Thermodynamics of aqueous electrolytes : temperature dependence of the heats of mixing of anions

The study of specific Ionic Interactions are facilitated by the study of heats of mixing of aqueous electrolytes. Much work has been done with systems at 25°C, but very little work has been done at hiqher temperatures. In addition, the vast majority of work In this type study has been done with common anion mixings. In order to gain knowledqe in the field of solute-solvent Interactions a study of common cation Interactions at elevated temperatures Is considered necessary. The systems studied were KCI-KBr-H20, KCI-KF-H20, KCI-KC2H302- H20, and KF-KC2H 0 -H20 at 1.0 molal and constant ionic strength. Temperatures studied were 40°, 60° and 80°C. A new adibatlc microcalorimeter was used in the work. AlI of the systems studied showed little or no temperature dependence. This result tends to add validity to the numerous results by other authors who state that the heat of mixing is mainly influenced by interactions occurring at the Interface of the primary and secondary hydration spheres of the ions in aqueous solutions