Synonyms: 2,7-Naphthalenedisulfonicacid, 3-hydroxy-4-[(4-nitrophenyl)azo]- (9CI); 2,7-Naphthalenedisulfonic acid,3-hydroxy-4-[(p-nitrophenyl)azo]- (7CI,8CI); 2-Naphthol-3,6-disulfonic acid,1-(p-nitrophenylazo)- (6CI);1-(p-Nitrophenylazo)-2-hydroxynaphthalene-3,6-disulfonic acid; NCI 45540; b-Naphtholviolet