MODEL RELEASED. Titration experiment. Student adding drops of phenolphthalein indicator solution to a solution of citric acid during a titration experiment. A burette will be used to measure the amount of alkali needed to neutralise the acid solution, with a chemical indicator (here, phenolphthalein) showing when the reaction endpoint has been reached. The indicator will initially be colourless, turning pink when the solution becomes alkaline as the acid is neutralised. The measured alkali volume will be compared to the known volume of acid, giving information on reaction chemistry and chemical concentrations.