Its solvent power is also utilized in the production of various colouring fluids, where the colouring matter would not dissolve in water alone; thus aniline violet, the tinctorial constituents of madder, and various allied colouring matters dissolve in glycerin, forming liquids which remain coloured even when diluted with water, the colouring matters being either retained in suspension or dissolved by the glycerin present in the diluted fluid.
The solution possesses a considerable tinctorial power, dyeing silk in the cold.
Thus the protoand per-salts of iron, as well as the protoand per-salts of tin, including also a large variety of tannin, sumac, divi-divi, chestnut, valonia, the acacias (Areca Catechu and Acacia Catechu from India), from which are obtained cutch and gambier, &c., are no longer used solely as mordants or tinctorial matters, but mainly to serve the object of converting the silk into a greatly-expanded fibre, consisting of a conglomeration of more or less of these substances."
Moreover, the chemical character of the tussur silk differs from that of the mulberry silk, and the fibre has much less affinity for tinctorial substances, which it takes up unevenly, requiring a large amount of dye-stuffs.
Cochineal owes its tinctorial power to the presence of a substance termed cochinealin or carminic acid, C17H18010, which may be prepared from the aqueous decoction of cochineal.