Phenolphthalein

2 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Phenolphthalein \Phe`nol*phthal"e*in\, or Phenol phthalein
  \Phenol phthalein\, n. (Chem.)
     A white or yellowish white crystalline substance, {C20H14O4},
     formed by condensation of the anhydride of phthalic acid and
     phenol. Its solution in alkalies is brilliant red, but is
     decolorized by acids. This reaction, being very delicate, is


     used as a pH indicator. It is sometimes used as a laxative in
     veterinary medicine.
     [Webster 1913 Suppl. +PJC]

From WordNet (r) 2.0 [wn]:

  phenolphthalein
       n : a laxative used in many preparations under various trade
           names; also used as an acid-base indicator in titrations
           involving weak acids and strong bases because it is
           brilliant red at high alkalinity and colorless below pH 8