The electrolytic cell is known as the Kellner – solvary cell. The anode consists of carbon (graphite) rods dipping into brine contained in a tank. A layer of mercury flowing in at the base of the tank serves as the cathode. Fresh brine is introduced at one end of the tank and comes out at the opposite end. At the anode chloride gas is liberated and then collected 2Cl → Cl2 + 2e.
At the cathode the sodium forms an amalgam.
Na + Hg→ Na/Hg. The amalgam is treated with water in another tank.
2 Na/Hg (l) + 2H20(l) → 2Na0H(aq) + H2(g) + 2Hg
