Gibbs Energies of Transfer of Fluoride Salts from Water to Aqueous Alcohol Mixtures

Gibbs energy of transfer data for LiF and NaF from water to aqueous alcohol mixtures, obtained from solubility measurements, are examined via the Born equation. In spite of its well-known deficiencies, the simple Born model accounts for much of the observed variation of ΔtG°(MF, w→w+ROH), particularly for NaF. This unexpected success of the Born model appears to result from the fortuitous cancellation of the donor and acceptor contributions to the solvation of the cations and anions by these closely related co-solvents. Examination of the deviations between the observed and calculated ΔtG° values also suggests that they are partly due to uncompensated ion-pairing effects, especially for LiF.