Abstract
Stable suspensions of magnetic particles exhibit specific features making them an innovative liquid material for numerous applications as well as for basic research. In particular ferrofluids can be used for density separation of non-magnetic materials immersed in the liquid under the influence of magnetic fields. In this article the basic properties and applications of ferrofluids will be reviewed, and the principles of magnetic density separation will be discussed on the basis of the available literature. In addition we will try to show the possibility and problems of a commercial use of this technique.