1,4-Benzenedisulfonic acid, 2-[3-acetyl-4-[5-[3-acetyl-1-(2,5-disulfophenyl)-1,5-dihydro-5-oxo-4H-pyrazol-4-ylidene]-1,3-pentadien-1-yl]-4,5-dihydro-5-oxo-1H-pyrazol-1-yl]-, sodium salt (1:?)