Reduction of the alkali and alkaline earth halides in high-frequency discharges. I. Hydrogen discharge

Abstract

The halides of the alkali and alkaline earth metals have been reduced in a hydrogen discharge at 2450 Mc/s. The alkaline earth halides appear to react according to the overall equation MCl2 + H → MCl + HCl, and the monohalide subsequently disproportionates to an equimolar mixture of dihalide and metal. However, this reaction is not always in accord with thermodynamic predictions, which suggests that further elaboration of the reducing species is necessary. Halides of the alkali metals are reduced to metal, and the relative reaction rates range from 86 for lithium iodide to 1 for potassium bromide. Although for each metal, with the exception of potassium, the rate is least for the fluoride and greatest for the iodide as might be expected from the heats of formation, neither heat of formation nor bond energy appears to be the major factor involved in the rate of reduction, and an interesting relationship with the dimerization tendency of the halides is suggested. The role of halide sublimation rate and the distribution of energies in the active species are also discussed.