Abstract: Apparatus and method are disclosed for producing nanometer-range particle dispersions utilizing an immersion mill having a rotor for processing feedstock within a bed of media contained within a containment wall. An auxiliary chamber provides a chamber wall surrounding the containment wall and feedstock is passed from the bed of media, through the containment wall and into the auxiliary chamber while the media is contained within the bed of media. The feedstock is drawn from the bed of media, through the containment wall, and out of the auxiliary chamber, with an external pumping mechanism arranged for operation independent ofrotation of the rotor, whereby the containment wall is maintained unbroken by any direct connection between the rotor and the external pumping mechanism and remains effective in containing the media within the bed of media.