Ciba-geigy Corporation

Ferenc Rakoczi

Rudiger Oxenius

Vladimir Arnold

Bruno Fortsch

Ernst Burgi

Amines which are sparingly soluble in water are diazotised by first preparing a melt or solution of said amines and then precipitating them from the melt or a solution in an organic solvent by adding water, and then diazotising the resultant suspension. In this procedure, the reaction times are appreciably shorter than those of conventional processes.

Process for the diazotisation of primary aromatic amines which are

The invention relates to an automatically controlled continuous method of eliminating excess nitrite in diazotization solutions of aromatic amines, which comprises controlling the addition of the agent employed for eliminating the nitrite ions by means of an electrochemically controlled variable. The process permits a smooth monitoring of the nitrite ion concentration in diazotization solutions. It is advantageous that the determination of the electrochemical controlled variable is almost instantaneous and that the addition of agent for removing nitrite ions can be controlled in simple manner via the fluctuations in the potential.

Method of eliminating excess nitrite in diazotisation solutions

The invention relates to a method of determining and controlling the diazonium ion concentration in diazotization solutions and/or in azo coupling reactions, which comprises determining said diazonium ion concentration by means of IR spectroscopy from the intensity of the N.tbd.N stretching frequency. The method is extremely selective and virtually trouble-free and permits the simultaneous determination of the concentration of different diazonium salts in mixtures.

Growing community of inventors

Zurich, Switzerland

Ferenc Rakoczi