METALS COATED WITH FILMS OF LOW SURFACE ENERGYnAS REFERENCE ELECTRODES FOR THE MEASUREMENTS OF CONTACT POTENTIAL DIFFERENCES

摘要

The central problem in the measurement of the contact potentials of solid and liquid surfaces in gaseous atmospheres is the stability of the contact potential of the reference electrode to which the potential difference between the two is referred. Noble metals, such as gold or platinum, are usually employed as reference electrodes, but, in gaseous atmos¬pheres, their contact potentials can change significantly because of vapor adsorption on the reference surfaces. This occurs even on aged metals, the effect of adsorbed water vapor being especially great. But a metal which has been coated with a low-energy film, such as Teflon or FEP Teflon resin, exhibits little change in the contact potential in a wide variety of polar and nonpolar vapors. This is demonstrated .by the results of recent studies of metals in a nitrogen atmos¬phere in which the water-vapor content was varied from 1% to as high as 91% R. H. Teflon-coated metal reference elec¬trodes have proved to be remarkably stable under these con¬ditions.