Volumetric and Viscometric Studies of Amino Acids in Vitamin B6 Aqueous Solutions at Various Temperatures

The densities and viscosities of glycine, l-alanine, l-valine, l-threonine, and l-arginine in (0.1 to 0.4) mol·kg–1 vitamin B6 aqueous solutions were measured and studied over the entire molality range at (293.15, 303.15, 313.15, and 323.15) K and atmospheric pressure. The apparent molar volume (Vϕ), limiting partial molar volume (Vϕ0), and limiting partial molar volume of transfer (ΔtrVϕ0) were obtained according to the experimental density data. The viscosity data were employed to determine the viscosity B coefficients, the free energies of activation per mole of solvent (Δμ10⇌) and solute (Δμ20⇌). The influences of temperature, molality, and solute structure on these parameters were discussed in terms of molecular interactions. The contributions of the charged end group (NH3+, COO–) and CH2 group to the limiting partial molar volumes and viscosity B coefficients were obtained through their linear correlation as a function of the number of carbon atoms in the alkyl chains of the studied amino acids.