1-amino-9,10-dihydro-9,10-dioxo-4-[3-[[2-(sulphothio)ethyl]sulphonyl]anilino]anthracene-2-sulphonic acid, potassium sodium salt

1-Amino-9,10-dihydro-9,10-dioxo-4-[[3-[[2-(sulfothio)ethyl]sulfonyl]phenyl]amino]-2-anthracenesulfonic acid/sodium/potassium,(1:x:x) salt