Influence of the temperature on the heat of formation of nickel monoxide at high temperature

In order to see whether the heat of formation ΔH⁰ of the insulating transition metal monoxides shows any change at high temperatures, this property has been accurately measured for NiO by the electrochemical method in the temperature range 743–1323 K. The results show that ΔH⁰ changes from ? 56.10 kcal mol^?1 to ? 55.66 ± 0.08 kcal mol^?1 as the temperature is increased through 913 K. The significance of the heat of formation is discussed from the viewpoint of electronic structure of this compound.