The standard partial molar volumes of ions in solution

The standard partial molar volumes of univalent ions in a variety of solvents are calculated as the sum of their intrinsic volume and a (negative) electrostrictive volume or, for tetraalkyl- or aryl ions, structural contributions. The shell-by-shell calculation of the electrostriction according to Marcus and Hefter takes into account the mutual dependence of the relative permittivity and the electrical field strength of the solvent around the ion. It leads to good agreement between the calculated and the experimental values for all solvents, both dipolar aprotic and hydrogen bonding, for which data for univalent ions are available. In particular, this approach permits an independent estimation of the standard partial molar volumes of alkali metal halides in anhydrous formic acid, not included in the former comparisons.