Determination of Gibbs Energy of Formation of Cuspidine (3CaO centre dot 2SiO_2 centre dot CaF_2) from the Electromotive Force Method Using CaF2 as the Solid Electrolyte

摘要

The standard Gibbs energy change for the following reaction has been directly determined by electromotive force (EMF) measurement using CaF_2 as the solid electrolyte in the temperature range from 1313 to 1329K. 3CaO centre dot 2SiO_2 centre dot CaF_2(s) + CaO(s) velence 2(2CaO centre dot SiO_2)(s) + CaF_2(s); DELTA_r G deg/kJ velence 15.9 - 0.0192T (+-0.2) From the preceding results, the standard Gibbs energy of formation of cuspidine has been evaluated for the first time as DELTA_f G deg (cuspidine)/kJmol~(-1) velence -5198 + 0.825T(+-12) The chemical potential diagram for the CaO-SiO_2-CaF_2 system has been developed at 1323 K based on the thermodynamic data obtained in the present study.