Bayer Aktiengesellschaft

Kurt Breig

Harald Gleinig

Bernd Berger-Lohr

Gunther Boehmke

Karl Linhart

Georg Dehmel

Norbert Hamm

Concentrated stable solutions of cationic azo dyestuffs of the formula ##STR1## wherein A denotes the radical of an aromatic-carbocyclic or aromatic-heterocyclic diazo component,

Process for the preparation of solutions of cationic azo dyestuffs

Cationic dyestuffs of the general formula ##STR1## wherein R.sub.1 represents hydrogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 - to C.sub.4 -alkoxy, nitro or halogen,

Process for the preparation of cationic dyestuffs

Cationic dyestuffs of the general formula ##STR1## wherein R.sub.1 represents hydrogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 - to C.sub.4 - alkoxy, nitro or halogen,

Fluctuations in concentration of the starting materials during continuous diazotization are taken into account by passing a component stream from the receiver to the diazotization vessel through an analyser where, for a short residence time, the nitrite content is determined by an electrochemical measuring technique. A required nitrite excess is adjusted in the receiver on the basis of this measurement. By virtue of the pH-value, however, a diazotization reaction still does not take place in the receiver.

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Cologne, Germany

Kurt Breig