Synonyms: 2,7-Naphthalenedisulfonicacid, 3-hydroxy-4-[(4-sulfo-1-naphthalenyl)azo]- (9CI);2-Naphthol-3,6-disulfonic acid, 1-(4-sulfo-1-naphthylazo)- (6CI);1-(4-Sulfonaphthylazo)-2-hydroxynaphthalene-3,6-disulfonic acid;1-(4'-Sulfo-1'-naphthylazo)-2-naphthol-3,6-disulfonic acid;3-Hydroxy-4-(4-sulfonaphthylazo)-2,7-naphthalenedisulfonic acid;3-Hydroxy-4-[(4-sulfo-1-naphthyl)azo]-2,7-naphthalenedisulfonic acid; C.I. AcidRed 27 free acid