Heat capacities and related thermal data for diethyl phthalate crystal, glass, and liquid to 360 K

Abstract

Experimentally determined heat capacity values, precise to within 0.1 percent, and related thermal data are reported for quenched and annealed diethyl phthalate glasses from 10 °K to the glass transformation temperature, T g (around 180 °K), for the liquid from T g to 360 °K, and for the crystal from 10 °K to the melting temperature (269.9 °K). The mole fraction of liquid-soluble, solid-insoluble impurity in the sample as determined by fractional melting was 0.0012. Common thermodynamic properties calculable from the experimental data are reported. The heat capacities of the two glasses differ by more than the uncertainty of the measurements, and both lie below that of the crystal in the range from 30 to 75 °K. At low temperatures, just above 10 °K, the heat capacities of the glasses rise as much as 8 percent above that of the crystal.