Vapour pressure and volumetric studies in aqueous solutions with ascorbate ions

Vapour pressures of water over saturated solutions of l-ascorbic acid and calcium-l-ascorbate were measured in the 280 K to 318 K temperature range and the activities of water, osmotic coefficients and the molar enthalpies of vaporization were derived from them. Densities of aqueous solutions of l-ascorbic acid, magnesium-l-ascorbate and calcium-l-ascorbate were determined at 5 K temperature intervals, from T = 288.15 K to T = 333.15 K. Densities served to evaluate the apparent molar volumes, V_2,φ{symbol}(m,T), the cubic expansion coefficients, α(m,T) and the changes of isobaric heat capacities with respect to pressure, (∂C_P / ∂P)_T,m. They were qualitatively correlated with the changes in the structure of water when ascorbic acid and magnesium and calcium ascorbates are dissolved in it.