Synonyms: 1,2-Benzenediol,4,4'-(3H-2,1-benzoxathiol-3-ylidene)bis-, S,S-dioxide;Pyrocatechol violet(6CI);Pyrocatechol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)di-, S,S-dioxide(8CI);3H-2,1-Benzoxathiole,3,3-bis(3,4-dihydroxyphenyl)-, 1,1-dioxide;Catechol violet;NSC 8805;PKF;Pyrocatechin sulfonephthalein;Pyrocatechin violet;Pyrocatecholsulfonephthalein;