The determination of the standard Gibbs energies of ion transfer between water and heavy water by using the three-phase electrode approach

For the first time, the standard Gibbs energies of transfer of anions and cations across the nitrobenzene/heavy water interface are reported as measured by an electrochemical technique. The data have been obtained with the help of three-phase electrodes consisting of a nitrobenzene droplet that contains an electroactive compound (either decamethylferrocene to transfer anions or iron(III) tetraphenyl porphyrin chloride to transfer cations), a graphite electrode on the surface of which the droplet is attached, and a solution of the salts with the transferable ions in heavy water. The difference between these Gibbs energies of transfer and those of transfer between light water and nitrobenzene allows calculating the Gibbs energies of transfer between light water and heavy water. The latter vary in the interval from -0.50 to +0.50 kJ/mol with confidence intervals ranging from +/-0.054 to +/-0.117 kJ/mol. (C) 2003 Elsevier B.V. All rights reserved.