Acid-Base Effects in Molten Electrolytes

Abstract

The acid-base concept in molten electrolytes gives a systematic description of the variations in electrochemical and redox properties resulting from changes in medium composition. Several types of acidity (oxoacidity, chloroacidity …) have to be considered in order to make quantitative comparisons. Some important cases of melts for which the notion of oxoacidity is appropriate are examined: 1) The water-alkaline oxide system, i.e. molten hydroxides and water-hydroxide mixtures; 2) Molten pyrosulfates and hydrogen sulfates, which lead, within the same temperature range, to the most acidic media; 3) Alkali nitrates, which appear from this point of view in an intermediate position. Variations of redox potential versus the acidity-basicity level for several electrochemical systems are considered.