Dyes


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Dyes

 

colored organic compounds used to color fabrics, leather, furs, paper, plastic, cured rubber, wood, and other materials. Dyes also include colorless compounds from which a colored substance is formed after it is applied to the material (for example, dyes for cold dyeing and optical bleaches).

Since ancient times natural dyes, such as alizarin and indigo, have been obtained from plants and, less frequently, from animals. The first synthetic dyes were produced independently in 1856 by the Polish chemist J. Natanson (fuchsin) and the English chemist W. H. Perkin (mauve); the commercial production of mauve began in 1857. In 1869 alizarin was synthesized by the German chemists K. Graebe and K. T. Liebermann, and soon a large number of other synthetic dyes were produced that were superior in quality to natural dyes. By the beginning of the 20th century, synthetic dyes had almost completely replaced natural dyes. The synthesis of dyes became possible after the discovery by N. N. Zinin of the general method of producing aromatic amines (the Zinin reaction). In the early 1970’s more than 9, 000 dyes were produced industrially, and the number is growing each year. The world production of dyes exceeds 600, 000 tons per year.

Dyes are divided according to chemical structure into the following groups: nitro dyes, nitroso dyes, azo dyes, arylmethane dyes, quinone imine dyes, sulfur dyes, indigoid dyes, anthraqui-none dyes, polycyclic dyes, phthalocyanine dyes, polymethine dyes, and azomethine dyes. According to their region and method of use, dyes are divided into acid, direct, vat, sulfur, mordant, basic, cation, reactive, oxidizing, and disperse dyes; pigments and lacquers; fat-, alcohol-, and acetone-soluble dyes; dyes for cold (ice) dyeing; and dyes for leather, aluminum, fur, and wood.

The color index of dyes—that is, their ability to selectively absorb visible light rays—is associated with their chemical structure—the presence of a sufficiently extensive system of coupled double bonds, often including heteroatoms. The dye adheres to the dyed material (substrate) because of the formation of chemical bonds with it (covalent bonds in the case of active dyes or ionic bonds in the case of acid dyes), as well as by the forces of adsorption and by hydrogen bonds (direct dyes); many dyes form water-insoluble particles (vat dyes, sulfide dyes, and dyes for cold dyeing), which “stick” in the pores of the substrate. Adhesives are also used to keep the dye on the material (if the dye is part of lacquers, enamels, or paints), as are polymer films. During use of the material its dye must not change substantially under the influence of light, weak acids and bases, washing, rubbing, or pressing. The stability of a dye depends on many factors, including chemical structure, the type of bond with the substrate, and the nature of the substrate. For example, basic dyes are unstable on wool but are sufficiently durable for use on polyacrylonitrile fiber. The stability of dyes under various influences is measured on a five-point scale, except for light stability, which is measured on an eight-point scale.

Dyes are used not only to color various materials but also in color and black-and-white cinematography and photography, in analytical chemistry, in medicine (as diagnostic materials), in biochemical research, in liquid lasers, and as photoconductive components of various physics instruments.

The raw materials for dye production include benzene, naphthalene, anthracene, pyrene, and other aromatic and heterocyclic compounds, as well as various acids, bases, salts, and alcohols. The first step is the production of intermediate products, which are further treated to produce dyes by the processes of condensation, diazotization, azo compounding, and oxidation. The production of dyes is often a complex process, consisting of ten or more stages.

REFERENCES

Kogan, I. M. Khimiia krasitelei, 3rd ed. Moscow, 1956.
Venkataraman, K. Khimiia sinteticheskikh krasitelei, vols. 1-2. Leningrad, 1956-57. (Translated from English.)
Stepanov, B. I. Vvedenie v khimiiu i tekhnologiiu organicheskikh krasitelei. Moscow, 1971.
Chekalin, M. A., B. V. Passet, and B. A. Ioffe. Tekhnologiia organicheskikh krasitelei i promezhutochnykh produktov. Leningrad, 1972.

M. A. CHEKALIN

References in classic literature ?
The inhabitants eat the stalks, which are subacid, and tan leather with the roots, and prepare a black dye from them.
In those days to dye the hair excited comment, and Philip had heard much gossip at home when his godmother's changed colour.
Why, dye know, he gave me such a feeling that he knew everything, that I was plumb ashamed of myself.
Emily remembered the rouge on her cheeks, and the dye on her hair, when they had first seen each other at the school.
Well," said Marilla sarcastically, "if I'd decided it was worth while to dye my hair I'd have dyed it a decent color at least.
But I didn't mean to dye it green, Marilla," protested Anne dejectedly.
The peddler said it was warranted to dye any hair a beautiful raven black and wouldn't wash off.
The peddler had certainly spoken the truth when he declared that the dye wouldn't wash off, however his veracity might be impeached in other respects.
You know, I said, that dyers, when they want to dye wool for making the true sea-purple, begin by selecting their white colour first; this they prepare and dress with much care and pains, in order that the white ground may take the purple hue in full perfection.
Then now, I said, you will understand what our object was in selecting our soldiers, and educating them in music and gymnastic; we were contriving influences which would prepare them to take the dye of the laws in perfection, and the colour of their opinion about dangers and of every other opinion was to be indelibly fixed by their nurture and training, not to be washed away by such potent lyes as pleasure-- mightier agent far in washing the soul than any soda or lye; or by sorrow, fear, and desire, the mightiest of all other solvents.
I mean, that we are liable to be imposed upon, and to confer our choicest favours often on the undeserving, as you must own was your case in your bounty to that worthless fellow Partridge: for two or three such examples must greatly lessen the inward satisfaction which a good man would otherwise find in generosity; nay, may even make him timorous in bestowing, lest he should be guilty of supporting vice, and encouraging the wicked; a crime of a very black dye, and for which it will by no means be a sufficient excuse, that we have not actually intended such an encouragement; unless we have used the utmost caution in chusing the objects of our beneficence.
Sir, there is a villain at that Maypole, a monster in human shape, a vagabond of the deepest dye, that unless you get rid of and have kidnapped and carried off at the very least--nothing less will do--will marry your son to that young woman, as certainly and as surely as if he was the Archbishop of Canterbury himself.