p-[4-[[1,5-dihydro-3-methyl-5-oxo-1-(4-sulphophenyl)-4H-pyrazol-4-ylidene]methyl]-4,5-dihydro-3-methyl-5-oxo-1H-pyrazol-1-yl]benzenesulphonic acid

4-[[4,5-Dihydro-4-[[[1,5-dihydro-3-methyl-5-oxo-1-(4-sulfophenyl)-4H-pyrazol]-4-ylidene]methyl]-3-methyl-5-oxo-1H-pyrazol]-1-yl]benzenesulfonic acid