PEIKNYL VIOLETS.—In the purification of di-phenyl-rosanilinc blues, blue and violet colouring matters are obtained. The blue obtained by heating equal parts of rosaniline and aniline for four hours at 149°-160° (300°-320° F.) is, whilst being boiled with dilute muriatie acid (1 acid to 9 water), freed from the unaltered bases, which contain the violet. This violet is not pure, but, according to the purification, are obtained violet-red or dahlia, and violet-blue or panne ; between these are found all shades of violet. By even the most careful manipulation, it is uot always possible to get the same shades, consequently the exact shades required are obtained by mixing the blues and reds.
Mono-phenyl-rosaniline (red-vlolet).—Rectified aniline, 14 kilo., is gradually added to acetate of rosauiline, dried at 100° (212° F.), 10 kilo., in a still, so as to collect the aniline which comes off. The rosaniline salt is first heated gently by itself ; thc cohobation with aniline is continued for one hour, when the heat is raised to 190° (374° F.). Samples of the product are drawn out every few minutes, so as to watch the production of colour, which should be a very red violet. The mixture is allowed to cool a little, when it is softened with a little benzol, which removes the aniline, and a brown colouring matter, whilst the rosaniline and other products are precipitated. Tho precipitate is throvvn on a strainer, dried, and dissolved in hydrochloric acid; from this, the violet is thrown down by the addition of tt large quantity of water, well washed, and dried.
Di-phenyl-rosaniline (blue-violet).—Rosaniline salt, 10 kilo., and aniline, 20 kilo., are treated, as above, for at least ono and a half to two hours. Acetate rosaniline is sometimes used. The product is examined from time to time, and when the tint is obtained, the vessel is removed or allowed to cool. Alcohol, 4-5 lit., are added, to soften it, and the whole ie poured into a large quantity of alcohol, to which hydrochloric acid is added. The colouring rnatter is precipitated by adding a saturated solution.of common salt, and is well washed on a flannel strainer with acidulated water.
Ethyl and methyl rosanilines.—Ethyl and methyl violets are now largely made from methyl-aniline (see 'Violet de Paris), so that the costly production of Hofmann's violets from iodides of ethyl or methyl has become of interest principally as a source of other importaid colours. The modus operandi (No. 1291,1863) is as follows :—One part by weight of rosaniline, 2 parts by weight of iodide
of ethyl, and about 2 parts of strong methylated spirit are heated together in a suitable vessel, to a temperature of 138° (212° F.), for three to four hours, or until the whole of the rosaniline is converted into the new colouring matter. The syrupy mass obtained on cooling is dissolved in methylated spirit or alcohol, aud may be used at once for dyeing and printing. The iodine ie thus recovered :— The product either before or after dissolving in spirit is boiled with an alkali, by which the base is precipitated, whilst iodide potassium remains in solution. The base is washed aud dissolved, together with an acid (as hydrochloric), in alcohol, or in place of hydrochloric acid and alcohol, acetic acid and water ; these solutions can be employed for dyeing and printing, giving to silk and wool beautiful violet, blue-violet, and red-violet tints. Instead of iodide of ethyl, the iodides and bromides of methyl, amyl, propryl, and capryl may be employed, but not so conveniently, as they are more expensive. Three shades of violet, viz. R, reddish violet ; B, blue-violet ; and BB, a light violet, were formerly supplied in this material. For red-violet.—Ten kilo. of rosaniliue, 100 lit. alcohol, 8 kilo. iodide of ethyl or methyl, and 10 kilo. caustic soda or potash ; the mixture is heateil for two hours at 115°-130° (239°-266° F.). For blue-violet.—Ten kilo. nf rosaniline, 100 lit. alcohol, 5 kilo. iodide methyl, 5 kilo. iodide of ethyl, and 13 kilo. caustic soda or potash. For light-violet.—Ten kilo. of rosaniline, 20 kilo. iodide of methyl, 100 lit. ethylic alcohol, and 10 kilo. caustic potash. The solutions of iodide ethyl and methyl should be added very gradually, as also the caustic solutions. Other intermediate shades may be obtained by varying the tions. Iodide of methyl gives a more decided blue shade than the iodide of ethyl, and the colouring matter is also more soluble in water than the iodide of ethyl product. The products are the iodohydrate of cthyl-rosanilioe or of methyl-rosanifine ; both are purified in the same way. The salts of both bases are soluble in alcohol, wood-naphtha, acetic and mineral acids ; the colours obtained from the salts of trimethyl-rosaniline are much brighter than those from salts of the other base, whilst salts which contain both bases are still more beautiful as dyes.