Abstract: An apparatus for the separation of solutions by pervaporation includes a raw solution chamber through which a raw solution is conducted from which a part is to be separated, a permeation chamber disposed adjacent the raw solution chamber but separated therefrom by a membrane which permits evaporation therethrough of part of the solution into the permeation chamber from which the vapors are removed, a heating structure arranged adjacent the raw solution chamber in direct contact with the raw solution therein for replenishing to the solution the heat consumed by pervaporation of part of the solution through the membrane.