has role phenol red 3,3-bis(p-hydroxyphenyl)-3H-2,1-benzoxathiole 1,1-dioxide 354.056 354.37600 3H-2,1-Benzoxathiole 1,1-dioxide in which both of the hydrogens at position 3 have been substituted by 4-hydroxyphenyl groups. A pH indicator changing colour from yellow below pH 6.8 to bright pink above pH 8.2, it is commonly used as an indicator in cell cultures and in home swimming pool test kits. It is also used in the (now infrequently performed) phenolsulfonphthalein (PSP) test for estimation of overall blood flow through the kidney. 4,4'-(1,1-dioxido-3H-2,1-benzoxathiole-3,3-diyl)diphenol 4,4'-(3H-2,1-benzoxathiol-3-ylidene)bisphenol S,S-dioxide BELBBZDIHDAJOR-UHFFFAOYSA-N Beilstein:326470 C19H14O5S CAS:143-74-8 CHEBI:31991 Drug_Central:3439 InChI=1S/C19H14O5S/c20-15-9-5-13(6-10-15)19(14-7-11-16(21)12-8-14)17-3-1-2-4-18(17)25(22,23)24-19/h1-12,20-21H KEGG:C12600 KEGG:D01200 Oc1ccc(cc1)C1(OS(=O)(=O)c2ccccc12)c1ccc(O)cc1 PSP Phenol red Phenolsulfonphthalein alpha-hydroxy-alpha,alpha-bis(p-hydroxyphenyl)-o-toluenesulfonic acid gamma-sultone chebi_ontology phenols 2,1-benzoxathiole sultone arenesulfonate ester acid-base indicator two-colour indicator