Ammonium vanadates

Vanadium pentoxide, vanadium(V) oxide, V2O5, is the most important compound in this oxidation state. It is a coloured solid (colour due to charge transfer, p. 60), the colour varying somewhat (red -> brown) with the state of subdivision it is formed when vanadium (or some of its compounds) is completely oxidised, and also by heating ammonium vanadate)V) ... 

The vanadium pentoxide catalyst Is prepared as follows Suspend 5 g. of pure ammonium vanadate in 50 ml. of water and add slowly 7 5 ml. of pure concentrated hydrochloric acid. Allow the reddish-brown, semi-colloidal precipitate to settle (preferably overnight), decant the supernatant solution, and wash the precipitate several times by decantation. Finally, suspend the precipitate in 76 ml. of water and allow it to stand for 3 days. This treatment renders the precipitate granular and easy to 6lter. Filter the precipitate with suction, wash it several times with cold 5 p>er cent, sodium chloride solution to remove hydrochloric acid. Dry the product at 120° for 12 hours, grind it in a mortar to a fine powder, and heat again at 120° for 12 hours. The yield of catalyst is about 3 - 5 g. 

Conversion of fused pentoxide to alloy additives is by far the largest use of vanadium compounds. Air-dried pentoxide, ammonium vanadate, and some fused pentoxide, representing ca 10% of primary vanadium production, are used as such, purified, or converted to other forms for catalytic, chemical, ceramic, or specialty appHcations. The dominant single use of vanadium chemicals is in catalysts (see Catalysis). Much less is consumed in ceramics and electronic gear, which are the other significant uses (see Batteries). Many of the numerous uses reported in the Hterature are speculative, proposed. 

Vanadium Carbide. Vanadium pentoxide [1314-62-17, V2O5, or vanadium trioxide [1314-34-7] VO3, are the most satisfactory oxides for the preparation of VC. Vanadium pentoxide is best prepared by igniting chemically pure ammonium vanadate [7803-55-6] NH VO, in the presence of moist oxygen to avoid reaction with nitrogen V2O3 is obtained by reduction of V2O3 with hydrogen (see Vanadium compounds). 

SODIUM AMMONIUM VANADATE SODIUM ARSAHILATE SODIUM ARSENATE SODIUM ARSENITE... 

B. Phosphovanadomolybdate method Discussion. This second method is considered to be slightly less sensitive than the previous molybdenum blue method, but it has been particularly useful for phosphorus determinations carried out by means of the Schoniger oxygen flask method (Section 3.31). The phosphovanadomolybdate complex formed between the phosphate, ammonium vanadate, and ammonium molybdate is bright yellow in colour and its absorbance can be measured between 460 and 480 nm. 

Reagents. Ammonium vanadate solution. Dissolve 2.5 g ammonium vanadate (NH4V03) in 500 mL hot water, add 20 mL concentrated nitric acid and dilute with water to 1 mL in a graduated flask. 

Prepare a series of standards from potassium dihydrogenphosphate covering the range 0-2 mg phosphorus per 100 mL and containing the same concentration of acid, ammonium vanadate, and ammonium molybdate as the previous solution. Construct a calibration curve and use it to calculate the concentration of phosphorus in the sample. 

Phthalocyanine 2 can be prepared from 3-phenylphthalic acid (1) and vanadium(III) chloride in the presence of urea and ammonium vanadate at high temperature in a melt.401... 

I-A1ON0-2-NAPHIH0L-4-SULE0NIC acid, 11, 72 16, 91 17, 91 Aminonaphtholsulfonic acids, coupling to form azo dyes, 16,16 p-Aminophenol, 16, 39 Aminopiperole, 16, 6 /3-Ahinopropionic acid, 16, 1 4-Aminoveratrole, 16, 4 Ammonium dichromate, 16, 74 Ammonium formate, 17, 77 Ammonium thiocyanate, 16, 74 Ammonium vanadate, 13, 1 to w-Amyl alcohol, IS, 17 hri.-Amyl alcohol, 13, 68 -Amylbenzene, 10, 4 -Amyl borate, 13, 17 -Amyl bromide, 16, 41 iso-Amyl iodide, 13, 62 n-Amyl iodide, 13, 62 n-Amybnagnesium bromide, 16, 41... 

Rastogi, R. P. et al., Indian J. Chem., Sect. A, 1980, 19 A, 317-321 Reaction in this hybrid rocket propellant system is enhanced by presence of ammonium vanadate. 

By oxidizing cyclohexanol wilh nitric acid containing ammonium vanadate. Deutsche Hydrierwerke A. G., Ger. pat. 473,96° (d926)- [c- A- 23, 2988 (1929).]... 

Test 2 Mandelin s Test Dissolve 0.5 g of ammonium vanadate in 1.5 mL of water and dilute to 100 mL with sulfuric acid. Filter the solution through glass wool. Add a drop of the reagent to the primaquine phosphate sample on a white tile. A orange — violet color is produced [2]. 

Ahmad and Shukla [11] determined primaquine and other antimalarial aminoqui-nolines by vanadium titration. The drugs were determined by oxidation with aqueous ammonium vanadate solution and back titration of the unconsumed reagent with aqueous acidic ammonium ferrous sulfate with V-phenyl anthranilic acid indicator. 

Aniline black (Cl Oxidation Base 1) is a complex polymeric phenazine that can be produced on cotton fabric by impregnation with aniline hydrochloride and suitable inorganic oxidants, such as sodium chlorate, ammonium vanadate and copper hexacyanoferrate(II). Aniline black is also made directly for use as a pigment (Cl Pigment Black 1). 

Anthrapyrimidine and its substituted derivatives are obtained by condensation of 1-aminoanthraquinone (or its derivatives) with formamide or aqueous form-aldehyde/ammonia in the presence of an oxidant, such as ammonium vanadate or m-nitrobenzosulfonic acid. A newly developed, more simple route proceeds via formamidinium chloride, which is prepared from 1-aminoanthraquinone with di-methylformamide and thionyl chloride or phosphorus oxychloride. Cyclization in a solvent in the presence of ammonium acetate affords the desired product ... 

A technique of developing Aniline Black directly on the fiber was found by Lightfoot in the period between 1860 and 1863. In accordance with this process, the fiber is soaked with aniline, aniline hydrochloride, and sodium chlorate in the presence of an oxidation catalyst (e.g., ammonium vanadate, potassium hexa-cyanoferrate(II)). The compound is developed at 60 to 100°C and then oxidized further with sodium chromate. It should be noted, however, that Perkin had already synthesized a black compound which he called Aniline Black as early as 1856. He oxidized aniline (containing toluidine) with potassium dichromate and separated Aniline Violet from the resulting black mixture (Aniline Black). 

The limit test for phosphate is based upon the formation of ayellow colour reaction with molybdovanadic reagent (combination of ammonium vanadate and ammonium molybdate) in an acidic medium. However, the exact composition of the molybdovanadophosphoric acid complex is yet to be established. 

L — maltolate the coordination environment of the vanadium in K[V02(malt)2] H2O is approximately octahedral, the two 0x0 ligands being in cis positions. [K(H20)e] units link adjacent vanadium(V) complex anions to give a chain structure 166). The main products of aerobic oxidation of [V O(dmpp)2l in aqueous solution are [V02(dmpp)] and [VOo(dmpp)2]. High pH favors these V products, whereas at low pH V species predominate 171). Vanadium(V) also forms a VO(OR)(malt)2 series, readily prepared from ammonium vanadate, maltol, and the appropriate alcohol in a water-alcohol-dichloromethane medium 172), and 3-hydroxy-4-pyridinonate analogues V0(0R)L2 on oxidation of their oxovanadium(IV) precursors in solution in the appropriate alcohol ROH 168). 

Vanadium molybdate reagent - Note wear PPE to prevent injury from concentrated nitric acid. Separately dissolve 20 g of ammonium molybdate and 1 g of ammonium vanadate in water, transfer to a 250-ml beaker and swirl to mix. Slowly add 140 ml nitric acid (approximately 70% m/m HNO3), carefully transfer to a 1-1 volumetric flask, make up to the mark with water and mix. 

Vanadate-molybdate reagent - mix the ammonium molybdate solution with the ammonium vanadate solution in the ratio 2 3 molybdate vana-date. For optimum reproducibility, make up fresh each day just before use. 

Elemental composition P 43.64%, 0 56.36%. The pentoxide is dissolved in water and the ultimate hydrolysis product, H3PO4, is analyzed for PO4 by ion chromatography. Alternatively, the solution is treated with ammonium molybdate—ammonium vanadate reagent to produce a yellow colored vanado-molybdophosphoric acid. Absorbance or transmittance of the solution may be measured at a wavelength between 400 to 490 nm, depending on. concentration of P04. The solution must be diluted for analysis. The solution may further be reduced with stannous chloride to form an intensely colored molybdenum blue for measuring absorbance or transmittance at 690nm. 

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