Ron D. Weir

Conversion of temperatures and thermodynamic properties to the basis of the International Temperature Scale of 1990 (Technical Report)

Tables of temperature differences between the International Temperature Scale of 1990 (ITS-90) and earlier temperature scales (IPTS-68, EPT-76, IPTS-48, and ITS-27) are presented. These tables also contain values of the derivatives of these differences with respect to temperature. Analytical equations to reproduce the temperature difference (Tg0 T6g) and its f i i t derivative are also given. This information is needed for the adjustment of thermodynamic results to the basis of the ITS-90. Thus, for the most accurate thermodynamic results, it is preferable to change the temperatures of the original work to the ITS-90 and then recalculate the thermodynamic results on this basis. However, conversion formulae based upon a Taylor expansion of the enthalpy have been derived previously by Douglas (J . Res. Nutl. Bur. Stand., Sect. A 73, 451-470 (1969)). These equations are greatly simplified when the differences between the two temperature scales are small. Approximate effects resulting from the conversion from the IPTS-68 to the ITS-90 and from the IPTS-48 to the ITS-90 for existing calorimetric determinations of heat capacity, enthalpy, and entropy have been calculated with the equations of Douglas for ND4Re04(s), BaSnF4(s), a-A1203(s), Be0-A1,03(s), Be0.3A1203(s), and Mo(s). The results of these calculations are given in tables which can be used to assess conveniently the approximate effects on thermodynamic properties due to the differences in these temperature scales. It is found that only the most accurate thermodynamic results require examination and possible adjustment because of a change in the temperature scale.

The heat capacity and derived thermophysical properties of the high TC superconductor YBa2Cu3O7−δ from 5.3 to 350 K

The heat capacity of the perovskite high‐TC superconductor YBa2Cu3O7−δ was measured from 5.3 to 350 K in an adiabatic calorimetric cryostat. A break in the heat‐capacity curve, associated with the critical temperature for superconductivity was observed between 90.09 and 92.59 K. The transition temperature was identified as 91.44 K, and ΔCp,m was calculated to be 0.559R at that temperature. The lattice heat capacity was evaluated by means of the recently developed Komada/Westrum phonon distribution model and the apparent characteristic temperature ΘKW was calculated to be 107.7 K. The excess electronic heat capacity for the superconducting phase was evaluated and the energy gap was identified as 234. R K. Excess contribution, resulting from magnetic impurities, was noted below 20 K. Thermodynamic properties at selected temperatures are presented.

Thermodynamic properties of ammonium haloplatinates: II. Heat capacity and thermodynamic functions of deuterated ammonium hexachloroplatinate (ND4)2PtCl6 at temperatures from 5 K to 350 K

The heat capacity of deuterated ammonium hexachloroplatinate (ND 4 ) 2 PtCl 6 was measured at temperatures from 5 K to 350 K by adiabatic calorimetry. One λ-shaped anomaly, absent in the undeuterated salt, was found in the curve for heat capacity against temperature. This λ-shaped transition reaches its maximum C p,m ≈ 59.3· R at (27.2±0.05) K with Δ trs S o m = (1.216±0.004)· R , characteristic of an order-disorder transition. Smoothed values of the standard thermodynamic quantities for pure (ND 4 ) 2 PtCl 6 are tabulated at temperatures up to 350 K.

Thermodynamic properties of ammonium haloplatinates I. Heat capacity and thermodynamic functions of ammonium hexachloroplatinate (NH4)2PtCl6 from 6 K to 348 K

Abstract The heat capacity of ammonium hexachloroplatinate (NH4)2PtCl6 was measured from 6 K to 348 K by adiabatic calorimetry. The heat-capacity curve is sigmate without anomalies. It rises rapidly from T → 0 to 250 K where the C p, m R value is 30.1 and increases by only 7 per cent from 250 K to 350 K. Values of the standard thermodynamic quantities are tabulated to 350 K.

Thermodynamic properties of tungsten ditelluride (WTe2) I. The preparation and lowtemperature heat capacity at temperatures from 6 K to 326 K

The heat capacity of the dichalcogenide: tungsten ditelluride, WTe2, was measured over the temperature range 5.5

The thermodynamics of ammonium scheelites. III. An analysis of the heat capacity and related data of deuterated ammonium perrhenate ND4ReO4

An analysis of the heat capacity of deuterated and undeuterated NH4ReO4 has been carried out in which the effects of the anisotropy of the thermal expansion have been considered, an approach hitherto not used for ammonium compounds. In the ammonium scheelites, the axial thermal expansion coefficients are very large, but of opposite sign, and as a result the volume of the scheelite lattice is nearly independent of temperature. It is shown that the correction from constant stress to constant strain results in a major contribution to the heat capacity of this highly anisotropic lattice. The difference between the experimental and calculated values of heat capacity, referred to as ΔCp, is expressed as the sum of the contributions from the anisotropy and the rotational heat capacity. The results of the analysis show that the rotational contribution is much smaller then previously thought. However, the exact contribution of the anisotropy cannot be calculated at this time because the elastic constants are not k...

Specific heat of a high‐Tc perovskite superconductor YBa2Cu3O8−δ

Specific heat measuremnts on high transition temperature perovskite superconductor were conducted from 5.3 K to 345 K. The sample was prepared by mixing stoichiometric amounts of Yttrium oxide, BaO, and CuO so as to yield a 1:2:3 ratio of metals. T he decrease in specific heat at the transition temperature ‐ 91 K is discussed.(AIP)

The thermodynamics of ammonium scheelites IV. Heat capacity of ammonium metaperiodate NH4IO4 from 8 to 324 K

The heat capacity of the scheelite salt ammonium metaperiodate, NH4IO4, was measured from 8 to 324 K using adiabatic calorimetry. The heat capacity against temperature curve shows an excess with a maximum around 200 K as is typical of other ammonium scheelites. A small peak in the curve near 270 K resulted from melting a saturated aqueous solution trapped in the lattice. Values of the standard molar thermodynamic quantities for NH4IO4 are presented up to 320 K. Values for Cp, mo(298.15 K)R, Δ0TSmo(298.15 K)R, and Φmo(298.15 K, 0)/R are (18.58±0.02), (23.03±0.04), and (11.20±0.02), respectively.

The thermodynamics of ammonium scheelites II. Heat capacity of deuterated ammonium perrhenate ND4ReO4 from 7.5 to 320 K

The heat capacity of the scheelite salt deuterated ammonium perrhenate ND4ReO4 was measured from 7.5 to 320 K without detection of any phase transition. An anomalous peak found between 270 and 280 K resulted from fusion of a saturated solution of D2O trapped in the lattice. Values of the standard molar thermodynamic quantities for pure ND4ReO4 are presented up to 320 K.

Novel pressurized solvent extraction vessels for the analysis of polychlorinated biphenyl congeners in avian whole blood.

Persistent organic pollutants remain a serious threat to many food-chain systems. New pollutants continue to emerge. The present study has created novel extraction vessels which are compatible with readily available commercial instrumentation to validate the analysis of one class of persistent organic pollutants, polychlorinated biphenyls (PCBs), in avian blood. The volumes used can be reasonably sampled without sacrificing individuals, or comprising breeding or migratorial success. The procedure consists of the pressurized solvent extraction (PSE) of analytes in a novel PSE extraction vessel. The new extraction cell contains a 38-cm long, coiled, re-packable, in situ clean-up column. Lipid elimination, using Florisil, occurs within the coiled region of the extraction vessel, eliminating the requirement for post extraction clean-up. For development, 0.2 g samples of chicken whole blood have been used. Extract volumes are reduced from (30 to 10) cm(3), compared to unmodified systems. The new PSE vessel with its integrated clean-up method showed satisfactory performance for the analysis of ten environmentally relevant PCB congeners in chicken whole blood samples with recoveries in the range of (70-130)%. Detection limits using gas chromatography coupled with large volume injection ion-trap mass spectrometry (GC-LVI-ITMS-MS) were in the range of (0.05-0.5) ng g(-1). The relative standard deviations for all congeners investigated were better than 5%. This is the first PSE validation to have been conducted on unaltered whole blood samples.