Bromothymol blue is synthesized by addition of elemental bromine to thymol blue in a solution in glacial acetic acid.
To prepare a solution for use as pH indicator, dissolve 0.10 g in 8.0 cm N/50 (a.k.a. 0.02 Normal) NaOH and dilute with water to 250 cm. To prepare a solution for use as indicator in volumetric work, dissolve 0.1 g in 100 cm of 50% (v/v) ethanol.