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.

OXALIC ACID.

Oxalic acid, a most powerful acid, occurs combined chiefly with potash juices of plants of the genus oxalis and rumex. Artificially it was obtained by the action of nitric acid upon sugar and starch, but has been prepared latterly by treating spent dyestuffs with alkalies. Oxalic acid forms colorless transparent crystals, which are inodorous, intensely sour, and do not grow moist upon exposure. Should they become damp, some nitric or sulphuric acid, used in the preparation, has not been thoroughly removed. It is soluble in its own weight of boiling water, but requires about eight times its weight of water at 65° Fah. Oxalic is one of the largely used acids in feather dyeing, being used in a number of light colors for the purpose of developing the color. In developing blues it is invaluable. Other colors it will totally destroy, violet or safranine, for example; and it is used in place of sulphuric acid for the purpose of extracting color.

INDIGO BLUE.

Indigo is derived from several plants of warm climates. In the plant the color exists as a yellowish liquid; but when extracted and exposed to the action of the air it becomes insoluble, and takes an intensely blue color. The cultivation of the plant is carried on chiefly in India, Java, Egypt and Louisiana. Indigo comes in the market in lumps, which, if of good quality, presents a deep bluish purple color, and exhibits a fine reddish coppery lustre if rubbed with a hard, polished body. If very hard or heavy, or when the color is very dull, blackish, greenish or brownish, the quality is below the standard. It is, however, of very little consequence in ostrich feather dyeing, and its impurities would scarcely at any time be noticeable. It should, however, dilute thoroughly in boiling water, and if there remain a sediment of any proportion, the indigo is impure. Sulphuric acid is generally used to develop the color.

SULPHURIC ACID.

Sulphuric acid, commonly called oil of vitriol, a common, yet very important, acid. Although not used to any great extent in ostrich feather dyeing, it occurs in commerce in various states and degrees of purity. It was at one time prepared by distilling dried copperas at a high temperature. It is now obtained in greater purity from the alkaline bisulphates. It is a clear colorless oily fluid, weighing about eighteen pounds to the gallon. If mixed with cold water, a great increase of temperature takes place. It rapidly destroys organic bodies, depriving them of their oxygen and hydrogen, and leaving the carbon behind, as a blackish mass. If any particle of organic matter falls into a carboy of acid, it is decomposed, and imparts a dark color to the liquid. It takes up water from the air rapidly, if left uncorked, and thus dilutes itself. Its use in feather dyeing is principally to extract colors that are too dark.

COPPERAS.

Copperas is generally prepared from the soft, white variety of iron pyrites, frequently found to a great extent in the coal measures. These, on exposure to air and moisture, decompose the latter, taking up oxygen, and are thus converted into sulphate of iron. Copperas forms pale greenish blue semi-transparent crystals, containing forty-five per cent. of water. If this be expelled, there remains a dull whitish powder. The crystals dissolve readily in one and one-half times their weight of cold water, and less than half their weight of boiling water. The direct uses of copperas have very much diminished in feather dyeing; as for dyeing black in conjunction with logwood it has been almost entirely superseded by bichromate of potash. In drabs and in saddening down light colors it is, to a certain extent, still used. It is used in