Concentration of the Extractant:

As expected, the extraction increases with the increasing extractant concentration. Invariably, a straight line is obtained in the plots of log [Extractant] vs log D. The slope of the straight line corresponds to the number of extractant molecules involved in the formation of the extracting species.

Ideally, for making these plots, the equilibrium concentration of the extractant in the organic phase should be used. It is difficult to find out the unbound concentration of the extractant in the organic phase. Moreover partitioning of the extractant between the organic and aqueous phase may also take place. This partitioning of the extractant between the two phases can be evaluated and if the need be, the correction is to be introduced.