DIFFERENTIAL AND INTEGRAL ENTHALPIES OF SOLUTION OF AKERMANITE AND PSEUDO-WOLLASTONITE IN THE MELTS OF THE SYSTEM CA2MGSI2O7-CASIO3 - ISOPLETHAL ENTHALPIES IN THIS SYSTEM

It was found that the enthalpy of mixing at formation of the melts in the Ca2MgSi2O7-CaSiO3 system from melts of Ca2MgSi2O7 and CaSiO3 is ze ro within the temperature limits from 1673 to 1930 K, Consequently, th e differential and integral heats of solution of akermanite and pseudo -wollastonite in the melts of this system are equal to their heats of fusion at the corresponding temperature. Using the non-isothermal Hess law and the phase diagram, isoplethal enthalpies were calculated in t his system within the temperature range from 298 to 1920 K. The enthal py and entropy of crystallization for the eutectic melt at the eutecti c temperature T-e = 1673 K was determined to be Delta(cryst) H(eut.mel t, T-e) = (-78.3 +/- 2.4) J mol(-1) and Delta(cryst)S(eut.melt, T-e) = (-46.8 +/- 1.4) J mol(-1) K-1, respectively.