The transient oxidation of the electrode material or a constituent of the electrolyte has been used to generate an internal reference system. This technique is convenient for standardizing the reference electrodes used in fused electrolytes at high temperatures. Applications are described for the model case of fused NaCl + KCl, where the internal reference system is either the couple Pt2+/Pt (platinum working electrode) or the couple Cl2/Cl- (oxidation of the constitutive Cl- ions at a carbon electrode). The standard potentials of the internal systems are determined from cyclic voltammetry.