Article
Article
Acid-base indicator
Article By:
Hanson, Allen L. Formerly, Department of Chemistry, Saint Olaf College, Northfield, Minnesota.
Last reviewed:February 2018
DOI:https://doi.org/10.1036/1097-8542.004600
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An organic compound that changes color with the acidity or basicity (pH) of a solution; also known as a pH indicator. Indicators are weak organic acids or bases that exist in more than one structural form (tautomers), of which at least one form is colored. Intense color is desirable so that very little indicator is needed; the indicator itself will thus not affect the acidity of the solution to which it is added. Indicators do not precisely measure pH, but change color over a pH range (Fig. 1). See also: Acid and base; pH; Tautomerism
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