Ciba-geigy Corporation

Alexander Hamilton

Colin Nelson

John B Blackburn

Christopher Newton

Alexander H MacLennan

A pigment composition, suitable for use in modern offset and letter press inks, comprising:

Pigment compositions based on acetoacetarylide derivatives

A stabilized opaque form of C.I. Pigment Yellow 74 comprises a mixture of

Stabilized opaque form of C.I. Pigment Yellow 74

Automatically controlled continuous process for the diazotization or tetrazotization of aromatic amines in which the rate of addition of the inorganic nitrite is controlled by a polarovoltric method. The process comprises adding regularly and continuously to a reactor an aqueous slurry or solution of the amine containing sufficient acid for the diazotization process and simultaneously adding to the reactor a solution of an inorganic nitrite at a rate which is automatically regulated by a polarovoltric controller to ensure that a pre-selected concentration of unreacted nitrous acid is maintained in the reactor throughout the whole period of the reaction.

Continuous diazotization process, wherein the rate of addition of

Azo dyestuff coupling process in which the amount of excess diazo or coupling component is continuously monitored and the addition of diazo component or coupling component to the reaction is automatically controlled by means of an automatic chemical analyzer which incorporates a dialyzer module, which process is characterized in that azo metal salt pigments derived from sulphonated intermediates can be obtained by precipitating the pigment by adding a water-soluble metal salt to the water-soluble sulphonated azo dyestuff at some stage prior to the passage of the sample stream through the dialyzer.

Dialysis monitored preparation of metal salts of azo pigments

Azo pigment coupling process in which the amount of excess diazo or coupling component is continuously monitored and addition of diazo component or coupling component to the reaction is automatically controlled by means of an automatic chemical analyzer which incorporates a dialyser module. The process involves a method of automatically controlling the coupling reaction by a continuous-flow chemical analyzer which continuously samples the reaction mixture and analyzes it for unreacted diazo or coupling component by dialysis and colorimetry, and automatically adjusts the rate of addition of this component to the reaction mixture to keep the concentration of unreacted component within a pre-set range during the period of the reaction.

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Glasgow, United Kingdom

Alexander Hamilton