PURPOSE: To enable the diazotization of an aromatic amine, advantageously from the viewpoint of quality and cost, by controlling the amount and rate of addition of a nitrite according to the concentration of the nitrite determined from the heat of reaction of the nitrite and the compound to be reacted with the nitrite.
CONSTITUTION: An aromatic amine is diazotized by reacting with an inorganic nitrite under acidic condition in an aqueous system. A specimen collected by a metering pump 1 is mixed with air sent by a metering pump 2, the temperature of the mixture is stabilized by a heat-exchanger 5 and the specimen is mixed and reacted (7) with a compound (e.g. sulfamic acid) reactive with the nitrite and supplied by a metering pump 3 through the heat-exchanger 5. The temperatures before and after the reaction are measured by temperature sensors 6, 8, the temperature difference (corresponding to the concentration of the nitrite) is converted to an electric signal with a temperature difference converter 9 and the amount and/or rate of addition of the nitrite are controlled by an automatic controller based on the signal. The excessive nitrite used in the reaction can be decreased by this process.
MURAMATSU SADAO
CHIBA ATARU
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