CHROME DYES. 141 



essay in the Yerliandl. z. Beford. d. Gewerbfl. in Preussen, 

 1846, on the process of shading with blue on woollen-yarn. 



Chromate of Lead, as a Cr old-yellow for Cotton. — The gold- 

 yellow color with a silky lustre, on cotton-yarn, is prepared 

 by mordanting in a solution of subacetate of lead, and then 

 passing it through bichromate of potassa, acidulated with nitric 

 acid ; after thoroughly rinsing in water, it is dipped for a few 

 minutes into an alcoholic tincture of saffron, and dried in the 

 shade without previous washing. (Innerosterr. Industr. und 

 Gewerbebl. 1847.) 



Ghrome Dyes. — Kurrer (Ch. Gaz. viii. 461, and Lond. 

 Journ. Aug. 1850) has made some valuable contributions to 

 the chemistry of colors, in an essay on chrome dyes. As 

 these latter resist the action of light, acids, and alkalies, they 

 may be considered fast colors. The new methods of preparing 

 the different shades, with the requisite proportions of materials 

 to be employed, are given in the original paper, which may be 

 profitably consulted. 



Sea-green. — Prepared by dissolving hydrated peroxide of 

 chrome in dilute hydrochloric acid, carefully neutralizing ex- 

 cess of acid with caustic potassa, and evaporating solution to 

 46° B. The chrome oxide is precipitated from solution of 

 bichromate of potassa by arsenious acid. 



For cylinder-printing, either starch or gum tragacanth may 

 be used for thickening ; but the gum is preferable, because it 

 gives colors of greater depth and richer tone. 



The prints are brightened, after being stretched over night 

 in a cool place, by passing them through caustic potash-lye of 

 2° B., airing, pressing, washing, drying, and, finally, by im 

 mersion in a bath of acetate of copper, rinsing, and drying, 



Olive. — The addition of catechu-brown to the chloride of 

 chrome, in varying proportions, produces the different shades 

 of olive. 



Pearl-gray. — This tint is obtained by a mixture of sulphate 

 of chrome and chrome alum. The prints are finished by im- 

 mersion in milk of lime, rinsing in hot and cold water, and 

 drying. 



