Solvents, molten chloride

There are two other methods for producing ferrite powders that deserve attention molten-salt synthesis and shock-wave loading. In molten-salt synthesis, Fe203 and the corresponding carbonate, oxide, hydroxide or nitrate needed to produce the ferrite phase are dry blended with a mixture of NaCl and KCl. This reaction mixture, in a Pt crucible, is placed in a furnace at 800-1100 °C for lh the chloride solvent is melted and provides an efficient heating medium for the reaction. After cooling, the solvent is separated from the ferrite by dissolution in water. The product can be finally collected by filtration. Ba and Sr hexaferrite powders have been prepared by this method (Arendt, 1973). Submicron, high-quality crystallites with a low ferrous content were obtained. 

Thus alkali sulphides are soluble in liquid sulphur dioxide, alkali fluorides in bromine (III) fluoride and alkali chlorides in molten iodine monochloride. For many other ionic compounds the energy released in the reaction with an acceptor solvent is often too small to allow reasonable solubilities. 

Voyiatzis, G.A., Pavlatou, E.A., Papatheodorou, G.N. et al. (1993) Reduction products of pentavalent niobium and tantalum in fused chloride solvents, m International Symposium on Molten Salt Chemistry and Technology, Vol. 93/99 (eds M.-L. Saboungi, H. Kojima, J. Duruz and D. Shores), The Electrochemical Society, Inc., Honolulu, pp. 252-264. 

McLaughlin, D.R and Stoltz, R.A. (1988) Zirconium and hafnium tetrachloride separation by extractive distillation with molten zinc chloride lead chloride solvent. US Patent 4737 244. 

Fig. 30. Infrared and visible spectra of nickel centers in molten chloride salts. Molten salt solvents and temperatures for each spectrum are as follows (A) CsCl, 680 C. (B) RbCl, 730°C. (C) KCI, 815°C. (D) NaCl, 822-C. (E) LiCl, 640°C. (F) MgCU, 740 C. 228.2 > (Uncorrected for errors in e.)...

Most of the earlier studies were carried out in molten nitrates and chlorides. Recently some studies have been made in more basic solvents molten alkali acetates, thiocyanates, hydroxides, and carbonates. Molten LiOAc-NaOAc-KOAc (20-35-45 mole %) (liquidus temperature IST C) was employed as a solvent by Bombi et to study the polarographic... 

In France, Compagnie Europnene du Zirconium (CEZUS) now owned jointly by Pechiney, Eramatome, and Cogema, uses a separation (14) based on the extractive distillation of zirconium—hafnium tetrachlorides in a molten potassium chloride—aluminum trichloride solvent at atmospheric pressure at 350°C. Eor feed, the impure zirconium—hafnium tetrachlorides from the zircon chlorination are first purified by sublimation. The purified tetrachlorides are again sublimed to vapor feed the distillation column containing the solvent salt. Hafnium tetrachloride is recovered in an enriched overhead fraction which is accumulated and reprocessed to pure hafnium tetrachloride. 

Anhydrous stannous chloride, a water-soluble white soHd, is the most economical source of stannous tin and is especially important in redox and plating reactions. Preparation of the anhydrous salt may be by direct reaction of chlorine and molten tin, heating tin in hydrogen chloride gas, or reducing stannic chloride solution with tin metal, followed by dehydration. It is soluble in a number of organic solvents (g/100 g solvent at 23°C) acetone 42.7, ethyl alcohol 54.4, methyl isobutyl carbinol 10.45, isopropyl alcohol 9.61, methyl ethyl ketone 9.43 isoamyl acetate 3.76, diethyl ether 0.49, and mineral spirits 0.03 it is insoluble in petroleum naphtha and xylene (2). 

Electroplated coatings (Section 12.1) Aluminium can be electroplated from molten salts or organic solvents. It can be plated on to other metals from fused aluminium chloride melts, e.g. 75[Pg.467]

If you electrolyze a solution containing a compound of a very active metal and/or a very active nonmetal, the water (or other solvent) might be electrolyzed instead of the ion. For example, if you electrolyze molten sodium chloride, you get the free elements ... 

Relatively little attention has been devoted to the direct electrodeposition of transition metal-aluminum alloys in spite of the fact that isothermal electrodeposition leads to coatings with very uniform composition and structure and that the deposition current gives a direct measure of the deposition rate. Unfortunately, neither aluminum nor its alloys can be electrodeposited from aqueous solutions because hydrogen is evolved before aluminum is plated. Thus, it is necessary to employ nonaqueous solvents (both molecular and ionic) for this purpose. Among the solvents that have been used successfully to electrodeposit aluminum and its transition metal alloys are the chloroaluminate molten salts, which consist of inorganic or organic chloride salts combined with anhydrous aluminum chloride. An introduction to the chemical, electrochemical, and physical properties of the most commonly used chloroaluminate melts is given below. 

In many ways, chloroaluminate molten salts are ideal solvents for the electrodeposition of transition metal-aluminum alloys because they constitute a reservoir of reducible aluminum-containing species, they are excellent solvents for many transition metal ions, and they exhibit good intrinsic ionic conductivity. In fact, the first organic salt-based chloroaluminate melt, a mixture of aluminum chloride and 1-ethylpyridinium bromide (EtPyBr), was formulated as a solvent for electroplating aluminum [55, 56] and subsequently used as a bath to electroform aluminum waveguides [57], Since these early articles, numerous reports have been published that describe the electrodeposition of aluminum from this and related chloroaluminate systems for examples, see Liao et al. [58] and articles cited therein. 

Water is involved in most of the photodecomposition reactions. Hence, nonaqueous electrolytes such as methanol, ethanol, N,N-d i methyl forma mide, acetonitrile, propylene carbonate, ethylene glycol, tetrahydrofuran, nitromethane, benzonitrile, and molten salts such as A1C13-butyl pyridium chloride are chosen. The efficiency of early cells prepared with nonaqueous solvents such as methanol and acetonitrile were low because of the high resistivity of the electrolyte, limited solubility of the redox species, and poor bulk and surface properties of the semiconductor. Recently, reasonably efficient and fairly stable cells have been prepared with nonaqueous electrolytes with a proper design of the electrolyte redox couple and by careful control of the material and surface properties [7], Results with single-crystal semiconductor electrodes can be obtained from table 2 in Ref. 15. Unfortunately, the efficiencies and stabilities achieved cannot justify the use of singlecrystal materials. Table 2 in Ref. 15 summarizes the results of liquid junction solar cells prepared with polycrystalline and thin-film semiconductors [15]. As can be seen the efficiencies are fair. Thin films provide several advantages over bulk materials. Despite these possibilities, the actual efficiencies of solid-state polycrystalline thin-film PV solar cells exceed those obtained with electrochemical PV cells [22,23]. 

Ionic liquids are, quite simply, liquids that are composed entirely of ions. Thus, molten sodium chloride is an ionic liquid a solution of sodium chloride in water (a molecular solvent) is an ionic solution. The term ionic liquids was selected with care, as it is our belief that the more commonly used phrase molten salts (or simply melts) is referential, and invokes a flawed image of these solvents as being high-temperature, corrosive, viscous media (cf. molten cryolite). The reality is that room-temperature ionic liquids can be liquid at temperatures as low as — 96°C, and are typically colorless, fluid, and easily handled. To use the term molten salts to describe these novel systems is as archaic as describing a car as a horseless carriage. Moreover, in the patent and recent academic literature, ionic... 

Though much effort has been spent on possible utilization of poly(thio-formaldehyde), no uses for the polymer have been developed. Most samples of the polymer cannot be melt fabricated because they are unstable in the molten state. Solvent fabrication is also impossible because the polymer is insoluble. There are two types erf poly(thioformaldehyde) that are said to be stable at high temperatures, which are polymers made by treatment of trithiane with boron trifluoride etherate and the acetylated anomalous form obtained from sodium hydrosulfide and methylene chloride. These also have not found utility. 

A 1 2 mixture of l-methyl-3-ethylimidazolium chloride and aluminum trichloride, an ionic liquid that melts below room temperature, has been recommended recently as solvent and catalyst for Friedel-Crafts alkylation and acylation reactions of aromatics (Boon et al., 1986), and as solvent for UV/Vis- and IR-spectroscopic investigations of transition metal halide complexes (Appleby et al., 1986). The corresponding 1-methyl-3-ethylimidazolium tetrachloroborate (as well as -butylpyridinium tetrachlo-roborate) represent new molten salt solvent systems, stable and liquid at room temperature (Williams et al., 1986). 

The electrolyte surrounding the central positive electrode is sodium tet-rachloroaluminate, which melts at 157 °C and acts as a solvent for the nickel(II) chloride, and this is separated from the molten sodium in the outer compartment by a /1-alumina tube which, again, serves as a fast ion conductor for Na+. The cell operates at 300 °C and delivers up to 2.58 V. 

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