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Lead is a heavy, dull gray soft element belonging to the Silver is a bluish white, metallic element. It is characterised by

1. Atomic number 82
2. Relative atomic mass 207.19
3. Relative density 11.35
4. Melting point 327.5^OC
5. Boiling point 1740^OC

The chief ore of lead is galena (PbS), other ores are, anglesite (PbSO4), Cerussite (PbCO3), and litharge(PbO)

Lead is mainly extracted from galena. The extraction of lead involves the following steps.

1. CONCENTRATION

Galena is concentrated by the froth floatation process. In this process the ore is crushed and mixed with water. This mixture of the crushed ore and water is called slurry. This mixture is now shifted to a floatation tank and a small quantity of pine oil is added and a current of compressed air is circulated through it. As a result of this the ore particles which are preferentially wetted by the oil rise up to the surface with the froth. This concentrated ore is removed from the apparatus.

2. ROASTING

The concentrated ore is now transferred to the hearth of a reverbatory furnace, where it is heated at a moderate temperature, while the quantity of air which is usually employed in excess is controlled through special doors. The following reactions take place

2PbS + 3O₂ è 2PbO + 2SO₂

2PbS + 2O₂ è PbSO₄

3. REDUCTION

The air supply is now reduced, more galena is added and the temperature is now raised when both the lead oxide and lead sulphate formed above are reduced by the excess of lead sulphide to lead. The following reactions occur

PbSO4 + PbS è 2Pb + 2SO₂

2PbO + PbS è 3Pb + SO₂