Thermodynamics of the lithium--lithium deuteride system
Pressure-composition-temperature data were collected for the Li--LiD system in the ranges 0 to 750 Torr, 1 to 99 mol percent LiD, and 705 to 871/sup 0/C by measuring equilibrium deuterium pressures over encapsulated Li--LiD mixtures. The data yielded a family of five P/sub D/sub 2///sup /sup 1///sub 2// vs. N/sub LiD/ isotherms whose shapes indicate the existence of two homogeneous terminal solutions that are separated by a wide miscibility gap. Beginning at the consolute point (1000 +- 10/sup 0/C, 61 +- 3 mol percent LiD), the gap widens to a range of 21.3 to 99.0 mol percent LiD at the monotectic temperature (689/sup 0/C). The mole-fraction solubility at the Li-rich gap boundary and plateau pressures above and below the monotectic temperature may be represented by N'/sub LiD/(satd) = exp(2.604 -- 3992T/sup -1/), P/sub P1,l/(Torr) = exp (21.21 -- 16940T/sup -1/), and P/sub P1,s/(Torr) = exp(28.04 -- 23510T/sup -1/), respectively. The data yielded the equilibrium constant (K(atm/sup -/sup 1///sub 2//) = exp(-6.630 + 7995T/sup -1/)) for the reaction Li(soln) + /sup 1///sub 2/D/sub 2/(g) reversible LiD(soln) and expressions for the chemical potentials and activity coefficients of each species as functions of temperature and composition. Activity coefficients, evaluated at N/sub LiD/ ..-->.. 0 and N/sub Li/ ..-->.. 0, were combined with the equilibrium constant to generate temperature-dependence equations for various constants associated with dilute solutions. For the Li-rich limit, the Sieverts' constant (K' = N/sub LiD//(P/sub D/sub 2//)/sup /sup 1///sub 2//) is given by K'(mol fraction LiD/atm/sup /sup 1///sub 2//) = exp(-6.138 + 5599T/sup -1/). Advantages of the Ostwald coefficient in describing the distribution of the dissolved species between liquid and gas phase are discussed.
- Research Organization:
- Argonne National Lab., IL
- OSTI ID:
- 7216775
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 81:6; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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ALKALI METAL COMPOUNDS
ALKALI METALS
DEUTERIDES
DEUTERIUM COMPOUNDS
ELEMENTS
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HYDRIDES
HYDROGEN COMPOUNDS
LITHIUM
LITHIUM COMPOUNDS
LITHIUM DEUTERIDES
LITHIUM HYDRIDES
LOW PRESSURE
MEDIUM VACUUM
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PHASE STUDIES
THERMODYNAMICS
VERY HIGH TEMPERATURE