Abstract Phenolphthalein is one of the most common acid-base indicators.It is colorless when pH is below 8.2 and red when pH is between 8.2 and 10.0.But little attention was paid to the phenomenon of phenolphthalein fading slowly and colorless eventually in strong alkaline solution.By measuring absorbance change of solution of phenophthalein while it fades slowly in strong alkaline solution,rate constant and reaction order of phenolphthalein are determined.This experiment can help students understand basic concepts of chemical kinetics better.
