dry polymer is fed from a hopper into the funnel - shaped path of a mixing structure which has upper and lower nozzle portions cooperating to define a frustoconical nozzle opening or eductor which provides communication between the path and a surrounding annular chamber . water is delivered along the side of the chamber so that it swirls through the nozzle opening and is ejected into the funnel - shaped path in a conical swirling stream which mixes with dry powder falling along the path and forms a venturi to draw the powder along the path . the swirling mixture is injected into the top of a vertical rotating tube which extends down into a container and carries an elongated hollow impeller at its lower end . the water polymer mixture is further mixed in the tube and sprayed through the impeller into an upper mixing compartment of the container . liquid is drawn through openings in the bottom of the impeller to facilitate the mixing action . the mixture is then passed to a lower aging compartment , from which it is fed to auxiliary mixing and diluting means . control means prevents feeding of the dry polymer in the absence of the conical water stream .