3-[Methyl(2-sulfoethyl)amino]-6-[[2-[4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]ethyl]amino]-9-(2-sulfonatophenyl)xanthylium/sodium,(1:x)

dihydrogen -3-[methyl(2-sulphonatoethyl)amino]-6-[[2-[4-[[2-(sulphonatooxy)ethyl]sulphonyl]phenyl]ethyl]amino]-9-(2-sulphonatophenyl)xanthylium , sodium salt