5-Oxo-1-(4-sulfophenyl)-2-pyrazoline-3-carboxylic acid disodium salt

disodium 4,5-dihydro-5-oxo-1-(4-sulphonatophenyl)-1H-pyrazole-3-carboxylate

1-(4-Sodiooxysulfonylphenyl)-5-oxo-2-pyrazoline-3-carboxylic acid sodium salt