Engineering Aspects in Chlor-Alkali Operations

Mercury is a unique liquid metal at room temperature and forms various compounds or alloys, termed amalgams, with many metals which may be classified into three types61  

Gallium-type amalgams with Fe, Ni, Co, Mn, Cr, Al, and Ga which are amalgamated with difficulty, and 

Zinc-type amalgams with Zn, Cd, Pb, Tl, Sn, and Bi are easily amalgamated and readily soluble in mercury. They exhibit the same potential as the pure metal and are suited for phase separation. 

Sodium-type amalgams with Na, K, Rb, Cs, Ca, Si, and Ba react completely with low solubility in mercury. They can be formed electrolytically and exhibit half-wave potentials positive to the M/M+ standard electrode potential. 

Solubilities and the physicochemical data related to these amalgams are readily available in the literature.62-65 Of these, sodium amalgam is of importance from the operational viewpoint of mercury cells. The phase diagram of sodium amalgam has been well established (see Fig. 10), and there are various compounds of 

---