The enthalpy of sublimation and thermodynamic functions of fermium
- Transuranium Research Laboratory (Chemistry Division), Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6375 (US)
The enthalpy of sublimation of fermium (Fm), element 100, has now been determined directly by measuring the partial pressure of Fm over alloys, for the temperature range of 642 to 905 K. The partial pressures were determined using Knudsen effusion and target collection techniques. Dilute (10{sup {minus}5}--10{sup {minus}7} atom %) solid alloys of Fm and mixtures of Fm and Es in both Sm and Yb solvents were studied. The presence of Es in two of the alloys allowed a direct comparison of the behavior of Fm and Es, where the latter could be used as a reference. It was possible to calculate enthalpies of sublimation and a hypothetical vapor pressure/temperature relationship for pure Fm metal by selecting Yb as the solvent most likely to form a nearly ideal alloy with Fm. From the experimental vapor pressure data, we derived average Second Law values of 33.8{plus minus}3 kcal/mol and 23.5{plus minus}3 cal/mol deg for the enthalpy and entropy of sublimation of Fm at 298 K. Third Law enthalpy values were also calculated using the experimental partial pressure data and entropies estimated from derived free energy functions and heat capacities for the solid and gaseous forms of Fm. The average Third Law values (34.8 kcal/mol and 25.1 cal/mol deg, respectively, at 298 K) are in agreement with those obtained via the Second Law. These results establish that Fm, like Es (element 99), is a divalent metal. The finding that Fm metal is the second divalent actinide element experimentally establishes the trend towards metallic divalency expected in the second half of the actinide series.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5304886
- Journal Information:
- Journal of Chemical Physics; (USA), Vol. 91:11; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
FERMIUM
SUBLIMATION HEAT
ENTROPY
HIGH TEMPERATURE
KNUDSEN FLOW
PARTIAL PRESSURE
THERMODYNAMIC PROPERTIES
ACTINIDES
ELEMENTS
ENTHALPY
FLUID FLOW
GAS FLOW
METALS
PHYSICAL PROPERTIES
TRANSITION HEAT
TRANSPLUTONIUM ELEMENTS
TRANSURANIUM ELEMENTS
360104* - Metals & Alloys- Physical Properties