tetrasodium [(9,10-dihydro-9,10-dioxoanthracene-2,6-diyl)bis(sulphonylimino)]bismethanesulphonate

[[(9,10-Dihydro-9,10-dioxoanthracene)-2,6-diyl]bis[sulfonyl(sodioimino)]]bis(methanesulfonic acid sodium) salt