What Is a Redox Indicator in Chemistry

A redox indicator is an indicator compound that changes color at specific potential differences.A redox indicator compound must have a reduced and oxidized form with different colors and the redox process must be reversible. Further, the oxidation-reduction equilibrium needs to be reached quickly. Only a few classes of compounds are useful as redox indicators: Phenanthroline and bipyridine metal complexes: The metallorganic systems change color as the metal changes its oxidation state.Organic redox compounds: In these indicators, a proton participates in the redox reaction. An example of this type of indicator is methylene blue. Redox Indicator Examples The molecule 2,2-Bipyridine is a redox indicator. In solution, it changes from light blue to red at an electrode potential of 0.97 V. Sources Hewitt, L.F. Oxidation-Reduction Potentials in Bacteriology and Biochemistry. Oxidation-Reduction Potentials in Bacteriology and Biochemistry. 6th Ed. (1950).Ram W. Sabnis, Erwin Ross, Jutta KÃ ¶the, Renate Naumann, Wolfgang Fischer, Wilhelm-Dietrich Mayer, Gerhard Wieland, Ernest J. Newman, Charles M. Wilson (2009). Ullmanns Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a14_127.pub2