2,4-Dimethyl-5-((5-((4-sulfophenyl)azo)-2,4-dihydroxyphenyl)azo)benzenesulfonic acid, disodium salt 72749-81-6 Benzenesulfonic acid, 5-((2,4-dihydroxy-5-((4-sulfophenyl)azo)phenyl)azo)-2,4-dimethyl-, disodium salt