Thermodynamic Properties of Synthetic Sapphire (α-Al2O3), Standard Reference Material 720 and the Effect of Temperature-Scale Differences on Thermodynamic Properties

Abstract

Comparison of the National Institute of Standards and Technology's Standard Reference Material 720 certificate values for heat capacity with those obtained from recent experimental determinations indicated the possibility of a systematic error in the certificate values. Selected experimental determinations of enthalpy increments and heat capacities were fitted in order to obtain a representation of the thermodynamic properties of a-Ab03, a sample of which is the standard reference material (SRM720) for calibration of some types of calorimeters. The fitted equation and calculated values of the heat capacity, the relative enthalpy, and the entropy are given. The new values are more accurate and result from a better representation of the experimental values than did the 1982 SRM720 certificate values. Additionally, the general problem of the effect of changes in practical temperature scales on ther-mOdynamic properties is briefly discussed, using the results fur a:-Ah03. A recent report from the IUP AC Commission on Thermodynamics gave a method for the conversion of thermodynamic properties for changes in practical temperature scale. The IUPAC method is shown to be not generally correct. A better methorl for estimation of these changes is given.

Heat Capacities and Derived Thermodynamic Functions of 1-Propanol between 10 K and 350 K and of 1-Pentanol between 85 K and 370 K

“…Oxford Instruments calibrated the thermometer with an uncertainty of 0.001 K using the ITS-90 10 temperature scale. Measurements on n-heptane 11,12 and synthetic sapphire 13,14 verified the uncertainty of the heat capacity measurements. No deviations from the recommended values larger than 0.2% were found.…”

“…At 350 K however, our value for the molar heat capacity of 1-propanol is 1.2% higher than the value reported by ref 7. To check our values, we remeasured the heat capacity of synthetic sapphire between 300 K and 400 K; the maximum deviation from the recommended values 14 found was 0.07%. Remarkably however, is that the heat Not measured were the alcohols with n ) 4, n ) 9, n ) 11, n ) 14, n ) 16, and n ) 21. b, experimental data; 4, calculated values.…”

Determination of heat capacities and thermodynamic properties of two structurally unrelated but isotypic calcium and manganese(II) 2,6-naphthalene dicarboxylate-based MOFs

“…The heat capacity calibration was made by running a standard sapphire (Al 2 O 3 ) at the experimental temperature. The accuracy of TMDSC is established by comparing the measured heat capacity of standard sapphire with previously reported values [35]. The calibration method and the experiment were performed at the same conditions as follows: (1) sampling interval: 1.00 s/pt; (2) zero heat flow at 428.15 K; (3) equilibrate at 183.15 K; (4) isothermal for 5.00 min; (5) temperature ramp at 10 K min -1 to 673.15 K.…”

Calorimetric study of block-copolymers of poly(n-butyl acrylate) and gradient poly(n-butyl acrylate-co-methyl methacrylate)

“…The heat-flow rate was initially calibrated with the heat of fusion of indium (28.45 J g 1 ). The heat capacity obtained was then refined by correction with a reference run of sapphire over the same temperature range as the sample [17]. The calorimeter asymmetry between the empty reference and sample calorimeters was eliminated with an empty-pan run used as a baseline for the heat-flow rate of the sample and calibration runs.…”