Phenolphthalein Definition

This is the chemical structure of phenolphthalein.
This is the chemical structure of phenolphthalein. Ben Mills/PD
by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated March 08, 2017

Phenolphthalein Definition: Phenolphthalein is an organic compound often used as an pH indicator.

Phenolphthalein turns pink in pH greater than 8.3 and colorless in acidic solutions.

The chemical formula for phenolphthalein is C20H14O4.