10.2 : 電極_概要

The potential and current within two-electrode cells are typically measured using a combination of a reference electrode and either a working electrode or an indicator electrode.

In a potentiometric test, the indicator electrode responds proportionally to the analyte's concentration through a redox reaction.

Common types of indicator electrodes include inert metal electrodes, reversibly reactive metal electrodes, and ion-selective membrane electrodes.

Reference electrodes, like the saturated calomel electrode and the silver–silver chloride electrode, have a constant potential at a given temperature, regardless of changes in the analyte composition. They work best when the current flowing through them is low, providing a fixed reference potential for the indicator electrode.

The relative potential of the indicator electrode is measured with respect to the fixed reference potential provided by the reference electrode.

However, for methods where current flow is needed, a third electrode—known as an auxiliary electrode or counter electrode—can be added. These auxiliary electrodes allow current to flow through the cell to complete the electrical circuit.