Sulfonaphtholazoresorcinol

3-Hydroxy-4-[(2,4-dihydroxyphenyl)azo]-1-naphthalenesulfonic acid

1-[(2,4-Dihydroxyphenyl)azo]-2-hydroxy-4-naphthalenesulfonic acid

4-[(2,4-dihydroxyphenyl)azo]-3-hydroxynaphthalene-1-sulphonic acid