Process for preparing ferriferrocyanide pigments

摘要

The subject invention relates to a process for preparing ferriferrocyanide pigments. The process comprises (a) forming an aqueous reaction mixture comprising (i) a ferrous salt, (ii) a compound selected from the group consisting of sulfuric acid, hydrochloric acid, an inorganic potassium salt, and mixtures thereof, and (iii) an alkali metal ferrocyanide such that the molar ratio of (i) to (ii) to (iii) is about 1:1 to 0.9:1.5 to 1:1; (b) oxidizing the acidic solution by aeration; (c) heating the aerated solution to from 10 DEG C. to 90 DEG C.; and (d) recovering the pigment.