Abstract: Diaryl pigments having excellent dried ink transparency and improved process heat stability are prepared by carrying out the coupling of a bisdiazotized substituted 4,4' diaminobiphenyl with acetoacetanilides and/or pyrazolinones in the presence of an added quantity of one or more substituted aromatic amines containing at least one sulfonic or carboxylic acid substituent, or their salts. The pigments exhibit improved tolerance to variations in drying temperatures and to high drying temperatures, and have improved transparency when present in dried ink formulations.

Abstract: The subject invention relates to a process for preparing ferriferrocyanide pigments. The process comprises(1) forming a reaction mixture containing a ferrous salt and an alkali metal ferrocyanide;(2) adding an alkaline compound to said reaction mixture in an amount sufficient to raise the pH to at least 9;(3) oxidizing the basic solution by aeration;(4) heating the solution to a temperature of from 10.degree. C. to 90.degree. C. and(5) recovering the pigment.The advantage of the process is that no significant amount of Berlin White intermediate is formed. Consequently, it is unnecessary to use sulfuric acid to dissolve the Berlin White before oxidation. Moreover, oxidation is achieved by aeration. This is cost effective and reduces the stress to the environment. The resulting pigments are useful in coloring printing ink and carbon paper.