Densities, molar volumes, and isobaric expansivities of (d-xylose + hydrochloric acid + water) systems

Densities of (d-xylose + HCl + water) have been measured at temperature in the range (278.15 to 318.15) K as a function of concentration of both d-xylose and hydrochloric acid. The densities have been used to estimate the molar volumes and isobaric expansivity of the ternary solutions. The molar volumes of the ternary solutions vary linearly with mole fraction of d-xylose. The standard partial molar volumes V2,ϕ∘ for d-xylose in aqueous solutions of molality (0.2, 0.4, 0.7, 1.1, 1.6, and 2.1) mol · kg−1 HCl have been determined. In the investigated temperature range, the relation: V2,ϕ∘=c1+c2{(T/K)-273.15}1/2, can be used to describe the temperature dependence of the standard partial molar volumes. These results have, in conjunction with the results obtained in water, been used to deduce the standard volumes of transfer, ΔtV∘, of d-xylose from water to aqueous HCl solutions. An increase in the transfer volume of d-xylose with increasing HCl concentrations has been explained by the stronger interactions of H+ with the hydrophilic groups of d-xylose.