CALORIMETRIC INVESTIGATION OF THE LIQUID ALLOYS OF AG + TE AND OF THE AG2TE SOLID COMPOUND AT HIGH-TEMPERATURE

The enthalpies of formation ΔHf of Ag+Te alloys have been measured in the temperature range 728 < T K < 1378, by direct reaction calorimetry. At 1210 K, the highest temperature investigated, the enthalpy of formation of Ag2Te solid compound is -15.90 kJ mol-1 with reference to solid Ag and liquid Te. The study of its variation with temperature yields a negative excess heat capacity, CpE = -3.8 J K-1 mol-1, in the same reference state. In the liquid state, the integral enthalpy of formation shows a sharp minimum at xTe = 0.333, corresponding to the formation of Ag2Te-type associates and the partial molar enthalpy of tellurium undergoes a jump at this mole fraction as predicted by C. Wagner many years ago. The fact that in the liquid state, ΔHf is temperature independent up to 1378 K, indicates a high stability of these associates. © 1979.