(i) Froth floatation method: This method is used to remove gangue from sulphide ores. In this process a suspension of the powdered ore is made with water, some pine oil (collector) and stablisers are added. A rotating paddle agitates the mixture and draws air in it. The froth is light and it skimmed *.
(ii) Electro refining of metals:** In this method, the impure metal is made to act as anode. A strip of the same metal in pure form is used a cathode. They are put in a suitable electrolyte containing soluble salt of the same metal.
Sb, Ag, Au, Pt, Cu, Zn may be refined by this process.
(iii) Zone refining: This method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal. A circular mobile heater is fixed at one end of a rod of the impure metal. The molten zone moves along with the heater. The pure metal crystallises out of the melt and impurities pass on into the adjacent molten zone.
