Silicate, molar free energy

The molar free energy of mixing, AG of a silicate is represented by the expression... 

The stability constants of both magadiite and kenyaite have been measured by Bricker (187), who concluded that the minerals are stable in alkaline waters rich in sodium and soluble silica. It appears that at pH 9 these crystalline sodium silicates are actually less soluble in water than amorphous silica. The Gibbs molar free energies of formation were also calculated as -1,762.2 kcal for magadiite and -2,603.5 kcal for kenyaite. 

Determination of the standard molar Gibbs free energies of formation of the silicates of cobalt and nickel by solid-state galvanic cells involving the CaF2-based composite electrolyte, J. Chem. Thermodyn., 32, (2000), 931-935. Cited on pages 243, 244,437. 

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