A theory of electrical conductivity of molten salt. IIThe electrical conductivities of molten CuCl, HgCh, HgBr2, SnCh, Inla, ZnI2, ZnCh, TlCl, TIBr, TIl, and HgI2 were measured to temperatures as high as 1200°C. Maxima in conductivity as the temperature was increased were found in the first six salts. Since molten BiCla, BiBr3, Bil s , CdI 2 , Gals, pure water, and aqueous solutions containing weak and strong electrolytes also exhibit a conductivity maximum at elevated temperatures, it is concluded that this behavior is general to aU fluids at sufficiently high temperature and sufficiently reduced density. These maxima in fused salts are attributed to increasing covalency or ionic association as the density decreases.

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Vol. 63 as shown by the initial circled point on the curve in dows and examining the mica surfaces under the electron microscope, and Joseph Gabor, Bernard Girman and Norman Isaacs for assistance in the experimental work.

The excess free energy of mixing of molten reciprocal salt solutions (A+, B+, X—, Y—) has been calculated up to the second order by the perturbation method of Reiss, Katz, and Kleppa. The result is a power series containing integral powers of the ion fractions (concentrations). This demonstrates that mixtures of two salts of the same valence type cannot be considered as a mixture of a salt with a dielectric solvent. The first term in the series is proportional to the free-energy change for the reaction AX+BY→AY+BX and is the same as the theory of Flood, Fo/rland, and Grjotheim. The results of the symmetric approximation based upon the quasilattice model are consistent with the first term and one of the second-order terms. The remaining second-order terms are related to the excess free energy of mixing in the binary systems AX—AY, BX—BY, AX—BX, AY—BY and are of a form first suggested by Fo/rland. This theory, thus, gives a relatively rigorous justification to aspects of previous theories of reciprocal salt solutions which were based upon restrictive models and assumptions.

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