Studies in ion solvation in non-aqueous solvents and their aqueous mixtures. Part X. Free energies of transfer of the alkali-metal chlorides from water to a 20%(w/w) dioxan–water mixture at 25°. Amalgam electrodes and the digital voltmeter

Abstract

E.m.f. measurements on the double cell Ag–AgCl|MCl(m⁸),S|M(Hg)|MCl(m^w),W|AgCl–Ag, where S is a 20%(w/w) dioxan–water mixture, and W is water, are reported for the alkali-metal chlorides MCl. The measurements were greatly facilitated by the use of a digital voltmeter and ancillary data-logging equipment. Values of ΔG_t°, the free energy of transfer between molar standard states in the two solvents, are calculated for these electrolytes; they increase as the cationic radius increases, contrary to the predictions of classical theory. Values of ΔH_t° and ΔS_t° are also calculated. The three thermodynamic functions are discussed in conjunction with the corresponding data for some other electrolytes, the figures giving general support to the interpretations already advanced in this Series.