Ammonium vanadate test

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]. 

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. 

Mandalin tast A presumptive test for amphetamines and alkaloids. The Mandelin recent is a 1% solution of ammonium vanadate (NH4VO3) in concentrated sulphuric acid. Different substances j e different colours. Mescaline, for example, produces an orange colour, heroin abrown colour, and amphetamine ablue-green colour. 

The analysis of steroids is complicated by the similarity of the drugs structures, but can be achieved with standard forensic analysis tools. Color tests with ammonium vanadate (Mandolin s reagent) has been reported to be the... 

With the exception of the iron i, uranyl, and vanadium compounds of oxine, all metal oxinates are yellow to orange. The ferric, uranyl, and vanadium compounds are black-green, red-brown, and black-brown, respectively. Oxinates of the types (II) and (III) can be formed not only by the wet method but also by melting metal salts and oxides with oxine (m.p. 75° C). The solubility of metal oxinates in molten oxine appears to play a role in the fusion reactions. The production of dark oxine melts is indicative of the presence of iron or vanadium. Accordingly, if vanadium is to be detected by an oxine fusion, iron and uranium must be absent. They can be removed by igniting a small portion of the test material and extracting the residue with ammonia. Any ammonium vanadate dissolves out. 

Procedure 0.5 — 1 ml of ammonium vanadate solution is added to 3—5 ml of the tested solvent, followed by the 8-hydroxyquinoline solution. The volume of aqueous solutions of the reagents added should not be larger than that of the organic solvent being analyzed. 

Salts of Vanadic Acid. Pour 3-4 ml of a sodium vanadate solution into each of two test tubes. Add to one of them a silver nitrate solution, and to the other a saturated ammonium chloride solution. Write the equations of the reactions. 

Tannin test When a neutral or acetic acid solution of a vanadate is treated with an excess of 5 per cent tannic acid, a deep blue (or blue-black) colouration is obtained. If ammonium acetate is present, a dark-blue (or blue-black) precipitate separates. The precipitate or colouration is destroyed by mineral acids. 

Chromates, vanadates, and cerium salts give colour reactions with the reagent and should therefore be absent. Iron salts give a yellow colour with hydrogen peroxide, but this is eliminated by the addition of concentrated phosphoric acid. Fluorides bleach the colour (stable [TiFa] ions are formed), and large amounts of nitrates, chlorides, bromides, and acetates as well as coloured ions reduce the sensitivity of the test. A decrease in the intensity of the yellow colouration upon the addition of ammonium fluoride indicates the presence of titanium. 

Reduced chalcogens. An acidified vanadate gives no precipitate with H2S, which reduces it to V. Ammonium sulfide forms a thiovanadate. Treating an ammo-niacal solution of vanadate with H2S gives a violet-red color, a very good test in the absence of Mo. Aqueous VS4 " is deep violet but it decomposes to brown oxygenated species even in basic solution. Acidification then causes incomplete precipitation of V2S5, soluble in alkalis, alkali carbonates, and sulfides. 

---