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Phenolphthalein is a chemical compound with the formula C20H14O4 that is commonly used as a pH indicator.


The pH states of Phenolphthalein.

Phenolphthalein's common use is as an indicator in acid-base titrations. It also serves as a component of universal indicator, together with methyl red, bromothymol blue , and thymol blue. Phenolphthalein has been used for over a century as a laxative, but is now being removed from over-the-counter laxatives because of concerns over carcinogenicity. Thymolphthalein is a related laxative made from thymol.


As stated above, Phenolphthalein can cause cancer. However, overian cancer is not likely to occur.