Temperature heat capacity data

Thus, values for C°p m T, S°m T, (H°m T - H°m 0) and (G°mT H°m0) can be obtained as a function of temperature and tabulated. Figure 4.16 summarizes values for these four quantities as a function of temperature for glucose, obtained from the low-temperature heat capacity data described earlier. Note that the enthalpy and Gibbs free energy functions are graphed as (// , T - H°m 0)/T and (G T — H q)/T. This allows all four functions to be plotted on the same scale. Figure 4.16 demonstrates the almost linear nature of the (G°m T H°m 0)/T function. This linearity allows one to easily interpolate between tabulated values of this function to obtain the value at the temperature of choice. 

Unfortunately, there axe at this time no low temperature heat capacity data on polymers of known crystallinity so that absolute entropies at 25° C can be calculated. This gap in our knowledge of polymers represents a scientific vacuum that will rapidly be filled1. 

NdRu4Sbi2 is metallic and undergoes some type of magnetic transition near 1.3 K. The magnetic susceptibility follows a Curie-Weiss law above 50 K with an effective moment of 3.45/u.b and a Weiss temperature of -28 K. Crystal fields likely effect the susceptibility and magnetic interactions for temperatures below 50 K. Low temperature heat capacity data confirm the bulk nature of the magnetic transition (Takeda and Ishikawa, 2000b). 

Justice (9) reported low temperature heat capacity data (13 to 310 K) and presented smoothed thermodynamic functions. 

High temperature heat content data by Moore (6) were Joined by Shomate correlation with low temperature heat capacity data... 

As there Is no low temperature heat capacity data reported in the literature, the entropy of NbCl,.(cr) at 298.15 K is... 

There is no low temperature heat capacity data for a-PbP2(cr). We estimate S (298.15 K)... 

These data contain a broad lambda type transition with a heat capacity peak at 227.5 K. Powers and Blalock (9) measured high temperature enthalpy data for KOH(cr) in both the a and B phases in a Bunsen ice calorimeter. Their enthalpy data are scattered and not precise enough to accurately define the heat capacities for the a phase. Therefore, the selected heat capacities between 298 and 516 K are estimated by graphical extrapolation of the low temperature heat capacity data. Heat capacities for the B phase are from Powers and Blalock (9). 

The entropy, S (298.15 K) = 18.585 cal K" mol", is obtained from the low temperature heat capacity data of Smith et al. (5), based on S (20 K) = 0.197 cal k" mol". This starting entropy was obtained by the authors from a T extrapolation of the data. Recently, McBride and Westrum (1 ) have shown that the T limiting law is Inappropriate for MoS and a T law is suggested for this and other compounds with lamellar lattices. They have also shown that the heat capacity data of Smith et al. for MoS... 

There is no low temperature heat capacity data reported in the literature for T < 298 K. In order to have the 3rd law results of the equilibrium data agree with the combustion data, an entropy value of the order of 13-14 cal K mol would be necessary. At this point, however, the 3rd law drifts would be all positive. S (298.15 K) 10.2 cal K mol would lead to a more satisfying variation in the 3rd law drifts for the condensed phase equilibrium data but an intermediate value S (298.15 K)... 

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. 

The low temperature heat capacity data (52-296 K) are taken from Weller and Kelley (6). High temperature enthalpies of NiS Qg were measured by Conard et al. (7) via drop calorimetry. We have joined these values smoothly with the low temperature C ... 

This expression fits the enthalpy and heat capacity data very well, and merges with the low temperature heat capacity data of [19530SBAVES], since a constraint on C° at 298.15 K was imposed in the fitting. These data agree very well with those selected by this review. The data at higher temperatures (> 2900 K) are not entirely consistent with the enthalpy calculated from the C° measurements of [1996RON/H1E], who showed that the transition is second order, with a peak in the heat capacity at (3090 10) K, as discussed in Section Vll.1.2. 

DETERMINATION OF BARRIERS TO INTERNAL ROTATION FROM LOW-TEMPERATURE HEAT CAPACITY DATA. 

For low temperature heat capacity data, see Vining and Shelton (1983), Tf = 8.40... 

HojFcjSij crystallizes with the SCjFCjSij-type of structure P4/mnc, a = 10.39(1), c = 5.44(1) (X-ray powder analysis, Braun, 1980). Ho2FejSi5 orders antiferromagnet-ically at = 2.9 K. Magnetic susceptibility data = 10.4(1) jUg and = 0.3(7)] as well as Mossbauer spectra indicate the absence of a magnetic moment at the iron site (Braun et al., 1981). For sample preparation, see Dy2FejSi5. For low temperature heat capacity data, see Vining and Shelton (1983), = 2.82 K. Yarovets (1978)... 

Yb2Fc3Si5 crystallizes with the ScjFejSij-type of structure [P4/mnc, a = 10.36(1) and c= 5.385(8)] Braun (1980) by means of X-ray powder diffraction. Arc melted samples were said to contain 20 vol% of impurity phases. No homogeneous sample could be obtained from sintered mixtures of Yb and FejSij at 900°C in an evacuated silica tube. For low temperature heat capacity data, see Vining and Shelton (1983) antiferromagnetic ordering was reported at T j = 1.70 K. 

High-temperature heat capacity data for ThN are summarized in rows 6 to 9 of Table 5. The data estimated by Rand [8] and given by the equation... 

---