An experimental apparatus has been assembled for the study of high-gradient magnetic separations of para- and dia-magnetic particles suspended in a liquid. The components of this system include a cryogenic magnet, equipment for light-intensity measurements, and a dynamic light-scattering technique for transient particle-size measurements. The flocculation of paramagnetic hematite particles of approximately 200-nm diameter under the influence of a uniform magnetic field is experimentally investigated. The effect of solution pH on particle growth as a result of flocculation is examined with and without the presence of the magnetic field. Results show that the flocculation rate of hematite particles increases with the intensity of the magnetic field.