Ammonium tungstate, preparation

Ammonium tungstate [11140-77-5] (NH 2 0cannot be obtained from an aqueous solution because it decomposes when such a solution is concentrated. It is prepared by the addition of hydrated tungstic acid to Hquid ammonia. 

W-Sb oxides were prepared by mixing aqueous solutions of ammonium tungstate and antimony tartarate, followed by drying in an air-circulated oven at 120 C and then calcination at 650 C. 

Preparation of Normal Ammonium Tungstate. Weigh 0.5 g of tungstic acid in a test tube, put the latter into a cooling mixture (solid carbon dioxide with acetone), and pour in 1-2 ml of liquid ammonia. Stir the contents of the test tube with a cooled glass rod and let the ammonia evaporate. Examine the precipitated crystals under a microscope. What is the composition of the product ... 

Bring together in a liter flask 1 g. of ammonium phosphate, 15 g. of ammonium tungstate, 3 g. of ammonium vanadate, 20 cc. of ammonium hydroxide, and 700 cc. of water. The ammonium tungstate and vanadate may be prepared from the corresponding anhydrides WO3 and VAX, which are more available. 

In the early literature it was reported that Si02-Al203 [10,11] and supported tungsten oxide [11] had high activity and selectivity for -caprolactam. Tungsten oxide catalysts prepared from the hydrolysis of WClg and supported on silica gel were more caprolactam selective than the catalyst prepared from ammonium tungstate... 

Ammonium tungstate Ammonium tungstate(VI) EINECS 234-364-9 Tungstate (Wi2(0H)204i-), decaammonium. Preparation of ammonium phosphotungstate and tungsten alloys. Crystals freely soluble in H2O. Climax Molybdenum Co. Sigma-Aldrich Fine Chem. 

Correlations between gas response RJR ) and partial pressure of nitrogen dioxide as observed with W03-based devices at various temperatures, (a) Granular WO3 as pyrolyzed from ammonium tungstate, (b) lamellar WO3 with crystallites of about 13 nm in size prepared through a colloidal process. 

Tungsten nitride supported on y-alumina was synthesized by the chemical vapor deposition (CVD) method in a stream of WCle, NH3, H2, and Ar gases at 700°C under reduced pressure (45). Carbon supported W2N was prepared from ammonium tungstate solution and carbon (Vulcan XC72R) by the incipient wetness method followed by calcination at 773 K vmder N2 atmosphere and then the TPR procedure with NH3 flow at 1023 K (46). 

A new photocatalyst, carbon-coated W18O49 active under visible light, was successfully synthesized by the same process as carbon-coated Ti02 a mixture of para-ammonium tungstate ((NH4),oW,204,5H20) with PVA was prepared in the aqueous solution and then heat-treated at 800°C for 1 h in inert atmosphere [200,201], Its activity was studied through the aqueous phase decomposition of MB, Ph, and dimethylsulfoxide ( 113)280 (DMSO) under both UV and visible light. 

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