up l k e

through the bulk metal to the metal/salt interface. A 20 kA three- major advantages over current methods of refining UBC scrap. 0layer refining cell will produce only 214 kg of magnesium per day or approximately, 850 kg of refined aluminum per day. This is a relatively small amount and consequently, the three-layer cell would not be appropriate. Zone refining,2,3 which is based on the differen-tial solubility of impurities in solid and liquid phases of aluminum can also be used, but the process is slow and metal throughput is poor. Used beverage cans ~UBCs! are the largest source of secondary aluminum in the Western world. In 1996 alone, the US produced 108 billion4 aluminum beverage cans ~representing 1.5 million tonnes of scrap aluminum! of which 63 billion were recycled. UBCs constitute two aluminum alloys: the lid, that is rich in magnesium ~2.5%Mg,0.3%Mn! and the body, rich in manganese ~1.5%Mg,1.2%Mn!. On melting, the cans produce a mixed alloy