Visual indicator that reacts with excess titrant or
titrand with a color change at the end-point of a redox titration.
Example:
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.
Source:
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)