THERMODYNAMIC INVESTIGATION OF THE RH-GE AND IR-GE BINARY-ALLOYS

The enthalpies of formation DELTA(f)H(m) of the Ir-Ge and Rh-Ge alloys were measured at 1266 K with respect to composition by direct reactio n calorimetry (drop method) with the help of high temperature Calvet-t ype calorimeters. The values lead to the following equation valid for 0 < x(Ir) < 0.21 and 0 < x(Rh) < 0.32 DELTA(f)H(m)/kJ mol-1 = x(Ir)(1 - x(Ir))(- 112.47 - 372.44x(Ir) + 1095.47x(Ir)2) [GRAPHICS] The thermo dynamic behaviour of the melts is characterized by strong negative dev iations from ideality suggesting some chemical short-range order. It w ill be interesting to investigate in future work the thermodynamic pro perties of these two binaries in the concentrated range and their temp erature dependence.