Volumetric and Viscometric Studies of Amino Acids in Mannitol Aqueous Solutions at <i>T</i> = (293.15 to 323.15) K

Densities and viscosities of glycine, l-alanine, l-valine, l-threonine, and l-arginine in aqueous solutions of (0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) mol·kg^–1 mannitol have been measured in the temperature range of (293.15 to 323.15) K under atmospheric pressure; then the measured densities and viscosities of experimental systems were correlated. These data were further used to calculate the apparent molar volumes (<i>V</i>_φ), the limiting partial molar volumes (<i>V</i>_φ⁰), the limiting partial molar volumes of transfer (Δ_tr<i>V</i>_φ⁰), the viscosity <i>B</i>-coefficients, and the free energies of activation per mole of solvent (Δμ₁^0≠) and solute (Δμ₂^0≠). The results were interpreted through solute–solute interaction and solute–solvent interaction on the basis of the cosphere overlap model and transition state theory

Volumetric and Viscometric Properties of Alcohol Amines + Ethanol Binary Mixtures

The densities and viscosities of four binary mixtures [1-amino-2-propanol + ethanol, <i>N</i>-(2-aminoethyl) ethanolamine + ethanol, 3-amino-1-propanol + ethanol, <i>N</i>-(2-aminoethyl)-1,2-ethanediamine + ethanol] were measured at <i>T</i> = 293.15, 303.15, 313.15, and 323.15 K. The volumetric and viscometric properties, such as excess molar volume <i>V</i>^E, partial molar volume <i>V̅</i>, partial molar volume at infinite dilution <i>V̅</i>^∞, apparent molar volume <i>V</i>_φ, viscosity deviation Δη, and activation energy for viscosity flow <i>E</i>_a, were calculated from the experimental densities and viscosities, respectively. The excess molar volume and viscosity deviation were correlated by the Redlich–Kister equation, and the volumetric and viscometric properties were analyzed on the basis of intermolecular interactions between alcohol amine and ethanol molecules

Formation of Droplets of Shear-Thinning Non-Newtonian Fluids in Asymmetrical Parallelized Microchannels

Fluids containing polymers are frequently utilized in the chemical industry and exhibit shear-thinning characteristics. The flow distribution of non-Newtonian fluids in parallelized microchannels is a key issue to be solved during numbering-up. Numbering-up means increasing the number of parallelized microchannels. In this study, a high-speed camera is used to explore the distribution of fluid flow as well as the uniformity and stability of droplets in conceptual asymmetrical parallelized microchannels. Cyclohexane and carboxymethylcellulose sodium (CMC) aqueous solutions are used as the continuous phase and dispersed phase, respectively. The effects of fluctuation of pressure difference around the T-junction, the hydrodynamic resistance in microchannels, and the shear-thinning property of fluids on flow distribution and droplet formation are revealed. The uniformity and stability of droplets in microdevices with various cavity settings are compared, and an optimal configuration is proposed. Finally, prediction models for the flow distribution of shear-thinning fluids in asymmetrical parallelized microchannels are established

Modeling and Simulation of Thermodynamic Properties of l‑Alanyl‑l‑Glutamine in Different Solvents

The solubility of l-alanyl-l-glutamine (Ala-Gln) in pure water and ethanol–water mixed solvents was measured using a synthetic method from 283.15 to 313.15 K. Molecular dynamics simulation was carried out to explain the effect of ethanol content on the solubility of Ala-Gln. The radial distribution function was used to evaluate the interactions between solute molecules and solvent molecules. The solubility data was correlated by four thermodynamic models, including the hybrid model, Wilson model, NRTL model, and UNIQUAC model. It was found that the NRTL model could give better correlation results than the other models. The dissolution properties of Ala-Gln solutions, including the free Gibbs energy, the dissolution enthalpy, and the dissolution entropy, were calculated by using the modified van’t Hoff equation