On carbonate stability in caesium iodide melt

Abstract

The equilibrium of carbonate dissociation (CO₃²⁻ = CO₂↑ + O²⁻, pK) in molten CsI was studied in the 650–800°C temperature range with a step of 50°C by a potentiometric method using a membrane oxygen electrode as an indicator. The stability constant of CO₃²⁻ was found to decrease from 4.47 (650°C) to 3.44 (800°C). The dependence of pK on temperature was described by the equation pK = − 2.80 + 6.77 × 10³T⁻¹. Carbonate stability in molten CsI was less than that in Na⁺ and K⁺ containing alkali halide melts. This was caused by lower stability of Cs₂CO₃ as compared with K₂CO₃ and Na₂CO₃.