3-Pyridinemethanesulfonic acid, 5-5-4-2-2-(ethenylsulfonyl)ethoxyethylamino-6-fluoro-1,3,5-triazin-2-ylamino-2-sulfophenylazo-1-ethyl-1,2-dihydro-6-hydroxy-4-methyl-2-oxo-, disodium salt