disodium 4-[[2,4-dihydroxy-3-[(2-hydroxy-4-nitrophenyl)azo]-5-[(4-nitrophenyl)azo]phenyl]azo]-5-hydroxynaphthalene-2,7-disulphonate;4-[[2,4-Dihydroxy-3-[(2-hydroxy-4-nitrophenyl)azo]-5-[(4-nitrophenyl)azo]phenyl]azo]-5-hydroxy-2,7-naphthalenedisulfonic acid disodium salt