ANILINE BLAOK8.—These are produced by the action of oxidizing agenta on anilines, genemlly in contact with the fabrica to be dyed, though paste blacks are sent out by some naakers. The anilinoa employed in blacks and greys for calico-printing, &e., generally contain 60-65 per cent. liquid, boiling at 180°-185° (356°-365° F.)—pure aniline, 18-22 per cent., boiling at 185°-192° (365°-377° F.); aniline and toluidine, 8 per cent., boiling at 192°-198° (377-388° F.) ; toluidine ; and 4-6 per cent. xylidine, &c. Their ap. gr. should be 2°-3i° B. ; thoae of higher ap. gr. may contain nitro-benzol, while in those below 2° there is much toluidine, which injures the black. When fractionized, these anilines ahould distil almoat entirely at 160°-190° (356° 374° F.). Coupler's anilinea, which distil at 180°-185° (356°-365° F.), are said to produce the richest blacka. Paeudotoluidine, and the products boiling at 185°-192° (365°-378° F.), give " blue blacks." Toluidine, and the products boiling above_192° (378° F.), give rusty blacks ; on this account, they are rejected.
The salts of aniline cannot be used indiscriminately for producing blacks ; nearly all the aalts with organic acids give very unsatisfactory resulta, as do even those obtained with mineral acids, if perfectly neutral ; the solution must be acid, and in this way, it ia posaible pal tially to regulate the character of the black. The hydrochlorate and disulphate with excess of acid are usually employed.
A description of. Lightfoot'a and aimilar methods of obtaining aniline blacks belonga more appropriately to the department of the dyer, and will be treated in the article on Dyeing and Calico-Printing.
Attempts have been made to prepare a black dyo from anilino in the same form as other colours, Coupier proposea to mix 175 parts commercial aniline with an equal quantity nitro-benzol, adding 200 parts hydrochloric acid, 16 parts iron filings, 2 parts copper filings, and heating the whole for six to eight hours at 160°-200' (320°-392° F.) in an enamelled iron pot fitted with a condenser.
The operation ia complete when the mass can be drawn into threada. Thia black is soluble in acids, alcohol, and wood-naphtha ; for use, it ia dissolved in sulphuric acid.
Lueaa' black is a soft, hlack mass, composed of hydrochlorate aniline and acetate copper. It produces a black of very good tone, and can be obtained at a low price.
The black supplied by A. Muller, of Zurich, is obtained by dissolving in lit. water, ehlorate potash, 20 grms.; sulphate copper, 30 glans.; chloride ammonium, 16 grms.; hydroehlorate aniline, 40 grms. The mixture is heated in a salt-water bath at about 30° (86° F.); after a few minutes, it froths and swells up ; if, at the end of aome hours, it becomes pasty without turning quite black, the beating is continued. The paste ia exposed to the air for some daya, washed on a filter till no salts are found in the filtrate, and ia removed from the filter as a, deep-black paste, containing about 50 per cent. of dry colour. A blue-black is obtained from this, by finally washing with 20 grma. soluble blue in 1 lit. water. These colours are raixid up with much albumen, which ia the principal drawback to their use. The dry black, ground up, and mixed with a solution of gum, is said to equal the heat Indian-ink. Milller'a black is largely used.