Sciencemadness Discussion Board

Copper/Lead iodide + HAc = I2?

Fantasma4500 - 7-3-2019 at 06:53

so ive been trying to make some copper iodide and today ended up turning it into lead iodide to seperate it out properly and efficiently
however the lead iodide was contaminated with some hydroxides/carbonates, so i added some 30% HAc and warmed it for a while
now the lead iodide seems to dissolve, giving me once again the dreaded golden solution of elemental iodine, how is this happening?
initially i wanted to make tin iodide due to its nice colour, but as i mixed up SnCl2 and NaI solutions it turned all of the NaI into I2, i thought tin was supposed to be reducing even? how does i go about magically oxidizing ionic iodine into elemental iodine, of what i remember you need an oxidizing agent such as chlorine to produce elemental iodine from iodide, but it surely is iodine. covering a beaker up for a while with aluminium foil will turn the foil into aluminium iodide - evidently by heating it, vapors of iodine will be formed

as a bonus, when i was letting the lead iodide sit for a while copper started coming out of the solution discolourizing the once bright yellow powder, thus why i added HAc.

i have even managed to turn the iodide solution into elemental iodine while just evaporating off the water - with excess NaOH.

vmelkon - 29-3-2019 at 17:45

Is SnCl2 soluble in water? It sounds like it is not since tin is similar to lead or it is only slightly soluble.
One possible reaction is that if you have a solution of iodide (It could be NaI, KI, SnI2), it reacts with CO2 and O2 from the air.

4 KI + 2 CO2 + O2 → 2 K2CO3 + 2 I2
4 NaI + 2 CO2 + O2 → 2 Na2CO3 + 2 I2
2 SnI2 + 2 CO2 + O2 → 2 SnCO3 + 2 I2

Fantasma4500 - 22-5-2019 at 02:55

yes tin chloride is 84g/100mL at 0*C
ive noticed solutions of iodide eventually produces a bit of elemental iodine, maybe its really about carbonate, though i dont see why elemental iodine shouldnt react with carbonate as iodine is quite strong stuff, can easily put holes in stainless steel, but it would explain what went down with the tin solution

vmelkon - 30-5-2019 at 08:29

Quote: Originally posted by Antiswat  
yes tin chloride is 84g/100mL at 0*C
ive noticed solutions of iodide eventually produces a bit of elemental iodine, maybe its really about carbonate, though i dont see why elemental iodine shouldnt react with carbonate as iodine is quite strong stuff, can easily put holes in stainless steel, but it would explain what went down with the tin solution


Yes, it looks like SnCl2 is quite soluble and a few sources say it hydrolyses and forms Sn(OH)Cl which is insoluble.
So, tin chemistry is different from lead.

Iodine reacts with certain metals such as iron because it is halogen and thus can pull the electron from the metal atom.

Metacelsus - 30-5-2019 at 09:57

FYI: HAc is acetaldehyde. I'm pretty sure you mean AcOH (acetic acid).

Anyway, under acidic conditions HI will be formed, and this can be oxidized by air to iodine. I suspect that metal salts (for example, lead) might be able to catalyze this reaction.