Clara A. Tovar, Enrique Carballo, Claudio A. Cerdeiriña, M Inmaculada Paz Andrade and Luis Romaní
Differential scanning calorimetry has been used to determine the excess heat capacity of liquid mixtures of triglyme and tetraglyme with cyclohexane, and tetraglyme with n-heptane, at 288.15, 298.15 and 308.15 K, at atmospheric pressure, throughout the composition range. The curves thus obtained as a function of composition were found to be W-shaped. The results are compared with those for other glyme–alkane mixtures. Changes in the W-shaped curves with temperature were virtually linear for mixtures which have an upper critical solution temperature (UCST) relatively distant from the measuring range; by contrast, excess heat capacities increased asymptotically near the phase separation region. The results are discussed in terms of order creation in the mixture that arises from concentration fluctuations near the UCST.