Aniline Dyes

A variety of synthetic colorants manufactured from coal tar (or from derivatives of benzene found therein) and used in the dyeing of textiles and clothing and in flexographic and screen printing inks. (Flexography itself was at one time called "Aniline Printing.") Aniline is a colorless, oily, slightly water-soluble organic compound (chemical formula C6H5NH2) derived from nitrobenzene and is also used in the manufacture of pharmaceuticals.

Aniline was one of the first synthetic dyes ever produced, and was the first commercially successful synthetic dye. Until the mid-nineteenth century, most dyes and colorants were derived from minerals (such as lapis lazuli) or from a variety of plants, insects, and, of course, mollusks (octopus and squid inks) and other shellfish. These dyes were expensive, and for the most part lacked permanence.

In 1856, an eighteen-year-old British chemist named William Perkin had been trying to solve the problem of malaria—a disease caused by the transmission of a microorganism by Anopheles mosquitoes—in British colonies in the Far East. It was found that the chemical quinine was an effective remedy for malaria, and British colonists had been importing it—at great expense—from the Dutch. (Interestingly, the British colonists found that quinine—which tasted terrible—was more palatable when mixed with tonic water. It still tasted terrible, but was rendered thoroughly drinkable when a bit of gin was added. Hence, the resulting gin and tonic is probably the only alcoholic beverage that could legitimately claim to have been developed for "medicinal purposes.") However, quinine was only obtained naturally from the bark of the cinchona plant, which at that time only grew in Peru and in Indonesian colonies owned by the Dutch, who charged a hefty price for it. Attempts to grow cinchona back in England failed, so William Perkin was charged with the responsibility of developing a means of creating quinine synthetically. He turned to coal tar, a waste product of the manufacture of gas, which was found to possess substances very close in chemical structure to quinine. One of Perkin's compounds, though not quinine, did end up staining a rag deep purple. He applied some of his dye to a fabric, and the purple color resisted sunlight and laundering. This was the first aniline dye. Giving up on the search for quinine, Perkin invested his father's life savings into dye production and became quite wealthy, although he unfortunately failed to patent his discovery. First the French, and later the German, chemical industry got into synthetic dyes, and suddenly synthetic colors were everywhere. (The word mauve, for instance, was originally the trade name of the French version of purple aniline dye.)

Although aniline is rarely used as a dye today, it stimulated a great deal of research and investment into synthetic colorants, which eventually led to the wide variety of pigments and colorants now available.

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