bolbol
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Production of Selenic acid by oxidizing Selenous acid with KMnO4?
What is the best way to get rid of redox reaction impurities when using KMnO4 as an oxidizing agent?
I've read online that it can be prepared by oxidizing Selenous acid - which can be prepared by dissolving selenium in nitric acid - by halogens or
KMnO4.
Selenic acid decomposes violently when heated so I don't think distilling would be a good idea. Just wondering if you guys think it would be possible
to obtain a pure product with this route...
I always preferred H2O2 since the side products are just oxygen and water but then again im not sure if it would work and even if it did I have no way
of getting peroxide above 3% purity
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rocketman
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selenic acid
there's a guy on youtube says, strong Hydrogen peroxide and selenium gives selenic acid. I think he is wrong. Opinions?
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vano
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Quote: Originally posted by rocketman  | | there's a guy on youtube says, strong Hydrogen peroxide and selenium gives selenic acid. I think he is wrong. Opinions? |
You are right. He is wrong. It is just mixture. I tried it. Months later when i add few drops of liquid in indicator it gets white. Thats mean there
was hydrogen peroxide, i used 50% H2O2. I dissolve selenium dioxide in this.
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Bedlasky
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Vano: Selenous acid CAN be oxidized by H2O2 in to selenic acid.
https://pubs.acs.org/doi/10.1021/ja01292a501
https://en.m.wikipedia.org/wiki/Selenic_acid
If you have exces of H2O2 in the solution, ofcourse it will react with indicator. This doesn't prove that H2SeO4 doesn't form.
[Edited on 13-2-2021 by Bedlasky]
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vano
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Bedlasky:There was no excess peroxide. It should have been a selenic acid monohydrate (melts at 26 ° C). I still think that a clean product is not
so easy to get in this way.
I have peroxide 50%, I use 3 grams of selenium. Write me the calculations and i will do as you think and see the result.
[Edited on 13-2-2021 by vano]
[Edited on 13-2-2021 by vano]
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Bedlasky
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When you oxidize H2SeO3 in to H2SeO4, there is lot of water in reaction mixture, so you obtain solution, not a solid.
If you dissolve 1g H2SeO3 (or 0,86g SeO2) in some water and add cca 0,6ml of 50% H2O2 (0,44ml according to stechiometry, but it is better use excess
because of tendency of H2O2 to decompose) - this should produce H2SeO4 solution. Maybe carefull heating in water bath will be needed. Maybe there is a
precise description in Brauer.
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vano
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I think one of the easiest ways to determine this is to use nickel chloride and a solution of neutralized acid. If it is nickel selenite it will have
a light green color, and if it is selenate it will have nickel sulfate like colour.
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Bedlasky
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I think that selenate is soluble.
You can do iodometric titration and calculate oxidation state of selenium.
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vano
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Yes i agree that method you mentioned is good. Maybe it is soluble, now i don't know exactly but i will find. Even the color of the solution makes it
easy to tell if it is selenate.
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vano
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It is soluble and in hydrates n = 1, 4 and 6. Some sources discribe it as a green solid, maybe low molecular hydrates have green(yellowish?
Anhydrous nickel selenite has yellow colour). there hexahydrate has sulfate like colour.
[Edited on 15-4-2021 by vano]
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