disodium 2-[[4-[[2-hydroxy-5-[(4-nitro-2-sulphonatophenyl)amino]phenyl]azo]phenyl]amino]-5-nitrobenzenesulphonate

2-[[4-[[2-Hydroxy-5-[(4-nitro-2-sodiosulfophenyl)amino]phenyl]azo]phenyl]amino]-5-nitrobenzenesulfonic acid sodium salt