Synonyms: 1H-Pyrazole-3-carboxylic acid, 4,5-dihydro-5-oxo-1-(4-sulfophenyl)-4-((4-sulfophenyl)azo)-, reaction products with guanidine hydrochloride N,N'-bis(mixed Ph, tolyl and xylyl) derivs.;1H-Pyrazole-3-carboxylic acid, 4,5-dihydro-5-oxo-1-(4-sulfophenyl)-4-(2-(4-sulfophenyl)diazenyl)-, reaction products with guanidine hydrochloride (1:?) N,N'-bis(mixed Ph, tolyl and xylyl) derivs.;5-oxo-1-(4-sulfophenyl)-4-[(E)-(4-sulfophenyl)diazenyl]-4,5-dihydro-1H-pyrazole-3-carboxylic acid - guanidine hydrochloride (1:1:1)