Synonyms: Pyrogallol red;3172-49-4;Pyrogallolsulfonephthalein;Spiro[3H-2,1-benzoxathiole-3,9'-[9H]xanthene]- 3',4',5',6'-tetrol,1,1-dioxide;yl)-;2-(4,5,6-trihydroxy-3-oxo-xanthen-9-yl)benzenesulfonate;Benzenesulfonic acid, 2-(4,5,6-trihydroxy-3-oxo-3H-xanthen-9-yl)-;Spiro(3H-2,1-benzoxathiole-3,9-(9H)xanthene)-3,4,5,6-tetrol, 1,1-dioxide;