6-[[2,4-Dihydroxy-3-[(4-nitrophenyl)azo]phenyl]azo]-4-hydroxy-3-[(2-hydroxy-3-nitro-5-sulfophenyl)azo]-2-naphthalenesulfonic acid

6-[[2,4-dihydroxy-3-[(4-nitrophenyl)azo]phenyl]azo]-4-hydroxy-3-[(2-hydroxy-3-nitro-5-sulphophenyl)azo]naphthalene-2-sulphonic acid