EFFECT OF TEMPERATURE ON W-SHAPED EXCESS MOLAR HEAT-CAPACITIES AND VOLUMETRIC PROPERTIES - OXAALKANE-NONANE SYSTEMS

Excess molar volumes V-m(E) of the mixtures diglyme (2,5,8-trioxanonan e; TON), triglyme (2,5,8,11-tetraoxadodecane; TODD), or tetraglyme (2, 5,8,11,14-pentaoxapentadecane; POPD; E181) + n-nonane have been obtain ed from density measurements at 278.15, 288.15, 298.15, and 308.15 K. In addition, a micro DSC II differential scanning calorimeter was used to obtain excess molar heat capacities C-p(E) at constant pressure fo r the same mixtures except for TON + n-nonane and at the same temperat ures except for 279.15 K. These results allowed us to calculate the fo llowing mixing quantities in the complete range of concentration: alph a, (partial derivative V-m(E)/partial derivative T)(p), and (partial d erivative H-E/partial derivative p)(T) at 298.15 K. The excess molar v olumes are positive with large maximum values located in the central c oncentration range with the exception of POPD + n-nonane ar 278.15 K, which has a central miscibility gap. For these mixtures, C-p(E) has a W-shaped concentration dependence: two minima separated by a maximum.