The thermodynamic approach to a study of electrolytic solutions aims at determining the extent and direction of a chemical reaction by considering the energy changes which take place. These energy changes may be measured experimentally from some property of the system thus giving thermodynamic functions without considering the mechanism of the solution process or alternately, by purely theoretical calculations based on a postulated model for the process. The validity of any theories connected with this latter aspect, which is a difficult and complicated one, are tested by their agreement with the former. Hence any experimental study of a system such as the solubility of an electrolyte with which this work is concerned could, if accurate thermodynamic functions are obtained, supply a small contribution to the knowledge of a mechanism for such a reaction.