2,7-Naphthalenedisulfonic acid, 4,4'-(carbonylbis(imino(5-dimethoxy-2-methyl-4,1-phenylene)azo))bis-, tetrasodium salt 82996-64-3 EINECS 280-086-6 Tetrasodium 4,4'-(carbonylbis(imino(5-dimethoxy-2-methyl-4,1-phenylene)azo))bisnaphthalene-2,7-disulphonate