Bromothymol blue (3 ', 3'-dibromtimolsulfoftalein) - triphenylmethane dye slightly soluble in water, the acid-base indicator.
Bromothymol blue registers changes in the pH in the range from 5.8 to 7.6, changing its color from yellow to blue through shades of green. Neutral values (pH = 7,0) correspond to grass-green color. Acid dissociation constants (pKa) of bromothymol blue is 7.10.
Analytical himiibromtimolovy blue used in the acid-base titration and determination of neutral pH value (pH = 7,0) in the titration (gains grass-green shade).
Bromothymol blue is used as a colorant in bacteriology in the composition of the nutrient medium as well as fotosensibilizatorav copiers.