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1.10.17: Gibbs Energies- Salt Solutions- Lattice Models

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    Lattice models for salt solutions have attracted and continue to attract interest [1]. Ions in a salt solution are regarded as occupying lattice sites, the lattice parameter increasing as a solution is diluted; solvent molecules occupy the interstices of the lattice. This model for salt solutions generates interest because the distribution of ions about a central reference j-ion is therefore known. This theory requires that \(\ln \gamma_{\pm}\) is a linear function of \(\left(\mathrm{m}_{\mathrm{i}} / \mathrm{m}^{0}\right)^{1 / 3}\) for salt-i; the cube-root law. This dependence is observed for reasonably concentrated salt solutions [2]. Unfortunately convincing evidence for lattice structures is not forthcoming. For example, the electrical conductivities of salt solutions cannot be understood in terms of lattice structures.

    Footnotes

    [1]

    1. J. C. Ghosh, J. Chem. Soc., 1918, 449, 627, 707, 790.
    2. H. S. Frank and P. T. Thompson, in Structure of Electrolytic Solutions, ed. W. J. Hamer, Wiley, New York, 1959, p.113.
    3. J. E. Desnoyers and B. E. Conway, J. Phys. Chem., 1964,68, 2305.
    4. L. Bahe, J. Phys. Chem., 1972,76, 1062, 1608.
    5. C. W. Murphy, J. Chem. Soc. Faraday Trans. 2, 1982,78, 881.
    6. B. N. Ghosh, J. Ind. Chem. Soc., 1983,60, 141, 607; 1981,58, 675; 1984,61, 213.
    7. I. Horsak and I. Slama, Collect. Czech. Chem. Commum., 1987,52, 1672.

    [2] R. A. Robinson and R. H. Stokes, Electrolyte Solutions, Butterworths, London, 2nd. edition revised,1965, pp. 226

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