A New Method for Determining Excess Gibbs Energies in Binary Metal-Carbonate Solid Solutions

W. H. Casey, P. A. Rock, M. M. McBeath, E. M. Walling and J. Chung

Department of Land, Air and Water Resources and the Department of Geology, University of California, Davis, CA 95616, USA
Department of Chemistry, University of California, Davis, CA 95616, USA
Department of Land, Air and Water Resources, University of California, Davis, CA 95616, USA
Department of Chemistry, University of California, Davis, CA 95616, USA
Department of Land, Air and Water Resources University of California, Davis, CA 95616, USA

Summary: This electrochemical method provides a direct measure of the desired thermodynamic data, as opposed to techniques that obtain similar data from small differences between large numbers. The precision of the measured cell voltages for reversible double cells is in the range of ±0.05 to 0.50 mV, which makes the method sufficiently sensitive to detect small changes in the Gibbs energies. In addition, calculation of the Gibbs energies does not require a model for speciation of solutes in complex mixtures, there is also no correction for a liquid-liquid junction potential, and the reversibility of the cell reaction can be established.

Mineralogical Magazine; August 1994 v. 58A; no. 1; p. 156-157; DOI: 10.1180/minmag.1994.58A.1.84
© 1994, The Mineralogical Society
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