Abstract: A mixing apparatus for mixing particulate material is described in which a plurality of different shaped blades are employed for thorough rapid mixing as the material moves downward through a mixing chamber and for impelling the mixed material downward through a discharge opening at the bottom of such chamber. A pair of convoluted lower mixing blades, which spiral downward and inward, are used to mix, to impel the material downward through the discharge opening, and to scrape such material from the conical bottom surface of the mixing chamber. First and second pairs of longitudinal intermediate mixing blades of different lengths positioned above the convoluted blades mix and scrape the material from the cylindrical side surface of the mixing chamber.