Chromate(2-),[3-[(5,8-dichloro-2-hydroxy-1-naphthalenyl)azo]-4-hydroxybenzenesulfonamidato(2-)][3-hydroxy-4-[(2-hydroxy-1-naphthalenyl)azo]-7-nitro-1-naphthalenesulfonato(3-)]-,disodium (9CI)