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7. Electrochemistry eLearn.Punjab

7.6 ELECTROCHEMICAL INDUSTRIES

7.6.1 Manufacture of Sodium Metal from Fused NaCl

On the industrial scale, molten sodium metal is obtained by the electrolysis of fused NaCl in the
Downs cell. This electrolytic cell is a circular furnace. In the center there is a large block of graphite,
which acts as an anode while cathode around it is made of iron as shown in figure 7.4.

Fig. 7.4 Downs Cell for production of Sodium Metal

7.6.1.1 Working of Downs Cell

The fused NaCl produces Na+ and Cl- ions, which migrate to their respective electrodes on the
passage of electric current. The electrodes are separated by steel gauze to prevent the contact
between the products. The CI- ions are oxidized to give CI2 gas at the anode. It is collected over the
anode within an inverted cone-shaped structure. While Na+ are reduced at cathode and molten Na
metal floats on the denser molten salt mixture from where it is collected in a side tube. Following
reactions take place during the electrolysis of the molten sodium chloride:
Molten NaCl ionizes as:

Half-cell reaction at anode (oxidation)

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