Phenolphthalein is widely used as a pH indicator in various chemical experiments and laboratory procedures. It is particularly useful in acid-base titrations, where it changes color from colorless in acidic solutions to pink or magenta in basic solutions, typically around a pH of 8.3 to 10. This property makes it an essential tool for determining the endpoint of titrations, ensuring accurate measurements of acidity or alkalinity.

In addition to its role in titrations, phenolphthalein has been historically used in medical applications as a laxative. However, its use in this capacity has significantly declined due to concerns about potential carcinogenic effects and other health risks. Despite this, it remains a valuable chemical in educational settings for teaching students about pH and chemical reactions.

Phenolphthalein is also employed in forensic science to detect the presence of blood. When mixed with hydrogen peroxide and a catalyst, it can produce a visible color change in the presence of hemoglobin, aiding in crime scene investigations. Its versatility and distinct color-changing properties continue to make it a useful chemical in both scientific and practical applications.