Abstract: In apparatus for separating the components of a mixture, the mixture is admitted to a first inlet which communicates with a working region which may be defined by a cylindrical tube. A fluid under pressure is admitted to a chamber through a second inlet. The chamber also communicates with the working region. The fluid forms a spiralling flow which draws the mixture into the working region in the form of a vortex. In the apparatus, the chamber communicates with the working region by way of a throat, and the mixture is conveyed from the working region along an outlet.