The fraction of the total quantity of a substance extracted (usually by the solvent) under specified conditions, i.e. where is the mass of A extracted and is the total mass of A present at the start.
- may be expressed as a percentage, .
- The term extractability is qualitative and should not be used as a synonym for fraction extracted.
- If the aqueous phase is extracted with successive portions of solvent, the phase volume ratio (solvent/feed) being each time, the fraction extracted is given by: If and this expression is a concept of value in chromatography theory.
- The fraction extracted is also known as the recovery factor, especially for a multistage process.
PAC, 1993, 65, 2373 (Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)) on page 2384