3. The concentration of reagents such as sodium carbon-
ate in solution served to reduce the exposure time required to reach the maximum iron reduction achiev- able at each level of power.
4. The use of ultrasound is beneficial to the electrostatic separation of heavy mineral concentrates into their separate mineral components. This is achieved in part through the removal of surface coatings which tend to mask the separation characteristics of the mineral grains. However, there are also strong indications that in the presence of sodium carbonate there is an