The theory of multi-stage separation is described. By using or more stages the partition curves and Ep values are remarkably improved. The role of the multi-density separation is outlined. The fact is stressed that for many processing problems, concerning minerals and coal, performing 2 or more cuts at different densities may be very important for obtaining a remarkable improvement in the quality of products, process efficiency and economy. The importance of the rheological properties of the medium is stressed, and the main features of modern medium circuits and control systems are covered. Some recent industrial applications are reported.
