Sodium (Down's Process)
2nd Year Chemistry Notes
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Sodium (Down's Process)
Introduction
On large scale, sodium is manufactured by electrolysis of fused sodium
chloride. The process was given by scientist Dawn, therefore, it is
called Dawn's Process.
Construction of Down's Cell
A special electrolytic cell known as Dawn's cell is used for the
electrolysis of sodium carbonate. The cell consists of a cylindrical
shape iron basin lined inside by firebricks. The iron cathode is
separated from anode by iron gauze diaphragm. Anode consists of a carbon
rod, which is present between two iron cathodes. The electrolytic
solution consists of a mixture of sodium chloride (NaCl) and calsium
chloride (CaCl2). Calsium Chloride (CaCl2) is added to decrease the
melting point of sodium chloride from 801ºC to 600ºC.
Working of Dawn's Cell
When electric current is passed through molten NaCl, the sodium ion
migrates towards cathode. It gains and electron and converts into molten
sodium metal, which floats inside the cathode compartment. This molten
sodium metal is allowed to pass through pipe 'p' which collects it in a
vessel 'V' outside the cell.
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2nd Year Chemistry Notes