Ammonium molybdates tungstates

It has been found that around 0.05 y M0O3, WO3 or V2O6 can be detected in a solution of ammonium molybdate, tungstate or vanadate. If very slight... 

Arsenites may also be determined by this procedure but must first be oxidised by treatment with nitric acid. Small amounts of antimony and tin do not interfere, but chromates, phosphates, molybdates, tungstates, and vanadates, which precipitate as the silver salts, should be absent. An excessive amount of ammonium salts has a solvent action on the silver arsenate. 

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 ... 

Thiosalts and Sulphides of Molybdenum and Tungsten. Pour 2-3 ml of an ammonium molybdate solution into one test tube and 2-3 ml of a sodium tungstate solution into another one. Add 2-3 drops of a 25 % ammonia solution to each solution and pass a stream of hydrogen sulphide through them from a Kipp gas generator. What compounds form Acidify the solutions with a 10% hydrochloric... 

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. 

The carbonates, sulphates, and borates are decomposed. The sulphides of the alkalies and alkaline earths are decomposed while the sulphides of arsenic, antimony, molybdenum, zinc, cadmium, tin, iron, lead, copper, mercury, and palladium are not attacked. Cobalt sulphate is not attacked, while the sulphates of the alkalies and alkaline earths are attacked and dissolved. Alkali tungstates, ammonium arsenite and arsenate, copper arsenite, ammonium magnesium arsenate, ammonium molybdate and vanadate, potassium cyanide and ferrocyanide are decomposed. Paraffin is not attacked shellac, gum arabic, gum tragacanth, copal, etc., are decomposed. Celluloid is slowly attacked. Silk paper, gun cotton, gelatin, parchment are dissolved. M. Meslans 22 has studied the esterification of alcohol by hydrofluoric acid. 

When HCl is added to a hot solution of a tungstate the insoluble, yellow acid, H2WO4, separates. A cold solution yields soluble, colourless H2WO4.H2O. The material which separates when nitric acid is added to a cold solution of ammonium molybdate is the hydrate MoOg.HgO. It is yellow when cold, but becomes colourless when heated, being converted to H2M0O4. 

Volumetric methods are not as reliable as the gravimetric and are mainly serviceable for comparative purposes. In one method, WO3 is dissolved in excess of standard sodium hydroxide, and the excess titrated a similar method uses ethylamine to dissolve the WO3, the excess being then titrated with oxalic acid. Silica, tantalum, and columbium do not interfere with the latter method. An attempt to reduce tungsten to the blue oxide, then titrate back with ferric alum in the presence of thiocyanate, has not been successful. Somewhat more accurate results are obtained by precipitating a neutral solution of ammonium tungstate with an excess of lead acetate and titrating the excess lead by means of ammonium molybdate-4... 

The effects of ammonium chromate, ammonium dichromate, ammonium molybdate, and ammonium tungstate as additives on the catalytic performance of rhodium catalysts for the hydroformylation of Cg-oleftns and 1-dodecene were investigated. Modification of the rhodium catalyst with ammonium salts resulted in moderate increase in aldehyde yields and decrease in rhodium losses in the distillation process for the separation of products from the catalyst [11]. 

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