Halide melt hydrolysis

Examinations of the interactions of ionic halide melts-solvents with gaseous reagents of acidic or basic character, which include high-temperature hydrolysis of molten alkali-metal halides, their purification from oxygen-containing admixtures, and studies of the dissociation of strong and weak Lux bases (such as COf-, OH-, 0 ) in melts of different acidity. 

Pure oxygen-less melts contain no oxide ions in any form, and, therefore, such pure melts cannot serve as donors of O2-. The melts, which are solvents of the second kind, can affect acid-base interaction on their background in two manners by fixation of oxide ions entering in the melt and by solvation of the conjugate acid or base. However, the ionic solvents of the second kind, used in practice for different measurements and applied purposes, contain admixtures of oxide-ion donors, which are formed in the melt from initial admixtures of oxo-anions such as SO4-, COf- or OH-. The second way of appearance of oxide ion admixtures in molten media is characteristic of the melts based on alkali metal halides the process of high-temperature hydrolysis of the said halide melts results in the formation of hydroxide ions and, after their dissociation, of oxide ions ... 

For the preparation of the LiCl-KCl eutectic, reasonable purity anhydrous LiCl is readily available, although in the United States, the fully purified eutectic can be obtained. Otherwise, treatment with dry HCl followed by dry CI2 prior to preelectrolysis at 2.7 V, and, finally, filtration, is recommended. Similar procedures, with suitable modifications to the gas purges and electrolysis voltages, may be adopted for MgCl2-KCl, NaCl-KCl, CaC -KCl, ZnC -KCl, and for the bromides and iodides. Advantageously, vitreous carbon crucibles can be used for halide melts they are reusable and can form the counterelectrode. Purity of these systems may again be assessed voltammetri-cally. Surprisingly, water is reversibly soluble at low partial pressures, but hydrolysis occurs at a 18 mm ... 

Bismuth oxychloride (BiOCl) is a colorless fine powder, which melts at 232°C and boils at 447°C. It is practically insoluble in water and alcohols, but readily soluble in hydrochloric acid and nitric acid. Above 570°C, it liberates BiCb to be transformed into a Bi405Cl3 compound. Among bismuth oxyha-lides, only the oxychloride is available commercially at a cost of US 30.00 ( 7500) for a sample of 99% purity and US 98.60 ( 24 400) for a sample of 99.99% purity per 50 g. However, other oxyhalides can readily be prepared by partial hydrolysis of trivalent bismuth halides or by the interaction of basic bismuth nitrate (BiO(N03)) with the corresponding sodium halide in aqueous... 

High-temperature hydrolysis of melts based on alkali metal halides... 

In the vapor all three halides are distinctly molecular, as they are also in solutions. Relative to ionic HgF2, the other halides have very low melting and boiling points (Table 18-11). They also show marked solubility in many organic solvents. In aqueous solution they exist almost exclusively ( 99%) as HgX2 molecules, but some hydrolysis occurs, the principal equilibrium... 

Processes taking place in ionic melt-solvents are considerably affected by impurities contained in the initial components of the melt or formed during preparation (mainly, melting) of solvents due to the high-temperature hydrolysis of melts or their interactions with container materials (AI2O3, SiOj, etc.) or active components of atmosphere (O2, CO2, etc.). The list of these impurities is wide enough and includes multivalent cations of transition metals, different complex anions (0x0- or halide anions). The effect of the mentioned admixtures on the processes in ionic melts depends mainly on the degree of their donor-acceptor interactions with constituent parts of the melt. 

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