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Sodium activity measurements in the sodium-aluminium system Mitchell, John Christopher


Sodium activity data has been obtained for the sodium - aluminum system for sodium concentrations in aluminum between N[subscript Na] = 25 x 10-⁶ and 75 x 10-⁶. Additional data has allowed the calculation of activity data up to N[subscript Na] = 300 x 10-⁶. The concentration interval N[subscript Na] = 25 x 10-⁶ to 300 x 10-⁶ encompasses those sodium concentrations normally found in commercial pot-line operation. The sodium activity data has been collected by using a two-phase distribution equilibration of sodium between a lead-rich and an aluminum-rich phase. The sodium-lead system was used as a reference for the determination of the activity of sodium. The sodium exhibits large positive deviations from ideality in the sodium-aluminum system. The sodium activity shows a strong dependence on the sodium concentration of the aluminum phase for sodium concentrations below N[subscript Na] = 100 x 10-⁶. The activity data for aluminum in the sodium-aluminum system has been obtained by the Gibbs - Duhem integration of the sodium activity data. The data for the aluminum indicates that the activity of aluminum can be considered equal to its mole fraction over the entire range of miscibility of the sodium-aluminum system.

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