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

Printable Version  
Author: Subject: Issues with starch-iodide test strips
Elemental Phosphorus
Hazard to Others
***




Posts: 144
Registered: 11-11-2016
Location: Is everything
Member Is Offline

Mood: No Mood

[*] posted on 27-11-2019 at 14:25
Issues with starch-iodide test strips


I've been trying to use starch-iodide test strips to test concentrations of acetone peroxide in solutions intended to decompose it. The starch-iodide strips clearly work, since touching them to the pure peroxide they turn dark immediately. After they go in the ammonia solution, even with peroxide touching them, they don't react. I was wondering if ammonia in some way screws up the action of the starch-iodide strips. Thanks in advance for the answers.
View user's profile View All Posts By User
wg48temp9
National Hazard
****




Posts: 296
Registered: 30-12-2018
Member Is Offline


[*] posted on 28-11-2019 at 06:48


Iodine reacts with a solution of ammonia in water to form nitrogen triiodide. Perhaps that reaction interferes with your test paper reaction.



i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.
View user's profile View All Posts By User
Pumukli
International Hazard
*****




Posts: 510
Registered: 2-3-2014
Location: EU
Member Is Offline

Mood: No Mood

[*] posted on 28-11-2019 at 09:22


I think the formation of NI3 is a slow reaction while I2 and starch reacts quickly. So I'm surprised by your result but can't explain it. :)
View user's profile View All Posts By User
Ubya
International Hazard
*****




Posts: 892
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline

Mood: I'm a maddo scientisto!!!

[*] posted on 28-11-2019 at 11:55


the oxidation of iodide by peroxide works in acidic solution, maybe the ammonia makes the strips basic enough that peroxide doesn't oxidizes it anymore




---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
View user's profile View All Posts By User
Elemental Phosphorus
Hazard to Others
***




Posts: 144
Registered: 11-11-2016
Location: Is everything
Member Is Offline

Mood: No Mood

[*] posted on 28-11-2019 at 14:26


I think Ubya must be right, I tried some strips in a concentrated sodium hydroxide solution and they wouldn’t react either.
Thanks for the replies.
Also, is there any other way to verify the decomposition of the peroxide? Does it shine under a UV light or some other form of illumination, or is there a non-pH sensitive peroxide test? Maybe I’d be best off just visually verifying that no peroxide crystals are left.
View user's profile View All Posts By User
Pumukli
International Hazard
*****




Posts: 510
Registered: 2-3-2014
Location: EU
Member Is Offline

Mood: No Mood

[*] posted on 29-11-2019 at 03:03


Probably he is right. When I tried to use KI-starch a few weeks ago I used to detect hypochlorite. And hypochlorite works on KI even in basic solution, hence my confusion. :)
View user's profile View All Posts By User
Elemental Phosphorus
Hazard to Others
***




Posts: 144
Registered: 11-11-2016
Location: Is everything
Member Is Offline

Mood: No Mood

[*] posted on 11-12-2019 at 09:31


Speaking of all that, does anyone have access to this paper who can post a pdf?

https://onlinelibrary.wiley.com/doi/10.1111/j.1556-4029.2009...
View user's profile View All Posts By User
Ubya
International Hazard
*****




Posts: 892
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline

Mood: I'm a maddo scientisto!!!

[*] posted on 11-12-2019 at 10:14


sci-hub.tw/10.1111/j.1556-4029.2009.01130.x




---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
View user's profile View All Posts By User

  Go To Top