Determination of the Specific Heat Capacities of Aqueous Solutions of Pentose

Abstract A laboratory-constructed isoperibol twin calorimeter of dry shield type (J. Chem. Thermodyn., 13, 89 (1981)) was used for measurements of the specific heat capacities of aqueous solutions of d-xylose, d-ribose, d-, and l-arabinose at ca. 30 °C. The partial molar heat capacity at infinite dilution, Cp.2∞ was determined. Values of Cp.2∞ obtained are: d-xylose 281±2, d-ribose 271±2, d-arabinose 278±3, and l-arabinose 270±4 J K−1 mol−1. Measurements of the heat capacity of these pentoses in the solid state, Cp.2* were carried out and the parameter ΔCp.2∞≡Cp.2∞–Cp.2* was evaluated. Values of ΔCp.2∞ are smaller than the corresponding values for hexose obtained previously. Similarly as had been the case for hexose, the additivity parameters of the group contribution on Cp.2∞ of solute estimated from the data on other nonelectrolytes were not acceptable for pentose. From this point the interactions working between solute of saccharide and the solvent water are considered to have characters largely different from those of other nonelectrolyte.