Abstract: The device comprises a vertically movable platform for supporting extraction flasks placed above compressed-air impellers. Withdrawal of the top liquid phase from each flask is performed by means of a vertical suction duct, the top end of which has its opening within a non-return chamber at a higher level than the opening of a tube which provides a communication with a pressure-reducing Venturi tube, ejector-nozzle and discharge pipe. The lower end of the suction tube is connected to a plurality of nozzles having their openings at the periphery of each extraction flask and extending in the same horizontal plane which can be set at a predetermined level.