Synonyms: Benzenesulfonicacid, 4-[(2,4-dihydroxyphenyl)azo]- (9CI); Benzenesulfonic acid,p-[(2,4-dihydroxyphenyl)azo]- (8CI); Benzenesulfonic acid,p-[(dihydroxyphenyl)azo]- (6CI); C.I. Acid Orange 6 (free acid) (7CI);2,4-Dihydroxyazobenzene-4'-sulfonic acid;4-(2,4-Dihydroxyphenylazo)benzenesulfonic acid