Abstract: A method of separating lighter and heavier particles in a solids mixture includes entraining the mixture in a liquid of a specific gravity intermediate the specific gravities of the lighter and heavier particles, and feeding the liquid through a first opening into one end of a rotating vessel. The vessel is designed so that the liquid attains a dynamic equilibrium at which an annular, centrifugally-induced, substantially static, revolving volume of the liquid of stable internal surface is confined by the vessel about the axis of rotation, while further liquid flows on within the stable internal surface. Heavier particles are centrifugally directed into the annular volume, while lighter particles remain entrained in on-flowing liquid which flows out a second opening in the other end of the vessel.