Vanadium iodide

Preparation. Commercially it is prepared mainly as ferro-vanadium alloy. It can be obtained by aluminothermic reduction of the oxide. Pure V may be obtained through the de Boer-Van Arkel process by iodide thermal decomposition (vanadium iodide is decomposed on an electrical heated W wire). 

Refining of Vanadium. In addition to the purification methods described above, vanadium can be purified by any of three methods iodide refining (van Arkel-deBoer process), electrolytic refining in a fused salt, and electrotransport. 

The known halides of vanadium, niobium and tantalum, are listed in Table 22.6. These are illustrative of the trends within this group which have already been alluded to. Vanadium(V) is only represented at present by the fluoride, and even vanadium(IV) does not form the iodide, though all the halides of vanadium(III) and vanadium(II) are known. Niobium and tantalum, on the other hand, form all the halides in the high oxidation state, and are in fact unique (apart only from protactinium) in forming pentaiodides. However in the -t-4 state, tantalum fails to form a fluoride and neither metal produces a trifluoride. In still lower oxidation states, niobium and tantalum give a number of (frequently nonstoichiometric) cluster compounds which can be considered to involve fragments of the metal lattice. 

Vanadates. Vanadates are reduced by iodides in strongly acid (hydrochloric) solution in an atmosphere of carbon dioxide to the vanadium(IV) condition ... 

The liberated iodine and the excess of iodide is determined by titration with standard potassium iodate solution the hydrochloric acid concentration must not be allowed to fall below 7JVf in order to prevent re-oxidation of the vanadium compound by iodine chloride. 

V02+) by chromium(VI) (HCrO ), when carried out in the presence of iodide ions, results in formation of triiodide ions, I3,4 This reaction occurs rather rapidly, whereas both HCrO and vanadium(V) (VOJ, a product) oxidize I- so slowly that these reactions can be ignored. The net reactions with and without I" are... 

Induced reactions. Consider the scheme shown4 to account for the effect of iodide ions on the reaction of vanadium(IV) and chromium(VI), as in Eq. (2-3). Derive an expression for the ratio of [Vv]/tl2] for experiments in which [CrIV] is much less than [Vlv] and [l-]. Show what rate constants or ratios can be evaluated. 

Salt effects. The rate of reaction of vanadium(V) with iodide ions is independent of ionic strength.28 The rate law is v = fc[V(V)][I ][H+]2. What is the charge on the predominant V(V) species in these solutions ... 

Luther and Rutter have observed the induced oxidation of iodide during the reactions between chromic acid and vanadium(IV), vanadium(ri[), and vana-dium(II) ions. In all the three systems ci = 2, therefore it is probable that the coupling intermediates are chromium(V) species, these being, especially the two latter systems, too complicated for a detailed kinetic treatment to be given. 

Induced oxidation of iodide caused by vanadium(IV) and vanadium(ri) presumably involves steps analogous to those in the iron(II)-chromium(VI)-iodide system. Some data obtained by Luther and Rutter are summarized in Tables 9 and 10. 

Iodargyrite, natural occurrence of, 22 668 Iodates, 14 374-375 Iodate solutions, 14 362 Iodic acid, 14 375 Iodide analysis, of water, 26 41 Iodide ion, 14 367-368 25 488 Iodide-refining method, 26 149 for vanadium, 25 520 Iodides, 14 374 thorium, 24 763 tungsten, 25 379-380 uranium, 25 439... 

Li2S204 being the SEI component at the Li anode and the solid discharge product at the carbon cathode. The Li—SOCI2 and Li—SO2 systems have excellent operational characteristics in a temperature range from —40 to 60 °C (SOCI2) or 80 °C (SO2). Typical applications are military, security, transponder, and car electronics. Primary lithium cells have also various medical uses. The lithium—silver—vanadium oxide system finds application in heart defibrillators. The lithium—iodine system with a lithium iodide solid electrolyte is the preferred pacemaker cell. 

Iodide ion-selective electrode The iodide electrode has broad application both in the direct determination of iodide ions present in various media as well as for the determination of iodide in various compounds. It is, for example, important in the determination of iodide in milk [44,64,218, 382, 442], This electrode responds to Hg ions [150, 306, 439] and can be used for the indirect determination of oxidizing agents that react with iodide, such as 10 [305], lOi [158], Pd(II) [117, 347,405] and for the determination of the overall oxidant content, for example in the atmosphere [393], It can also be used to monitor the iodide concentration formed during the reactions of iodide with hydrogen peroxide or perborate, catalyzed by molybdenum, tungsten or vanadium ions, permitting determination of traces of these metals [12,192,193, 194, 195]. The permeability of bilayer lipid membranes for iodide can be measured using an I"... 

Major constituents (greater than 5 mg/L) Minor constituents (O.Ol-lO.Omg/L) Selected trace constituents (less than 0.1 mg/L) Bicarbonate, calcium, carbonic acid, chloride, magnesium, silicon, sodium, sulfate Boron, carbonate, fluoride, iron, nitrate, potassium, strontium Aluminum, arsenic, barium, bromide, cadmium, chromium, cobalt, copper, gold, iodide, lead, Uthium, manganese, molybdenum, nickel, phosphate, radium, selenium, silver, tin, titanium, uranium, vanadium, zinc, zirconium... 

Chemical deoxygenation of sulfoxides to sulfides was carried out by refluxing in aqueous-alcoholic solutions with stannous chloride (yields 62-93%) [186 Procedure 36, p. 214), with titanium trichloride (yields 68-91%) [203], by treatment at room temperature with molybdenum trichloride (prepared by reduction of molybdenyl chloride M0OCI3 with zinc dust in tetrahydrofuran) (yields 78-91%) [216], by heating with vanadium dichloride in aqueous tetrahydrofuran at 100° (yields 74-88%) [216], and by refluxing in aqueous methanol with chromium dichloride (yield 24%) [190], A very impressive method is the conversion of dialkyl and diaryl sulfoxides to sulfides by treatment in acetone solutions for a few minutes with 2.4 equivalents of sodium iodide and 1.2-2.6 equivalents of trifluoroacetic anhydride (isolated yields 90-98%) [655]. 

Vanadium metal is prepared from pentoxide, V2O5, by reduction with calcium at elevated temperatures. Presence of iodine lowers calcium reduction temperature to 425°C because of heat of formation of calcium iodide. Pentoxide also may be converted to the trichloride, VCI3, and the trichloride reduced with magnesium metal or magnesium-sodium mixture at high temperatures to form high purity ductile metal. Alternatively, a fused mixture of vanadium chloride, sodium chloride, and hthium chloride may be electrolyzed to produce the metal in high purity. 

Pentafluorocthyl iodide is of practical interest, particularly as a precursor of higher perfluoroal-kyl iodides. There are several patents for the preparation of the key compound from tetra-fluoroethene, iodine pentafluoride and iodine at 75-80 C in the presence of catalysts anti-mony(III) fluoride, titanium(lV) chloride, boron trifluoride, vanadium(V) fluoride, niobium(V) fluoride, and molybdenum(Vl) fluoride.11-13 The agents iodine monofluoride" and bromine monofluoride" can add to branched pcrfluoroalkcnes, e.g. perfluoro-2-methylbut-2-ene gives perfluoro-2-iodo-2-methylbutane.1415... 

Anhydrous VO 2 has not yet been prepared and most reports of iodides of Viv are not firmly based. I" can reduce vanadium(IV). 

Those submicron particulates which enter the alveolar sacs may undergo various degrees of absorption, depending upon the solubility of their components, or are transported to the base of the ciliated bronchiolar epithelium (54). Alveolar absorptive efficiency for most trace elements is 50-80% (50). Retention or absorption is not necessarily a simple function of solubility. Silver iodide, for example, is rapidly absorbed from the lungs even though it is weakly soluble in water (56). Likewise, insoluble elemental lead deposited in the respiratory passages is absorbed, but the mechanism involved remains to be elucidated (49). Vanadium probably accumulates in human lungs in insoluble forms... 

Hydrated Vanadium Tri-iodide, VT3.6H20, is prepared by reducing, electrolytically, a solution of vanadium pentoxide, V2Os, in hydriodic add, until the product becomes green more hydriodic add is then added and the whole allowed to stand over lime and concentrated sulphuric add at 0° C. Small green needles separate, which have the same crystalline form as the hydrated trivalent halides of titanium, iron, and chromium. These crystals are extremely hygroscopic and deliquesce in air to a brown liquid8 which is extremely unstable. 

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