Phenolphthalein sample (center) with original bottle (left) and in solution at acidic and neutral pH (colorless) and basic pH (pink)
| IUPAC name
| Systematic IUPAC name
| Other names
|Molar mass||318.33 g/mol|
|Density||1.3 g/cm3 (at 20 °C)|
|Melting point||262.5 °C (504.5 °F; 535.6 K)|
|0.04 g/100 ml|
|Solubility|| Very soluble in acetone, ethanol and pyrene|
Soluble in chloroform, diethyl ether, and toluene
Slightly soluble in carbon disulfide
Insoluble in benzene, hexane, petroleum ether
|Vapor pressure||6.7·10-13 mm Hg at 25 °C|
|Safety data sheet||Acros Organics|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Phenolphthalein is an organic chemical compound, often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions.
Phenolphthalein is colorless at acidic and neutral pH and pink at basic pH.
Phenolphthalein is sold by various chemical suppliers.
- 2 C6H5OH + C6H4C2O3 → C20H14O4
- Base indicator
- Ferroxyl indicator solution
- Kastle–Meyer test
Phenolphthalein, if taken orally, is mildly toxic, a suspected carcinogen and a powerful laxative. Several decades ago, it was commonly used as such in medicine. Today, less toxic laxatives are used.
Phenolphthalein should be kept in closed bottles, away from acidic vapors.
- Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V4 3297