Sciencemadness Discussion Board

KI+HNO3->KIO3 fail?

fusso - 4-7-2019 at 01:28

Trying to make some iodate by adding excess HNO3 to 0.5g KI (assume byproduct is NO2) and I2 is formed but didn't disappear to form HIO3 even after a few days. Why?

[Edited on 190704 by fusso]

Sulaiman - 4-7-2019 at 01:44

HNO3 is an oxidising acid, the result that you got is the expected one
https://chemiday.com/en/reaction/3-1-0-6575

Ubya - 4-7-2019 at 02:07

https://www.sciencedirect.com/science/article/pii/0022190275...
It works but you need azeotropic nitric acid, maybe your acid was not strong enough?

fusso - 4-7-2019 at 02:10

@Sulaiman I do expect HNO3 to oxidise I- to I2, but I also expect HNO3 to oxidise I2 up to HIO3 too:(
@Ubya Do you have the rest of the paper?

[Edited on 190704 by fusso]

Boffis - 4-7-2019 at 03:46

@fusso, wouldn't it be better to liberate the free iodine first and then oxidise it with nitric acid? It would certainly be more economical on the nitric acid. Also check out Brauer's book in the SM library.

Are you aware of the chlorate oxidation process for producing iodates/iodic acid? This route is covered in great detail in the Inorganic Preparations series of books which can be downloaded from the internet.

Ubya - 4-7-2019 at 04:08

@fusso
https://zero.sci-hub.se/1597/fb68cdbc1bce08575418686b47aff11...

Boffis - 4-7-2019 at 06:36

Mmmmm Ubya, that's an interesting paper but turning the data in it into a useful prep. is going to require a pretty good chemist. Brauer contains a workable method with both nitric acid and nitric acid+H2O2.

The main issue I see with these methods is the low molar efficiency based on nitric acid. While nitric acid is cheap it is getting increasing difficult to obtain for the amateur. Mind you so is 30% H2O2.

Ubya - 4-7-2019 at 08:17

Quote: Originally posted by Boffis  
Mmmmm Ubya, that's an interesting paper but turning the data in it into a useful prep. is going to require a pretty good chemist. Brauer contains a workable method with both nitric acid and nitric acid+H2O2.

The main issue I see with these methods is the low molar efficiency based on nitric acid. While nitric acid is cheap it is getting increasing difficult to obtain for the amateur. Mind you so is 30% H2O2.

i know, it's not a preparative paper, more a study on kinetics, but at least demonstrates that it is possible to use nitric acid, it just needs to be concentrated enough, that was my point

fusso - 4-7-2019 at 20:24

@Boffis unfortunately I don't have any chlorates:(

clearly_not_atara - 5-7-2019 at 09:40

"The oxidation of iodine to iodate by hydrogen peroxide", Guy Schmitz, Physical Chemistry Chemical Physics, 2001.

Now that's a journal name!

Attachment: schmitz2001.pdf (117kB)
This file has been downloaded 338 times

Tsjerk - 5-7-2019 at 12:06

Quote: Originally posted by clearly_not_atara  
Physical Chemistry Chemical Physics


Haha, and they even have an impact factor of almost 4!