Fig. 4. Vapor pressure of selected elements as a function of temperature. trolyzed, forming oxygen at each anode and an aluminum, silicon, iron and titanium alloy at each cathode. Oxygen gas would rise from each anode through the electrolyte providing circulation of the electrolyte and leave the cell at the top while the metal alloy would settle to the bottom and be tapped periodically. Calcium and magnesium compounds from the ore would accumulate in the electrolyte and have to be removed. A technique to accomplish this will be discussed in the next section. Search for an inert anode material is being pursued actively by various aluminum companies. Not only would inert anodes alleviate the need for frequent replacement of consumable anodes but would also permit collection of essentially pure oxygen. Tin oxide (SnO2) mixed with various other oxides such as ferric oxide (Fe2O3) and nickel oxide (NiO) have been suggested for inert anodes (5). Refractory hard metals, titanium diboride (TiB2) in particular, presumably will make suitable inert cathodes (6). 7. ELECTROLYTE PURIFICATION AND RECYCLING SYSTEM Since calcium fluoride and magnesium fluoride are thermodynamically more
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