Decomposition voltage mercury cell

Hence, the thermodynamic decomposition voltage of a mercury cell operating at SO C with 0.2% Na amalgam is equal to 3.058 V as shown below. 

The cell is filled with 100 ml. of saturated BaClg solution. The electrolysis proceeds at a current of 1.75-2.5 amp. and 6-7 v. The current should be shut off after 2.5 hours, since beyond that time there occurs a sharp voltage rise, evolution of gas at the cathode and decomposition of the amalgam. Sometimes, crystalline amalgam particles deposit on the mercury surface and interfere with the electrolysis. This deposition may be prevented by slow agitation with a stirrer, or the crystals may be pushed into the body of the mercury with a glass rod. 

---