Up to this point we have been restricted to cases where there is a single solute to recover. Both the stage-by-stage McCabe-Thiele procedures and the Kremser equation can be used for multisolute absorption and stripping if certain assumptions are valid. The single-solute analysis by both procedures required systems that 1) are isothermal, 2) are isobaric, 3) have a negligible heat of absorption, and 4) have constant flow rates. These assumptions are again required.
To see what other assumptions are required consider the Gibbs phase rule for a system with three solutes plus a solvent and a carrier gas. The phase rule is
F = C − P + 2 = 5 − 2 + 2 = 5
Five degrees of freedom is a large number. In ...