PARTIAL MOLAR VOLUMES AND EXPANSIBILITIES OF SOME D-PENTOSES AND D-HEXOSES IN AQUEOUS-SOLUTION

The densities of aqueous solutions of some monosaccharides (D-pentoses and D-hexoses) were measured up to 2.5 mol kg-1in the temperature range from 293.15 to 318.15 K. The mean molar volumes of the solutions were found to be linearly dependent on the mole fraction of the solute. Thus, the partial molar volumes of solvent and solute, respectively, are concentration-independent; i.e., the partial molar volume of the solvent is equal to the molar volume of pure solvent, and the partial molar volume of the solute is equal to its value at infinite dilution. For the systems investigated, the dependence of the partial molar volumes of the solute on temperature was found to be linear. Therefore, the partial molar expansibilities of the solutes are concentration- and temperature-independent. The thermal expansion coefficients of the solute tend to decrease slightly with Increasing temperature. The thermal expansion coefficients of the solutions at 298.15 K as a function of solute mole fraction were fitted to a second-degree polynomial. In addition, from the partial molecular volumes of the solutes and the respective molecular volumes of the solid solutes, it was shown that the empty volume associated with the solute molecule in aqueous solution is small and roughly the same as the empty volume associated with this molecule in the solid state. © 1990, American Chemical Society. All rights reserved.