09049 IUPAC Gold Book - redox indicator 10.1351/goldbook.09049 09049 current 1 Visual indicator that reacts with excess titrant or titrand with a color change at the end-point of a redox titration. Titration of iodine by thiosulfate (\(\ce{SO3S^{2−}}\)) uses a starch solution to produce a strong blue color. At the end-point, when all diiodine is reacted, the solution becomes colorless. titrand https://goldbook.iupac.org//terms/view/09051 PAC, 2025, 97, 137. 'Glossary of terms for mass and volume in analytical chemistry (IUPAC Recommendations 2024)' on page 5 (https://doi.org/10.1515/pac-2023-0903) https://goldbook.iupac.org/terms/view/09049/html https://goldbook.iupac.org/terms/view/09049/json https://goldbook.iupac.org/terms/view/09049/plain Citation: 'redox indicator' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.09049 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-07-23T20:24:56+00:00