9,10-Dihydro-1,8-dihydroxy-4,5-dinitro-9,10-dioxo-2,7-anthracenedisulfonic acid 2-potassium salt

potassium hydrogen -9,10-dihydro-1,8-dihydroxy-4,5-dinitro-9,10-dioxoanthracene-2,7-disulphonate