Oxoacidic properties of potassium halide melts at 800°C

The equilibrium CO32- = CO2+O2- (pK) in molten potassium halides (KCl, KBr and KI) and KCl-NaCl eutectic at 800°C was investigated to compare the oxoacidic properties of the melts. A potentiometric cell involving Pt(O2)|ZrO2(Y2O3) membrane oxygen electrode was used to detect the equilibrium O2- molalities. The obtained pK values were 3.2±0.2 (KCl), 2.4±0.2 (KBr), 4.4±0.2 (KI) and 3.6±0.2 (KCl-NaCl) allowing arrangement of the melts studied in the following sequence: KI–KClNaCl–KCl–KBr with the melt acidities increasing within 2 pI units. The oxides solubilities were found to decrease sequentially from the chloride to the iodide melt.