Solvation behavior of some vitamins in aqueous solutions of sodium chloride at different temperatures and at atmospheric pressure

• V2° and B values have been determined for vitamins in aqueous NaCl solutions.
• ΔtrV2°, ΔtrB do not vary regularly with temperature and concentration of NaCl.
• Studies show complex interactions between vitamins and NaCl.

Densities ρ, and viscosities η, of aqueous solutions of l-ascorbic acid, nicotinic acid, thiamine hydrochloride and pyridoxine hydrochloride have been determined in different concentrations of sodium chloride at temperatures 288.15–318.15 K. These data were used to calculate apparent molar volumes V2,ϕ, partial molar volumes at infinite dilution V2°, and viscosity B-coefficient (B). The corresponding transfer parameters at infinite dilution (ΔtrV2° and ΔtrB) have been calculated using the data in water reported earlier on these vitamins. The dB/dT values have also been calculated. Results have been discussed in terms of solute–solute and solute–solvent interactions, which are found to be very complex in these systems. Activation free energy of viscous flow has also been calculated for these vitamins + sodium chloride + water systems.

Representative plot of apparent molar volume (V2,ϕ) vs molality (mA) as a function of temperature for l-ascorbic acid in aqueous sodium chloride solutions at mB = 0.2 mol kg−1. V2,ϕ values for l-ascorbic acid increase with temperature as well as with the molality of the vitamin as the color on the plot changes from blue to orange. The deep blue color represents the lowest V2,ϕ values at 288.15 K and orange color represents the highest V2,ϕ values at 318.15 K.Figure optionsDownload as PowerPoint slide