pre-equilibrium

in solvent extraction
  1. Preliminary treatment of a solvent in order to convert the extractants into a suitable chemical form.
  2. Preliminary treatment of either phase with a suitable solution of the other phase (in the absence of main extractable solute(s)) so that when the subsequent equilibration is carried out changes in the (volume) phase ratio or in the concentrations of other components are minimized.
Notes:
  1. The use of equilibration in this sense is confusing and should be avoided.
  2. The term conditioning may be used as a synonym for pre-equilibration.
Source:
PAC, 1993, 65, 2373 (Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)) on page 2378