Chromium, 2,4-dihydro-4-[(2-hydroxy- 5-nitrophenyl)azo]-5-methyl-2-phenyl-3H-pyrazol-3 -one 4-hydroxy-3-[(2-hydroxy-1- naphthalenyl)azo]benzenesulfonamide N-[7-hydroxy-8-[(2-hydroxy- 5-nitrophenyl)azo]-1-naphthalenyl]acetamide sodium complexes