Abstract: The classification of small particles is performed by utilizing the oscillation of particles as they pass through electric fields. The apparatus utilizes vertically spaced sieve electrodes which are at the same or at a different potential as a particle charging device. The particle charging device transfers particles to an attracting electrode at a point located directly opposite the particle transfer zone. In this manner, oscillating particles are dropped between two vertical sieves and classification is accomplished as the particles move to the screen by virtue of their oscillation.