Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Production of Selenic acid by oxidizing Selenous acid with KMnO4?
bolbol
Hazard to Others
***




Posts: 162
Registered: 3-1-2015
Member Is Offline

Mood: No Mood

[*] posted on 17-3-2015 at 09:34
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
View user's profile View All Posts By User
rocketman
Harmless
*




Posts: 17
Registered: 28-1-2012
Member Is Offline

Mood: No Mood

[*] posted on 12-2-2021 at 23:35
selenic acid


there's a guy on youtube says, strong Hydrogen peroxide and selenium gives selenic acid. I think he is wrong. Opinions?
View user's profile View All Posts By User
vano
National Hazard
****




Posts: 437
Registered: 22-3-2019
Location: Georgia, Kutaisi
Member Is Offline


[*] posted on 13-2-2021 at 00:07


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.




A narrow road cannot keep back Death, nor a rocky one; by him all are levelled, weak and strong-hearted; in the end the earth unites in one place youth and greybeard. Better a glorious death than shameful life!
—The Knight in the Panther's Skin
View user's profile View All Posts By User
Bedlasky
International Hazard
*****




Posts: 769
Registered: 15-4-2019
Location: Angband
Member Is Offline


[*] posted on 13-2-2021 at 04:32


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]




If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

"An old friend once told me something that gave me great comfort. Something he had read. He said that Mozart, Beethoven and Chopin never died. They simply became music." Dr. Robert Ford, Westworld
View user's profile Visit user's homepage View All Posts By User
vano
National Hazard
****




Posts: 437
Registered: 22-3-2019
Location: Georgia, Kutaisi
Member Is Offline


[*] posted on 13-2-2021 at 04:56


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]




A narrow road cannot keep back Death, nor a rocky one; by him all are levelled, weak and strong-hearted; in the end the earth unites in one place youth and greybeard. Better a glorious death than shameful life!
—The Knight in the Panther's Skin
View user's profile View All Posts By User
Bedlasky
International Hazard
*****




Posts: 769
Registered: 15-4-2019
Location: Angband
Member Is Offline


[*] posted on 14-2-2021 at 09:18


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.




If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

"An old friend once told me something that gave me great comfort. Something he had read. He said that Mozart, Beethoven and Chopin never died. They simply became music." Dr. Robert Ford, Westworld
View user's profile Visit user's homepage View All Posts By User
vano
National Hazard
****




Posts: 437
Registered: 22-3-2019
Location: Georgia, Kutaisi
Member Is Offline


[*] posted on 15-4-2021 at 09:01


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.



A narrow road cannot keep back Death, nor a rocky one; by him all are levelled, weak and strong-hearted; in the end the earth unites in one place youth and greybeard. Better a glorious death than shameful life!
—The Knight in the Panther's Skin
View user's profile View All Posts By User
Bedlasky
International Hazard
*****




Posts: 769
Registered: 15-4-2019
Location: Angband
Member Is Offline


[*] posted on 15-4-2021 at 09:15


I think that selenate is soluble.

You can do iodometric titration and calculate oxidation state of selenium.




If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

"An old friend once told me something that gave me great comfort. Something he had read. He said that Mozart, Beethoven and Chopin never died. They simply became music." Dr. Robert Ford, Westworld
View user's profile Visit user's homepage View All Posts By User
vano
National Hazard
****




Posts: 437
Registered: 22-3-2019
Location: Georgia, Kutaisi
Member Is Offline


[*] posted on 15-4-2021 at 09:24


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.



A narrow road cannot keep back Death, nor a rocky one; by him all are levelled, weak and strong-hearted; in the end the earth unites in one place youth and greybeard. Better a glorious death than shameful life!
—The Knight in the Panther's Skin
View user's profile View All Posts By User
vano
National Hazard
****




Posts: 437
Registered: 22-3-2019
Location: Georgia, Kutaisi
Member Is Offline


[*] posted on 15-4-2021 at 09:31


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]




A narrow road cannot keep back Death, nor a rocky one; by him all are levelled, weak and strong-hearted; in the end the earth unites in one place youth and greybeard. Better a glorious death than shameful life!
—The Knight in the Panther's Skin
View user's profile View All Posts By User

  Go To Top