Abstract
The standard molar enthalpies of formation Δ f H m o of the intermetallic compounds IrTi, IrZr, IrHf, and OsTi have been determined by high-temperature mixing calorimetry at (1473 ± 2) K. The following values of Δ f H m o/(kJ·mol −1) are reported: IrTi, −(168.6±7.5); IrZr, −(171.3 ± 7.7); IrHf, −(193.3 ± 9.6); OsTi, −(136.9 ± 7.2). There are no calorimetric values for these compounds in the literature. The new results are compared with recently published predicted values. Comparisons are made also with our own experimental values for the 1-1 compounds of Ti, Zr, and Hf with Pt, Pd, Rh, and Ru, and with reported results for the compounds of Ti with Ni, Co, and Fe, and of Zr with Ni and Co. With few exceptions these comparisons show increasing negative enthalpies of formation from the 3d to the 4d to the 5d late transition metals, and also from Ti to Zr to Hf. A more detailed analysis shows certain similarities in observed trends between the compounds of (Fe, Co, Ni) and (Os, Ir, Pt) which are not shared by the corresponding compounds of (Ru, Rh, Pd).
Published Version
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