Ammonium tungstate

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. 

Orally in rats, the toxicity of sodium tungstate was highest, tungsten trioxide was intermediate, and ammonium tungstate [15855-70-6] lowest (59,60). In view of the degree of systemic toxicity of soluble compounds of tungsten, a threshold limit of 1 mg of tungsten per m of air is recommended. 

Ammonium tungstate (VI) [11120-25-5] M 283.9, pK] 2.20, pK2 3.70 (for tungstic acid, H2WO4). Crystd from warm water by adding EtOH and cooling. 

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. 

The series of deviation from a strictly octahedral crystal field follows the sequence ammonium tungstate > tungstic acid > WO3 [14]. The s->d transition becomes allowed as distortion of the octahedral environment increases. Viewed as a fingerprint technique. Figure 6 shows that the bulk of W present in both WZ (calcined) and PtWZ(acac, reduced) behaves as WO3, as also shown by our XRD data [10], sugesting that only a small extent of W reduction is expected to have taken place during catalyst conditioning prior to reaction. 

Ammonium thiosulfate solutions, in photography, 19 214 Ammonium tungstate, 25 381-382 Ammonium xylenesulfonate, cosmetic surfactant, 7 834t... 

When mixed with caustic soda solution, cadmium oxide forms precipitate of cadmium hydroxide. Many insoluble cadmium salts are obtained by such precipitation reactions. For example, mixing aqueous solutions of cadmium nitrate with ammonium tungstate results in precipitation of cadmium tungstate. 

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 ... 

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 ... 

Ammonium tungstate [11120-25-5] M 283.9. Crystd from warm water by adding EtOH and cooling. 

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. 

Boil the solution for about 6 hr. At first, the solution is colorless but soon changes to yellow and then to red, and to this point the ammonium tungstate dissolves very rapidly. Filter off the slight residue, evaporate to a density of 1.115, and allow to stand overnight. Evaporate the mother liquor for a second crop. The crystals are dark red in color and are octohedra or cubes in form. 

Magnesium Tungstate. [CAS 1357.3-11-0. (magnesium w-ollranraie) Mg WO., while crystals. D 5.66. soluble in acids, insoluble in water and alcohol, formed by interaction of solutions of magnesium sulfate and ammonium tungstate. Use Fluorescent screens for X-rays, luminescent paint. 

Ammonium Tungstates.— The normal salt cannot be obtained by dissolving tungstic acid in aqueous ammonia, since on concentration ammonia is lost and an acid salt remains. That the normal tungstate is present in solution would appear evident from the fact that calcium chloride precipitates the normal calcium tungstate. It may be obtained as a white mass by the addition of hydrated tungstic acid to liquid ammonia. The normal tungstate is very soluble in water and readily loses ammonia. 

A hydrate, 5(XH4),20.12W0g.6H20, has been obtained by the addition of acetic acid to a solution of ammonium tungstate. 

Uranium Tungstate. -When ammonium tungstate is added to a solution of uranium tetrachloride, a brownish-green ijrecipitate of composition U(W0,).2.W0g.6H20 is obtained. This compound is used in... 

Ammonium dithiotimgstate, (XHi)., VO.jS2, is obtained as yellow crystals w hen hj-drogen suliAide is passed into a strong aramoniacal solution of ammonium tungstate. The cr) stals are triclinic pinacoids, with axial ratio a b c=0-703 1 0-3392. The salt is stable when dry, but decomi>oses when moist. 

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