Phenolphthalein is widely used as a pH indicator in acid-base titrations. In acidic or neutral solutions, it remains colorless, but it turns a distinct pink color in basic solutions, typically at a pH around 8.3 to 10. This property makes it a valuable tool in chemistry labs for determining the endpoint of titrations involving strong acids and bases. Beyond titrations, it is also employed in educational settings to demonstrate pH changes visually. Additionally, phenolphthalein has been used in medical applications, particularly as a laxative, though its use for this purpose has declined due to safety concerns. In forensic science, it is utilized in the Kastle-Meyer test to detect the presence of blood, where it reacts with hemoglobin to produce a pink color. Its versatility in various fields underscores its importance as a chemical reagent.