Ammonium molybdate, reaction with

Molybdenite (M0S2) forms soft, thin flakes, which are very similar to graphite. Molybdenum trioxide (M0O3) is a white powder that is yellow in heat and insoluble in water and most acids. It is easily soluble in alkaline solution, with molybdates being formed. Ammonium molybdate together with phosphates forms a yellow-colored complex and precipitates in nitric acid solutions. If acidified molybdate solutions are treated with reducing agents, they become deep blue (molybdenum blue). Both reactions are used in the colorimetric determination of phosphorus. 

The reaction velocity is comparatively slow, but increases with increasing concentration of acid. The addition of three drops of a neutral 20 per cent ammonium molybdate solution renders the reaction almost instantaneous, but as it also accelerates the atmospheric oxidation of the hydriodic acid, the titration is best conducted in an inert atmosphere (nitrogen or carbon dioxide). 

This process is to ensure that the silica is in the correct form for reaction with ammonium molybdate. If the solution is too hot, the red colour may not develop. 

Platinum phthalocyanine (PcPt) is prepared by the reaction of phthalonitrile286,288 or isoindolinediimine114,117,288 with platinum(ll) chloride in a solvent such as 2-(dimethyl-amino)ethanol under the catalytic influence of l,8-diazabicyclo[5.4.0Jundec-7-ene. Another possibility is the fusion of phthalonitrile and pialinum(II) chloride58,156,157 or dipotassium tet-rachloroplatinate(II) (K2PtCl4) in the presence of urea, ammonium molybdate(Vl) and sodium sulfate.289... 

The first example of a heterogeneously catalyzed hydroamination of an alkene appeared in a 1929 patent in which it is claimed that NHj reacts with ethylene (450°C, 20 bar) over a reduced ammonium molybdate to give EtNH2 [24]. An intriguing reaction was also reported by Bersworth, who reacted oleic acid with NH3 in the presence of catalysts like palladium or platinum black or copper chromite to give the hydroamination product in quantitative yields [25]. However, this result could not be reproduced [26]. 

The reactants are phthalic anhydride, urea and copper(n) chloride, which are heated in a high-boiling aromatic solvent such as 1,2,4-trichlorobenzene, nitrobenzene or m-dinitrobenzene in the presence of a catalyst, usually ammonium molybdate. The solvent also acts as a heat-transfer medium. On heating to 120 °C an exothermic reaction begins and this temperature is maintained for about an hour. The temperature is then raised to 160-180 °C and kept constant for 6-12 hours. During this time ammonia and carbon dioxide are evolved, together with some solvent the reaction is complete when ammonia evolution ceases. The remaining solvent is then removed by either steam or vacuum distillation. The yield is 90-95%. For many years the solvent process was in almost exclusive use. 

The solvent process involves treating phthalonitrile with any one of a number of copper salts in the presence of a solvent at 120 to 220°C [10]. Copper(I)chloride is most important. The list of suitable solvents is headed by those with a boiling point above 180°C, such as trichlorobenzene, nitrobenzene, naphthalene, and kerosene. A metallic catalyst such as molybdenum oxide or ammonium molybdate may be added to enhance the yield, to shorten the reaction time, and to reduce the necessary temperature. Other suitable catalysts are carbonyl compounds of molybdenum, titanium, or iron. The process may be accelerated by adding ammonia, urea, or tertiary organic bases such as pyridine or quinoline. As a result of improved temperature maintenance and better reaction control, the solvent method affords yields of 95% and more, even on a commercial scale. There is a certain disadvantage to the fact that the solvent reaction requires considerably more time than dry methods. 

Phthalic anhydride and urea, together with copper(I)chloride and ammonium molybdate, are heated to 200°C in trichlorobenzene. The ratios between the components are the same as in the baking process. Carbon dioxide and ammonia are released to yield Copper Phthalocyanine Blue. The reaction is complete after 2 to 3 hours, producing a yield between 85% and more than 95%. 

Note In this experiment, the phosphorus in water samples is determined by visible spectrometry following a reaction of the phosphates in the sample with potassium antimonyl tartrate, ammonium molybdate, and ascorbic acid. All glassware should be washed in phosphate-free detergent prior to use to avoid phosphate contamination. 

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. 

Table II. Reaction Conditions and Results for Hydrogenation of Mequinenza Lignite with Sulfided Ammonium Molybdate Catalyst...

Molybdic and Tungstic Anhydrides. Place several ammonium molybdate crystals onto the lid of a crucible and first heat them carefully, and then roast them strongly. What occurs Perform a similar experiment with ammonium tungstate or tungstic acid. Write the equations of the reactions. At what temperature do molybdic and tungstic anhydrides sublime ... 

Pour 2-3 ml of a 10 % nitric acid solution into 2-3 ml of a 20 % ammonium molybdate solution. What substance precipitates What is its colour Wash the precipitate with water by decantation and divide it into two parts. React one part of the precipitate with an excess of concentrated hydrochloric acid and the other with a 20% sodium hydroxide solution. Explain the results. Write the equations of the reactions. Under what conditions does molybde-num(Vl) oxide dihydrate form ... 

Reduction of MoIybdenum(VI) and Tungsten VI) Compounds. Pour 3 ml of an ammonium molybdate solution into each of four test tubes, acidify with a 2 N hydrochloric acid solution, and heat up to boiling. Add solutions of sulphuric acid, hydrogen sulphide, and tin(Il) chloride to three of the tubes, respectively, and throw one or two small pieces of zinc into the last tube. Perform similar experiments using sodium tungstate as the initial reactant. Write the equations of the reactions. 

Molybdenum and Tungsten Peroxide Compounds. Pour ammonium molybdate and sodium tungstate solutions into separate test tubes, acidify them with sulphuric acid, and add several drops of a 1 % hydrogen peroxide solution to each tube. How does the colour of the solutions change Write the equations of the reactions. 

Several gas detector tubes are used in conjunction with common colorimetric reactions to detect butadiene. The reactions include the reduction of chromate or dichromate to chromous ion and the reduction of ammonium molybdate and palladium sulfate to molybdemun blue (Saltzman Harman, 1989). 

Ground together a mixture of phthalic anhydride (10 mmol, 1.54 g) and copper chloride (2.5 mmol, 0.425 g) and put it to a clean reaction vessel together with urea (1.2 g. 20 mmol), and ammonium molybdate (0.47 g, 2.0 mmol). 

The principle of the colorimetric test is based on the reaction of orthophosphate with ammonium molybdate under acidic conditions to form a heteropoly... 

---