That value of pH in an aqueous phase at which the distribution ratio is unity at equilibrium.
50% of the solute is extracted
) only when the phase ratio is unity.
PAC, 1993, 65, 2373
(Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations
on page 2385
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. https://doi.org/10.1351/goldbook