21. Furthermore, it is prohibited to place any textile or leather articles colored with azo dyes on the market. 22. All dyers should ensure that the supply company is fully informed about the legislation of the prohibited azo dyes . 23. Methyl orange is an example of an azo dye that is used in the laboratory as a pH indicator. 24. Azoic dyeing is a technique in which an insoluble azo dye is produced directly onto or within the fiber. 25. When the azo dye agent ( N-alpha-naphthyl-ethylenediamine ) is added a pink colour develops. 26. "' Chrysoine resorcinol "'is a synthetic azo dye which was formerly used as a food additive. 27. A strain of this species isolated from effluent from a textile factory was found to be able to degrade azo dyes . 28. Accordingly, the production of benzidine azo dyes was discontinued in the 1980s " in the most important western industrialized countries ". 29. Therefore, there may be a connection between the increase of the disease and the amount of usage of these azo dyes . 30. After contact exposure under light, the residual diazo is converted to a stable azo dye with an aqueous solution of coupler.
