trisodium 2,5-dichloro-4-[(4Z)-4-[[5-[[4-chloro-6-[(4-sulfonatophenyl) amino]-1,3,5-triazin-2-yl]amino]-2-sulfonato-phenyl]hydrazinylidene]-3 -methyl-5-oxo-pyrazol-1-yl]benzenesulfonate