ANILINE is an oily organic liquid classi fied as a base. Its formula is C4I-15NH.. It is commonly known as a derivative of coal-tar, but that substance contains only from I/.3 to of 1 per cent of aniline, and the difficulties of separating it are so formidable that it is never derived from coal tar directly.
When pure, aniline is colorless, but commer cial aniline turns gradually brownish on ex posure to air and light, due to a small admix ture of thiophene. Aniline solidifies at 18° F., and boils at Its vapor is inflammable, .burning above the liquid with a large, smoky flame. Aniline is an actively corrosive poison. It has a peculiar nauseating odor, and its fumes exert decided, poisonous effects upon workmen handling it.
Aniline was first discovered by Unveiclorben in 1826. He found it among the products of the destructive distillation of indigo. In 1834 it was identified by Runge in coal-tar. With the dis covery of the first aniline color, emauveine,D by Perkin, in 1856, aniline became a valuable com mercial product. It is now prepared from nitro benzene with the aid of clean borings of soft cast iron in an acid solution. Into a still fitted with an agitator are placed a part of the nitro benzene and a small quantity of the iron borings with water and hydrochloric acid. Steam is turned in and the contents are thus boiled and constantly stirred. The distillate is turned back into the still and the remainder of the nitroben zene and iron borings are fed in at intervals.
When the distillate ceases to contain nitro benzene the operation is at an end, and the still will contain only aniline oil, water and iron chloride and oxide. A charge of 1,000 pounds of nitrobenzene requires about 1,000 pounds of iron borings and yields about 765 pounds of aniline oil in about 10 hours' operation. The final purification of the crude aniline oil is con ducted in a vacuum still.
Commercially, three forms of aniline oil are recognized: (1) Aniline oil for blue, which is unmixed aniline; (2) aniline oil for red, which is a mixture of aniline with ortho-toluene and para-toluene, and (3) aniline oil for saframine, which is a mixture containing aniline and ortho toluidine. See COAL-TAR COLORS.
With chlorates, in the presence of metallic salts, aniline gives the indispensable dyestuff Aniline Black. It is also extensively used as raw material for many other colors used in dyeing. In the manufacture of drugs aniline is used as the starting point for the production of acetanilide, antipynne, antifebrin, etc. Nitrated aniline has been experimented with as an explo sive. It is claimed to be peculiarly adapted for use in detonators, primers, etc., and for mines and torpedoes. It is estimated that the output of aniline in the United States for the calendar year 1916 was 11,000 tons.