phe·nol·phthal·ein 
(fē′nōl-thălēn′, -thălē-ĭn, -thālēn′, -thālē-ĭn)
(fē′nōl-thălēn′, -thălē-ĭn, -thālēn′, -thālē-ĭn)n.
A white or pale yellow crystalline powder, C20H14O4, used as an acid-base indicator, in making dyes, and formerly in medicine as an over-the-counter laxative.