This project focuses on the study of the polymeric membrane swelling during the separation of industrially interesting mixtures. Further, we want to make use of this phenomenon for the pervaporation flux increase by addition of an appropriate substance, whose presence in the separated mixture could via interactions with the membrane material lead to its swelling. Our new original sweeping-gas apparatus will be used for the transport study in polymeric membranes. From experiments on this apparatus it is possible to evaluate fluxes, diffusion coefficients, permeant equilibrium sorption in polymeric membranes and, in addition, sorption in the steady state of a vapor permeation process. Especially the sorption data in the steady state are very demanding for a more realistic description of the vapor permeation and could help to estimate the swelling of the polymeric membrane. GA104/09/1165