Skip to main content
Select Source:

phenolphthalein

phenolphthalein (fē´nôlthăl´ēən), or 2,2-Bis(p-hydroxyphenyl) phthalide, C20H14O4, crystalline organic compound. It is used medicinally as a laxative and is widely employed in the laboratory as an indicator of the acidity or basicity of solutions. In pure water it is insoluble, but it is soluble in basic solutions or in ethanol or acetone. In a solution with pH greater than 8 (pH 8 is mildly basic) phenolphthalein is pink to red in color, but at pH less than 8 it is colorless. Phenolphthalein is a phenol derivative of phthalic anhydride.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"phenolphthalein." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 17 Aug. 2017 <http://www.encyclopedia.com>.

"phenolphthalein." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (August 17, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/phenolphthalein

"phenolphthalein." The Columbia Encyclopedia, 6th ed.. . Retrieved August 17, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/phenolphthalein

phenolphthalein

phenolphthalein A dye used as an acid-base indicator. It is colourless below pH 8 and red above pH 9.6. It is used in titrations involving weak acids and strong bases. It is also used as a laxative.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"phenolphthalein." A Dictionary of Biology. . Encyclopedia.com. 17 Aug. 2017 <http://www.encyclopedia.com>.

"phenolphthalein." A Dictionary of Biology. . Encyclopedia.com. (August 17, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/phenolphthalein

"phenolphthalein." A Dictionary of Biology. . Retrieved August 17, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/phenolphthalein