pink or red powder
As indicator, pH 3.0 yellow; pH 4.6 purple.
An electrophoresis tracking dye also used as an acid-base indicator
ChEBI: 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
size marker for monitoring the progress of agarose gel and polyacrylamide gel electrophoresis. It has also been used as an industrial dye.
Crystallise the dye from *C6H6 or Me2CO/AcOH, and dry it in air. It is an indicator: at pH 3.0 it is yellow and it is purple at pH 4.6. [Beilstein 19/3 V 458.]