Revaluation of equilibrium quotient between titanium ions and metallic titanium in NaCl–KCl equimolar molten salt

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Abstract In this study, the effect of oxide ion on the equilibrium between titanium ions and metallic titanium was investigated in NaCl–KCl equimolar molten salt. The soluble species containing Ti 3+ and O 2− was not confirmed in the molten salt by absorption spectroscopy. The result of XRD for the solidified sample containing Ti 3+ and O 2− implies that O 2− reacts with Ti 3+ and Cl − to form TiOCl(s). The concentration quotient of the equilibrium between titanium ions (Ti 2+ , Ti 3+ ) and metallic Ti, K c , was revaluated at 740 °C as follows: 3 T i 2 + ⇄ 2 T i 3 + + Ti , K c = 8.0 × 10 − 2 mol L − 1 = 1.2 × 10 − 1 mol k g − 1 . In addition, the solubility product of TiOCl(s) in NaCl–KCl equimolar molten salt, K sp , at 700 °C was determined using the results of absorption spectra, K sp = 1.2 × 10 − 2 mol 2 L − 2 = 5.1 × 10 − 3 mol 2 k g − 2 .