Enthalpies of Mixing in Binary Liquid Alkali Iodide Mixtures

Abstract

The enthalpies of mixing of the binary liquid alkali iodide mixtures have been measured at 740°C. The results are compared with similar data for the binary alkali bromide, chloride and fluoride mixtures. They indicate that it is not possible to represent the enthalpies of mixing for a wider range of binary fused salt systems by any simple general formula. However, the results for all the considered binary iodides alone are well represented by a single semiempirical expression ΔHM = N1N2(U0++ − 540δ122kcal/mole. In this expression N1 and N2 are the mole fractions of the two components; δ12 = (d1 − d2) / d1d2, where d1 and d2 are characteristic interionic distances in the two salts, while U0++ represents a numerical estimate of the positive contribution to the enthalpy of mixing which arises from the London–van der Waals interaction between second nearest neighbor cations.