Temperature coefficients of half-wave potentials and entropies of transfer of cations in aprotic solvents

Abstract

Temperature coefficients of polarographic half-wave potentials for Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Tl⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ba²⁺, Pb²⁺, bis(biphenyl)chromium(I) tetraphenylborate, ferrocene and perylene have been derived from measurements vs. Ag/Ag⁺(0.01 mol dm^–3) electrodes kept at 25 °C in 0.1 mol dm^–3 solutions of tetrabutylammonium perchlorate in dimethyl sulphoxide, N,N-dimethylformamide, hexamethylphosphoric triamide and propylene carbonate. Entropies for the above mentioned redox couples and for Ag⁺ were calculated for reversible electrode reactions on the basis of the assumption of a negligible thermal diffusion potential. This assumption was also employed to calculate single-ion entropies of transfer from N,N-dimethylformamide into dimethyl sulphoxide, propylene carbonate and hexamethylphosphoric triamide.