Reaction in fused salts

Metathetical reactions in fused salts (e.g., FeP04 + Fe203 -I- POCI3) in molten NaCl. 

Thermodynamic data have also been calculated for carbon—oxygen reactions in fused salts [7, 8], The oxidation of solid carbon principally yields carbon dioxide at low temperature and carbon monoxide at high temperature. In this case, at constant temperature, the CO/CO2 concentration ratio at solid carbon depends on pressure. The carbon—oxygen electrode is used as reference to investigate cryolite—alumina melts at c. 1000°C [9] and molten slags at higher temperatures. 

F.R. Duke and S. Yamamoto, Acid-Base Reactions in Fused Salts. I. The Dichromate-Nitrate Reaction, J. Am. Chem. Soc. 80 (1958) 5061-5063. 

Zinc chloride sodium chloride Reactions in fused salts Dehydration of alcohols... 

Calcium carbide Reactions in fused salts with chlorosilanes... 

Disilylacetylenes. Ga-carbide added to dry LiGl-KGl-melt, then trimethylchloro-silane passed at 400° during 29 hrs. into the stirred mixture bis(trimethyl-silyl)acetylene. Y 77% based on startg. m. consumed conversion 36.5%. Also bis(trimethylsilyl)carbodiimide s. J. Stenzel and W. Sundermeyer, B. 100, 3368 (1967) review of reactions in fused salts s. Ghemie in unserer Zeit 1 (5), 150 (1967) G. A. 68, 87320. 

All reactions of metals in aqueous or non-aqueous solutions or in fused salts where one area of the metal surface is predominantly anodic and the other is predominantly cathodic so that the sites are physically identifiable. 

In certain applications it has not always been easy to hnd suitable metallic container materials, particularly in the nuclear-energy industry, where, for certain applications, corrosion resistance of the same order as that required by the fine chemical industry has to be achieved in order to prevent contamination of the process stream. Such difflculties have stimulated the study of corrosion in fused salts and have led to a fairly high degree of understanding of corrosion reactions in these media. 

The subject is also closely related to fuel-ash corrosion which in most cases is caused by a layer of fused salts such as sulphates and chlorides Attention has been focused on the electrochemistry of this type of corrosion and the relevant thermodynamic data summarised in the form of diagrams . Fluxing and descaling reactions also resemble in some respects reactions occurring during the corrosion of metals in fused salts. A review of some of the more basic concepts underlying corrosion by fused salts (such as acid-base concepts and corrosion diagrams) has appeared. ... 

Protolytic reactions can also occur in fused salts. The solvent participates in these reactions provided that at least one of its ions has protogenic and/or protophilic character. An example of a solvent in which the cation is aprotic and the anion protophilic is ethylpyridinium bromide (m.p. 114°C). The acid HA is protolysed in this solvent (HA -I- Br HBr + A"). Hydrogen bromide acts as a solvated proton and the acidity is expressed as... 

Iron halides react with halide salts to afford anionic halide complexes. Because iron(III) is a hard acid, the complexes that it forms are most stable with F and decrease in both coordination number and stability with heavier halides. No stable I complexes are known. [FeF5(H20)]2 is the predominant iron fluoride species in aqueous solution. The [FeF6]3 ion can be prepared in fused salts. Whereas six-coordinate [FeClJ3 is known, four-coordinate complexes are favored for chloride. Salts of tetrahedral [FeClJ can be isolated if large cations such as tetraphenylarsonium or tetraalkylammonium are used. [FeBrJ is known but is thermally unstable and disproportionates to iron(II) and bromine. Complex anions of iron(II) halides are less common. [FeClJ2 has been obtained from FeCl2 by reaction with alkali metal chlorides in the melt or with tetraethylammonium chloride in deoxygenated ethanol. 

First, we note that the charge ordering of the solvent can impose itself on the distribution of products in reaction. Chiappe and Pieraccini [40] report that in their study of electron transfer between Micheler s ketone and tetracyanoethene, they observed that the formation of a radical ion pair to be preferred over formation of a single, neutral complex. Such a preference is only observed for the most highly polar molecular liquids, and is analogous to the spontaneous ionization of metal atoms in fused salts noted above. This represents a novel phenomenon for moderately polar solvents, though its generality is unclear at this time. 

Along with the anode reaction, the so-called anode effect, a phenomenon often observed in fused salt electrolysis (see Chapter 4), may occur. In the present case, it may be due to a surface film of the type CVX formed on the anode material. This film on the one hand protects the carbon against destruction (and is the reason for high anodic overpotentials) in normal operation and, on the other hand, under more or less known conditions may block electron transfer completely. These conditions depend strongly on the electrolyte composition (purity) [46,47]. Additives, such as lithium fluoride, may be helpful in preventing the anode effect by wetting the electrode material. 

The sulfur-sodium polysulfide system has received the attention of electrochemists but few of the studies have been under conditions comparable to sodium-sulfur battery operating conditions. The thermodynamics of the system have been studied by means of open-circuit potentials (17,27), and dynamic measurements have been made in fused salts (28). The most pertinent studies are those of sulfur-polysulfide electrochemistry in the actual sulfur-polysulfide melts (24, 29, 35). The results of these studies seem to indicate that both the oxidation and reduction reactions are rapid, although the oxidation reaction is hindered by the formation of an insulating sulfur film. These studies also concluded that the electrode reaction sequences were quite complex because of the multitude of polysufide species. As the system becomes better characterized more quantitative descriptions are possible as evidenced by a recent work which modeled the resistive drop through an actual sulfur impregnated graphite electrode in order to correlate the spatial distribu-... 

The chemistiy of fused systems is, of course, mainly concerned with those liquids containing at least two components. For the present some of the factors which appear important with regard to chemical properties and reactions in molten salts will be considered in a general manner. Specific examples of the behavior of salt mixtures in electrochemical, kinetic, spectroscopic, thermodynamic, oxidation-reduction, synthetic, and other studies will be presented in the following sections. 

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