Phenolphthalein is a common acid-base indicators used for titration. It is colorless in acidic (pH < 8.2) and fuchsia at a pH overs 8.2. In strongly basic media (pH over 10) it will slowly become colorless.
While the reaction from the neutral form to the doubly negatively charged is fast, going from [ɸɸ]-2 to [ɸɸH-1]-3 is relatively slow.
The goal of this experiment is determine the kinetic parameters of this second reaction, the conversion of the fuchsia to colorless form obtained that can be observed in strongly basic media.