2,7-Naphthalenedisulfonic acid, 4-((2,4-dihydroxyphenyl)azo)-5-hydroxy-, disodium salt 63589-22-0 Disodium 4-((2,4-dihydroxyphenyl)azo)-5-hydroxynaphthalene-2,7-disulphonate EINECS 264-346-6