Effect of temperature on W-shaped excess molar heat capacities and volumetric properties: Oxaalkane-nonane systems

Excess molar volumes vii , of the mixtures diglyme (2,5,8-trioxanonane: TON ), triglyme (2,5,8,1 I-tetraoxadodecane: TODD), or tetrag[yme 12.5,8.11,14-pentaoxapentadecane: POPD: El81 ) +n-nonane have been obtained from density measurements at 278.15, 288.15,298.15, and 308.15 K. In addition, a micro DSC It diflʹerential scanning calorimeter was used to obtain excess molar heat capacities CII at constant pressure for the same mixtures except for TON + n-nonane and at the same temperatures except tbr 278.15 K. These results altowed us to calculate the following mixing quantities in the complete range of concentration: ~. (Ol.ʹll,/OT),,, and (OHʹ:/~p)r at 298.15 K. The excess molar volumes are positive with large maximum wdues located in the central concentration range with the exception of POPD +n-nonane at 278.15 K, which has a central miscibility gap. For these mixtures, (2q~i has a W-shaped concentration dependence: two minima separated by a maximum.