1,2-Benzenediol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)bis-, S,S-dioxide 115-41-3 3H-2,1-Benzoxathiole, 3,3-bis(3,4-dihydroxyphenyl)-, 1,1-dioxide Catechol violet NSC8805 PKF Pyrocatechinsulfonephthalein Pyrocatechol Violet Pyrocatechol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)di-, S,S-dioxide