Osmotic coefficient data for Na2SiO3 and Na2SiO3–NaOH by an isopiestic method and modeling using Pitzerʹs model

Osmotic coefficient and water activity data for Na2SiO3 and mixed Na2SiO3–NaOH aqueous solutions were obtained at 25°C by employing the isopiestic method. The binary Pitzerʹs parameters, β(0), β(1), and Cφ, for Na2SiO3 and the mixing parameters, θOH−SiO2−3 and ΨNa+OH−SiO2−3 were estimated using the osmotic coefficient data. The experimental osmotic coefficient data were correlated well with Pitzerʹs model. Mean activity coefficients of Na2SiO3 and NaOH for the solutions were predicted by Pitzerʹs model with the parameters obtained. Finally, the presence of metasilicic species, when sodium metasilicate (Na2SiO3·9H2O) is dissolved in aqueous alkaline solution, was established by titration with hydrochloric acid.