A froth flotation machine (40) having a rotary air-supply shaft (42) vertically disposed in a vessel (41) includes an impeller (50) comprising a series of interconnected blades (52,53). Extending radially and fixedly depending from a flat impeller plate (52) is a pumping blade extending over one-half the distance from the plate outer periphery to the shaft. Blade (53) is an air-inducing vane of lesser radial length which aids in inducing air from shaft (42) to pumping blades (52). The vane has a height less than 50% of the height of the pumping blade. The pumping blade has an L/H ratio of from 0.8 to 1.4 where L is its radial length and H is its vertical height. Slurry is pumped by the blades (52) from bottom of the vessel through a central aperture in a surrounding fixed stator base (56) having stator bars (55) extending upwardly and forming parallel-sided passageways (63,64) for pumped fluid.
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