Extraction of Metals

Once the ore is calcined or roasted, the process of reduction obtains the metal. The extraction of metal from the calcined or roasted ore consists of two steps viz.,

• Removal of the Earthly impurities.

• Reduction of the ore to the metal.

The Earthly impurities are removed by adding suitable substance called flux which when heated, combines with the earthly impurities to form easily fusible mass known as slag, is called flux. There are two types of fluxes.

Acidic flux

Acidic flux like silica (SiO₂) is used to remove basic earthly impurities (gangue) such as lime (CaO) or MgO.

Basic flux

Basic fluxes like lime (CaO), magnesium oxide (MgO) are used to remove acidic gangue such as SiO₂.

Slag

When a flux combines with the earthly impurities, an easily fusible mass is obtained which is called slag. The slag is lighter and insoluble in the molten metal. So it can be easily removed from the surface of the molten metal. Molten mixture of calcium and magnesium silicates forms slag.

After removing the Earthy impurities, the metals are obtained from the calcined or roasted ore by the process of reduction. This can be either chemical reduction or electrolytic reduction processes. The choice of the method depends upon various factors.