[NeadPay]Bromothymol Blue, also known as bromothymol blue, is an acid-base indicator and adsorption indicator with the chemical formula of C27H28O5SBr2, which is easily soluble in ethanol, ether, methanol and dilute alkaline hydroxide solution. Slightly soluble in benzene, toluene and xylene, slightly soluble in water, almost insoluble in petroleum ether. The English abbreviation is BTB. It is often used as a respiratory reagent for aquatic organisms in biological experiments.