Fused salt systems

BeryUium reacts with fused alkaU haUdes releasing the alkaU metal until an equUibrium is estabUshed. It does not react with fused haUdes of the alkaline-earth metals to release the alkaline-earth metal. Water-insoluble fluoroberyUates, however, are formed in a fused-salt system whenever barium or calcium fluoride is present. BeryUium reduces haUdes of aluminum and heavier elements. Alkaline-earth metals can be used effectively to reduce beryUium from its haUdes, but the use of alkaline-earths other than magnesium [7439-95-4] is economically unattractive because of the formation of water-insoluble fluoroberyUates. Formation of these fluorides precludes efficient recovery of the unreduced beryUium from the reaction products in subsequent processing operations. 

Electrochemically, the system metal/molten salt is somewhat similar to the system metal/aqueous solution, although there are important differences, arising largely from differences in temperature and in electrical conductivity. Most fused salts are predominantly ionic, but contain a proportion of molecular constituents, while pure water is predominantly molecular, containing very low activities of hydrogen and hydroxyl ions. Since the aqueous system has been extensively studied, it may be instructive to point out some analogues in fused-salt systems. 

Flood s equation physchem A relation used to determine the liquidus temperature in a binary fused salt system. fladz i.kwa zhan flores CHEM A form of a chemical compound made by the process of sublimation. flor ez 1... 

ZnCl2 vapour pressures, activities and partial molar energies have been determined for the fused salt system shown in equation (7). Deviations from ideality at high ZnQ2 concentrations are attributed to partial covalent bonding in ZnCl2, while deviations at low ZnCl2 concentrations are attributed to formation of complex ions.958,959... 

Reference Electrodes For Use in Fused-Salt Systems. The kinds of investigations that require reliable reference electrodes in molten salts duplicate those in aqueous electrolytes. Specifically, these include (1) thermodynamic... 

The literature on fused-salt systems is too vast to survey here, but good access to the literature is provided in two reviews.55,56 Both contain useful information on solvent systems and suitable reference electrodes. 

In fused-salt systems, reduction of traces of water (if present) or of the metal cations ordinarily will be the cathodic limiting process. 

There also is difficulty in accommodating fused-salt systems in a classification scheme designed primarily for organic solvents, because the dielectric constants are not comparable and the measures of solvent polarity appropriate to organic solvents are not generally useful in fused salts. Therefore, fused-salt systems are not discussed, nor are they included in the general classification scheme. 

This principle serves as the basis for a number of models of fused salt systems. Perhaps the best known of these is the Temkin model, which uses the properties of an ordered lattice to predict thermodynamic quantities for the liquid state [79]. However, certain other models that have been less successful in making quantitative predictions for fused salts may be of interest for their conceptual value in understanding room temperature ionic liquids. The interested reader can find a discussion of the early application of these models in a review by Bloom and Bockris [71], though we caution that with the exception of hole theory (discussed in Section II.C) these models are not currently in widespread use. The development of a general theoretical model accurately describing the full range of phenomena associated with molten salts remains a challenge for the field. 

Forland T., Thermodynamic Properties of Fused-Salt Systems in Fused Salts, B. R. Sundheim, ed., McGraw-Hill, New York, 1964, p. 63. 

Systems of reciprocal salt mixtures. The fused salt system of the ions Na" ", K+, Cl , and Br has the following restriction due to electro-neutrality... 

Thermodynamic characteristics of the NH4Cl-NaAlCl4 fused salt system have been derived from measurements of vapour pressures generated by such mixtures, as a function of temperature. At low mole fractions of NH4Q, and temperatures below 650 K, the chief component is HCl, with very little NH3 or NH3,AlCl3. ... 

R.W. Laity, Electrodes in Fused Salt Systems. In D.J.G. Ives and G.J. Janz (eds). Reference Electrodes, Academic Press, New York (1961), p. 524. 

Barber, WA. and Sloan, C.L. (1961) Solubility of calcium carbide in fused salt Systems. J. Phys. Chem, 65, 2026-2028. 

Laity RW (1961) Electrodes in fused salt systems. In Ives DIG, Janz GJ (eds) Reference electrodes. Theory and practice. Academic, New York, pp 524—606... 

Kleppa OJ, Meschel SV (1963) Thermochemistry of anion mixtures in simple fused salt systems, n. Solutions of some salts of M04- and M042- anions in the corresponding alkali nitrates. J Phys Chem 67 2750-2753... 

Biquard M, Letellier P, Fromon M (1985) Vapor pressure in the water-ammonium nitrate mixture at 298.15 K. Thermodynamic properties of the water-fused salt system. Can J Chem 63 3587-3595... 

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