Calorimetric investigation of the solid compounds of the Au–Pb system

The three intermediate compounds of the Au–Pb system were synthesised by melting the pure components in suitable proportions and annealing at a temperature just below their melting point. Their structural states were verified by X-ray studies. The enthalpy of formation of the compounds was measured by dissolution calorimetry (drop method) at 650K in liquid lead using a high temperature Tian–Calvet calorimeter. The measurements lead to: h f ( Au 0.667 Pb 0.333, cr, 298 K)=−3.1 kJ mol −1 h f ( Au 0.333 Pb 0.667, cr, 298 K)=−3.2 kJ mol −1 h f ( Au 0.25 Pb 0.75, cr, 298 K)=−1.6 kJ mol −1