The Semi-ideal Solution Theory. 3. Extension to Viscosity of Multicomponent Aqueous Solutions

Viscosities were measured for the ternary aqueous systems NaCl–mannitol(C6H14O6)–H2O, NaBr–mannitol–H2O, KCl–mannitol–H2O, KCl–glycine(NH2CH2COOH)–H2O, KCl–CdCl2–H2O, and their binary subsystems NaCl–H2O, KCl–H2O, NaBr–H2O, CdCl2–H2O, mannitol–H2O, and glycine–H2O at 298.15 K. A powerful new approach is presented for theoretical modeling of the viscosity of multicomponent solutions in terms of the properties of their binary solutions. In this modeling, the semi-ideal solution theory was used to associate the solvation structure formed by each ion and its first solvation shell in a binary solution with the solvation structure of the same ion and its first solvation shell in multicomponent solutions. Then, the novel mechanism proposed by Omta et al. (Science, 301:347–349, 2003) for the effect of a single electrolyte on the viscosity of water was extended to describe the influence of solute mixtures on the viscosity of water, including electrolyte mixtures, nonelectrolyte mixtures, and mixtures of electrolytes with nonelectrolytes. The established simple equation was verified by comparison with measured viscosities and viscosities reported in literature. The agreements are very impressive. This formulation provides a powerful new approach for modeling this transport property in solutions. It can stimulate further research in establishing a dynamical analogue to that formulated for the thermodynamics of multicomponent solutions. It is also very important for the study of hydration of ions.