Heretofore unpublished enthalpy data which were used in the derivation of smooth enthalpy and heat-.capacity data for NBS SRM 720 (a-A1, 2 0, heat capacity and enthalpy standard) are presented along with some details of the high-temperature experiments. Recent NBS low-temperature measurements on SRM 720 are smoothed by a least-squares spline technique and a revised table of certified values for enthalpy and heat capacity of a-Al,() from 10 K to near the meltng point (2250 K) is presented.
The heat capacity of o-terphenyl has been measured with an adiabatic calorimeter for the crystal from 2°K to Tm (329.35°K), for the glasses from 2°K to Tg (around 240°K) and for the liquid from Tg to 360°K, on a sample with less than 0.005 mole % impurity. The heat of fusion and the entropy of fusion are 17 191 J mole−1 and 52.20 J°K−1· mole−1, respectively. The residual entropy of the glasses at 0°K is about 15 J°K−1· mole−1. Above 170°K, the heat capacity of the o-terphenyl crystal is nearly proportional to the temperature to within 1%. Configurational entropy of the supercooled liquid, estimated from the result of this investigation, is used to relate the relaxation properties of glass-forming liquids according to the theory of Adam and Gibbs. Good agreement is found for both viscosity and NMR correlation frequency data.
Experimentally determined heat capacity valu es, precise to within 0.1 percent, and related thermal data are reported for quenched and annealed diethyl phthalate glasses from ]0 oK to the glass transformation te mperature, Tg (around 180 O K) , for the liquid from T" to 360 oK, and for the crystal from 10 oK to the melting temperature (269.9 O K). The mole fraction of liquid·soluble, solid·insoluble impurity in the sample as determined by fractional melting was 0.0012. Co mmon thermodynamic properties calc ulable from the experimental data are reported. The heat capacities of the two glasses differ by more than the uncertainty of the meas urements, and both lie below that of the crystal in the range from 30 to 75 oK. At low temperatures, just above 10 oK, the heat capacities of the glasses rise as much as 8 percent above that of the crystal.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.