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How did the Downs cell process produce sodium metal from molten sodium chloride?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — alkali metal Modern version of the periodic table of the elements (printable).

The Downs cell process, introduced in 1926, replaced the earlier Castner process for the industrial production of sodium metal. In this method, a mixture of sodium chloride and calcium chloride is electrolyzed. The addition of calcium chloride is essential because it lowers the melting point of the salt mixture, allowing the process to operate more efficiently. During electrolysis, the molten mixture is dissociated to produce both sodium metal and chlorine gas.1