2,4-Dihydro-4-[[5-nitro-2-(sodiooxy)phenyl]azo]-5-methyl-2-phenyl-3H-pyrazol-3-one

2,4-dihydro-4-[(2-hydroxy-5-nitrophenyl)azo]-5-methyl-2-phenyl-3H-pyrazol-3-one, sodium salt