Synonyms: (1,1'-Biphenyl)-2,2'-disulfonic acid, 4,4'-bis(2-(4,5-dihydro-3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)diazenyl)-, compd. with N,N'-diphenylguanidine (1:2);(1,1'-Biphenyl)-2,2'-disulfonic acid, 4,4'-bis((4,5-dihydro-3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)azo)-, dihydrogen, compd. with (guanidine, N,N'-diphenyl-) (1:2);(1,1'-Biphenyl)-2,2'-disulfonic acid, 4,4'-bis((4,5-dihydro-3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)azo)-, compd. with N,N'-diphenylguanidine (1:2);4,4'-Bis((4,5-dihydro-3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)azo)(1,1'-biphenyl)-2,2'-disulphonic acid, compound with N,N'-diphenylguanidine (1:2)