Trihalides vapor pressure

Carbothermic reduction in the presence of an alloying element, such as copper, iron, or silicon, to decrease aluminum vapor pressures decreases volatility problems but requires a further stage to recover aluminum from the alloy product. It may be selectively dissolved from the alloy with a more volatile metal, such as mercury, lead, or zinc, and then the aluminum recovered by distillation. Or, the tendency for aluminum halides to form more volatile monohalides at high temperatures, which revert to the trihalides at lower temperatures (Eq. 12.25) may be employed. 

Substantial efforts have been devoted to the determination of the equilibrium partial pressures and the thermodynamics of vaporization of the trihalides. The first systematic investigation of vapor pressures of the trifluorides is the series of mass spectrometric measurements of Margrave and coworkers (Zmbov and Margrave, 1966 Kent et al., 1966 Besenbruck et al., 1967 Zmbov and... 

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