Bromothymol blue (also known as bromothymol sulfone phthalein and BTB) is a pH indicator.It is typically sold in solid form as the sodium salt of the acid indicator.
Bromothymol blue is a pH indicator which is sparingly soluble in water, benzene but is soluble in ethanol. It is insoluble in petroleum ether.Bromthymol blue is a weak acid.This reagent is yellow in acidic solutions, blue in basic solutions and green in neutral solution.