ACTIVITY COEFFICIENTS OF SILICOTUNGSTIC ACID; ULTRACENTRIFUGATION AND LIGHT SCATTERING

Activity coefficients of silicotungstic acid (0.0004-0.04 M) in aqueous solution were measured by equilibrium ultracentrifugation. The results agree with the Debye-Huckel theory for a 1-4 electrolyte, with a distance of closest approach parameter of 7.6 angstrom. A few ultracentrifugations of sodium silicotungstate indicate that the activity coefficients of this solute are similar. Turbidities of silicotungstic acid solutions are reported; they agree with the values predicted from ultracentrifugation results. Turbidities expected for two-component electrolyte-water systems at low concentration are discussed. Densities and refractive indices of silicotungstic acid solutions are presented.