phenolphthalein

n. (Chemistry) crystalline chemical compound (used as a laxative)

Phenolphthalein is a chemical compound with the formula C20H14O4 (often written as "HIn" in shorthand notation). Often used in titrations, it turns colorless in acidic solutions and pink in basic solutions. If the concentration of indicator is particularly strong, it can appear purple. In solutions containing a pH below 0, phenolphthalein turns a bright orange color.
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Noun
1. 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
(hypernym) laxative

n. phenolphthalein, (Chemistry) crystalline chemical compound (used as a laxative)

An organic compound used as an acid-base indicator. The compound is colorless in acidic solution and pink in basic solution (with the transition occuring around pH 8.3). Phenolpthalein was used for many years as a laxative in very low concentrations- high concentrations are toxic!