Abstract
The molar excess enthalpies HE for aqueous solutions of 1, 2-propanediol (1, 2-PD) and 1, 3-propanediol (1, 3-PD) have been measured at 298.15K over the whole concentration range by an isothermal dilution calorimeter. All the solutions exhibit negative enthalpies of mixing. The minimum value of HE for aqueous solution of 1, 2-PD is smaller than that of aqueous solution of 1, 3-PD. The curve of HE against x1 (mole fraction of propanediol) for aqueous solution of 1, 2-PD is highly skewed with sharp minimum at x1 ≅ 0.21 and inflections at x1=0.51. The partial molar excess enthalpies of all the propanediols are almost constant in the middle of the composition range. These results are interpreted qualitatively in terms of specific molecular interactions in aqueous solution.
