Purification of metal Refining
Some Important Terms
(a) Gangue : Ores are usually contaminated with large amount of impurities such
as soil, sand etc. called gangue.
(b) Roasting : The sulphide ores are converted into oxides by heating strongly in
Metals And Non-Metals
the presence of excess air. This process is called roasting.
2ZnS + 302 ——> 2Zn0 + 2802
(c) Calcination : The carbonate ores are changed into oxides by heating strongly
in limited air. This process is called calcination.
ZnCO, ———> ZnO + CO2
(d) Reduction : Metal oxides are reduced to corresponding metals by using
reducing agent like carbon.
ZnO + C > Zn+ CO
Refining of Metals
The most widely used method for refining impure metal is electrolytic refining.