Ammonium vanadate, meta

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... 

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. 

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