2-Naphthalenesulfonic acid, 5,5'-[thiobis(4,1-phenyleneazo)]bis[6-hydroxy-, disodium salt 2-Naphthalenesulfonic acid, 5,5'-[thiobis(p-phenyleneazo)]bis[6-hydroxy-, disodium salt 6661-25-2 C.I. 25110 Milling Red G NSC73416