Hypovanadous salts

In some cases, however, the modus operandi is modified. In the oxidation of hydriodic acid with chromic acid, the data indicate that while liberation of iodine takes place, the vanadous or hypovanadic salt employed as the catalyst also undergoes oxidation to vanadate.2 The vanadium compound here belongs to the class of catalysts known as inductors, and the reaction is comparable to the oxidation in aqueous solution of sodium sulphite with sodium arsenite, whereby both sodium sulphate and sodium arsenate are produced. 

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. 

Reduction of add solutions of vanadium pentoxide to the tetravalent state also takes place with bismuth amalgam 5 magnesium gives the trivalent salts of vanadium, while by using zinc, zinc coated with cadmium, electrolytically deposited cadmium, or sodium amalgam in the absence of air, divalent vanadium salts are obtained in solution.7 Vanadous salts and hypovanadous salts are, however, much more conveniently prepared by electrolytic reduction of acid solutions of vanadium pentoxide in an atmosphere of carbon dioxide.8... 

Vanadium Tetrafluoride, hypovanadic fluoride, VF4, is produced by the action of anhydrous hydrogen fluoride on the corresponding chlorine compound, VC14, at temperatures from —28° to 0° C. It is an extremely deliquescent brown powder which readily undergoes hydrolysis with water, so that it does not give rise to double salts as in the case of the trifluoride. Its density at 23° C. is 2 9749. It decomposes above 325° C., yielding a mixture of the pentafluoride and the trifluoride 1... 

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... 

Hypovanadic Bromide, vanadium tetrabromide, VBr4, has not hitherto been isolated, but it is of interest to note that a double salt of composition VBr4.SbBr3.7HaO has been obtained by dissolving antimony tribromide and vanadium pentoxide in hydrobromic acid and adding bromine. ... 

Hydroxides Vanadium dihydroxide V(OH)2. brown precipitate by reaction of NaOH solution with hypovanadous acid (one of the most powerful of reducing agents) lavender solution vanadous hydroxide V OH)3, green precipitate by reaction of NaOH solution with vanadous salt, green solution. 

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