Chlorides eutectic compositions

Saturation temperatures of sodium chloride dihydrate at these temperatures NaCl 2H2O separates leaving the brine of the eutectic composition (E). 

The electrodeposition of chromium in a mixture of choline chloride and chromium(III) chloride hexahydrate has been reported recently [39]. A dark green, viscous liquid is obtained by mixing choline chloride with chromium(III) chloride hexahydrate and the physical properties of this deep eutectic solvent are characteristic of an ionic liquid. The eutectic composition is found to be 1 2 choline chloride/chromium chloride. From this ionic liquid chromium can be electrode-posited efficiently to yield a crack-free deposit [39]. Addition of LiCl to the choline chloride-CrCl3-6H20 liquid was found to allow the deposition of nanocrystalline black chromium films [40], The use of this ionic liquid might offer an environmentally friendly process for electrodeposition of chromium instead of the current chromic acid-based baths. However, some efforts are still necessary to get shining... 

For the investigation of the rhenium electrochemical behaviour in chloride-fluoride melts, we used NaCl-NaF electrolyte of eutectic composition. Rhenium was introduced into... 

AN.HCl) by half an equivalent amount of mono sodium salt of (R,R)-tartaric add (TANa). The crystalline salt of undesired (K)-AN.TA precipitates. After filtration of the diastereoisomeric salt the pure (S)-AN.HCl can be crystallized from the mother liquor by salting out (addition of sodium chloride into the filtrate) while the racemic AN.HCl remains in solution. Since the enantiomeric excess crystallized from the filtrate we can speak about conglomerate behaviour. However, the compound may be a racemate forming material, if the purity of the (S>R)-AN.HC1 enantiomeric mixture is higher than the eutectic composition (eeeu for AN.HCl). 

This behaviour may suggest a sequence of reduction processes for some possible nickel complex compounds in the presence of an ionic medium containing chloride anions and ammonium cations (from the eutectic composition acting as a solvent) 0i Coop>er, 1996 Zheng et al., 2005). 

Fig. 2. The system sodium chloride—water, showing the eutectic temperature, —21.12°C, and composition, 23.31 wt % NaCl.

Commercial appHcations of calcium chloride and its hydrates exploit one or more of its properties with regard to aqueous solubiUty, hygroscopic nature, the heat gained or lost when one hydrated phase changes to another, and the depressed freezing point of the eutectic solution at a composition of about 30% by weight calcium chloride. 

Lithium chloride is used in the production of lithium metal by electrolysis. It also is used in metallurgy as a eutectic melting composition with potassium chloride (LiCl 41 mol% KCl 59 mol%). Other applications are in low temperature dry-cell batteries as a dehumidifier in air conditioning in welding and soldering flux as a desiccant in fireworks and in mineral waters and soft drinks. 

For the zinc chloride choline chloride mixtures the eutectic is observed at a 2 1 composition, whereas for the tin chloride choline chloride mixtures it is observed at 2.5 1. This is presumably because SnCl2 is less Lewis acidic than ZnCl2 and hence more SnCl2 is require to push the equilibrium for the reaction SnCl2 + SnCl3 5 S Cls- to the optimum Sn2Cl5 composition. 

These problems have been overcome by the Downs process, which uses a 58 wt% calcium chloride-42% sodium chloride electrolyte at an operating temperature of 580-590°C. This composition represents a compromise between the melting point of the salt mixture and the sodium purity. The eutectic mixture contains 66.8 wt% CaCl2 and 33.2 wt% NaCl and melts at 505°C. Increasing CaCl2 content reduces the melting point of the mixture and increases the concentration of calcium in the cathode metal due to the equilibrium... 

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