Determination of gibbs energy of formation of cuspidine (3Cao.2Sio 2.CaF2) by transpiration method

Abstract

The standard Gibbs energy change of the following reaction of cuspidine (3CaO · 2SiO2 · CaF2) with water vapor has been determined by a transpiration method as 3CaO · 2SiO2 · CaF2(s) - H2O(g) = 2(2CaO · SiO 2)(s)+2HF(g) ΔrG°/kJ=265-0.116T (±16) (1 22 <1 469) From this result, the standard Gibbs energy of formation of cuspidine has been evaluated as, ΔAfG°(cuspidine)/kJ mor1-1 = -5 178+0.813T(±19) (1 221 <1 469) The constituent activities of the CaO-Si02-CaF2 system and fluorine emission from the system at elevated temperatures have been evaluated based on the obtained thermodynamic data.