Abstract: The invention relates to a method and an apparatus for monitoring the quality of an ore delivered to flotation concentration and the state of a slurry prepared from said ore. In the method, two or more working electrodes (6, 7, 8) featuring a cross sensitivity are immersed in the slurry to be monitored and the differences of potentials between each pair of electrodes is measured, whereby no reference electrodes are needed. The working electrodes (6, 7, 8) may comprise an argentite electrode, a platinum electrode and a molybdenum electrode, in which case the following differences of potentials between electrodes are being measured: ?(Ag—Pt), ?(Ag—Mo) and ?(Pt—Mo).

Abstract: Method and apparatus for controlling the flotation process of sulphide ores including separation of sulphide minerals from pyrite in an alkaline environment created by lime. The method comprises measuring the molybdenum electrode potential of an aqueous slurry of the ore and adjusting the addition of lime based on the measured molybdenum electrode potential to maintain the molybdenum electrode potential of the slurry in a preselected range. The apparatus comprises means (6) for measuring the molybdenum electrode potential and a control unit (7) for controlling the addition of lime to the slurry based on the measured molybdenum electrode potential of the slurry.