After the concentration of ores, the sulphide or carbonate ores of some metals are converted into metal oxides because it is easier to obtain metals from their metal oxides as compared to metal sulphides or metal carbonates. The sulphide ores of metals can be converted into their oxides by roasting while the carbonate ores of metals can be converted into their oxides by calcinations.
1. Roasting
It may be defined as the process of strongly heating a sulphide ore in the presence of air to convert it into metal oxide. For example,
2ZnS + 3O2 
2ZnO + 2SO2
(Zinc sulphide + Oxygen → Zinc Oxide + Sulphur dioxide)
2PbS + 3O2 2PbO + 2SO2
Lead sulphide + Oxygen → Lead Oxide + Sulphur dioxide)
2. Calcinations
It may be defined as the process of strongly heating a carbonate ore in the absence of air to convert it into metal oxide. For example,
CaCO3 CaO + CO2
(Calcium carbonate → Calcium oxide + Carbon dioxide)
Test your understanding and answer these questions:
- What do you understand by calcination and roasting of ores?