Reactions of calcium silicates in solution in liquid calcium fluoride

Abstract

The system CaO+SiO₂ has been studied at 1420°C in the composition range 0.1 M CaSi₂O₅+0.9 M CaF₂ to 0.1 M Ca₃SiO₅+0.9 M CaF₂, through the infra-red spectra of quenched thin films and by transpiration measurements of the SiF₄ pressure developed over the solutions. Thermochemical results suggest a fluorination of the silicate ions, in 0.1 M CaSi₂O₅,+0.9 M CaF₅, decreasing at higher oxide concentrations. Spectroscopic results show that the ions in quenched solutions are closely similar to those in crystalline silicates, and that meta-silicate ions exist as chain-ions rather than rings. It is suggested that fluoro-silicate ions would be unstable on quenching, and would therefore be present in insufficient concentration to give rise to Si—F bands identifiable in the infra-red spectra of quenched solutions.