ABSTRACT
Often, only one operation of extraction is not sufficient. Very often, some quantity of solute remains in solvent A after one extraction, whence the idea to repeat the operation of extraction several times with new parts of fresh solvent. In this chapter, the methodology is studied from a simplified viewpoint, that is to say, the solvents A and B are immiscible and the extractor solvent (B) is always the same at each stage as it is at the same value of the volume. The principles of calculation are the same as in the previous chapter. They show the following fundamental points; the whole yield is better than with one stage of extraction only. Moreover, when one has a total volume VB of extractive solvent at disposal, it is better from the standpoint of the whole yield to operate through n stages; each of volume VB/n rather than with only one stage of volume VB. All these results are demonstrated in the chapter.
