In the electrolysis of NaCl by Down’s process, chlorine is obtained as a by-product. This process involves the electrolysis of a fused mixture of NaCl and CaCl₂ at 873K. during electrolysis, sodium is liberated at the cathode and Cl₂ is liberated at the anode.

If an aqueous solution of NaCl is electrolysed, H₂ is evolved at the cathode and Cl₂ is obtained at the anode. the reason being that E⁰ of Na⁺/Na redox couple is much lower (E⁰ = - 2.71 V) than that of H₂O (E⁰_H2O/H2) = - 0.83V ) and hence water is reduced to H₂ in presence of Na⁺ ions. However, NaOH is obtained in the solution.