The viscosity and refractive index of the solutions of room-temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF 6 ] in tetrahydrofuran, dimethylsulfoxide, methanol, and acetonitrile have been measured at 298.15 K. The density and speed of sound for solutions of [BMIM][PF 6 ] + tetrahydrofuran or dimethylsulfoxide have also been measured. The changes in viscosity and molar refraction, the excess molar volume, and deviation in isentropic compressibility have been adequately fitted to the Redlich-Kister polynomial.

Viscosity values of the ternary aqueous mixed electrolyte solutions have been correlated with models based on the Eyring's absolute rate theory and the electrolyte NRTL, modified NRTL, and Wilson theories for calculating the excess Gibbs energy of activation of the viscous flow. Utilization of the mixing rule assumption in the viscosity parameter of Einstein's relation has made it possible to use the binary parameters of the local composition models in extending of these equations to the ternary electrolyte systems. Performance of the investigated models in the correlation of the viscosity data of the ternary mixed electrolytes + H 2 O systems is good. A new semiempirical equation has also satisfactorily been used to correlate the viscosity of the ternary aqueous multielectrolyte solutions. The quality fitting of this semiempirical equation is much better than the aforementioned local composition models. A simple exponential equation with consideration of the temperature dependency has also been used to correlate the viscosity values of solute. Usage of calculated solute viscosity in the suitable mixing rule made it possible to predict the viscosity of aqueous mixed electrolyte solutions. The agreement between the predicted and experimental viscosity values of aqueous multielectrolyte solutions is excellent over the entire composition and temperature range.

A local composition model is developed for the representation of the excess Gibbs energy of polymer solutions. The model consists of two contributions due to the configurational entropy of mixing, represented by the Freed FloryÀHuggins relation, and to the enthalpic contribution, represented by local compositions through nonrandom factor. The model is applied to correlate the solvent activity of binary polymer solutions. The new excess Gibbs energy equation was used along with the absolute rate theory of Eyring for modeling the dynamic viscosity of binary polymer solutions in the entire concentration range at different temperatures considering different molar mass of polymers. The fitting quality of new model has favorably been compared with polymer-NRTL, segment-based-liquid-NRTL, polymer-Wilson, polymer-NRF and polymer-NRF-Wilson models. The validity of the proposed model is especially demonstrated for the whole range of polymer concentrations at different temperatures using different molar masses of polymers. The segment-based approach provides a more physically realistic model for large molecules when diffusion and flow are viewed to occur by a sequence of individual segment jumps into vacancies rather than jumps of the entire large molecule. Therefore, the correlation of viscosity values for nanofluids was also tested with the proposed Eyring-modified NRF model developed with respect to the segment-based approach. The performance of this model in the fitting of viscosity values of nanofluids are compared with the previously used liquid-NRTL model. Results show that this segment-based model is most valid in the fitting of viscosity values of nanofluids in the entire concentration range at different temperatures.

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Water activity in aqueous solutions containing diphenhydraminehydrochloride, DPH-HCl, (D+)-galactose, (D−)-fructose, (D+)-lactose, and sucrose was measured using an improved isopiestic method at T = 298.15 K. Vapor pressure values were calculated from the measured water activity data. Nonrandom two-liquid (NRTL), NRF-NRTL, mNRTL, Wilson, TNRF-mNRTL and modified NRTL proposed by Xu local composition-based models were applied for correlating the water activity data for binary and ternary aqueous solutions containing the DPH-HCl drug and saccharides considered in this work. All of these models satisfactorily predicted the water activity data for the systems investigated. Water activity data and decreasing vapor pressure were utilized to highlight the solute−solvent interactions.

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The density and speed of sound of the solutions of poly(propylene glycol) 400, in ethanol and 2-propanol at T ) (288.15 to 328.15) K, and dynamic viscosity of these solutions at T ) (298.15 to 328.15) K have been measured experimentally over the entire range of compositions and atmospheric pressure. From these experimental data, the excess molar volume, V m E , excess molar isentropic compression, κ E s,m , and deviation of logarithm of viscosity, ∆ ln η, have been determined for each composition. V m E , κ E s,m , and viscosity data have been adequately fitted to the Redlich-Kister and NRTL models.