## fraction extracted, $$E$$

https://doi.org/10.1351/goldbook.F02503
The fraction of the total quantity of a substance extracted (usually by the solvent) under specified conditions, i.e. EA = QA.Q'A where QA is the mass of A extracted and QA' is the total mass of A present at the start.
Notes:
1. $$E$$ may be expressed as a percentage, $$\% \, E$$.
2. The term extractability is qualitative and should not be used as a synonym for fraction extracted.
3. If the aqueous phase is extracted with $$n$$ successive portions of solvent, the phase volume ratio (solvent/feed) being $$r$$ each time, the fraction extracted is given by: $E_{n} = 1 - \left ( rD + 1 \right )^{-n}$ If $$n = r = 1$$ and $$E_{1} = \frac{D}{1+D}$$ this expression is a concept of value in @C01075@ theory.
4. The fraction extracted is also known as the @R05206@ factor, especially for a multistage process.
Source:
PAC, 1993, 65, 2373. 'Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)' on page 2384 (https://doi.org/10.1351/pac199365112373)