1.10.17: Gibbs Energies- Salt Solutions- Lattice Models
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]
- J. C. Ghosh, J. Chem. Soc., 1918, 449, 627, 707, 790.
- H. S. Frank and P. T. Thompson, in Structure of Electrolytic Solutions, ed. W. J. Hamer, Wiley, New York, 1959, p.113.
- J. E. Desnoyers and B. E. Conway, J. Phys. Chem., 1964, 68 , 2305.
- L. Bahe, J. Phys. Chem., 1972, 76 , 1062, 1608.
- C. W. Murphy, J. Chem. Soc. Faraday Trans. 2, 1982, 78 , 881.
- B. N. Ghosh, J. Ind. Chem. Soc., 1983, 60 , 141, 607; 1981, 58 , 675; 1984, 61 , 213.
- 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