Abstract: A rotor shaft extends axially through an interior cylinder defined by a housing. The shaft is mounted for rotation at one end. A flow of medium consistency stock is introduced axially to the cylinder, while a chemical inlet supplies bleaching chemicals axially to a rotor mounted on the shaft. The head of the rotor has turbine passages which accelerate the impinging bleaching chemicals along radial lines to be thus distributed across the whole aperture of the cylinder. Tapered vanes extend from the rotor adjacent to the rotor head and create circulating vortices which mix the bleach chemicals with the pulp. As the tapered vanes extend radially toward the cylindrical walls of the cylindrical housing, the vortices extend to the housing walls. The finely mixed bleaching chemicals and pulp are then forced through a foraminous cylinder which separates the interior of the cylindrical housing from an outlet volute by vanes which extend to near engagement with the foraminous cylinder.