| abstract |
Oxidation dyes, in particular for dyeing hair, on the basis of 5,6-dihydroxyindol are particularly stable, if they contain a salt of 5,6-dihydroxyindol and a strong mineral acid in an aqueous carrier with a pH value between 1 and 3. Hydrochloride is particularly useful, and it is preferably produced by mixing the synthesized solution with an at least equivalent amount of hydrochloric acid, without isolating the free 5,6-dihydroxyindol, the organic solvent is removed by evaporation, the salt is dissolved in water and a pH value between 1 and 3 is set. |