Studies on the Acid-Base Properties of the AlBr₃-NaBr Melts

The acid-base properties of the AlBr₃-NaBr melts were examined on the basis of the EMF measurements of an aluminum-aluminum concentration cell and the following information was obtained: 1. The AlBr₃-NaBr melts show a composition-dependent Lewis acidity that is similar to that found in the chloroaluminate melts. 2. The equilibrium constants of the two chemical equilibria (Eq. [4] and [5]) that characterize these melts have been determined: K′₁= 3.5, K₂ = 4.0 × 10⁻⁶. 3. For the same cationic constituent, the amount of “free” halide in the chloroaluminate melt is less than that in the bromoaluminate melt. This implies that the molecular dimer (Al₂Br₆) is very stable and behaves as a strong Lewis acid in the bromoaluminate melts. Manuscript submitted Feb. 1, 1988; revised manuscript received Feb. 6, 1989. Kyoto University assisted in meeting the publication costs of this article.