Heat capacity high temperature

High-temperature heat capacity of Appendix A. The transition and melting points of ... 

Enthalpy increment measurements to derive the high-temperature heat capacity have been reported for all lanthanide trifluorides except PmF3, as summarised in table 7. The results of the various authors are compared using the reduced enthalpy increment function ... 

Recommended high temperature heat capacity functions for the solid lanthanide trifluorides... 

In analogy with the approach that has been described in the section on the low-temperature heat capacity, the high-temperature heat capacity of the LnXj compounds can be described as the sum of the lattice and excess contributions (eq. (1)). However, whereas at low temperature the lattice heat capacity mainly arises from harmonic vibrations, at high temperatures the effects of anharmonicity of the vibrations, of thermal dilation of the lattice and of thermally... 

The experimental basis for the recommended heat capacity of the tribromides and triiodides is marginal and more low- as well as high-temperature heat capacity measurements are required. 

The lack of auxiliary data such as crystal field energies for the tribromides and triiodides further limits the value of the semi-empirical approach used here to estimate high temperature heat capacities. 

Steele, W.V., Chirico, R.D., Nguyen, A., Knipmeyer, S.E. (1995) Vapor pressure, high-temperature heat capacities, critical properties, derived thermodynamic functions, and barriers to methyl-group rotation, for the six dimethylpyridines. J. Chem. Thermodyn. 27, 311-334. 

The salt is stable up to 600°C and begins to lose weight above that temperature.103 The phase transitions and high temperature heat capacity have been studied by Mustajoki,104 but the lack of... 

Mocala, K., Navrotsky, A. Sherman, D. M. (1992) High-temperature heat capacity of C03O4 spinel Thermally induced spin-unpairing transition. Phys. Chem. Minerals, 19, 88—95. 

Roberts ( 1 1) surveyed the superconductive properties of the elements and recommended a critical temperature of 1.175 0.002 K for Al(cr). Since this temperature is so low, the effects of superconductivity on the thermodynamic functions are not considered. The entropy contribution due to superconductivity will be less than 0.002 J X mol . The data of Giauque and Meads (j ) and Downie and Martin (3) agree at temperatures up to 150 K but drift apart by 0.2 J X mol at 200 X and 0.17 J X mol at 300 K, with the Downie and Martin study being lower. The Takahashi (4, 5) study is even lower at 298 X. The high temperature heat capacity values are derived from the enthalpy study of Ditmars et al. (9). Their curve is intermediate between those derived from previous studies (4, 5, 6, 7, 8) and implies a flatter Cp curve near the melting point (in comparison to previous interpretations). Numerous other heat capacity and enthalpy studies are available but were omitted in this analysis. A detailed discussion of the Group IIIA metals (B, Al, and Ga) is in preparation by the JANAF staff. 

The crystal data compilation of Donnay and Ondlk ( ) tabulated both ZrCl and ZrBr as cubic structures. Thus, the adopted heat capacity values are estimated so as to parallel those for ZrCl. The heat capacity values below 300 K are calculated by summing contributions due to hindered translations, librations, and internal vibrations of the crystal. The parameters used in the calculations are determined by a correlation with corresponding parameters for ZrCl (6) and a consideration of the sublimation data for ZrBr (6). The high temperature heat capacities are obtained graphically. 

H. Krlkorian, "Estimation of High-Temperature Heat Capacities of Carbides," University of California, UCRL 6785,... 

Low temperature heat capacities (56.3 - 291.6 K) were measured by Anderson ( ). The high temperature heat capacities are derived by a Shomate analysis of anoothed enthalpies reported by Kelley (6). Kelley obtained the smoothed values from unpublished high temperature (400-743 K) enthalpy measurements by Shomate (7). The data were joined smoothly at 298.15 K and extrapolated graphically above 743 K. The entropy was obtained from the heat capacities using S"(56.2) - 0.57 cal K mol. ... 

The low temperature heat capacities, 18-390 K, were measured by Saba and Purukawa (3). The high temperature heat capacities, 273-1173 K, were measured by Victor et al. (4). These two sets of heat capacity data were joined smoothly and extrapolated to 2000 K by Saba and Purukawa ( ). 

The high temperature heat capacities for the a and B phasis are estimates based on the experimental enthalpy studies in Zalensinskii and Zulinski (8), Jauch (9), and Eastman et al. (10) with the two constraints that the values mesh smoothly with the low temperature results and show a similarity with the Mg and Sr results. 

Moore (8) measured high temperature enthalpy data from 670.5 to 941 K by drop calorimetry. The low temperature heat capacities and high temperature enthalpy data were smoothly joined at 298.15 K. The C values above 941 K were obtained by graphical extrapolation. Getting and Gregory ( ) measured high temperature heat capacities in the temperature range from 60 to... 

The low temperature heat capacities, 52.67-296.29 K were obtained from Weller (6). The high temperature heat capacities were measured by Schottky (7, 282 C), Ewald (8, 275-373 K), Krestovnlkov and Peigina (9, 288-873 K), and Chiznikov and Khirik (IJO,... 

McDonald et al. ( ) measured the high temperature enthalpies of ZrF (cr) at temperatures 283.9-1225.8 K in a copper block drop calorimeter. Smith et al. (4) used a Bunsen ice calorimeter for the enthalpy measurements in the temperature range 273-1150 K. These two sets of enthalpy data are not in good agreement. It is possible that the discrepancies are due to the difference in crystal structure of the samples used (see "Transition Data" for more information). In order to join smoothly with the low temperature heat capacities at 298.15 K, the high temperature heat capacities derived from the enthalpy data of McDonald et al. 

Formation," for details. Therefore the value, S (298,15 K) = 25.71 + 3.2 = 28.91 cal K mol for FeSO (cr), was adopted. The heat capacities above 294.9 K were estimated by comparison with those for MnSO (cr). The high temperature heat capacities, 870.3-1082.3 K, were determined by Southard and Shomate (7). The two sets of data were joined smoothly at 298.15 K by use of Shomate-function plot. 

The low temperature heat capacities are obtained from the data of Kostyukov (7), 3.72 - 295.5 K. The C data reported by Gunther (8) are consistently lower than the adopted ones in the temperature range 74.0 - 90.5 K but considerably higher at 292.7 K. The high temperature enthalpies have been determined by Fleldhouse (9), 413.2 - 914.3 K and Vogt (jM[), 878.15 - 953.15 K. The derived high temperature heat capacities are joined smoothly with the low temperature values and extrapolated smoothly above 953.15 K. 

Low temperature heat capacities are from the data (53 - 295 K) of Kelley (7). Wagner 8) measured the average heat capacities in the temperature range 580 - 1570 K. Using his data we derive the high temperature heat capacities which are joined smoothly with the low temperature values by a constrained fitting technique. The C values at 903 = 1258 K and above 1258 K are —1—1 ... 

Low temperature heat capacities are from the data (52 - 296 K) of Shomate (3). High temperature enthalpies have been measured (402 - 1720 K) by Naylor and Cook (4). High temperature heat capacities are derived from the enthalpies by a fitting technique which constrains the curve to join smoothly with the low temperature values. The entropy is based on S (52 K) = 0.45 cal k mol . ... 

High temperature enthalpies have been measured (392 - 1817 K) by Orr (3 ). High temperature heat capacities are derived from the enthalpies by a fitting technique which constrains the curve to Join smoothly with the low temperature values. 

There are no experimental high temperature heat capacity or enthalpy studies. The adopted heat capacity, which is assumed to represent the high temperature crystal form, is based on the estimate of Gronvold and Westrum (9), C = 26.36 + 7.88 x 10" T =... 

There are numerous high temperature heat capacity and enthalpy measurements for Nb(cr). The various studies are listed... 

The low temperature heat capacity values are based primarily on the studies by Keesom and Clark ( ) and Busey and Giaque (2). The adopted values are actually those suggested by Busey and Giauque (2 ) with slight changes above 280 K so as to smoothly join the high temperature heat capacity data. 

King et al. (7) have measured the low temperature heat capacities (53-297 K) and high temperature enthalpy changes (396-1800 K) by drop calorimetry. The low temperature and high temperature heat capacities were joined smoothly at 298.15 K. The entropy... 

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