Basicity-Gibbs Free Energy Relationships for Binary Alkali Silicates

摘要

In present paper there are presented such correlations for the silica-alkali systems (M_2O - SiO_2) where reliable thermodynamic data exists from the thermal equilibrium diagrams. It was observed that with the saturation of SiO_2 tetrahedron with metal ions, the difference in basicity between the reactants is diminished, in the order SiO_2 → disilicate → metasilicate → orthosilicate, and that confirms the role of driving force for these reactions of the acid-base interaction between oxides and the intermediate silicates formed. Also, there were proposed some correlations between the standard formation Gibbs free energy, (△G°_298), and basicity percentage, pB, for the binary compounds from the same oxide systems. Considering the fact that for a system at equilibrium, reaction constant Kp depends on the reaction free Gibbs energy (△~R(g~0)_298) and temperature, a correlation between basicity difference through basicity percentage, pB, and △~R(g~0)_298 is proposed.