1,3-Naphthalenedisulfonic acid, 7,7'-(carbonylbis(imino(3-methoxy-4,1-phenylene)azo))bis-, tetrasodium salt 68227-41-8 EINECS 269-353-8 Tetrasodium 7,7'-(carbonylbis(imino(3-methoxy-4,1-phenylene)azo))bisnaphthalene-1,3-disulphonate