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Azo Free Dyes

Azo dyes are any synthetic dyes whose molecular structure contains a nitrogen group. They comprise approximately 70 percent of all fabric colouring dyes, even though there is considerable concern about their carcinogenic status, water solubility, skin absorption potential, and pollution during manufacture and usage


General Chemical Formulae of Azo Compounds

Natural Dyes

Dyes made from natural substances, usually from the bark, leaves, roots, flowers, or wood of a plant. There are also insects, notably cochineal and lac, that make dyes.

Natural dyes include plant dyes, animal dyes and mineral dyes. Until the late nineteenth century these were the only dyes used for coloring weaving yarns.

Azo compounds are compounds bearing the functional group R-N=N-R’, in which R and R’ can be either aryl or alkyl. IUPAC defines azo compounds as: “Derivatives of diazene (diimide), HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g. PhN=NPh azobenzene or diphenyldiazene. “[1] The more stable derivatives contain two aryl groups. The N=N group is called an azo group. The name azo comes from azote, the French name for nitrogen that is derived from the Greek a (not) + zoe (to live).