Vanadous oxalates

M solution of Arsenazo I (Neothorin, Uranon, 3-(o-arsenophenylazo)-chromotropic acid), which gives a violet color with Th (blue with U) (Idn. Limit 5 y Th). Be, Cr+ , F, tungstate, vanadate, oxalate and silicate interfere with the detection of thorium. Uranyl salts can be extracted as diethyl-dithiocarbamate with benzene. ... 

Lefebvre, J. (1957) Methode de la surface potentiometrique. II. Application a I etude de syst mes ii deux composants borates, vanadates, oxalate de magnesium. /. Chim. Phys., 54, 567-580. 

The most general method for the simultaneous analysis of oxyanions by gas chromatography is the formation of trimethylsilyl derivatives. Trimethylsilyl derivatives of silicate, carbonate, oxalate, borate, phosphite, phosphate, orthophosphate, arsenite, arsenate, sulfate and vanadate, usually as their ammonium salts, are readily prepared by reaction with BSTFA-TMCS (99 1). Fluoride can be derivatized in aqueous solution with triethylchlorosilane and the triethylfluorosilane formed extracted into an immiscible organic solvent for analysis by gas chromatography [685). 

Reduction with) ascorbic acid, hydrazine, or NH2OH HC1, CN-, EDTA, F-, H202, mannitol, oxidation to vanadate, triethanolamine, tiron Citrate, F-, H202, hydrazine, Na5P3O10, NH2OH HC1, oxalate, SCN-, tartrate, tiron, triphosphate, oxidation to tungstate(VI)... 

The gas can also be prepared by reducing potassium chlorate with oxalic acid,4 or with vanadic acid.5 According to W. Bray, a regular stream of chlorine dioxide is evolved without danger when a mixture of 40 grms. of powdered potassium chlorate, 150 grms. of crystallized oxalic acid, and 20 grms. of water is warmed in an oil bath to 60°. 

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... 

NH4)20.3V206.4H20 can be looked upon as ammonium, hexa-vanadate, (NH4)4V60j,.4H20 (see p. 63). It is obtained as transparent, ruby-red, monoclinic crystals when a solution of ammonium oxalate, saturated at 30° C., is treated with vanadium pentoxide and evaporated in a vacuum. Crystals containing 6HaO can also be obtained.3 It is very soluble in water. 

Oxalo-vanadates.—These compounds are obtained in large yellow prisms (side by side with red poly vanadates) by the action of vanadium pentoxide on boiling solutions of alkali oxalates, or by the action of normal alkali vanadates on acid oxalates. They have the... 

Niobic acid possesses the ability to form complex poly-acids with other acids (for example, with tungstic and oxalic acids). There are by no means as many of these known as in the case of vanadic acid, as they have not hitherto received much attention. 

Tracey, A.S., M.J. Gresser, and K.M. Parkinson. 1987. Vanadium(V) oxyanions. Interactions of vanadate with oxalate, lactate, and glycerate. Inorg. Chem. 26 629-638. 

Ehde, P.M., L. Pettersson, and J. Glaser. 1991. Multicomponent polyanions. 45. A multinuclear NMR study of vanadate(V)-oxalate complexes in aqueous solution. Acta Chem. Scand. 45 998-1005. 

Vanadium(IV) Oxide. Vanadium(IV) oxide (vanadium dioxide, V02) is a blue-black solid, having a distorted rutile (Ti02) structure. It can be prepared from the reaction of V2Os at the melting point with sulfur or carbonaceous reductants such as sugar or oxalic acid. The dioxide slowly oxidizes in air. Vanadium dioxide dissolves in acids to give the stable (V0)2+ ions and in hot alkalies to yield vanadate(TV) species, eg,. ... 

Manganese ions interfere (oxidized to permanganate) as do also mercury(II) salts, molybdates, and vanadates, which give blue to violet compounds with the reagent in acid solution. The influence of molybdates can be eliminated by the addition of saturated oxalic acid solution thereby forming the complex H2[Mo03(C204)]. 

Alternatively, place a drop of the reagent on drop-reaction paper and immediately add a drop of the test solution. A red ring forms round the spot. Se, Te, Sb(III), Sn(IV), tungstate, vanadate, and oxalate interfere. 

Vanadium, the first element in Subgroup oA, and neighbour to chromium, is found in association with molybdenum in certain complex compounds. For example, when boiling solutions of molybdo-oxalates react with vanadium pentoxide, crystalline products are obtained which are thought to be substituted vanadates containing the complex anion... 

One of the simplest methods of preparation is by decomposition of a thermally unstable compound. The nitrate or chloride is often preferred, sulphates tend to decompose at higher temperatures. Where the presence of residual traces of anion is to be avoided, the metal salts of organic acids are particularly useful. Formates, oxalates, acetates etc, decompose at low temperatures and often reduce the metal at the same time. For the preparation of catalysts from anions, the ammonium salt is frequently used. Metallic salts of complex acids can be used as a source of metal oxide mixtures. Decomposition of the appropriate chromate, tungstate, molybdate or vanadate will produce the mixed oxide. 

Vanadium (V, at. mass 50.94) occurs in the V, IV, III, and II oxidation states, vanadium(V) compounds being the most stable. In alkaline medium, the colourless vanadate VOs ions exist, whereas in strongly aeidic media, the yellow V02 cations are present. Within the intermediate pH range polymerized orange-yellow anionic forms occur. Vanadium(V) forms heteropoly acids with P(V), Mo(VI), and W(VI), and also peroxide complexes. Vanadium(IV) occurs as the blue vanadyl ion V02", stable in acid solutions and readily oxidized to vanadium(V) in alkaline solution. The VO cation is amphoteric. At pH 4, V0(0H)2 precipitates and at pH 9 it dissolves. Vanadium(IV) forms fluoride-, oxalate-, and... 

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