Abstract: Azo Pigments are made by subjecting a diazo component to an azo coupling reaction with the equivalent quantity of a coupling component difficultly soluble at less than 65.degree. C. in the aqueous/acid and aqueous/neutral pH-ranges. More specifically, an aqueous/acid-solution of the diazo component is continuously mixed at a temperature of less than 65.degree. C. within a period of less than 1 minute with the aqueous/alkaline solution of the coupling component and a predetermined pH between 2 and 9 is established by controlling the flow of the mass streams of diazo component and coupling component; in this way a portion of the coupling component is caused to undergo immediate reaction to the azo pigment to be made whereas the balance portion of the coupling component simultaneously commences precipitating as finely crystalline reactive matter, which is reacted in a post-reaction phase with unreacted diazo component to give the azo pigment to be made.

Abstract: Azo pigments are made by subjecting a diazo component to an azo coupling reaction with the equivalent quantity of a coupling component difficultly soluble at less than 65.degree. C. in the aqueous/acid and aqueous/netural pH-ranges. More specifically, an aqueous/alkaline solution of the coupling component is continuously mixed in a first reaction step with an aqueous solution of acetic acid, boric acid, phosphoric acid, hydrochloric acid or sulfuric acid at a temperature lower than 65.degree. C. within a period of less than 1 minute, during which the coupling component commenences precipitating at least partially as reactive matter; next, the suspension obtained is continuously mixed, in a second reaction step immediately following the first reaction step, with an aqueous/acid solution of the diazo component at a temperature of less than 65.degree. C.

Abstract: The invention relates to a process for the continuous manufacture of azo pigments, wherein a coupling component is reacted, inside a reaction zone filled with a previously produced suspension of the azo pigment to be made, with an aqueous solution of a diazo component at 10.degree. to 60.degree. C. and over periods of 0.2 to 4 hours.

Abstract: The disclosure relates to a process for controlling diazotization reactions. To this end, a reaction batch containing an aromatic amine and nitrous acid is vigorously agitated so as to continuously renew the surface area of the batch. The air above said surface area is exhausted at a constant rate and tested for its content of nitrous gases originating from partially decomposed nitrous acid. Nitrous acid or dissolved matter forming it under the reaction conditions is supplied to the feed amine in the proportions necessary to provide for a content between 5 and 300 ppm nitrous gases in the exhausted air.