72869-20-6 Benzenesulfonic acid, 2-(2-(2-sulfo-4-((4-((4-sulfophenyl)azo)phenyl)azo)phenyl)ethenyl)-5-((4-((4-sulfophenyl)azo)phenyl)azoxy)-, tetrasodium salt Stilbene-2,2'-disulfonic acid, 4-((4-((4-sulfophenyl)azo)phenyl)azo)-4'-((4-((4-sulfophenyl)azo)phenyl)azoxy)-, tetrasodium salt