Meta vanadate

Draw the structures for the ortho, pyro, and meta vanadate ions and give equations showing how they can be interconverted. 

Catalysts of different V O loadings from 3.5 to 8.0 wt% were prepared by adding requisite amounts of aqueous ammonium meta vanadate solution to calculated amounts of titania (anatase) support. Excess water was evaporated on a water bath and then oven dried at 120°C for 16 h. All the samples were finally calcined at 480°C for 6 h in air. 

The yellow, amorphous variety is unstable and its identity is a little doubtful. It is stated to be obtained sometimes from the red, amorphous form by evaporation of a solution of the latter in hydrochloric acid, and it may also result from the ignition of ammonium meta-vanadate or from the decomposition of vanadates by acids. According to Bleecker it is most conveniently prepared by the electrolytic decomposition of copper vanadate.5 It becomes brick red on being heated, and is similar to the red variety in its general properties, except that it appears to be less hygroscopic and less soluble its saturated aqueous solution contains between 300 and 400 mgm. per litre.6... 

Silver orthovanadate reacts with alkyl halides to give esters of vanadic acid. These are yellow liquids of general formula Alk.3V04, in which Aik. represents the alkyl radical. Esters of orthovanadic acid axe more stable than those of pyro- and meta-vanadic acids that is, the order of stability is the reverse of that which applies to the inorganic salts.3 The following orthovanadates have been prepared —... 

These hexavanadates, like the ortho and meta vanadates, are sparingly soluble in water. 

The meta vanadate may be recrystallized, if desired, by a replication of the foregoing extraction procedure. 

If the pH value in the PAR reagent is lowered to 8.8 by adding a phosphate buffer, gallium(III), vanadium(IV)/(V), and mercury (II) can be detected and may be separated from the other heavy metals with PDCA as the eluent [151]. Fig. 3-157 shows the separation of vanadium(V) that was applied as ammonium(meta)vanadate, NH4V03. Under these conditions, vanadium(IV) elutes after about 17 minutes the two most important oxidation states of vanadium being easily distinguished. Gallium(III), of particular importance for the semiconductor industry, elutes near the void volume. 

Dissolve 0.6 g ammonium monovanadate (ammonium meta-vanadate) in 22.S ml water and careliilly add 2.5 ml cone, sulfuric acid and 25 ml acetone. 

In the case when NaOH is used as the base-titrant, its addition after the second equivalence point (meta-vanadate/pyro-vanadate) gives rise to the third slightly pronounced pO drop, which corresponds to the formation of ortho-vanadate from pyrovanadate by the following equation ... 

On 26 August 1867 Roscoe gave the true valency of vanadium and the correct formulae of its compounds. On 12 September he wrote Please ask Joseph [Heywood, the lecture assistant] to send me per book post Pogg. Atm.j vol. 98, in which is Rammelsberg s paper on the isomorphism of vanadates and phosphates. There is no doubt in my mind that vanadic acid is VtO(, and it will be exceedingly interesting to work out the vanadates which must all be ei lained as phosphates. The ordinary white NHs salt is NH4VO3 (like NaPO,) and is a meta-vanadate. The bi-vanadates can also be explained, but all need re-preparation and analysis. Did I tell you that we have now got VjOs, V 04, V 0 V 0 (I wish we had V also) VtO.Cl, V-O.Ch, VsO,Cl and V.O.CU, or VOCl VOCl VOCl. ... 

Ellwood, P., 1964, Meta-Vanadates Scrub Manufactured Gas, Chem. Eng., July 20, pp. 

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