| PubChem= | SMILES=Oc1ccc(cc1)C3(OC(=O)c2ccccc23)c4ccc(O)cc4 | MeSHName= }} |Section2= |Section3= }} Phenolphthalein's a well-known chemical compound commonly pronounced [ˌfinɔl ˈθei lin]. It's the formula C20H14O4 and's often written as "HIn" or "phph" in shorthand notation. Often used in titrations, it turns colorless in acidic solutions and pink in basic solutions. If the concentration of indicator's particularly strong, it can appear purple. In strongly basic solutions,… (More on Phenolphthalein)