Hypovanadic oxide

Hypovanadic Oxide, V02, is amphoteric, and dissolves both in alkalis and acids. In passing from trivalent to tetravalent vanadium, however, the basic character of the oxide becomes less pronounced and... 

Vanadyl Difluoride, VOF2, is prepared by the action of anhydrous hydrogen fluoride on vanadyl dibromide, VOBr2. It is a yellow substance. Density at 19° C., 3-3956.s A hydrated vanadyl difluoride, V0F2.a, H20, is obtained as microscopic blue crystals when hypovanadic oxide, V02, is dissolved in excess of hydrofluoric acid and the solution concentrated slowly over sulphuric acid.1 The following double salts have been prepared, all of which are crystalline and fairly stable —5... 

Vanadyl Dibromide, VOBr2, is obtained by passing bromine vapour or, preferably, a mixture of sulphur bromide, SaBra, and bromine over a mixture of vanadium pentoxide and sulphur at a red heat the product is heated in vacuo at 240° C., whereupon the vanadyl dibromide is obtained as a yellow powder.8 An alternative method of preparation consists in heating vanadium oxytribromide, VOBr3, to 180° C.9 Vanadyl dibromide is no doubt present in the blue solution which results when hypovanadic oxide, VOa, is dissolved in hydrobromic acid. 

An oxybromide of possible constitution V02Br3.5H20 is known, but the constitution of this compound is a matter of doubt. It is obtained by dissolving hypovanadic oxide, V02, in dilute aqueous hydrobromic acid. Hydrochloric acid under similar conditions yields the compound VOaCl 2.8H20.s... 

Hypovanadous oxide resembles the metal in many of its properties. It is insoluble in water, but dissolves in acids without evolution of hydrogen to yield the lavender-coloured solutions which are characteristic of solutions of hypovanadous salts. These salts are, however, most conveniently prepared in solution by electrolytic reduction in an inert atmosphere of solutions of vanadium pentoxide in the various acids.7 Hypovanadous salts are isomorphous with salts of divalent iron, chromium, and manganese. On being treated with caustic alkalis, a brown precipitate of hypovanadous hydroxide, V(OH)a, is obtained, which rapidly oxidises to the greyish-green vanadous hydroxide, V(OH)s. 

Hypovanadic oxide is most conveniently obtained by heating any of the foregoing hydrates in the absence of air. It is also formed (a) from vanadium pentoxide by heating in admixture with the trioxide, carbon, or oxalic acid,6 and (b) from vanadous oxide by prolonged exposure to air.7... 

The red, amorphous form of vanadium pentoxide is the form most frequently met with in the laboratory. Its preparation has been described above. It melts at 658°10 or 675° C.u to a dark red liquid, but is not volatile even at high temperatures it can be vaporised only in the electric furnace.18 The fused solid conducts electricity, with formation of hypovanadic oxide, V02 18 the electrical conductivity has been measured.14 The oxide absorbs water on exposure to the air, the... 

With hydrobromic acid and hydriodic acid reduction may proceed to the trivalent state,9 and it has been shown that in the presence of acetic acid, hydrazine also produces vanadous oxide, V203, instead of hypovanadic oxide, V02 10... 

Vanadium pentoxide becomes markedly photo-sensitive when immersed in glycerol, benzaldehyde, cinnamic aldehyde, cuminol, or aqueous mannitol solution, and exposed to light. It blackens and undergoes reduction, giving rise, initially, to hypovanadic oxide, VOg. With aqueous solutions of citric acid or tartaric acid carbon dioxide is evolved during the change.9... 

Vanadyl Sulphates.—By treating hypovanadic oxide, V02, with sulphuric acid at about 200° C., or by reducing a sulphuric acid solution... 

Vanadyl Selenite, V02.Se02.2H20, is obtained in blue, microscopic crystals when the hydrate of hypovanadic oxide, V02.2Ha0, is dissolved in an aqueous solution of selenous acid and the solution evaporated.3 Efforts to prepare normal selenates and selenate alums of trivalent vanadium were unsuccessful, but several hydrated aceto-selenates of trivalent vanadium have been isolated.4... 

Alkali Vanadyl Nitrites.—By dissolving hypovanadic oxide, V02, in aqueous solutions of vanadyl nitrites the following alkali vanadyl nitrites have been prepared —... 

Vanadium Nitrates.—No nitrates of vanadium have been isolated. When hypovanadic oxide is dissolved in nitric acid the blue solution which results probably contains vanadyl nitrate, V0(N03)2, but on evaporation oxidation ensues and hydrated vanadium pentoxide is obtained. Blue solutions of vanadyl nitrate arc more conveniently obtained by precipitating vanadyl chloride with silver nitrate or vanadyl sulphate with barium nitrate. Addition of nitric acid to hexammino-vanadium trichloride yields hexammino-vanadium nitrate,10 [V (NH3)6](N03)3. 

Vanadyl Phosphates, V02.P205.3H20 and 2VO2.3P2O5.10H2O, are prepared in blue needles by the action of hypovanadic oxide on phosphoric add.2... 

Vanadyl Arsenates.—Two of these have been prepared by the action of hydrated hypovanadic oxide on solutions of arsenic acid 2V02.2As206.3H20 and 2V02.3As205.6H20. They are both sky-blue, crystalline compounds, and the latter rapidly becomes green on exposure to air.1... 

Vanadyl Cyanide.—Berzelius5 obtained vanadyl cyanide by the action of hydrocyanic acid on hydrated hypovanadic oxide in the absence of air. The product was not, however, analysed. 

Hypovanadic oxide, V02, and vanadium pentoxide, V205, both dissolve in hydrofluosilicic acid to yield a vanadyl fluosilicate and a vanadium fluosilicate, both of doubtful composition.14... 

Hydrogen sulfide, liquid, 111 Hydroxylamine, 87 Hydroxylamine hydrochloride, recovery of, 89 Hypochlorite solution, 90 Hypovanadous oxide, 106... 

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