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urenthesage
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[*] posted on 31-12-2022 at 04:11
Tungsten trioxide

Does anyone know a good solvent for recristalizing tungsten trioxide? Ive got a bunch I made as a byproduct and Id like to recristalize it.
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Junk_Enginerd
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[*] posted on 31-12-2022 at 05:05


My gut says it's not soluble in anything really, and wikipedia reinforces that by suggesting hydrofluoric acid as a solvent.
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Admagistr
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[*] posted on 31-12-2022 at 08:27


Quote: Originally posted by urenthesage  
Does anyone know a good solvent for recristalizing tungsten trioxide? Ive got a bunch I made as a byproduct and Id like to recristalize it.


I would dissolve it in NH4OH and decompose the ammonium tungstate,which is formed, by heat into WO3,NH3,H2O.
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woelen
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[*] posted on 31-12-2022 at 09:50


Getting crystalline WO3 most likely only can be done by melting or even evaporating the material and letting it solidify slowly again, so that it becomes crystalline. From aqueous solution you can make salts (e.g. the ammonium salt, as suggested above) or the acid H2WO4 and on heating this is converted to WO3, but you will only get a fine powder. Using the ammonium salt as intermediate can be a method of purification though. Let the ammonium salt crystallize and make it pure and then heat the salt.



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chornedsnorkack
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[*] posted on 10-1-2023 at 13:22


What is the water activity where WO3 is in equilibrium with its hydrates?
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Admagistr
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[*] posted on 10-1-2023 at 13:34


Quote: Originally posted by chornedsnorkack  
What is the water activity where WO3 is in equilibrium with its hydrates?


With water, WO3 produces weak tungstic acid-H2WO4, just traces of H2WO4 to shift the balance in favour of the product, I made Li2WO4 by boiling WO3+Li2CO3 in aqueous solution...
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chornedsnorkack
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[*] posted on 11-1-2023 at 08:26


For example, how does H2WO4 react with H2SO4?
It is ill complexing acid, so WO3 should not dissolve. However, H2SO4 is hygroscopic and gives reactions like
CuSO4*5H2O+5H2SO4=CuSO4+5(H2SO4*H2O)
so do you also have reaction
H2WO4+H2SO4=WO3+H2SO4*H2O?
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