A term used to quantify the difference in the free energy
of a solute ion in two different standard states often in two different liquid phases. The relationship is
is the transfer Gibbs energy and
is the number of ions in the solute.
It should not be confused with the mass transfer coefficient which represents the specific rate of transfer of a species from one phase to another.
It does not necessarily imply the physical transfer of a solute between two liquid phases.
PAC, 1993, 65, 2373
(Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993))
on page 2386
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook