separation factor, α A , B

in liquid-liquid distribution
The ratio of the respective distribution ratios of two extractable solutes measured under the same conditions.
α A , B = D A D B
  1. By convention the solutes designated as A and B in the above are chosen so as to make α > 1.
  2. The term separation coefficient is not recommended.
  3. The terms selectivitycoefficient and selectivity ratio are not synonymous and should not be used.
PAC, 1993, 65, 2373 (Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)) on page 2386
Orange Book, p. 107
See also:
Orange Book, p. 85