Phenolphthalein
Synonyms
1(3H)-Isobenzofuranone, 3,3-bis(4-hydroxyphenyl)-
Ap-La-Day
Ex-Lax
Feen-A-Mint
Laxatone
Laxettes
Modane
Thalinol
An acid-base indicator which is colorless in acid solution, but turns pink to red as the solution becomes alkaline. It is used medicinally as a cathartic.