- During the extraction of metals of low and medium reactivity from their respective sulphide ores.
- They are first heated in presence of atmospheric oxygen.
- This step will give out oxides of metal.
- This step is used as it is more efficient method to extract methods.
Ex: Cinnabar is heated in air to get mercuric sulphide oxidize to produce mercuric oxide.
2HgS + 3O2 → 2HgO + 2SO2
Mercuric oxide is further heat to get Mercury
2HgO → 2Hg + O2
Zinc is a metal of medium reactivity and its ore is Zinc Blende Zinc Blend is roasted to get Zinc oxide
2ZnS + 3O2 → 2ZnO + 2SO2
ZNCO3 → ZnO+ CO2
Zinc oxide when heated wit CO2 Zinc is obtained
ZnO + C → Zn+CO