Xanthylium, 9-(2-carboxyphenyl)-3,6-bis(diethylamino)-, 4-[2-(5-chloro-2-hydroxyphenyl)diazenyl]-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one 2,4-dihydro-4-[2-(2-hydroxy-5-nitrophenyl)diazenyl]-5-methyl-2-phenyl-3H-pyrazol-3-one 3-[2-[1-[[(2-ethylhexyl)amino]carbonyl]-2-oxopropyl]diazenyl]-2-hydroxy-5-nitrobenzoate cobaltate complexes