The standard molar enthalpy of formation of HfTe3O8

The molar enthalpies of solution of HfTe3O8, TeO2 and HfF4 in 10 mol dm−3 HF(aq) have been measured using an isoperibol-type calorimeter. From these results and other auxiliary data, the standard molar enthalpy of formation of HfTe3O8(s) has been calculated to be ΔfHm0(298.15 K) = −2129.1 ± 10.1 kJ mol−1. This value of enthalpy of formation of HfTe3O8 is consistent with the free energy of formation of HfTe3O8 determined in this laboratory by the transpiration technique.