| Member | Definition | Role |
|---|
| bromcresol purple | A member of the class of 2,1-benzoxathioles that is 2,1-benzoxathiole 1,1-dioxide in which both of the hydrogens at position 3 have been substituted by 3-bromo-4-hydroxy-5-methylphenyl groups. A hydrophilic dye that is used as a pH indicator and to measure serum albumin concentrations. | bromocresol purple |
| bromphenol blue | 3H-2,1-Benzoxathiole 1,1-dioxide in which both of the hydrogens at position 3 have been substituted by 3,5-dibromo-4-hydroxyphenyl groups. It is used as a laboratory indicator, changing from yellow below pH 3 to purple at pH 4.6, and as a size marker for monitoring the progress of agarose gel and polyacrylamide gel electrophoresis. It has also been used as an industrial dye. | bromophenol blue |
| bromthymol blue | A member of the class of 2,1-benzoxathioles that is 2,1-benzoxathiole 1,1-dioxide in which both of the hydrogens at position 3 have been substituted by 3-bromo-4-hydroxy-5-isopropyl-2-methylphenyl groups. | bromothymol blue |
| cresol red | A member of the class of 2,1-benzoxathioles that is 2,1-benzoxathiole 1,1-dioxide in which both of the hydrogens at position 3 have been substituted by 4-hydroxy-5-methylphenyl groups. | cresol red |
| phenolsulfonphthalein | 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. | phenol red |