Standard enthalpies of formation of some Th alloys with Group VIII elements (Co, Ni, Ru, Rh, Pd, Ir and Pt), determined by high-temperature direct synthesis calorimetry

The standard enthalpies of formation of seven alloys formed between Th, an element from Group III, and Co, Ni, Ru, Ph, Pd, Ir and Pt, elements from Gr oup VIII, have been determined by high-temperature direct synthesis calorim etry at 1473+/-2 K. The following values of DeltaH(f)degrees, in kJ (mol at om) (1), are reported: ThCo5, -17.0+/-2.3; ThNi5, -34.8+/-1.9; ThRu2, -28.9 +/-1.6; ThRh,, -60.3+/-2.8; ThPd3, -86.1+/-3.2; ThIr2, -78.0+/-3.4; and ThP t3, -89.7+/-5.1. The results are compared with predicted values from the Mi edema model and with available literature data on the Gibbs free energies o f formation for ThCo5, ThNi5, ThRu2 and ThRh3. The results are also compare d with an earlier calorimetric value of DeltaH(f)degrees for ThRh, (Kubasch ewski et al., Materials Thermochemistry, Pergamon, Oxford, 1993) and with t he standard enthalpies of formation for URu3, URh3, UPd3, as well as for Ce Ni5, CeRu2, CeRh3, CePd3 and CeIr2 previously reported in investigations ca rried out in this laboratory. (C) 2000 Elsevier Science B.V. All rights res erved.