The subject of electroanalytical chemistry encompasses all analytical techniques which are based on electrode potential and current measurements at the surfaces of electrodes immersed in the solution tested. Electroanalytical techniques are an extension of classical oxidation-reduction chemistry, and indeed oxidation and reduction processes occur at or within the two electrodes, oxidation at one and reduction at the other. Electrons are consumed by the reduction process at one electrode and generated by the oxidation process at the other. Electroanalytical techniques which measure or monitor electrode potential utilize the galvanic cell concept. Such techniques fall under the general heading of “potentiometry.” Examples include the pH measurement, ion-selective electrode measurement, and potentiometric titrations. The measurement of any voltage is a relative measurement and requires an unchanging reference point. In electroanalytical chemistry, the unchanging reference is a portable half-cell that is designed to develop a potential that is constant.