Jane E. Callanan

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

Thermodynamics of ammonium halopallidates. I: Heat capacity and thermodynamic properties of (NH4)2PdCl6 at temperatures from 6 K to 350 K

The heat capacity of ammonium hexachloropallidate (NH4)2PdCl6 was measured at temperatures from 6 K to 350 K by adiabatic calorimetry. The heat-capacity curve is smooth and without anomalies. It rises rapidly from T0 to T = 150 K where the Cp,m value is 26.62 · R (R = 8.31451 J · K−1 · mol−1). Above T = 150 K, the increase to 32.41 · R at 350 K occurs more slowly. Values of the standard thermodynamioc quantities are tabulated to T = 350 K.

Sublimation pressures of solid solutions III. NH4Cl + NH4Br

The total sublimation pressures of ammonium chloride, ammonium bromide, and of ten solid solutions of these salts, covering the entire composition range, have been measured by a static method from 250 to 320°C. The results were fitted to ln P = A − BT −1 + C ln T . The isothermal variation of total pressure with composition indicates that the solids deviate positively from Raoults law. The differences between the “second-law” and “third-law” values for the enthalpy of sublimation for the pure chloride and pure bromide are discussed. Results are presented for the variation with composition, at 550 K, of the enthalpy of sublimation, uncorrected for possible incomplete dissociation in the gas phase.

Crystallographic Studies of NH4Cl-NH4Br Solid Solutions

Both ammonium chloride and ammonium bromide undergo a transition, with rise in temperature, from an interpenetrating simple cubic (II) to a face-centered cubic (I) lattice at 183 and 137°C, respectively, and both the low- and high-temperature forms give a complete series of solid solutions. We have determined the lattice constants of the high-temperature solids at about 250° as a function of composition, and redetermined the lattice constants of the low-temperature solids at room temperature. The solutions were made by crystallization from water, followed by stirring in contact with mother liquor for at least three weeks at room temperature. Measurements were made with a Norelco-Philips diffractometer and recorder, with Cu K α radiation. For the high-temperature work, a simple, inexpensive heating apparatus was developed. The only previous data reported for the high-temperature forms are the lattice constants of the pure components given by Bartlett and Langmuir.13