4-(4-((3-Chloro-2-hydroxy-5-nitrophenyl)azo)-4,5-dihydro-3-methyl-5-oxo-1H-pyrazol-1-yl)benzenesulphonic acid 83784-13-8 Benzenesulfonic acid, 4-(4-((3-chloro-2-hydroxy-5-nitrophenyl)azo)-4,5-dihydro-3-methyl-5-oxo-1H-pyrazol-1-yl)- EINECS 280-844-6