CONDUCTIVITIES OF KF AND CSF IN METHANOL AT 25-DEGREES-C

Electrolytic conductivities of KF and CsF in methanol solution have be en determined at 25 degrees C. The single ion molar conductivities of the fluoride ion, obtained from the two salts are in excellent agreeme nt and indicate that the F- ion is highly solvated in methanol (MeOH). Combination of the present and literature data for related salts in b oth water and MeOH indicate that while the primary solvation of ions m ay be more extensive in H2O there is considerable enhancement of the s econdary solvation sheath in MeOH. Recalculation of high precision lit erature conductivity data using a consistent mathematical approach ind icates that ion pair formation constants for simple 1:1 electrolytes i n MeOH are 1 or 2 orders of magnitude greater than in H2O. This is sho wn to be entirely due to the less favorable solvation of ions in MeOH, as the Gibbs energies of transfer of the neutral ion pairs MX from H2 O to MeOH are also unfavorable. Calculations also show that ion associ ation in MeOH is strongly influenced by coulombic interactions whereas in H2O short range interactions are generally more important.