Content of sodium and lithium in aluminium during electrolysis of cryolite-based melts

The content of sodium and/or lithium in polarized and nonpolarized aluminiu m in contact with cryolite melts was determined in a laboratory cell. The c ryolite-based melts contained 0 to 20 mass % excess AlF3 and 0 to 2.5 mass % LIF. The cathodic current density ranged from 0 to 0.5 A cm(-2). The lith ium content in aluminium increases linearly with increasing concentration l ithium fluoride in the melt. It also increases with increasing cathodic cur rent density and decreasing cryolite ratio. On the other hand the sodium co ntent decreases with increasing concentration of LIF in the melt. This effe ct is more notable at higher current densities.