Single ion activity coefficients based on the electrical double-layer model. Na2SO4 aqueous solutions

✍ Scribed by Angelo Uzzo; Anna Daghetti; Sergio Trasatti

• Publisher: Elsevier Science
• Year: 1983
• Tongue: English
• Weight: 599 KB
• Volume: 28
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(83)85213-x

✦ Synopsis

Single ion activity coefficients for Na,SO, aqueous solutions have been determined by en$ measurements of rhe cells: sce/Na,SO+ (aq., #SO:--reversible electrode and sce/Na$O, (as., m)/Na+selective electrode; coupled with electric potential difference measurements for the cell: Hg (6 = const)/Na,SO, (aq., m)/scc. The extra-thermodynamic assumption behind this approach is that the electric potential drop across the compact layer at the I-Ig/solution interface in the absence of ionic specific adsorption is strictly independent of the eleclrolyte concentration. Results show that y+ is higher than y_ , somewhat less than expected on the basis of the simple difference in ionic charge. y+ and y-calculated with the aid of Stokes, Robinson and Bates' hydration theory have been found to deviate the other way round. In the light of these results some considerations can be made on the accuracy of Ciouyxhapman diffuse layer calculations. lNTRODUCTlON