Preparing concentrated azo dye solutions using nitrite salt as both coupling component and diazotizing agent

Process for the preparation of a concentrated, stable solution, with a low salt content, of a cationic azo dyestuff of the formula ##STR10## wherein A denotes the radical of an aromatic carbocyclic or aromatic heterocyclic diazo component,

• R denotes alkylene,
• R.sub.1 denotes hydrogen or alkyl,
• R.sub.2 denotes alkyl, alkenyl or aralkyl,
• R.sub.3 denotes alkyl,
• R.sub.4 denotes hydroxyalkyl having 2 or more C atoms,
• R.sub.5 denotes halogen, alkyl, alkoxy, aryloxy, C.sub.1 -C.sub.4 -alkylcarbonyl, C.sub.1 -C.sub.4 -alkylsulphonyl, benzoyl, C.sub.1 -C.sub.4 -alkylcarbonylamino, C.sub.1 -C.sub.4 -alkylsulphonylamino or benzoylamino,
• m denotes 0, 1, 2, 3 or 4, and
• An.sup.- denotes a carboxylic ion,
• and wherein
• the cyclic and acyclic substituents are unsubstituted or substituted by non ionic substituents,
• comprising reacting an amine of the formula
• A-NH.sub.2
• with a nitrite of the formula ##STR11## in an aqueous carboxylic acid in a concentration such that the final solution has a dyestuff concentration of from 10 to 60% by weight.