ANILINE BLUES.

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As the pure hydrochlorate of triphenylic rosaniline is less soluble than theaccompanying impurities, it is dissolved last and re-deposited first, and isseparated from the liquid. By repeating this treatment several times the bluecan be obtained pure.

The mother-liquors are carefully colle&ed, and distilled over lime. Alcoholpasses over first, then aniline, whilst the colouring matters remain along withthe lime. We shall still briefly describe some of the procedures used to obtainthe shades of blue known in commerce as B., B.B., B.B.B., &c.

The first of these shades is produced by heating, in the apparatus Fig. 19,the subjoined mixture, to the temperature of 180° C., for about two hours :—

2 kilos, pure rosaniline ;

3 kilos, pure aniline, distilling at 182“ to 185°, and free from hydrocarbons.

270 grs. crystallisable acetic or benzoic acid.

The choice of these two acids is not indifferent. Acetic acid furnishes coloursbetter adapted for wool, and benzoic for silk.

When the colour is found, by the trial method above described, to havereached the proper shade, the retorts are emptied into a wooden vessel con-taining 10 kilos, of concentrated hydrochloric acid, constantly stirring. Thewhole is then filtered, and the residue pressed, washed in a large amount ofwater acidulated with hydrochloric acid, and kept at the boiling-point byblowing in steam. This treatment is continued until the blue is quite reducedto a powder. It is then filtered and pressed again. The yield is 3J kilos, ofdry blue.

The preparation of the shade B.B. is quite similar, but the amount ofaniline used is increased from 3 kilos, to 5. To purify the result, the contentsof the retort are poured into a vessel of enamelled cast-iron, surrounded bycold water, to stop further reaction. When the product is cooled down to 150°add 7 or 8 kilos, of concentrated alcohol, and stir till the whole is perfedtlyhomogeneous. The apparatus is then placed in a water-bath, and heated tillthe alcohol begins to boil. It is then taken from the water-bath, allowed tocool, and the colour precipitated by adding—with constant stirring—ro to 12kilos, of hydrochloric acid. The whole is then filtered, always at the sametemperature of 45° if constant results are aimed at; the produdt is pressed,washed in abundance of water, and dried. The yield is 1 kilo. 323 grms.of B.B.

To obtain B.B.B., take 1 kilo, of B.B., finely ground and quite dry,

1 kilo, of alcohol, and 2 kilos, of aniline, and heat the mixture in the water-bath, with continued agitation till the mixture is uniform. The viscid liquidresulting is then poured into 25 kilos, of alcohol, and heated to boiling, when

2 kilos, of an alcoholic solution of soda are added, containing 20 per cent ofalkali. The solution is filtered, precipitated with a slight excess of hydro-chloric acid, allowed to settle for forty-eight hours, filtered, drained, and theresidue pressed. The blue obtained is washed with boiling water slightlyacidulated, colledted, and dried. One kilo, of B.B. yields thus about 800 grms.of B.B.B.

Soluble Blues.—The aniline blues hitherto described have the inconve-nience of being soluble only in alcohol. The analogy existing betweentriphenylic rosaniline and indigo suggested the use of sulphuric acid. In 1862Nicholson succeeded in obtaining a true sulpho-conjugate acid of triphenylic