The standard molar Gibbs energy of formation of barium tellurite, BaTeO 3 (s), was determined by the transpiration technique using pure oxygen as the carrier gas in the temperature range 1133 K to 1260 K. The condensate was exclusively identified as TeO 2 (s) by chemical analysis. From a quantitative chemical analysis of the condensed TeO 2 (s), the vapour pressure of TeO 2 (g) over pure BaTeO 3 (s) was calculated and is given by ln{ p(TeO 2 , g)/kPa ยฑ0.1} = 18.64 -30863.2 โข (K/T ). The Gibbs energy of formation of BaTeO 3 (s) was computed from the values of ln{ p(TeO 2 , g)/kPa} and the values of f G o m for BaO(s) and TeO 2 (g) taken from the literature and is given by
856.5 + 0.2067 โข (T /K). The enthalpy increments of BaTeO 3 (s) were measured using a high-temperature Calvet micro-calorimeter in the temperature range 304 K to 1000 K. Enthalpy increment values are represented by a polynomial of the form {H o (T ) -H o (298.15 K)}/(J โข mol -1 ) = -39 190 + 118.96 โข (T /K) + 4.235 โข 10 -3 โข (T /K) 2 + 9.975 โข 10 5 โข (K/T ), with an accuracy of ยฑ0.4 per cent over the interval (304 T /K 1000).