Chlorine is obtained as a byproduct of the Down process. A fused mixture of CaCl₂ and NaCl is electrolyzed at 873 K in this method. At the cathode, sodium is obtained, while Cl₂ is released at the anode.

Cl₂ is discharged at the anode when an aqueous solution of NaCl is electrolyzed. H₂ is produced at the cathode ( in place of Na ). This is due to the fact that H₂O’s standard reduction potential (E° = -0.83 V) is less negative than that of Na (E° = -2.71 V). As a result, H₂O will have a stronger propensity for being reduced at the cathode, resulting in H₂ discharge.

NaCl ⇒ Na⁺ + Cl ^–
At cathode : 2H₂O + 2e ^– ⇒ H₂ + 2OH ^–
At anode : Cl ^– ⇒ Cl + e^–
2Cl ⇒ Cl₂