Science, Tech, Math › Science Redox Indicator Definition (Chemistry) Print This is the chemical structure of 2,2'-bipyridine, a redox indicator. Brian Derksen/PD Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College 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. Learn about our Editorial Process Updated on August 07, 2018 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 Köthe, Renate Naumann, Wolfgang Fischer, Wilhelm-Dietrich Mayer, Gerhard Wieland, Ernest J. Newman, Charles M. Wilson (2009). Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a14_127.pub2 Cite this Article Format mla apa chicago Your Citation Helmenstine, Anne Marie, Ph.D. "Redox Indicator Definition (Chemistry)." ThoughtCo, Aug. 25, 2020, thoughtco.com/definition-of-redox-indicator-605602. Helmenstine, Anne Marie, Ph.D. (2020, August 25). Redox Indicator Definition (Chemistry). Retrieved from https://www.thoughtco.com/definition-of-redox-indicator-605602 Helmenstine, Anne Marie, Ph.D. "Redox Indicator Definition (Chemistry)." ThoughtCo. https://www.thoughtco.com/definition-of-redox-indicator-605602 (accessed April 20, 2024). copy citation