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Popular Science, heinäkuu 1930

Tinting wools and silks by a new "dyeless" process developed recently in France opens a new field for the experimental activities of the amateur chemist. Simple inorganic chemicals, readily obtainable at any supply house, are the only materials required.

The chemistry of the process differs radically from the customary dyeing results obtained through the use of aniline dyes or by the precipitation of an insoluble colored pigment, such as khaki, Prussian blue, chrome yellow, or green in the fiber of the fabric by successive chemical baths.

In the new process a single chemical bath is used, and it reacts directly with the organic materials contained in the fibers of the fabric. The result is that the bath, which may be colorless, actually produces a beautiful colored compound in the fiber. The colors produced are remarkably "fast" in natural and artificial light. This treatment does not affext the durability or flexible qualities of the cloth, and it does effectively kill moth larvae in woollen fabrics.

The coloring bath itself is an acidified solution of a metal salt, to which a small amount of sodium nitrite (not nitrate) has bee nadded. A wide range of colors is possible by the use of salts of different metals used either separately or in combination with each other, thus giving a wide and interesting field for experiment. Additional tints are obtained by the addition of 1½ parts in 1,000 of resorcin, pyrocatechin, or salicylic acid.

A representative coloring bath of the simplest type is composed of 1,000 grams of distilled water, 3 grams of iron sulphate crystals, 1½ grams of oxalic acid, 1½ grams of sulphuric acid, and 2½ grams of sodium nitrate.

Olive-green tints are obtained by the use of iron salts, the color being strengthened by the addition of resorcin. Grayish-chestnut tones are produced with salts of cobalt, which change to a brown when copper is added.

Orange is obtained with cobalt salts and resorcin, becoming pink with the addition of nickel salts. Yellow tones are accentuated by tin salts and purocatechin, and weakened by salts of aluminum and zinc.

The "dyeing," if it may be called that, requires about an hour when the solution is kept between 170° and the boiling point. It may be done at room temperature, but the material must be immersed for a much longer period.

Only fabrics of animal origin, such as wool, natural silk, and fur are successfully tinted as outlined, since they alone contain the natural chemicals required to dorm the color (an organo-metallic complex). However, by a preliminary treatment of phenol or tanin, which is fixed with tartar emetic, such vegetable fabrics as cotton, linen, and artificial silks may be colored by this process.

A. P. A.

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