LiCl, dissolution process

The properties of water near ionic salt surfaces are of interest not only for the understanding of the mechanism of dissolution processes but also for the understanding of the chemistry in the atmosphere next to oceans [205]. Experiments in UHV [205-208] indicate that the water-covered NaCl surface is quite stable at low temperatures. An early simulation study by Anastasiou et al. [209] focused on the arrangements and orientations of water molecules in contact with a rigid NaCl crystal. Ohtaki and coworkers investigated the dissolution of very small cubic crystals of NaF, KF, CsF, LiCl, NaCl, and KCl [210] and the nucleation [211] of NaCl and CsF in a... 

The last electrolyte system to be mentioned in connection with lithium electrodes is the room temperature chloroaluminate molten salt. (AlCl3 LiCl l-/ -3/ "-imidazolium chloride. R and R" are alkyl groups, usually methyl and ethyl, respectively.) These ionic liquids were examined by Carlin et al. [227-229] as electrolyte systems for Li batteries. They studied the reversibility of Li deposition-dissolution processes. It appears that lithium electrodes may be stable in these systems, depending on their acidity [227], It is suggested that Li stability in these systems relates to passivation phenomena. However, the surface chemistry of lithium in these systems has not yet been studied. 

The designation LiCl(12H20) represents a solution of 1 mol of LiCl dissolved in 12 mol of H2O. The heat of solution for tliis process at 298.15 K (25°C) and 1 bar is AH = —33 614 J. This means that a solution of 1 mol of LiCl in 12 mol of H2O has an enthalpy 33 614 J less than the combined enthalpies of 1 mol of pure LiCl(5) and 12 mol of pure H20(Z). Equations for physical changes such as this are readily combined with equations for chemical reactions. This is illustrated in the following example, which incorporates the dissolution process jnst described. 

When a solute is dissolved in a solvent, heat change generally occurs. A dissolution process may be exothermic or endothermic. Exothermic processes emit energy as heat. Endothermic processes absorb energy as heat. Temperature rises in an exothermic process, but falls in an endothermic one. When lithium chloride (LiCl) dissolves in water, the solution gets warmer and the temperature goes up. We can say that the dissolution of lithium chloride is exothermic. (Figure 6). 

Cellulose-cellulose composites have already been described in the literature. For example, fliey can be prepared by using cellulose solvents such as DMAC/LiCl. From a mixture of partially dissolved and undissolved cellulose, it is possible to regenerate die dissolved cellulose at any stage in the dissolution process. This leads to the formation of composites in which the undissolved cellulose constitutes the reinforcing component... 

The preparation of cellulose solutions suitable for SEC analysis in DMAc/LiCl is reasonably straightforward (35,51). The dissolution process requires preswelling of the cellulose in water or its activation in refluxing DMAc. Evidently, it is important that the pH of the cellulose be neutral initially (51) otherwise, considerable degradation may occur before the dissolution process is complete. 

A series of voltammograms obtained 1,18,24 and 45 hours after the CrCla dissolution in molten LiCl- Cl are reported in figure 5. They evidence the slowliness of the CrCls dissolution process. 

Molybdenum pentachloride dissolved in high-temperature alkali chloride-based melts, and concentrations of Mo(V) up to 0.2mol/dm were obtained. Its dissolution process was studied in LiCl-KCl, NaCl-KCl, NaCl-KCl-CsCl and NaCl-CsCl melts between 450 and 850 °C and in all the systems resulted in the formation of molybdenum(V) chloro-ions, which we show to be MoCl ". The symmetry of this species complies with ligand field theory as octahedral but some distortions may be present. 

The well-known fact that heating of initially insoluble pulps in DMAc/LiCl improves solubility or increases the dissolution rate of the material had thus to be attributed to pronounced cellulose degradation. The observed improved solubility was evidently accompanied by a progressive DP loss of the pulp. The solubility gain was thus not an activation of the pulp, but mainly a degradation process to material of lower molecular weight which naturally exhibited a higher solubility in the cellulose solvent. 

Heats of solution are readily calculated from these data. Consider the dissolution of 1 mol of LiCl(5) in 5 mol of H20(/). The reaction representing tiiis process is obtained as follows ... 

For processing of PBl, it is often dissolved in DMAc. Especially at a high PBl content, e.g., >20 wt%, formation of agglomerates reduces the shelf life of the solution, as indicated by an increase in solution viscosity and resin precipitation. Therefore, a small amount of LiCl (i.e., 1.5 wt%) may be added as stabilizer [20, 21]. Thin films prepared from such solutions can be washed to remove LiCl by immersion in water at 85 °C for 1 h [22]. To speed up the PBl dissolution, increased temperatures are often necessary. In some cases also pressure reactors are used to increase the temperature up to over 260 °C [23]. At these conditions, the water content of the polymer must be reduced by drying at >70 °C in vacuo and the water content of DMAc should be lower than 0.03 %, to avoid hydrolysis of the solvent. It was also reported that the solubility is reduced by the presence of oxygen, and an inert atmosphere (nitrogen or argon) was recommended [23]. 

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