These vessels are charged with a solution of magenta in methylated or wood spirit, and iodide of ethyl or methyl, in proportions according to the shade required, and the whole heated by steam for five or six hours, when the excess of alcohol and iodide of ethyl is distilled over. The resulting product is dissolved in water, filtered, precipitated with common salt, and well washed.
Like most of the other colours, Hofmann violets are salts of colourless bases. That of a red shade has a formula of C22H23N3, or C20H18(C2H5)N3; of a true violet shade C24H27N3,
or C20H17(C2H5)2N2; and of a blue shade of violet, of C26H31N3, or C20H16(C2H5)3N3. They are all moderately fast on wool and silk, although less so on cotton, and, as they can be produced in nearly every shade of violet, are in great use, having replaced most of the other violets.
The following processes have also been proposed for the production of aniline violet:
1. Oxidation of an aniline salt by means of a solution of permanganate of potassium. (Williams.)
2. Oxidation of an aniline salt by means of a solution of ferricyanide of potassium. (Smith.)
3. Oxidation of a cold and dilute solution of hydrochlorate of aniline, by means of a dilute solution of chloride of lime. (Bolley, Beale, and Kirkmann.)
4. Oxidation of a salt of aniline by means of peroxide of lead under the influence of an acid. (Price.)
5. Oxidation of a salt of aniline in an aqueous solution of peroxide of manganese. (Kay.)
6. Oxidation of a salt of aniline by free chlorine or free hypochlorous acid. (Smith.)