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vano
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I added ammonia solution on acid solution, white solid precipitated then it disappeared. But next i used ammonium sulfate and white salt precipitated.
I will wash and dry it tomorrow.
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vano
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I made it. I heat it with small torch. But why it has blue colour? Do you know decomposition temperature?
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vano
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Its look like Tungsten pentoxide.
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Bedlasky
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It is probably some mixed W(VI)/W(V) oxide. In your mixture must be some reducing agent, I don't know what reducing agent.
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vano
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I don't know. I washed powder three times.
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Bedlasky
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Really strange. I wonder if dust can react with this thing.
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vano
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I don't understand
[Edited on 14-2-2021 by vano]
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Bedlasky
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Dust is organic material, WO3 have mildly oxidizing properties - maybe they can react with each other. Even trace amount of W(V) can cause strong blue
colouration.
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vano
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Okay. Do you know acid thermal decomposition product? I have not seen anywhere, it is written that it decompose above 400 ° C and releases poisonous
gas. I can not understand why they do not write what is left and what gas is formed.
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Bedlasky
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PH3 comes to mind with phosphotungstic acid at such high temperatures.
But we are talking about decomposition of ammonium paratungstate - there are products just WO3, NH3 and H2O.
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vano
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Quote: Originally posted by Bedlasky  | PH3 comes to mind with phosphotungstic acid at such high temperatures.
But we are talking about decomposition of ammonium paratungstate - there are products just WO3, NH3 and H2O. |
No, i mean Phosphotungstic acid. Acid decomposition is easiest way, if product is useful reagent.
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clearly_not_atara
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I think it is very unlikely that phosphate in any phosphotungstate salt would be reduced to phosphine by ammonia or similar NH compounds; the
electrons are basically rolling uphill. Maybe if you attempted a carbothermal reduction.
[Edited on 04-20-1969 by clearly_not_atara]
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Bedlasky
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No, it isn't. How do you want to separate phosphate? It is much easier to crystallize ammonium paratungstate (which is far less soluble in water than
ammonium hydrogenphosphate) and decompose it.
| Quote: Originally posted by clearly_not_atara | | I think it is very unlikely that phosphate in any phosphotungstate salt would be reduced to phosphine by ammonia or similar NH compounds; the
electrons are basically rolling uphill. Maybe if you attempted a carbothermal reduction. |
But carbothermal reduction will lead also to reduction of W(VI) - so WO3 (which is desired product) won't be formed.
[Edited on 14-2-2021 by Bedlasky]
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vano
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I was given old things, this is one of them. Phosphotungstic acid was in this vial It had a very old label and it was written 1958 and the name, it is
strange why it has such a color.
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