194

DYEING AND CALICO PRINTING.

hydrochloric, or acetic acid. The salt formed is dissolved in boiling water.The solution is then filtered, and precipitated by the addition of common salt.The pure colour is thus precipitated, and is colledted on filters and dried. Itis perfectly soluble in pure water, even at common temperatures.

There are a variety of other analogous violets, as the mono-, di-, and tri-methyl, and ethyl mauvanilines. They are prepared in a manner correspondingto Hofmann’s violets, and have a bluer shade.

The mono- and tri-methyl iodhydrates of trimethylated rosaniline are stillmore nearly blue.

Lauth and Grimaux have formed a violet by causing benzyl to replace thesubstitutionable hydrogen in rosaniline. There is also a methylic benzylicand a phenylic methylic violet.

Perkin’s “ Britannia violet " is prepared in a very similar manner, bytreating 6 parts of rosaniline with 30 parts of methylic alcohol and 4 partsbromide of terebene.

Hofmann’s Violet (B).

Hofmann’s Violet (B).

The comparative strength, shade, and brightness of a violet are best ascer-tained by dyeing patterns of known weight. Their pure or mixed nature maybe tested by placing a drop of the solution upon blotting-paper, as directed formagenta. Instances occur where a violet consists of two portions,—the onesoluble in water and of a red colour, and the other dissolving only in spirit,with a blue. Sometimes a considerable portion yields to no solvent employedin dyeing, and on examination proves to be quite valueless.

Aniline violets maybe divided, as regards their application, into two classes—the insoluble (in water) and . the soluble. The former are dissolved inmethylated spirit, with the aid of heat, making the solution as strong aspossible. The substitution of glycerine for a part of the spirit will be foundto give very satisfadtory results. Wood-spirit may be used in place of alcoholwhere very blue tones are desired. Great care must be taken in filtering thesolutions. The soluble violets—those of Hofmann, Perkin’s “ Britannia,”and the “ Paris violet ”—are readily soluble in water, and have a greater