1-Naphthalenesulfonic acid, 3,3'-[1,2-ethenediylbis [(3-sulfo-4,1-phenylene)azo]]bis[4-hydroxy-, tetrasodium salt 2,2'-Stilbenedisulfonic acid, 4,4'-[(1-hydroxy-4-sulfo- 2-naphthyl)azo]-, tetrasodium salt 6962-42-1 NSC34931