LiCl-KCl eutectics

Lithium hydride is perhaps the most usehil of the other metal hydrides. The principal limitation is poor solubiUty, which essentially limits reaction media to such solvents as dioxane and dibutyl ether. Sodium hydride, which is too insoluble to function efficiently in solvents, is an effective reducing agent for the production of silane when dissolved in a LiCl—KCl eutectic at 348°C (63—65). Magnesium hydride has also been shown to be effective in the reduction of chloro- and fluorosilanes in solvent systems (66) and eutectic melts (67). 

A series of experiments have been undertaken to evaluate the relevant thermodynamic properties of a number of binary lithium alloy systems. The early work was directed towards determination of their behavior at about 400 °C because of interest in their potential use as components in molten salt batteries operating in that general temperature range. Data for a number of binary lithium alloy systems at about 400 °C are presented in Table 1. These were mostly obtained by the use of an experimental arrangement employing the LiCl-KCl eutectic molten salt as a lithiumconducting electrolyte. 

Methods have been developed (75) to prepare actinide metals directly from actinide oxides or oxycompounds by electrolysis in molten salts (e.g., LiCl/KCl eutectic). Indeed, the purest U, Np, and Pu metals have been obtained (19, 24) by oxidation of the less pure metal into a molten salt and reduction to purer metal (electrorefining. Section III,D). 

If an actinide metal is available in sufficient quantity to form a rod or an electrode, very efficient methods of purification are applicable electrorefining, zone melting, and electrotransport. Thorium, uranium, neptunium, and plutonium metals have been refined by electrolysis in molten salts (84). An electrode of impure metal is dissolved anodically in a molten salt bath (e.g., in LiCl/KCl eutectic) the metal is deposited electrochemically on the cathode as a solid or a liquid (19, 24). To date, the purest Np and Pu metals have been produced by this technique. 

During the electrorefining of uranium metal in a molten salt eutectic, a low current density favors the formation of large single crystals. Up to 5-cm single crystals of uranium metal have resulted from the large-scale (100 kg of U) electrorefining of uranium metal in molten LiCl/KCl eutectic (17). 

The potential of the Re -Re couple in LiCl-KCl eutectic at 500 °C is — 0.358 V vs. the standard Pt electrode). 2 2 oxidizes [TcClg] directly to TCO4, but CI2 first produces technetium( v) which is then oxidized to pertechnetate. No oxidation of technetium(iv) by atmospheric oxygen in the presence of sunlight could be achieved. 

Direct electrochemical studies of the hydride ion in a liCl—KCl eutectic at 425 °C at an iron electrode have shown that the anion is oxidized near 0.65 V versus Li+/Li in a one-electron process which leads to the formation of dihydrogen with high current efficiency via surface combination of... 

Uozumi, lizuka, and coauthors have published several studies on the electrochemical behavior of Pu at liquid cadmium cathodes in LiCl—KCl eutectic melts [128-130]. In one account [130] the authors studied the reduction of Pu " " to Pu° at the LiCl— KCl melt and liquid Cd interface and compared the results to those obtained at a solid Mo cathode surface. The electrode reaction at liquid Cd was found to be close to fully reversible with rapid. 

Li-Al electrodes behave well in molten salt electrolytes such as the LiCl-KCl eutectic, showing low polarization and good reversibility, with... 

The calcium-calcium chromate thermal cell has been established for many years. In the LiCl-KCl eutectic, the reaction product of this cell is a mixed lithium-calcium-chromium oxide. However,. this system cannot provide as high a specific capacity or energy density as the lithium-based systems described above. Furthermore, it suffers from parasitic chemical reactions which are exothermic and often uncontrolled. 

The classification system described earlier is limited to the simplest kinds of individual melts and is not intended to include mixtures. However, molten mixtures of these different classes of compounds are often more practical solvents than the melts of the individual compounds, due to their much lower melting points and other favorable properties, and this system of classification can usually be extended to these mixtures. For example, the very popular molten LiCl-KCl eutectic mixture is simply a binary ionic melt, whereas molten NaN03-KN03-LiN03 is a ternary polyanionic melt. Interestingly, the equimolar molten mixture of the simple ionic salt NaCl (a) and the molecular compound A1C13 (d) produces a simple polyanionic salt melt (b) composed of Na+ and A1C14 ions ... 

Plambeck [16] summarizes the important physical properties of the molten LiCl-KCl eutectic such as density, viscosity, and electrical conductivity and gives references to some other sources of this data. Tabulated physical property data for FLINAK are scarce but are available in experimental articles. 

Tungsten(II) in LiCl-KCL eutectic Karl Fischer reagent... 

Historically, a Ca metal negative electrode was used with a fusible salt electrolyte (LiCl/KCl eutectic) and a metal oxide cathode, e.g., K2Cr207 (2.8— 3.3 V). Since the 1980s, Li alloy negatives have gained popularity and supplanted... 

The production of the light actinide metals is usually accomplished through the reduction of tri- or tetrafluorides with an electropositive metal, for example, Ca, Zn, or Mg. The heavy actinides are typically made through the direct reduction of oxide phases. An alternative method to access the actinide metals is through pyrochemical methods. In this technique, actinides in high-temperature molten salts, for example, NaCl-KCl or LiCl-KCl eutectics, are electrolyzed... 

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