(Ion + molecule) equilibrium technique applied to the determination of the activities of Cr 2O 3 and NiO. Standard molar Gibbs energy of formation of NiCr 2O 4

Abstract

The method for determination of the activities of Cr 2O 3 and NiO at high temperatures based on measuring the equilibrium constants of reactions with negative ions: Cr 2O 3(s)3CrO 4 −+CrO 3 − , NiO(s)+CrO 3 −+CrO 4 −=NiO 2 −+Cr 2O 6 − , has been suggested. To produce measurable quantities of suitable ions in the saturated vapour small amounts of easily ionized substance (K 2SO 4 or K 2CrO 4) were added to the mixtures being investigated. The activities of Cr 2O 3 and NiO have been determined for heterogeneous (NiO + NiCr 2O 4) and (NiCr 2O 4 + Cr 2O 3) and the standard molar Gibbs energy of formation of NiCr 2O 4 from oxides has been calculated.