The Temperature Coefficients of Electrode Potentials

Abstract

The temperature coefficient of the potential of an electrode can be defined experimentally by reference to (a) the potential of the SHE at the same temperature, (b) the potential of the same electrode at some fixed temperature. These two definitions give rise to the "isothermal" and "thermal" temperature coefficients of electrode potentials. The isothermal coefficient is AS/nF where ~S is the reaction entropy of the "SHE//Electrode" cell. The thermal coefficient is S*/nF where S* is the entropy transported from the hot to the cold heat reservoir by the passage of n faradays of positive electricity through the cell from the cold to the hot electrode (before the onset of thermal diffusion). The entropy S* is divided into an entropy S*E of electrochemical transport which determines the electrode temperature effect, and an entropy S*. of migration transport which determines the thermal liquid junction potential.By assuming that S*~ is negligible in a saturated potassium chloride bridge, we have deduced that the thermal temperature coefficient of the SHE is +0.871 mv/~ [hot electrode (+) terminal] at 25~ The standard ionic entropy S* ~ of electrochemical transport of hydrogen ion is --4.48 cal/deg. Thermal temperature coefficients are computed for calomel, silver chloride, and copper sulfate electrodes and are compared with experiment. Thermal and isothermal temperature coefficients are computed and tabulated for nearly 300 standard electrode potentials.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.174.255.116 Downloaded on 2015-03-10 to IP Vol. 106, No. 7 COEFFICIENTS OF ELECTRODE POTENTIALS ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.174.255.116 Downloaded on 2015-03-10 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.174.255.116 Downloaded on 2015-03-10 to IP

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