The Electrochemical Measurement of Standard Free Energies of Formation for Fe₂SiO₄, Co₂SiO₄ and Ni₂SiO₄

Abstract

The standard free energies of formation of Fe₂SiO₄, Co₂SiO₄ and Ni₂SiO₄ were measured in the temperature range from 675° to 1000°C by a galvanic cell method, using 0.85ZrO₂. 0.15CaO as electrolyte.
The formation reactions are
2FeO (s) + SiO₂ (s) = Fe₂SiO₄ (s), 2CoO (s) + SiO₂ (s) =Co₂SiO₄ (s), and 2NiO (s) + SiO₂ (s) = Ni₂SiO₄ (s) foI whichΔG° Fe2SiO4= -10500± 80+ (4.853± 0.074) T cal/mol,
ΔG° Co2SiO4= -7270± 40+ (3.062± 0.040) T cal/mol,
ΔG° Ni₂SiO₄= -5270± 100+ (2.927± 0.093) T cal/mol
The accuracy of these measurements was discussed together with the thermochemical data of other investigators.