ELECTROANALYTICAL CHEMISTRY AND INTERFACIAL ELECTROCHEMISTRY 481 Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands THE SILVER-SILVER PERCHLORATE REFERENCE ELECTRODE IN PROPYLENE CARBONATE E. KIROWA-EISNER AND E. GILEADI Institute of Chemistry, Tel-Aviv University, Ramat-Aviv (Israel) (Received November 22rid, 1969) INTRODUCTION Propylene carbonate (PC) has attracted increasing attention in recent years as a non-aqueous solvent in electrochemistry 1, particularly in the field of high energy- density batteries 2. Two reference electrodes suitable for this solvent have been de- veloped : the Li/LiCIO4 electrode 3,4 and the TI(Hg)/T1CI/LiC1 electrode 5,6. Both act reversibly and yield reproducible values of the potential, when carefully prepared. They are, however, very sensitive to traces of oxygen, rather incovenient to prepare, and difficult to store. For these reasons, it was decided to search further for a suitable' reference electrode in PC, which will be easy, to prepare and store. The Cu/Cu 2+ electrode cannot be used because cuprous ions are formed spontaneously in a reaction between metallic copper and cupric ions. A white pre- cipitate formed and the potential was unstable. The Ni/Ni 2+ system was found to be characterized by a very slow response, reaching a steady state potential only after an extended period of time. The Ag/AgC1/C1- secondary electrode was rejected because the solubility of AgC1 in PC is greatly increased in the presence of C1- ions, due to complex formation 7. The Ag/AgC104 reference electrode was found to be very suitable. It is easily prepared, has a sufficiently high exchange current density and consequently has a quick response. It was found to be stable over a period of several weeks and could be easily stored. The preparation and some characteristics of this electrode will be described below. Very recently, the use of this type of reference electrode (Ag/Ag + (0.05 M), NaC104 (0.5 M)) was reported 8. However, no details of its performance were given. EXPERIMENTAL Reagents Propylene carbonate (Jefferson Chemical Company) was purified by distilla- tion at a pressure of 1 torr in an adiabatic fractional distillation column 9. High purity of the solvent was essential for satisfactory operation of the reference elec- trode. The electrolytes used, LiC104 and AgC104 (B.D.H.), were dried at a pressure of 1 torr at 100° and 50°C, respectively, for 24 h. A 0.5 M AgC104 stock solution was prepared and used. J. Electroanal. Chem., 25 (1970) 481~487