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DYEING AND CALICO PRINTING.

yield with the former substance a magnificent carmine-red colour. Natanson,in 1856, showed that when aniline and chloride of ethyl (Dutch liquid) are heatedtogether in sealed tubes to 200°, the mixture assumes a beautiful blood-redcolour. Professor Hofmann discovered a product resulting from the adlion oftetrachloride of carbon upon aniline, which yields a brilliant carmine coloursoluble in alcohol. It is, however, quite impossible to give, in our allottedspace, a historical review of the numerous discoveries made in this immensefield. The most distinguished investigators in this department are Messrs.Perkin, Verguins, Mansfield, Collas, Zinin, Gerber-Keller, Heilmann, Medlock,Nicholson, Girard and De Laire, Hofmann, Lightfoot, &c.

We will now proceed to examine, first, the primitive material aniline, andthe sources whence it is obtained, and, secondly, the coloured derivativeswhich it is capable of yielding.

Aniline (kyanol, of Runge ; crystalline, of Unverdorben; nitride of phenyland hydrogen ; phenylamine ; benzidam) has the composition C J2 H 7 N. Itcontains, in 100 parts—C, 77-41; H, 7-54; N, 15-05. When pure it is acolourless, highly-refradtive liquid, of the sp. gr. 1-028 at 15 0 C. Its vapour-density is 3*220. It boils at 182° C., and does not congeal at — 20° C. It isvolatile at the ordinary temperature of the atmosphere. It has a faintly aromaticunpleasant odour, and an acrid, burning taste. It is slightly soluble in water,from which it may precipitated by common salt. With alcohol, ether, aldehyd,and the fixed and volatile oils it can be mixed in every proportion.

Aniline combines diredtly with the hydracids and the hydrated oxacids, formingsalts similar to those of ammonia. These compounds are nearly all solublein water and alcohol, and are capable of assuming the crystalline form. Thealkalies and alkaline earths displace aniline from its combinations with acids,but aniline decomposes the salts of iron, zinc, and aluminium, precipitatingthe hydrated oxides of those metals. In contadl with air aniline rapidlyalters its colour, becoming brown, and is finally converted into a resinousmass. Its salts, when pure, are colourless, but in contadl with the air theygradually assume a reddish colour. Solutions of the aniline salts colour fir-wood and elder-pith a deep yellow, which is not discharged by chlorine.This colour is apparent when only 1-500,oooths of aniline is present.

Aniline and its salts may be detected by the following readtions :—When asmall quantity of any aniline salt is placed upon a plate of white porcelain, andmixed with a few drops of concentrated sulphuric acid, and a few drops of asolution of chromate of potassa are next added, a beautiful blue colour is formed,which very soon disappears. A solution of an alkaline hypochlorite, whenmixed with aniline or any of its salts, gives rise to a violet-blue colour, alsofugitive. If a single drop of a solution of 1 part aniline in 1000 parts dilutesulphuric acid (1 part monohydrated acid in 7 of water) is placed on a pieceof platinum-foil, and brought into contadl with the positive pole of a singleBunsen galvanic cell, an intense blue colouration is instantly produced,which passes successively to violet and rose-red when the drop is touched withthe negative pole.

Perfedtly pure aniline may be obtained by distilling indigo and isatine withthe hydrates of potash and soda. Anthranilic acid, a produdt of a hot, con-centrated solution of potassa upon indigo, is decomposed into aniline andcarbonic acid by distillation with caustic lime. It is scarcely needful to