- Agent containing quinonimine derivatives and used to colour keratin fibres, and associated method
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The invention relates to an agent for colouring fibres (A). Said agent is produced by mixing two constituents (A1) and (A2), and is characterised in that the constituent (A1) contains at least one quinonimine derivative of formula (I), and the constituent
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- Nitrosation process
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In the process of subjecting a compound selected from phenols, N,N-dialkylanilines and mixtures thereof to nitrosation reaction conditions using a nitrite in an aqueous system to prepare nitrosated products selected from benzoquinone oximes and p-nitroso-N,N-dialkylanilines, the nitrosation reaction is advantageously carried out in the presence of an acid stronger than nitrous acid an organic acid of pKa 2 to pKa 5 or a salt thereof and water, the quantities of the organic acid and water being up to 5 times by mole and up to 10 times by weight the quantity of the compound to be nitrosated, respectively.
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