220 ANILINE AND ANILINE

Gratrix employed an aqueous solution of nitrate ofcopper; and Lautii, in 1860, obtained a blue violetby means of binoxide of hydrogen. Phillips useda mixture of bleaching powder and sulphate of iron.These and numerous other processes for the manu-facture of violet dyes, with the exception of mauveine,have either never been adopted or have fallen intodisuse.

B. Hofmann's Violets. —In 1863 Ilofmann foundthat, by acting on fuchsine with methyl or ethyliodide or bromide, dyes result of character analo-gous to Bleu de Lyons, but of not so blue a shade.Like the phenylated fuchsines, these dyes acquireprogressively a bluer and bluer shade the further themetliylation is carried, but even the final product(trimethyliodide of trimethyl fuchsine) is only ablue violet. Curiously enough, the body precedingthis one in the list (dimethyliodide of trimethylfuchsine) is a fine green; whilst all the others (methyl-iodide of trimethyl fuchsine, trimethyl fuchsine,dimethyl fuchsine, and methyl fuchsine) are of shadesdecreasing in blue cast and increasing in red shade,the nearer the body stands in the list to the originalfuchsine. The dyes manufactured of this descriptionare divided into three classes, viz., Violet red (violetrouge), marked R; Violet blue (violet bleu), marked B ;and Violet lumiere, marked B B. They chiefly consistof mixtures of methyl fuchsine and dimethyl fuchsine;dimethyl fuchsine and trimethyl fuchsine; and ofnearly pure trimethyl fuchsine respectively (Girardand De Laire ). Similar mixtures of the correspond-ing ethyl derivatives also possess nearly the sametints, but are somewhat less blue.

The term “ Lumiere ” is technically applied to theseand other analogous dyes, in order to indicate theirgreat purity of tint; even by artificial light thecolour of goods dyed therewith remains the same:ordinarily the terms “ violet lumiere,” “bleu lumiere,”mean not so much special chemical compounds, asmixtures so prepared as to possess the desired quality,i.e., carefully freed from any constituents which couldinterfere with it.

Ethylic ethers, other than the iodides, chlorides, orbromides, also give rise to violet rosaniline derivatives(probably ethylated rosanilines); thus Levinsteinhas prepared a dyestuff under the name “Dorothea,”by the reaction of nitric ether on rosaniline.

C. Methyl Violets (Violet de Paris). —The prepara-tion of the alcoholic iodides required for Hofmann’sdyes being difficult and costly, chiefly on accountof the high price of iodine, attempts were speedilymade to attain the same result (viz., methylated orethylated fuchsines) by a cheaper process. Eauthhad found in 1861 that by the oxidation of methyland ethyl aniline, dyes are obtainable of beautifulviolet hues, but of not very permanent characters,the methyl aniline dyes being superior to those derivedfrom ethyl aniline; but no practical application ofthis discovery was made until 1866, when Bardysucceeded in manufacturing methyl aniline, anddimethyl aniline, at a cheap rate by heating togetheraniline hydrochloride and methylic alcohol. Thepublic taste in dyes having somewhat altered at this

DYES.— Violet and Maove.

time, and colours that would stand exposure tolight, &c., without alteration being no longer inexclusive denjand, Poirrier and Ciiappat com-menced the manufacture of violet and violet bluedyes, by the oxidation of the methyl aniline thusobtained.

The manufacture of these violets is now carriedon to a large extent, and there seems reason forsupposing that the trade will continue. Thereare certain differences noticeable between the twoclasses of dyes that in various cases lead to the pre-ference of the one rather than the other, accordingto the taste or practical experience of the dyer.Recent experiments of Hofmann (“ Deut. Chem.Ges. Berichto, vi. 352) tend, however, to show thatthe products are chemically identical.

D. Miscellaneous Violets and Mauves. —These arefor the most part formed by processes substantiallythe same as those by which these two main dyesare produced, the difference being in the nature ofthe body chosen to modify the rosaniline. Thus:—Wanklyn suggested the use of isopropyl iodide;Perkin of nascent methyl and ethyl bromides pro-duced by the action of heat on turpentine andbromide in presence of alcohol, and Lauth andGrimaux the use of benzyl chloride. Wise obtaineda violet by acting on fuchsine with valeric acid;Kopp heated tannate of fuchsine with wood spiritcontaining hydrochloric acid, thus probably obtainingHofmann’s methyl violet by the action of methylchloride. Smith heated fuchsine with salicylic acid,obtaining a fine violet; he also employed brominatedacetone derivatives, forming an analogous colour.

The Regina purple or Nicholson purple, patentedby Nicholson in 1862, was prepared by heatingrosaniline salts to about 210° C., and has probablyan analogous composition. Delvaux obtained asomewhat similar substance, together with a reddyestuff, by heating aniline hydrochloride with sandto 200°-220° C.; the red product was soluble inwater; the violet body being extracted from theresidue by means of alcohol.

In 1867 Girard, De Laire , and Chapoteau, pub-lished the results of an investigation on the bye pro-ducts of fuchsine-making; from these they extracteda violet and a mauve dye, termed by them respec-tively violaniline and mauvaniline. The same bodiesgive rise to various blue violets by operating onthem with methyl iodide, &c., in the way that Hof-mann’s violets are made. Previously to the publica-tion of these researches Schneider had found that aviolet dyestuff is produced along with the “azaleine ”prepared by means of mercuric nitrate ; and Peiisoz,De Luynes, and Salvetat had found a similar sub-stance in the product of the action of tin tetrachlorideon aniline ; Paraf had also published a process forobtaining from fuchsine residues red, puce, and violetdyestuffs (Bull. Soc. Chem. Paris , [2] vii. 92.)

In 1865 a violet was sold under the name ofDahlia Imperial,* said to be obtained from fuchsineresidues; it gave shades of great beauty, and com-

* The name Dahlia has also been applied to various otherproducts.