THE HEAT CAPACITY AND THERMODYNAMIC FUNCTIONS OF $beta$-URANIUM DEUTERIDE FROM 5 TO 350 K

Journal Article · Tue Mar 01 04:00:00 EST 1960 · Journal of the American Chemical Society (U.S.)

DOI:https://doi.org/10.1021/ja01490a012· OSTI ID:4180437

Abraham, B M; Osborne, D W; Flotow, H E; Marcus, R B

The heat capacity of UD/sub 3/ was measured in an adiabatic calorimeter from 5 to 350 deg K The enthalpy and entropy at 298.15 deg K calculated from the data are 2577 plus or minus 5 cal mole/sup -1/ and 17.20 plus or minus 0.03 cal deg/sup -1/ mole/sup -1/, respectively. The entropy and free energy of formation for UD/sub 3/ at 298.15 deg K as well as the heat of formation at the absolute zero were calculated from these data and the previously reported heat of formation and have the values --46.76 cal deg/sup -1/ mole/sup -1/, --17,080 cal mole/sup -1/, and --29,000 cal mole/sup -1/. It was found that the calculated and observed dissociation pressures are not in agreement. A similar discrepancy was found for UH/sub 3/ and it was suggested that the source might be a particle size effect in the dissociation pressure measurements or the heat of transition of the alpha -form of UH/sub 3/ to the beta -form. These heat capacity data were combined with the reported values for UH/sub 3/ to calculate the hydrogen and deuterium vibration frequencies in the compeunds. An anomaly in the heat capacity was observed which arises from the transition from the ferromagnetic state to the paramagnetic state. The maximum in the heat capacity is 11.72 cal deg/sup -1/ mole/sup -1/ and occurs at 167.6 plus or minus 0.5 deg K. It was estimated that 1.19 cal deg/sup -1/ mole/sup -1/ is the entropy change in the transition which is less than the expected value, R ln 2 = 1.38 cal deg/sup -1/ mole/sup -1/, from the Heisenberg theory of ferromagnetism. Measurements of the magnetization of UD/sub 3/ do not appear to be in accord with the thermal me asurements. (auth)

• Research Organization: Argonne National Lab., Lemont, Ill.
• Sponsoring Organization: USDOE
• NSA Number: NSA-14-011552
• OSTI ID: 4180437
• Journal Information: Journal of the American Chemical Society (U.S.), Journal Name: Journal of the American Chemical Society (U.S.) Vol. Vol: 82; ISSN JACSA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

CALORIMETERS
CHEMISTRY
DECOMPOSITION
DEUTERIUM COMPOUNDS
FREQUENCY
HYDRIDES
LOW TEMPERATURE
MAGNESIUM
MATHEMATICS
MEASURED VALUES
PRESSURE
SPECIFIC HEAT
THERMODYNAMICS
TRANSIENTS
URANIUM COMPOUNDS
URANIUM HYDRIDES
VIBRATIONS