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

Abstract The standard enthalpies of formation of seven alloys formed between Th, an element from Group III, and Co, Ni, Ru, Rh, Pd, Ir and Pt, elements from Group VIII, have been determined by high-temperature direct synthesis calorimetry at 1473±2 K. The following values of Δ H f o , in kJ (mol atom) −1 , are reported: ThCo 5 , −17.0±2.3; ThNi 5 , −34.8±1.9; ThRu 2 , −28.9±1.6; ThRh 3 , −60.3±2.8; ThPd 3 , −86.1±3.2; ThIr 2 , −78.0±3.4; and ThPt 3 , −89.7±5.1. The results are compared with predicted values from the Miedema model and with available literature data on the Gibbs free energies of formation for ThCo 5 , ThNi 5 , ThRu 2 and ThRh 3 . The results are also compared with an earlier calorimetric value of Δ H f o for ThRh 3 (Kubaschewski et al., Materials Thermochemistry, Pergamon, Oxford, 1993) and with the standard enthalpies of formation for URu 3 , URh 3 , UPd 3 , as well as for CeNi 5 , CeRu 2 , CeRh 3 , CePd 3 and CeIr 2 previously reported in investigations carried out in this laboratory.

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