The substance known as turmeric is the under-ground stem of a plant which grows in a wild state in some parts of China and India. It emits a strong, but pleasant odor, and its taste is peppery, aromatic and bitter at the same time. The plant, however, is cultivated in Java and Bengal; the latter country producing the better quality. Although turmeric is rich in coloring matter, its want of permanence is a hindrance to it. It is generally sold in powder, ground down very fine. It should be quite dry; if damp, it loses its color, turns a dull yellowish brown, and dyes flat shades. A good turmeric should show a beautiful lustre. It enters into a majority of the dark colors in feather dyeing, and, although used as a body for colors only, a great deal depends upon it as to the result.
BICHROMATE OF POTASH.
This dyestuff, known as red chrome and bichromate and often times simply as chrome, consists in one equivalent of potash, with two equivalents of chromic acid. It contains no water, and consequently cannot lose any weight by exposure to heat or dry air. It will not attract moisture from a damp atmosphere. It dissolves readily in ten times its weight of cold water, and is insoluble in alcohol. It forms bright red crystals, and the solution is of a deep orange yellow. Bichromate of potash is a most powerful oxidizing agent, and produces very complex and interesting changes in tinctorial bodies. It is an intense poison. Its most extensive application is now in the production of blacks, along with logwood; indeed, without its aid it would be next to an impossibility to produce a glossy and permanent black on ostrich feathers. In giving depth of shade to all dark colors it is used in preference to any thing else, and I have never found any to contain any adulteration that was perceptible, or that was a hindrance to its good qualities. It is used in ostrich feather dyeing always in a diluted form, in a very high temperature of water.
ARCHIL.
About the thirteenth century an Italian, Tederigi by name, during travels in the East observed the tinctorial powers of a certain class of plant of low organization, called lichens, and introduced the color into Europe under the name of archil. For this discovery he was amply rewarded by the government, besides amassing a large fortune, as the supply for years came from Florence. At first the weeds were collected on the shores of various islands in the Mediterranean; but on the discovery of the Canary Islands, in 1402, large quantities were obtained from there. Later on they were imported from Cape Verde; and now they are also obtained from Madagascar, Zanzibar, Angelo and Lima and various localities in South America.
The weed does not contain any coloring matter already formed, but under the influence of ammonia and the oxygen of the atmosphere gives rise to archil. The manufacture of archil was for centuries carried on in wooden troughs. Two hundred parts lichens were placed in the trough together with about two hundred and forty parts of decomposed urine, and the mixture well worked every three hours for forty-eight hours. Five parts of slaked lime, one part of arsenious acid and one and one-quarter parts of alum were then added, and the whole well stirred and allowed to ferment. The stirring was repeated, from time to time, for a month. The contents of the trough were then removed to casks, and left to stand, thus improving the color. Archil is also one of the most important dyestuffs used by the feather dyer, principally entering into the composition of garnet, plum, brown, etc. Contact with acid will destroy its coloring virtues by turning it a dull brown red.
SAFRANINE.
It is prepared by treating aniline oils successively with nitrous acid and arsenic acid, and one of an alkaline nitrate at about 212° Fah., for a short time. The product is extracted with boiling water, neutralized with an alkali filtered, and the color precipitated with common salt.
Pure hydrochloride forms thin reddish crystals, which are soluble in water and in alcohol, yielding a yellowish red solution. The most characteristic reaction of safranine is that when concentrated sulphuric acid is gradually added to its solution, the color changes to violet, then to blue, dark green and light green. Then, on diluting the solution with water, the same changes of color take place, only in the reverse order.
In feather dyeing safranine is used chiefly in making light colors of a pinkish hue; such as pink, terra cotta, and to give a tint to ecru, beige and such colors.