This paper is focused on how water may be separated from dioxan, butanone and butyric acid under constant operating conditions. The analysis is presented in terms of variations in the permeation flux, individual partial fluxes and separation factors. As in a membrane process, in order to separate a liquid mixture, pervaporation relies on differences in membrane permeability as well as the vapour pressures of the components in the mixture. It is found that the separation factors reach infinity as the total permeate pressure is reduced to the vapour pressure of the organic permeant. The permeation flux increases with increasing water concentration in the feed. A drop in the flux has been observed on addition of an extra component. The PVA membrane confirmed its hydrophilic characteristics by not allowing butyric acid and butanone to permeate. Values of the activity coefficients and diffusion coefficients are reported versus the vapour composition for binary, ternary and multi-component systems. The diffusion coefficient increases with a decrease in mole fraction of the component in the membrane.