Abstract: This invention relates to a process for the preparation of quinacridone pigments by(a) heating, at a temperature of about 80.degree. C. to about 145.degree. C., a reaction mixture containing(i) 2,5-dianilinoterephthalic acid, a 2,5-dianilino-3,6-dihydroterephthalic acid ester, and/or a derivative thereof,(ii) about 3 to about 15 parts by weight, per part of component (a)(i), of a dehydrating agent, and(iii) about 0.

Abstract: This invention relates to pigment compositions comprising an organic pigment treated with about 0.1 to about 20% by weight, based on the organic pigment, of an N-heteroarylamidomethyl pigment derivative having the formula (I) ##STR1## wherein, Q represents an organic pigment moiety,NHet represents a nitrogen-containing heteroaromatic group attached at a ring nitrogen atom to the carbonyl function of the amidomethyl linking group, andn is from 1 to 4.

Abstract: This invention relates to a process for the preparation of quinacridone pigments comprising(a) heating, at a temperature of about 80.degree. C. to about 145.degree. C., a reaction mixture comprising(i) 2,5-dianilinoterephthalic acid or a 2,5-dianilinoterephthalic acid derivative having one or more substituents in at least one aniline ring,(ii) about 2 to about 10 parts by weight, relative to component (a)(i), of a dehydrating agent, and(iii) about 0.01 to about 10 percent by weight, relative to component (a)(i), of a salt other than an iron salt;(b) drowning the reaction mixture from step (a) by adding said reaction mixture to about 3 to about 15 parts by weight, relative to component (a)(i), of a liquid in which the pigment is substantially insoluble;(c) isolating the quinacridone pigment; and(d) optionally, conditioning the quinacridone pigment.

Abstract: This invention relates to a process for the preparation of quinacridone pigments comprising(a) heating, at a temperature of about 80.degree. C. to about 145.degree. C., a reaction mixture comprising(i) 2,5-dianilinoterephthalic acid or a 2,5-dianilinoterephthalic acid derivative having one or more substituents in at least one aniline ring,(ii) about 2 to about 10 parts by weight, relative to component (i), of a strong acid, and(iii) at least about 0.4 mole percent, relative to component (i), of iron in the form of an iron salt;(b) drowning the reaction mixture from step (a) by adding said reaction mixture to about 3 to about 15 pads by weight, relative to component (i), of a liquid in which the pigment is substantially insoluble;(c) isolating the quinacridone pigment; and(d) optionally, conditioning the quinacridone pigment.