DYES, substances employed to impart colors of a measurable degree of permanence to fabrics. They are classified according to their origin as (1) natural organic dyes— in two groups, vegetable and animal; (2) mineral dyes and (3) artificial organic dyes, The first class includes such vegetable coloring agents as indigo and logwood, and such animal dyes as cochineal. The second class includes such mineral coloring agents as chrome yellow and Prussian blue. The third class is by far the largest and most important, as it embraces the thousand and more coal-tar colors, synthetic indigo, etc. With the exception of indigo and logwood, few of the natural organic dyes are in extensive use, having been in large part superseded by coal-tar dyes of simpler appli cation and more brilliant color. Those still in considerable use are as follows: Annatto or arnotto, prepared from the fermented seed of Bixa orellana, a tree grow ing in Central America, the Antilles and the East Indies. The dye principle is known as bixin. It is insoluble in water but dissolves readily in alkalis. It is used on cotton direct or with a tin mordant, and gives a hue of bright orange. At present it is used chiefly in tinting butter and cheese.
Archil or orchil is developed by fermenta tion with ammonia principally from the lichens Roccella and Lecanora: the first growing in the Canary and Cape Verde islands, the East Indies, Madagascar, Central and South Amer ica; the second on the coasts of Norway and Sweden, Scotland, Ireland and Wales: The active principle is orcein, an alkali salt of orcin. This dye is used in large quantities for indigo, and in conjunction with other dyes, on silk and wool, especially for carpet yarns. The color is of great body, and includes shades of red, magenta and violet. The dye appears in the market as a thick liquid called a paste called apersis,* and a brownish or purplish powder called ucudbear.* Berberine is found in the root of the bar berry and several other plants. Its active prin ciple bears the same name, and it is the only natural basic dye. It imparts a golden yellow to silk and leather, and also to cotton if mordanted.
Brazil Wood appears in the market as chips, raspings and extract, of various species of Ccesalpinia, natives of the West Indies, Central America, and of tropical South America, Africa and Asia. The wood yields two active dye principles, brasilin and brasilein, producing shades of pink, purple and crimson, which, how ever, are not fast in the laundry.
Camwood, and its allies Harwood and sandal wood, yield the coloring principle santalin, used chiefly in conjunction with logwood and fustic for producing compound shades, especially browns, on wool. The colors obtained range from dull red to claret-brown. It is also used to give "bottom') to woolen fabrics to be dyed with indigo later.
Cochineal, as marketed, consists of the dried bodies of the females of the coccus cacti, an insect found in Mexico and Central America and other tropical countries living on the opuntia cactus. The ((black') cochineal of commerce is produced when the insects are scalded before drying, the "silver') cochineal when they are dried in stoves without scalding. The coloring principle is carmine acid. Carmine is obtained by precipitation from the cochineal extract with acid salts. This dye is still much used for bright scarlet and crimson on wool with tin and alum mordants respectively. With chro mium and iron mordants cochineal gives purple and with a copper mordant, claret shades.
Cudbear, see Archil.
Cutch, also known as catechu and gambier, is the dried sap of the green wood and pods of the acacia and mimosa trees, and also of the Areca palm. The gambier cutch is obtained from the leaves of the Uncaria gambier, and is called °cubical cutch') because it is marketed in small cubes. The coloring principles in cutch are catechin and catechu-tannic acid. Both are used in the production of olives and browns on cotton and infrequently on wool. Catechu tannic acid dyes silk plush a rich seal brown, and with an iron mordant yields a fine black. It is also used as a obottomP for some of the basic coal-tar colors.