The development of sink and float separators for nomagnetic particles of different densities, which utilizes the levitation force of magnetic fluid has been recently proceeded. The system consists of magnetic field generator, separation cell, equipments for recovery of magnetic fluid smeared on the separated products and controlling system. This paper mainly describes the sink and float separation system developed in our laboratory. We used water based magnetic fluid which can be regenerated easily, and permanent magnets with a yoke as a magnetic field generator which are lower in price than electromagnets. If the intensity of external magnetic field and the field gradient are suitably controlled, it is possible to give the levitation force, for example, 10×980 dyne/cm3 to nonmagnetic particles. Thus, the magnetic fluid could be regarded as a liquid of high specific gravity. This phenomenon would be utilized in the separation of the mixture including various ore parpticles with different densities.
