CBSE Class 11-science Answered

Castner–Kellner cell

Downs cell

The Castner–Kellner cell is an electrolytic cell used industrially for the production of sodium hydroxide.

The Downs cell is used for the commercial preparation of metallic sodium, in which molten NaCl is electrolyzed.

These cells are of two types. The first type uses an electrolyte of sodium chloride solution, a graphite anode, and a mercury cathode. The other type of cell uses an electrolyte of sodium hydroxide solution, a mercury cathode, and an iron anode.

The Downs cell uses a carbon anode and iron cathode.

A saturated brine solution floats on top of the cathode which is a thin layer of mercury. Chlorine is produced at the anode, and sodium is produced at the cathode where it forms a sodium-mercury amalgam with the mercury.

The Downs cell has a central graphite anode surrounded by a cylindrical steel cathode. Chlorine gas produced at the anode is led away through a hood, over the anode. Molten sodium is formed at the cathode and collected through another hood around the top of the cathode cylinder