Progress of Color-Chemistry.

Scientific American 5, 1.2.1862

The arts are divided by some writers into two general classes - the useful and the ornamental; but distinctions of this character are not always correctly made. Thus the art of coloring as applied to textile fabrics has been classed among the ornamental as contradistinguished from the useful; but this is certainly an erroneous classification. The Creator of the world has not garnished the fields and forest with brilliant colors for the simple purpose of exciting pleasing emotions in man, but also for the opurpose of enabling him to distinguish between different objects. The art of coloring, therefore, embraces both the useful and the ornamental.

As applied simply to printing and dyeing, it has been ranged under qualitative chemistry, but in th present day it is vastly more expansive. Latterly, color-chemists have directed their chief efforts to synthetical chemistry in the manufacture of new artificial coloring compounds. By the old modes of operation, infusions of slowers, roots and woods were chiefly used to color cloth, but of late the mineral world has been favorite field of the chemist, and from radical colorless substances compounds are now produced which impart hues to the products of the loom, rivaling in brilliancy the colors of the flowers. As usual, France has attained the highest disdinction in the manufacture of such colors, conspicuous for which are MM. Renard frèred and Franc, of Lyons. We have exposed sample of their aniline red, crimson, purple and lilac colors - printed and dyed cotton, silk and wool - to solar light, for the past two months without injury to their permanency. They surpass in brilliancy those obtained from cochineal and orchil, and they appear to be more durable than the latter and as fast as the former.

A new aniline color, valled Bleu de Paris, has lately come into use for coloring silk and fine wool. It is made by heating sixteen parts by weight of aniline with nine parts of bichloride of tin, in a sealed tube, exposed for thirty hours to 180° of Centigrade. Aniline purples, reds and lilacs, mauves, solferinos, fuchsine, have been described in former volumes of the Scientific American, and may now be passed over.

A green color, called emeraldine is obtained by mixing a hydrochloric acid solution of aniline with chlorate of potassa, but it is dull and not suitable for dyeing lively tints. Some new chemical combination may render it as brilliant as the gem after which it has been named. A new beautiful yellow product for dyeing silk is obtained by submitting dinitraniline to the action of sulphide of ammonium. Picric acid, which colors a most delicate primrose shade on silk, used to be obtained from that expensive substance, indigo, but it can now be manufactured from carbolic acid, by first boiling it in strong nitric acid, then diluting it in boiling water. A solution of pictic acid and the sulphate of copper form a beautiful yellowish green.

Almost every color that can be named is now obtained from products of coal tar. The progress in this branch of chemistry during the past year has been very gratifying to the chemist, but the manufacturer, printer and dyer consider that these artificial colors are still too high in price.

Much attention should now be devoted to improve the processes of their manufacture so as to reduce their expence and thereby obtain cheaper chemical products.

Ei kommentteja :