Phenolphthalein is widely used as a pH indicator in various laboratory experiments and chemical analyses. It is particularly useful in acid-base titrations, where it changes color from colorless in acidic solutions to pink in basic solutions, typically around pH 8.2 to 10. This property makes it a valuable tool for determining the endpoint of titrations involving strong acids and bases.

In addition to its role in titrations, phenolphthalein has been used in educational settings to demonstrate pH changes and chemical reactions, helping students visualize the concept of acidity and alkalinity. It is also employed in some medical applications, such as in laxatives, although its use in this area has declined due to safety concerns.

Furthermore, phenolphthalein is utilized in forensic science for detecting the presence of blood, as it reacts with hemoglobin to produce a color change. This application is particularly useful in crime scene investigations. Overall, phenolphthalein's versatility in indicating pH and its reactivity with certain compounds make it a significant chemical in both scientific and practical contexts.