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UBC Theses and Dissertations

The activity of sodium in cryolite-aluminun melts Aylen, Peter Eric John


Activities of sodium in alumina-saturated cryolite-aluminum melts have been measured by the equilibration of a three phase system of cryolite, aluminum and lead. An approximate linear increase in the activity of sodium was noted on a log plot of activity as a function of NaF-A1F₃ weight ratios over the range pertinent to commercial reduction cell operation. Activities of sodium in cryolite-aluminum melts have been calculated by employing the equilibrium reaction between cryolite and aluminum metal and the thermodynamic data from-an analysis of the NaF-A1F₃ phase diagram. Differences between the reversible deposition potential for aluminum and sodium at one atmosphere partial pressure were calculated from the measured equilibrium sodium activities. The values obtained were of the order of .15 to .4O volts, increasing with decreasing NaF-A1F₃, ratio.

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