Bromothymol blue indicator is used as a chemical indicator for weak acids and bases. It acts as a weak acid in solutions. Bromothymol blue indicator is used in measuring substances that have low acid and base levels. Obstetricians use it to check for premature problems in a pregnancy. Middle school classes use bromothymol blue indicator to show the correlation between exercise and carbon
. dioxide. Check this link for more information on bromothymol blue indicator: http://www.absoluteastronomy.com/topics/Bromothymol_blue.