Phenolphthalein is a chemical compound commonly used as a pH indicator in titrations. It is colorless in acidic solutions and turns pink in basic solutions, typically around a pH of 8.2 to 10.0. This property makes it useful for determining the acidity or alkalinity of a solution. In addition to its role in laboratories, phenolphthalein has applications in various fields, including medicine and environmental science. It was historically used as a laxative, but this use has declined due to safety concerns. Today, it primarily serves as a teaching tool in chemistry education and research.