The factor by which the ratio of two substances in the feed must be multiplied to
give their ratio after treatment.
where

and

are the final and initial amounts of species
A
and

and

are the final and initial amounts of species
B.
Hence

where

is the
fraction extracted.
In terms of
,
,
(where

is the number of stages and

the phase ratio),
Source:
PAC, 1993, 65, 2373
(Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations
1993))
on page 2382
Cite as:
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.