Methyl-benzyl-diphenyl-amine.—Girttra and De Laire (1869, No. 3675) thus prepare this Bub etance : in a digester, are heated 11-3 parts chloride or bromide of benzol, or its homologues, with 1 part methyl-aniline or its homologues, at 210° (410° F.). By using a pressure of about 15 lb. in the same apparatus, the proportions may be : 2, the operation, in each case, lasting about three hours ; the same result is gained by leaving the mixture to itself for several days at the ordinary temperature. The product is purified by washing with caustic soda and water, and distilling if required.
Toluidine, Tolnylamine, or Amido-toluol. C61-14(CH,NHz).—There are two methods of obtaining this base on the commercial scale ; by reducing nitro-toluol, and by separating bases in commercial aniline; as the pure article is not required, the latter method is the one generally adopted, the product being more or less pure according to the lirnits between the fractionizings. Brimmeyr takes the fraction of commercial aniline which comes over in two successive fractionizings between 195° and 205° (383° and 401° F.), and separates the bases, first converted into oxalates. Reimann divides anilines into two classes, light and heavy ; light or Kuph-anilines contain 90 per cent. aniline, 5 per cent. toluidines, and none of the higher homologues ; whilst heavy or Bar-anilines contain 70 per cent. toluidinee, and SO per cent. of the higher homologues. By mixing these or similar anilines together in different proportions, articles suited to all requirements may be produced.
Heavy anilines are obtained from the nitro-compounds of low-class benzols containing much toluol ; the lighter oil which comes over in rectifying, is kept apart for the light anilines. Generally, two distinct kinds of heavy anilines are prepared : one from the nitro-compound of rectified toluol ; another from the nitro-compouud of toluol, containing more or less xylol. As a rule, the lightest anilines give little advantage over the heavier medium oils, which can be produced at rnuch less cost, and without much sacrifice in their qualities for colour-making. From such oils, it is always easy to obtain the lighter oils, for blacks, &c., by collecting what comes over in the manufacture of magenta, &c. The manufacture of anilines is not generally carried on at tar works ; but is more usually attached to a, distinct branch of the businees, in which the rectification of benzole, toluols, &e., forms the very important connecting link between tar-distilling and dye-making.
Xylidine.—This base may be formed from the nitro-compound of xylol, in the same way as aniline frorn nitro-benzol, as proposed by Bechamp. Hofmann and Martius have rendered it
probable that coal-tar xylidine should be considered as dimethyl-phenylamine, CoHa(CH3)2NH2.
Many other substances which exist in coal-tar and naphtha are intentionally omitted. With respect to the impurities and compositions of commercial anilines, a few words may be necessary ; so little is known of the influence of some of these so-called impurities, tbat it is impossible to direct a manufacturer in the rejection of an aniline, but it is easy to indicate for particular appli cations what is required. An important fact to be boroe in mind is, that aniline is not a definite compound to which chemical tests can be applied: purer tints and finer shades are often due to an accidental circumstance ; no manufacturer, without the strictest care, can always produce exactly the same anilines, and it is doubtful whether the cost of production would be justified by thc advantages which are supposed to arise. There is a point, however, to which the attention of the colour manu facturer must be directed : it frequently happens, with piece goods, that a singular variation of tint is perceptible even with the same vat of dye, and the same piece of fabric ; whether the dye stuff, or fabric, or both combined, have to answer for this, ought to be determined, otherwise aniline dyes may have to bear the blame which should be laid on a careless dyer, or they may even be used to detect admixtures of different fibres.
Rosandine. C„H,9/%1-3.—A great number of colouring matters hearing the names aniline red, magenta, azaleine, rubine, solferino, fuchsine, chryaline, roseine, erythrobenzine, &c., met with in commerce, are salts of this base in a greater or less degree of purity. By heating a mixture of aniline, toluidine, and pseudotoluidine with arsenic acid or other oxidizing agents, the crude colouring matter is produced. The proportions generally employed in this country are--aniline commercial, 1 part ; arsenic acid, 75 per cent. dry acid, l I-2 parts, by weight. On the Continent, 800 kilo. cornmercial aniline are mixed with 370 kilo. solution arsenic acid, 72'per cent. dry acid. The quantity of water used must be such, that the arsenic acid solution does not deposit crystals on cooling. The anilioe must contain a certain quantity of toluidine, and is known as " magenta aniline '' ; the most suitable for good rosaniline is that boiling het een 185° and 200° (356° and 392° F.).