Tungstic anhydride

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 ... 

Procedure Place 0.2 g of sample into a ceramic weigh boat. Mix in a small amount of comcat (100 g of tungstic anhydride and 15 g of 97% lithium metaphosphate) to facilitate combustion. Analyze the sample through the system. 

SYNS C.I. 77901 TUNGSTEN BLUE TUNGSTEN TRIOXIDE TUNGSTIC ANHYDRIDE TUNGSTIC OXIDE WOLFRAMITE... 

This oxychloride forms stable yellow crystals which readily sublime, but which also melt at 259° C. at much higher temperatures the substance largely dissociates into tungstic anhydride and the oxydetra-chloride. Partial decomposition is also effected by warming with water. ... 

Silica may be removed from impure tungstic anhydride by fusion with potassium hydrogen sulphate and e.xtraction of the alkali tungstate from the cooled mass with water. 

If hydrogen is passed through water at 85° C. and the mixture of hydrogen and water vapour then passed over tungstic anhydride at 900° C., the latter is reduced to the dioxide, WOa. The reaction is influenced by the amount of water vapour present, and the pentoxide, W2O5, results when the temperature of the water is maintained at 97° C. 

Lithium Tungstates.—The normal salt, solution when a suspension of tungstic anhydride in water is boiled with lithium carbonate, or when tungstic anhydride is added to fused lithium carbonate and the resulting mass extracted with water on evaporation, short, thick, oblique rhombic prisms separate, which readily dissolve in water yielding an alkaline solution. Lithium ditungstate is described by Anthon, but its existence is doubtfiil. 

Lithium tetratungdate, Li O-iWOg, remains as needle-shaped crystals after well washing with water the mass obtained by fusing together lithium carbonate (5 molecules] and tungstic anhydride (12 molecules). 

If tungstic anhydride is heated in a crucible with ammonium cUoridc, repeated additions of the latter compound being made until a product of constant weight is obtained, a black substance results w hich ajjpears to be an oxynitride of composition AVOg.WXa. 

Tungsten Subphosphide, W4P3.—By strongly heating a mixture of phosphoric acid and tungstic anhydride in a carbon crucible, lustrous steel-coloured crystals of this phosphide are obtained. The crystals are si.x-sided prisms of density 5-21. It conducts electricity well, is very" stable in air even at higher temperatures, and is very resistant to acids. When heated in a current of oxygen it bums brilliantly. It dissolves in a fused mixture of alkali carbonate and nitrate. 

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