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), Vol. 81:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
LITHIUM
PHASE STUDIES
THERMODYNAMICS
LITHIUM DEUTERIDES
HIGH TEMPERATURE
LOW PRESSURE
MEDIUM VACUUM
VERY HIGH TEMPERATURE
ALKALI METAL COMPOUNDS
ALKALI METALS
DEUTERIDES
DEUTERIUM COMPOUNDS
ELEMENTS
HYDRIDES
HYDROGEN COMPOUNDS
LITHIUM COMPOUNDS
LITHIUM HYDRIDES
METALS
400201* - Chemical & Physicochemical Properties