The Polarizabilities of Aqueous Ions

The molar refractivity Rd of an electrolyte is additive for the constituent ions if the ions are in an infinitely dilute solution. The expression used for the determination 

Extrapolation to infinite dilution yields Rd°° that has the dimension of a molar volume. The reported individual ionic values (Marcus 1997) are based on the arbitrary but reasonable value of / o°°(Na+)=0.65 x 10 m mol , for the infinitely diluted aqueous sodium ions, the same as for isolated ions (See p. 52), because of the inappreciable dependence of the polarizability of the ions on their environment. The values shown in Table 2.1 for isolated ions, / di, are in fact those obtained for ions in infinitely dilute solutions, independent of the solvent (though mostly for aqueous ions). The polarizabilities of the ions are obtained from the values by means of Eq. (2.2) and correlate to some extent with the sizes of the ions. 

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