Ceramics-Silikáty 22, (2) 97 - 108 (1978)

Mixing enthalpy ΔH_mix,l(x, T) of the melts in the system 2CaO.MgO.2SiO₂-CaO.MgO.2SiO₂ and the temperature dependence of enthalpy of the pure components were determined within the temperature range of approx. 1700-1873 K. Use was made of the double calorimetry method by which the values of relative enthalpy H_rel,l(x_m, T_m) in the system are determined from the sum of increases in enthalpy measured in the course of cooling in the drop calorimeter (ΔH_cool) as well as during dissolving in a calorimeter for the measurement of dissolution heat (ΔH_sol). The states of solutions in a mixture of concentrated hydrofluoric and nitric acids (2:1) at temperature T_bas = 298 K were chosen as the reference state. The values measured were used for plotting the relationship of H_rel,l(x, T) for temperatures T_m= 1723, 1773 and 1823 K; the H_rel,l(x, T) was described mathematically by an exponential function.