is first washed with a little boiling water, and then with a weak solution of caustic oda; it is finally crystallized from its solution in alcohol, or light petroleum spirit. If toluidine and its hydrochlorate are heated in the same way, ditoluylamine is obtained. When aniline or aniline salt is heated with toluidine or a toluidine salt, phenyl toluylamine is obtained. Commercial diphenylamine is thus a mixture of diphenyl-ditoluyl, and phenyl-toluyl-amine ; from it, diphenylamine blue is obtained, by oxidation or abstraction of hydrogen. Ditoluylamine givee a blue with a brownish-red tint, and phenyl-toluyl-amine gives a bluish or blue-violet ; but a mixture of the two, in the proportions of 11 to 18, yields a fine pure blue. It ie essential that the ammonia generated by the reaction should be removed from the digester ; otherwise a loss of 30-40 per cent. upon the product is incurred.
Methyl-diphenyl-amine. (C,HANCH3.—This base, according to C. Bardy (No. 376, 1870), is obtained by reacting upon diphenylamine or its salts, with methyl-alcohol, or its substitution products, at variable temperatures according to the substance employed. The product is treated with caustic alkali. Whatever process be employed, the new base is an oily substance, even at 0° (32° F.) ; its boiling-point is near that of diphenylamine, from which it is vcry easily distinguished, by the tact that with nitric acid it develops a colour identical with that of permanganate potash. It ie transformed into colouring matters, by treatment with any substance capable of eliminating hydrogen, whether directly or indirectly, to which reaction it very readily submits. Nitrate mercury at about 40° (10-1° F.), sometirnes acts so powerfully that the mixture begins to burn. Perehloride iron, at about 100° (212° F.), rapidly transforms it into a resinous substance, of brownish-red tint, which, when dissolved in alcohol, becomes a pure blue. Heated to 190°-200° (374°-392° F.) with sesquichloride carbon, it quickly gives a resinous substance, which affords a reddish-blue colour when dissolved in alcohol ; hydrochloric acid precipitates the blue colour of the solution, while a violet colour remains in the mother-liquor. The proportions of the reagents may vary between wide limits without preventing the production of the colours. These latter are purified in the samo way as aniline colours. Their solutions act directly as dyes.