Abstract: The invention pertains to a rotary mixer and disperser head consisting of a shaft to which is connected a mixing chamber that is to be disposed into a vat or the like for dispersing, dissolving or blending of solids liquids or gasses with other liquids. The mixing chamber has secured to its upper and lower ends a plurality of impeller blades which have an end thereof located outside the mixing chamber to direct material into the mixing chamber and out through openings in the side wall of the mixing chamber during the mixing and dispersing thereof. The mixer and disperser head also comprises shear arms having a sharpened leading edge, thereby providing an additional initial shear zone. The specific mixing chamber and its configuration provide for a very efficient mixing operation.