10.7 : 酸化還元滴定: 概要

A redox titration analyzes an oxidation–reduction reaction that occurs between the analyte and the titrant.

The analyte often must be treated with an auxiliary oxidizing or reducing reagent to uniformly convert the analyte to the single oxidation state required for titration.

The completion of the reaction is detected using a potentiometer or a visual indicator.

The visual indicators are of three types: redox indicators, starch indicators, and self-indicators.

Redox indicators are highly colored dyes exhibiting distinct colors in their oxidized and reduced states.

Most of the redox indicators are sensitive to changes in potential during titration. Plotting the potential against the volume of the titrant generates a titration curve.

The redox titration curves are S-shaped and show a steady rise in potential until a sudden jump is observed near the end point of the titration.

Starch indicators are used in iodine titrations, where starch combines with iodine to form a dark-blue complex.

Self-indicators, which can act as both the titrant and the indicator, can also be used in redox titrations.