Nitrox2
Hazard to Self
Posts: 62
Registered: 10-6-2025
Member Is Offline
Mood: No Mood
|
|
I2 with vinegar
I was unable to get any color change or precipitation while trying to precipitate I2 with vinegar and H2O2. I added extra vinegar cause I was worried
about the leftover sodium hydroxide affective the reaction equations stoichiometry that I was trying to understand.
|
|
|
MrDoctor
Hazard to Others
Posts: 249
Registered: 5-7-2022
Member Is Offline
|
|
were you checking the ph? did you make sure the solution was acidic when you added peroxide?
Also did you by chance heat the solution after acidifying it? i made that mistake and couldnt figure out why it would only turn a little yellow at
best, turned out there was no longer enough iodine present to precipitate, so the only visual change was the momentary i3 complex formed when there is
both iodide and iodine together. my iodine escaped by boiling away, as HI is volatile and my solution was absolutely saturated making it pretty easy
to do so. i forgot its pretty much volatile in every form but its iodide salt
|
|
|
bnull
National Hazard
Posts: 994
Registered: 15-1-2024
Location: East Woods
Member Is Offline
Mood: Fecking annoyed
|
|
Can you describe what you did? How much of each reagent was used, did you heat the solution, that sort of information.
I just made a quick teste with sodium iodide, vinegar, and hydrogen peroxide. Due to a faulty bottle cap, my sodium iodide absorbed water from the air
throughout last year and became a saturated solution (thank you very much, atmosphere!), and that's what I used. Vinegar was the usual red dyed 3%
variety, which was also the same concentration of hydrogen peroxide. I mixed vinegar and sodium iodide solution in a small test tube, swirled it a
little and then added hydrogen peroxide. The light red color of vinegar deepened to the deep red of iodine-iodide complex and after a few second
iodine began to crystallise on the wall of the tube. Tiny crystals that fell to the bottom on tapping the sides of the test tube. I can't see what you
did wrong but it works pretty well, even in the presence of the other substances in vinegar and hydrogen peroxyde.
The only possible explanations I can think of are (1) you mistook something else for sodium iodide (sodium chloride, for example) but I wouldn't bet
on it or (2) you forgot to add sodium iodide. Both situations have happened to me in the past; (1) was sodium acetate in place of oxalic acid last
week, botched an experiment but never mind.
Edit: Typo.
[Edited on 24-7-2025 by bnull]
|
|
|
Nitrox2
Hazard to Self
Posts: 62
Registered: 10-6-2025
Member Is Offline
Mood: No Mood
|
|
Heated 177mL 10% povidone iodine solution in a 500mL beaker
Added about 70g NaOH to about maybe 135mL tap water. Stirred.
Added NaOH solution to the beaker
Precipitate formed -- the povidone floating goop..
Filtered, collected filtrate
Reduced solution over heat till about 200mL of solution remained
Added a quite large splash of 6% vinegar
Topped it off with as much hydrogen peroxide as I could-
Observation: No precipitate / No color change
I may have still had povidone in solution when adding my vinegar / H2O2
*Nilered, reduced his filtrate to about 100mL before he filtered the floating povidone gunk, again, and added the acid / H2O2**
That's something that I may have done differently.
I'll admit, I could have been more meticulous here. I got pressured-
In my haste, I was hoping to at see at least some color change.
Which would be mostly what I was after, a y/n on vinegars utility-- I always see it talked about with stronger acid-- and I was wondering how
resourceful I could be
[Edited on 7-24-25 by Nitrox2]
[Edited on 7-24-25 by Nitrox2]
[Edited on 7-24-25 by Nitrox2]
|
|
|
bnull
National Hazard
Posts: 994
Registered: 15-1-2024
Location: East Woods
Member Is Offline
Mood: Fecking annoyed
|
|
It seems that you didn't neutralize the excess hydroxide.
I made another quick test. Sodium iodide plus some sodium hydroxide. Apart from a slight foaming, nothing else happened after addition of hydrogen
peroxide. So here lies your problem: the solution is still basic after you added vinegar. You can (1) keep adding more vinegar until a color appears,
deepens, and then fades as iodine precipitates or (2) use a more concentrated acid, like 10% hydrochloric acid for tile cleaning or pool grade sodium
bisulfate*. I'd go with the latter since it adds no water to the solution.
*: With an "a".
Edit: Typo. By the way, when close to neutralizing the base, there will be a fizzing from peroxide decomposition.
[Edited on 24-7-2025 by bnull]
|
|
|
MrDoctor
Hazard to Others
Posts: 249
Registered: 5-7-2022
Member Is Offline
|
|
adding a drop of the alkaline iodide to an excess of acid should result in an observable reaction
|
|
|
Nitrox2
Hazard to Self
Posts: 62
Registered: 10-6-2025
Member Is Offline
Mood: No Mood
|
|
Thanks, I've heard of peroxides forming, IIRC, with OTC %3 H2O2 solution, it was noted as being an actual explosion/detonation risk.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
