Vanadium dichloride

Electronic Grade Silicon (EGS). As the first step in the production of electronic grade silicon (EGS), an impure grade of silicon is pulverized and reacted with anhydrous hydrochloric acid, to yield primarily tricholorosilane, HSiClg. This reaction is carried out in afluidizedbed at approximately 300°C in the presence of a catalyst. At the same time, the impurities in the starter impure silicon reactto form their respective chlorides. These chlorides are liquid at room temperature with the exception of vanadium dichloride and iron dichloride, which are soluble in HSiCl3 at the low concentration prevailing. Purification is accomplished by fractional distillation. 

The metallic impurities present in an impure metal can be broadly divided into two groups those nobler (less electronegative) and those less noble or baser (more electronegative) as compared to the metal to be purified. Purification with respect to these two classes of impurities occurs due to the chemical and the electrochemical reactions that take place at the anode and at the cathode. At the anode, the impurities which are baser than the metal to be purified would go into solution by chemical displacement and by electrochemical reactions whereas the nobler impurities would remain behind as sludges. At the cathode, the baser impurities would not get electrolytically deposited because of the unfavorable electrode potential and the concentration of these impurities would build up in the electrolyte. If, however, the baser impurities enter the cell via the electrolyte or from the construction materials of the cell, there would be no accumulation or build up because these would readily co-deposit at the cathode and contaminate the metal. It is for this reason that it is extremely important to select the electrolyte and the construction materials of the cell carefully. In actual practice, some of the baser impurities do get transferred to the cathode due to chemical reactions. As an example, let the case of the electrorefining of vanadium in a molten electrolyte composed of sodium chloride-potassium chloride-vanadium dichloride be considered. Aluminum and iron are typically considered as baser and nobler impurities in the metal. When the impure metal is brought into contact with the molten electrolyte, the following reaction occurs... 

The electrolyte is made by in situ chlorination of vanadium to vanadium dichloride in a molten salt bath. Higher valent chlorides are difficult to retain in the bath and thus are not preferred. The molten bath, which is formed by sodium chloride or an equimolar mixture of potassium chloride-sodium chloride or of potassium chloride-lithium chloride or of sodium chloride-calcium chloride, is contained in a graphite crucible. The crucible also serves as an anode. Electrolysis is conducted at a temperature about 50 °C above the melting point of the salt bath, using an iron or a molybdenum cathode and a cathode current density of 25 to 75 A dnT2. The overall electrochemical deposition reaction involves the formation and the discharge of the divalent ionic species, V2+ ... 

The quality of the refined metal, and the current efficiency strongly depend on the soluble vanadium in the bath and the quality of the anode feed. As the amount of vanadium in the anode decreases, the current efficiency and the purity of the refined product also decrease. A laboratory preparation of the metal with a purity of better than 99.5%, containing low levels of nitrogen (30-50 ppm) and of oxygen (400-1000 ppm) has been possible. The purity obtainable with potassium chloride-lithium chloride-vanadium dichloride and with sodium chloride-calcium chloride-vanadium dichloride mixtures is better than that obtainable with other molten salt mixtures. The major impurities are iron and chromium. Aluminum also gets dissolved in the melt due to chemical and electrochemical reactions but its concentrations in the electrolyte and in the final product have been found to be quite low. The average current efficiency of the process is about 70%, with a metal recovery of 80 to 85%. 

Vanadium dichloride, Water See Vanadium dichloride Platinum, Water... 

Some samples of vanadium prepared by magnesium reduction of vanadium dichloride or vanadium trichloride are pyrophoric. 

Tungsten tetrabromide oxide, 0294 Uranium hexachloride, 4192 Uranium hexafluoride, 4375 Vanadium dichloride, 4118... 

Aqueous solutions of vanadous chloride (vanadium dichloride) are prepared by reduction of vanadium pentoxide with amalgamated zinc in hydrochloric acid [213], Reductions are carried out in solution in tetrahydrofuran at room temperature or under reflux. Vanadiiun dichloride reduces a-halo ketones to ketones [214], a-diketones to acyloins [215], quinones to hydroquinones [215], sulfoxides to sulfides [216] and azides to amines [217] (Procedure 40, p. 215). 

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]. 

When he began his researches on vanadium, its compounds were listed at .35 per ounce, and the metal itself was unknown. After all attempts at direct reduction of the oxides had failed, Roscoe attempted to reduce vanadium dichloride, VC12, with hydrogen. Rigorous exclusion of oxygen and moisture was necessary, and, since vanadium metal reacts violently with glass and porcelain, the chloride was placed in platinum boats inside a porcelain tube. The tube itself could not be made of platinum because of the porosity of that metal at red heat. 

The solution behaves generally like one of vanadium dichloride.3... 

Hypovanadous Chloride, vanadium dichloride, VC12.—Solutions of vanadium dichloride can be prepared by electrolytic reduction of higher chlorides,3 or by the addition of amalgamated zinc to a hydrochloric acid solution of vanadium pentoxide.4 The solution undergoes very rapid oxidation, hence the isolation of vanadium diehloride cannot... 

Anhydrous vanadium trichloride is a crystalline solid of the colonr of peach blossom. It is extremely hygroscopic, deliquescing to a brown liquid. It gives green solutions in alcohol and ether. Density at 18° C., 3-00. The absorption spectrum has been studied.8 On being strongly heated in hydrogen it is reduced to vanadium dichloride, VCla,... 

Chlorides Vanadium dichloride VCI2, green crystalline solid, a strong reducing agent vanadium trichloride VCI3, pink crystalline solid vanadium tetrachloride VC14, reddish-brown liquid, bp 148 0... 

Vanadium azide tetrachloride, 4160 Vanadium dichloride, 4112 Vanadium(III) oxide, 4849 Vanadium tetrachloride, 4171 Vanadium tribromide oxide, 0291 Vanadium trichloride, 4153 Vanadium trinitrate oxide, 4758 Vanadium, 4918 Vanadium(V) oxide, 4860... 

Potassium phosphinate, 4453 Sodium disulfite, 4802 Sodium dithionite, 4801 Sodium hydride, 4438 Sodium hypoborate, 0164 Sodium phosphinate, 4467 Sodium thiosulfate, 4798 Sulfur dioxide, 4831 Tetraphosphorus hexaoxide, 4861 Tin(II) chloride, 4064 Tin(II) fluoride, 4325 Titanium trichloride, 4152 Titanium(II) chloride, 4111 Tungsten dichloride, 4113 Vanadium dichloride, 4112 Vanadium trichloride, 4153 Zinc, 4921... 

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