Chloride melts

Other Metals. AH the sodium metal produced comes from electrolysis of sodium chloride melts in Downs ceUs. The ceU consists of a cylindrical steel cathode separated from the graphite anode by a perforated steel diaphragm. Lithium is also produced by electrolysis of the chloride in a process similar to that used for sodium. The other alkaH and alkaHne-earth metals can be electrowon from molten chlorides, but thermochemical reduction is preferred commercially. The rare earths can also be electrowon but only the mixture known as mischmetal is prepared in tonnage quantity by electrochemical means. In addition, beryIHum and boron are produced by electrolysis on a commercial scale in the order of a few hundred t/yr. Processes have been developed for electrowinning titanium, tantalum, and niobium from molten salts. These metals, however, are obtained as a powdery deposit which is not easily separated from the electrolyte so that further purification is required. 

Highway. Rock salt, solar salt, and in some cases in Europe, evaporated salt are used to maintain traffic safety and mobiUty during snow and ice conditions in snowbelt regions throughout the world. Sodium chloride melts ice at temperatures down to its eutectic point of —21.12°C. Most snowstorms occur when the temperature is near 0°C, where salt is very effective. More than 40% of dry salt produced in the United States is used for highway deicing. 

Alternatives to the fluidized-bed method process include the chlorination of titanium slags in chloride melts, chlorination with hydrogen chloride, and flash chlorination. The last is claimed to be particularly advantageous for minerals having a high impurity content (133—135,140). The option of chlorinating titanium carbide has also been considered (30). 

Zinc chloride melts at 275°C, bods at 720°C, and is stable in the vapor phase up to 900°C. It is very hygroscopic, extremely water-soluble, and soluble in organic Hquids such as alcohols, esters, ketones, ethers, amides, and nitrides. Hydrates with 1, 1.5, 2.5, 3, and 4 molecules of water have been identified and great care must be exercised to avoid hydration of the anhydrous form. Aqueous solutions of zinc chloride are acidic (pH = 1.0 for 6 M) and, when partially neutralized, can form slightly soluble basic chlorides, eg, ZnCl2 4Zn(OH)2 [11073-22-6] and Zn(OH)Cl [14031-59-5]. Many other basic chlorides have been reported (58). 

Anhydrous BaCl2 exists as monoclinic or cubic crystals. The transition to cubic occurs at 925 °C. Barium chloride melts at 962°C the dihydrate, which has monoclinic crystals, loses water at 113 °C. Barium chloride, which is very hygroscopic, is sold in moisture-proof bags and steel or fiber dmms. 

Hydroquinone may also be used in place of 4-chloroplienol. In this case an aluminum chloride—sodium chloride melt is usually employed. However, the yield is not satisfactory (43). It has also been reported that the reaction of hydroquinone with substantially stoichiometric phthaUc acid dichloride in the presence of anhydrous aluminum chloride in moderately polar solvents, such as nitrobenzene at around 100°C gives quinizarin (44). The reported yield is 65% after purification by crystallization from toluene. 

A signiflcairt property of the alkali metal halides is the solubility of the metals in their molten halides. Typical values of the consolute temperatures of metal-chloride melts are 1180°C in Na-NaF, 1080°C in Na-NaCl, 790°C... 

These facts would suggest that die electrolysis of molten alkali metal salts could lead to the inuoduction of mobile elecU ons which can diffuse rapidly through a melt, and any chemical reduction process resulting from a high chemical potential of the alkali metal could occur in the body of the melt, rather than being conhned to the cathode volume. This probably explains the failure of attempts to produce tire refractoty elements, such as titanium, by elecU olysis of a molten sodium chloride-titanium chloride melt, in which a metal dust is formed in the bulk of the elecU olyte. 

The hydrochloride obtained from the product, e.g., by dissolving in ether and treating with dry hydrogen chloride, melts at 168°C to 1 75°C. By recrystallization from moist dioxan this hydrochloride is separated into isomers melting at 162°C to 163°C and 1 75°C to 177°C, respectively. 

Bowron et al. [11] have performed neutron diffraction experiments on 1,3-dimethylimidazolium chloride ([MMIM]C1) in order to model the imidazolium room-temperature ionic liquids. The total structure factors, E(Q), for five 1,3-dimethylimidazolium chloride melts - fully probated, fully deuterated, a 1 1 fully deuterated/fully probated mixture, ring deuterated only, and side chain deuterated only - were measured. Figure 4.1-4 shows the probability distribution of chloride around a central imidazolium cation as determined by modeling of the neutron data. 

Fig. 2.33 Potential difference Kbetween a redox electrode and a nickel electrode immersed in an alkali chloride melt 700°C, argon atmosphere ...

One interesting feature of comparative experiments with a series of salts having a common anion is that the aggressiveness of the salts towards metals is dependent on the nature of the cation. The aggressiveness of chloride melts in contact with air is in the order... 

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]

Chlorination of ferroalloys (ferroniobium-tantalum) is a more economical and simple alternative [30]. The process is performed on a sodium chloride melt that contains iron trichloride, FeCU. Chlorine is passed through the melt yielding NaFeCl4, which interacts as a chlorination agent with the Fe-Nb-Ta alloy. Chlorination of ferroalloys allows for the production of pure tantalum and niobium pentachlorides, which are used further in the production of high purity oxides and other products. 

Analysis of the melting diagrams led to the conclusion that fluoride, fluoride-chloride and oxyfluoride-chloride melts containing niobium contain the complex ions NbF83 NbF7Cl3 Nb02F43 ... 

An analysis of the melting diagram led to the conclusion that, in fluoride and fluoride-chloride melts, tantalum forms the complex ions TaFg3 or TaF7Cl3, respectively [37,306]. 

Analysis of the physicochemical properties of fluoride and oxyfluoride melts reveals that the complex ions are characterized by coordination numbers that do not exceed seven. Fluoride melts consist of the complex ions MeF72 and MeFe. Molten chloride-fluoride systems initiate the formation of heteroligand complexes of the form MeFgCl2 . Oxyfluoride and oxyfluoride-chloride melts can contain oxyfluoride complexes MeOF63 at relatively low concentrations. The behavior of the more concentrated melts can be attributed to the formation of oxyfluorometalate polyanions. 

Only two processes of tantalum metal production are of worldwide commercial significance. These are the electrolysis of fluoride-chloride melts containing potassium heptafluorotantalate, K TaF , and tantalum oxide, Ta20s, and the reduction with sodium of K-salt or K—salt that is dissolved in potassium fluoride-chloride melts. 

A similar electrolyte, containing potassium heptafluoroniobate, K2NbF7, can be used for the electrolytic reduction of niobium [37, 542 - 544]. No industrial application, however, was found for the electrolysis of niobium in fluoride-chloride melts. 

Niobium undergoes a two-stage electrochemical reduction from potassium heptafluoroniobate, K2NbF7, that is dissolved in fluoride-chloride melts [550 -553] ... 

The anionic composition of the cathodic product is not the only parameter that can be controlled through electrolysis conditions. Grinevitch et al. [559] reported on the investigation of the co-deposition of tantalum and niobium during the electrolysis of fluoride - chloride melts. Appropriate electrodeposition conditions were found that enable to obtain either pure niobium or alloys. 

Similar results were reported by Freidin et al. [568]. Moreover, a correlation was reported [360] between the particle size of tantalum powder obtained by electrolysis of fluoride - chloride melts and its electric conductivity. 

Lithium chloride melts spontaneously above 613°C and forms a liquid that conducts electricity ... 

By using a liquid with a known kinematic viscosity such as distilled water, the values of Ci and Cj can be determined. Ejima et al. have measured the viscosity of alkali chloride melts. The equations obtained, both the quadratic temperature equation and the Arrhenius equation, are given in Table 12, which shows that the equation of the Arrhenius type fits better than the quadratic equation. 

Plugging solution for low temperature wells—contains plugging cement, water and molten chloride melt obtained as waste from titanium-magnesium production as complex chloride additive. Patent RU 1091616-C, 1995. 

In general, the electrolysis of a molten salt at inert electrodes produces the metal at the cathode, e.g., calcium from calcium chloride (melting point 774 °C). The anion is often a halide ion which, on discharge, yields the halogen, e.g., chlorine from calcium chloride. 

In analogy to the original preparation of Malachite Green lactone, pyromellitic anhydride has also been reacted with N, Ar-di me thy laniline in a zinc chloride melt to yield mixtures of the bisphthalides 29 and 30.109 However, far superior yields were obtained if reaction was carried out in two steps, as described in Scheme 12. The initial condensation was carried out... 

In chloride melts, the chlorine electrode (with graphite instead of platinum) is used as a reference electrode (see Table 3.3). 

The fifth paper in this chapter is by S. Kochetova and N. Tumanova of the National Academy of Sciences of Ukraine. It addresses subjects of electrolysis of molten carbamides. Authors report on interesting results of their study of the mechanisms of reactions occurring in the carbamide and carbamide-chloride melts using techniques of cyclic voltammetry in combination with gas chromatography and IR spectroscopy. 

ELECTROLYSIS OF CARBAMIDE-CHLORIDE MELTS AT INERT ELECTRODES... 

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