disodium 1-amino-9,10-dihydro-9,10-dioxo-4-[4-[(4-sulphonatophenyl)azo]anilino]anthracene-2-sulphonate

1-Amino-9,10-dihydro-9,10-dioxo-4-[[4-[(4-sulfophenyl)azo]phenyl]amino]-2-anthracenesulfonic acid disodium salt