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EMF Measurements in Molten Salts*

  • Jerry Braunstein
  • Helen Braunstein

Abstract

An e.m.f. measurement is capable, in principle, of providing directly the free energy of the cell process, and therefore all the thermodynamic information obtainable from the free energy and its derivatives. E.m.f. measurements may therefore provide free energies of formation of pure molten salts, free energies of mixing in binary molten salt mixtures, excess chemical potentials of selected components in multicomponent molten salt mixtures, and equilibrium constants for homogeneous and heterogeneous reactions of dissolved species. Because of the inherent accuracy of electrical measurements, e.m.f. measurements are capable of yielding accurate thermodynamic quantities. The essential requirements for accuracy include the establishment of local equilibrium within each phase in the cell and between adjacent phases; and, simultaneously, the maintenance of constraints against irreversible processes such as direct chemical reaction of the electrode materials and electronic conduction through the electrolyte. Such irreversible processes constitute chemical or electrical partial short circuits of the cell e.m.f., and invalidate the basic equilibrium thermodynamic equation relating the electromotive force of a cell. E (volts), to the electrical work obtainable from the cell reaction isothermally and isobarically, by reversible transfer of nF coulombs of charge, and hence to the Gibbs free energy change of the process occurring in the cell.

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© Springer Science+Business Media New York 1968

Authors and Affiliations

  • Jerry Braunstein
    • 1
  • Helen Braunstein
    • 1
  1. 1.Chemistry DivisionOak Ridge National LaboratoryTennesseeUSA

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