<p><strong>Phenolphthalein Definition: </strong>Phenolphthalein is an <a href="https://www.thoughtco.com/definition-of-organic-chemistry-604593" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">organic</a> <a href="https://www.thoughtco.com/definition-of-compound-605842" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="2">compound</a> often used as an pH indicator.<br/><br/>Phenolphthalein turns pink in <a href="https://www.thoughtco.com/definition-of-ph-in-chemistry-604605" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="3">pH</a> greater than 8.3 and colorless in acidic solutions.<br/><br/>The chemical formula for phenolphthalein is C<sub>20</sub>H<sub>14</sub>O<sub>4</sub>.</p><p><a href="https://www.thoughtco.com/phenolphthalein-indicator-solution-608145" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="4">Make Phenolphthalein Indicator</a></p>