4-(4-Amino-2-sulfophenylazo)-4,5-dihydro-5-oxo-1-(4-sulfophenyl)-1H-pyrazole-3-carboxylic acid

4-[(4-amino-2-sulphophenyl)azo]-4,5-dihydro-5-oxo-1-(4-sulphophenyl)-1H-pyrazole-3-carboxylic acid