Abstract: An agitator ball mill having a milling chamber and an agitator having a rotatably mounted and driven agitator shaft and accelerators arranged thereupon, wherein the accelerator that is arranged furthest downstream, that is, the accelerator closest to the milling material outlet, lengthens axially and extends along the axial length of the sieve.

Abstract: A process for separating particles of a cohesive form of a polydisperse compound or composition comprising nevirapine, nevirapine hemihydrate, mexiletine or mexiletine hydrochloride according to size is disclosed which comprises milling and sizing the particles in an apparatus which includes individual and/or nested sieves each of which may also include a quantity of beads, disks and/or other geometric or non-geometric shapes. The sieves can be rotated, vibrated or agitated in any and all combinations by various methods to achieve independently horizontal rotation and vertical reciprocation (similar to a merry-go-round) to efficiently segregate, size or mill cohesive and polydisperse powder particles to specific size ranges. The invention also contemplates a method for using the apparatus in the sizing and quantification of aggregated particles of cohesive disperse powders.