1,5-Naphthalenedisulfonic acid, 3,3'-(carbonylbis(imino(2,5-dimethyl-4,1-phenylene)azo))bis-, tetrasodium salt 6420-29-7 EINECS 229-154-9 Tetrasodium 3,3'-(carbonylbis(imino(2,5-dimethyl-4,1-phenylene)azo))bisnaphthalene-1,5-disulphonate