Volumetric and transport properties of ternary solutions of l-serine and l-valine in aqueous NaCl solutions in the temperature range (293.15–323.15) K

Highlights: • Extend data of density and viscosity for ternary l-valine/l-serine + NaCl + water systems. • Relevant parameters of volume and viscosity for amino acids have been determined. • Amino acids behave as structure–maker in aqueous NaCl solutions. • Viscosity models based on Eyring's theory. • Results in terms of solute–solvent interactions based on a co-sphere overlap model. In this paper we report new density and viscosity data of l-serine and l-valine in aqueous NaCl solutions as a function of amino acids molality at fixed salt concentration (0.1, 0.2, 0.5, 0.7 and 1.0 mol·kg⁻¹) and temperature T = (293.15, 298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K at atmospheric pressure of p = 0.1 MPa. From density, some derived properties such as the apparent molar volume, $V_{\varphi }$, limiting partial molar volume, ${\text{V}}_{\varphi }^{\text{0}}$, and expansibility, $E_{\varphi }^0$, standard molar volume of transfer, ${\Delta \text{V}}_{\varphi }^{\text{0}}$, and hydration number, $n_H$, were calculated and discussed in terms of solute–solvent interactions and structural effects. The Jones–Dole equation and transition state treatment were used to obtain the viscosity B coefficient, free energy of activation of viscous flow per mole of solvent, ${\Delta \mu }_1^{0\#}$, and per mole of solute, ${\Delta \mu }_2^{0\#}$, entropies, ${\Delta S}_2^{0\#}$, and enthalpies, ${\Delta H}_2^{0\#}$, of activation of viscous flow for amino acids. All the activation parameters were discussed in terms of transition state theory. The co-sphere overlap model was used to interpret the results. The structure making/breaking ability of the amino acids in solutions was also discussed.