Abstract:
The standard electrode potentials GE’) of M/M+ (M = Li, Na, K, Rb and Cs) electrodes in
aqueous solutions of dimethyl sulphoxide (DMSO) (containing 10, 20, 40 and 60 wt. % DMSO)
have been determined at 25°C from e.m.f. measurements of cells of the type: M(Hg)|MCl(/n), solvent]
AgCl-Ag, obtaining the activity of metals in amalgams with the help of a similar type of cell in water.
The free energies of transfer of MCI, AGt°(MCl) (mole fraction scale) from water to each of these
solvents computed from these values and those of sEXg-AgCi obtainable from the literature, rise
sharply from Li+ to Na+, and fall from Rb+ to Cs+ with a maximum between Na+ and Rb+. This is
considered as due to the superimposition of “ soft-soft ” interactions on the “ electrostatic inter
actions ” between the ions and the negative charge centres of hydrogen-bonded solvent complexes.
The AG? (I) values for individual ions, obtained by a method of “ simultaneous extrapolation ” arc
shown to be largely determined by the “ acid-base ” type ion-solvent interactions as observed in
methanol+water mixtures.
