Abstract: The apparatus comprises a container closed to free communication with the atmosphere, and means for maintaining therein a body of crude volatile liquid at a predetermined surface level with an evacuated space thereabove containing a low pressure mixture of evaporated volatile liquid vapor and incondensible gas, an array of heat conducting tubes immersed in said body of crude liquid with their lower ends entering into a closed drum member, a fan blower arranged to maintain a pressure differential for heating said mixture by compression and friction and impelling it into the upper ends of the tubes, whereby through heat exchange the vapor is condensed to liquid and passes into the drum member together with incondensible gas.