disodium 9,10-dihydro-1,4-dihydroxy-9,10-dioxo-3-(4-sulphonatophenoxy)anthracene-2-sulphonate

9,10-Dihydro-1,4-dihydroxy-9,10-dioxo-3-(4-sulfophenoxy)-2-anthracenesulfonic acid disodium salt