Osmotic coefficient data for Na 2SiO 3 and Na 2SiO 3–NaOH by an isopiestic method and modeling using Pitzer's model

Abstract

Osmotic coefficient and water activity data for Na 2SiO 3 and mixed Na 2SiO 3–NaOH aqueous solutions were obtained at 25°C by employing the isopiestic method. The binary Pitzer's parameters, β (0), β (1), and C φ , for Na 2SiO 3 and the mixing parameters, θ OH −SiO 2− 3 and Ψ Na +OH −SiO 2− 3 were estimated using the osmotic coefficient data. The experimental osmotic coefficient data were correlated well with Pitzer's model. Mean activity coefficients of Na 2SiO 3 and NaOH for the solutions were predicted by Pitzer's model with the parameters obtained. Finally, the presence of metasilicic species, when sodium metasilicate (Na 2SiO 3·9H 2O) is dissolved in aqueous alkaline solution, was established by titration with hydrochloric acid.