Three-electrode cells comprise (1) an indicator (or test) electrode or a @[email protected], at the surface of which processes that are of interest may occur, (2) a @[email protected] and (3) a third electrode, the auxiliary or counter electrode, which serves merely to carry the current flowing through the cell, and at the surface of which no processes of interest occur. If processes of interest occur at both the @[email protected] and the @[email protected] of a cell (as in differential amperometry or controlled current potentiometric @[email protected] with two indicator electrodes), the cell should be said to comprise two indicator (or test) working electrodes.
Orange Book, 2nd ed., p. 59 [Terms] [Book]