Contributions to molten salt chemistry by Ole J. Keppa

Abstract

Ole Kleppa and coworkers have accurately measured the enthalpies of mixing of a large number of binary molten salt systems. These results have also been proven to be useful in the analyses of phase diagrams and in creating a reliable database on free energies of mixing of a large number of systems. He made a general confirmation of a specific result by Hildebrand and Salstrom that excess free energies of mixing of simple binary molten salts could be represented by a simple polynomial, an important result for ionic systems with very long range ionic pair interactions. His measurements of the enthalpies of mixing of all binary alkali nitrates led to an expression which was close to that deduced from a simple model by Førland. This result also catalyzed the Conformal Ionic Solution Theory, the only theory fundamentally valid for molten salts. This theory later led to methods for accurately predicting the solution properties of multicomponent molten salt systems from data on the subsidiary binaries and the pure component salts. His measurements of binary systems with the two components having the same cation and two different anions indicated that deviations from ideality were generally very small. A theoretical extension of this conclusion to silicates and other polymeric slags led to reliable predictions of the solubilities (and sulfide capacities) of ionic compounds. Kleppa’s work has had a major influence on molten salt chemistry