[ fee-nawl-thal-een, -ee-in, -fthal-, -nol- ]

nounChemistry, Pharmacology.
  1. a white, crystalline compound, C20H14O4, used as an indicator in acid-base titration and as a laxative.

Origin of phenolphthalein

First recorded in 1870–75; phenol + phthalein

Words Nearby phenolphthalein Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use phenolphthalein in a sentence

British Dictionary definitions for phenolphthalein


/ (ˌfiːnɒlˈθeɪliːn, -lɪɪn, -ˈθæl-) /

  1. a colourless crystalline compound used in medicine as a laxative and in chemistry as an indicator. Formula: C 20 H 14 O 4

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for phenolphthalein


[ fē′nōl-thălēn′ ]

  1. A white or pale-yellow, crystalline powder used as an indicator for acid and basic solutions. In solutions that are either neutral or basic, it is colorless, while it is pink or red in solutions that are alkali. It is also used as a laxative and in making dyes. Chemical formula: C20H14O4.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.