STUDIES ON IONIC SOLVATION: PART III. NEW THEORY FOR CALCULATING HEATS OF HYDRATION OF MONOVALENT IONS AT 25 °C
From Part I of this series, the structure of solution around a completely hydrated monovalent ion could be visualized. On the basis of this picture, the ionic heats of hydration is to be due to three terms. These three terms are critically discussed and evaluated for the case of alkali metals and halide ions.The present theory shows that the Born–Bjerrum term contributes a significant part to the heat and that the ionic radius value included in this term must be dependent only on the charge and not on the ionic size. The most probable value is 2.4 Å for the positive ions and 2.9 Å for the negative ions.The calculated ionic heats of hydration, which are in good agreement with the experimental values, are compared with those of previous theories.