Iodine Leaching

[Dorcas Nimrod]

Greetings forum members. I'm studying the iodine leach, and there's something which stands out to me which I'm hoping someone with chemistry expertise can touch on, the creation of ammonium tri-iodide.

I'm familiar with nitrogen tri-iodide. It's definitely a substance to be respected, though In milligram quantities it's pretty benign. I don't advise making it deliberately, it usually detonates on the filter paper by the time it's dry. Ammonium tri-iodide is supposed to be a similarly sensitive explosive, I'd not heard of it until reading US patent # 5,137,700.

Nitrogen tri-iodide is made when ammonia and elemental iodine are combined. Ammonium iodide for leaching is made by adding H2O2 to the ammonia and iodine. The patent goes on to say

The addition of supplemental iodine to the aqueous ammonium iodide solution changes its color from a clear water-white to a deep dark brown. The dark brown color is due to the formation of ammonium tri-iodide

.

Since the etching/leaching solution is in fact made by adding an excess of elemental iodine, are we not making a solution of ammonium tri-iodide?

The ammonium iodide variant sounds like it's cleaner and more selective. As long as the solution is well hydrated, precipitated and recycled, and crust isn't building up, it should be perfectly safe. Does this basically mean we just have to be prompt and not let things sit around too long?

When Nitrogen tri-iodide is made, the iodine granules aren't dissolved and recrystallized, the iodine remains in the solid phase, and the granules just sort of disintegrate with a little dissolution. I'm not sure Nitrogen tri-iodide would even survive being completely dissolved and recrystallized in water. As I understand, it decomposes pretty quickly. Since the brown tint is essentially supposed to be dissolved ammonium tri-iodide, and not solid granules, I wonder if it would even survive crystallization and drying?

 

[Lino1406]

There is no mechanism for nitrogen tri iodide from ammonium tri iodide. Anyway KI3 can be used instead.

 

[Dorcas Nimrod]

There is no mechanism for nitrogen tri iodide from ammonium tri iodide. Anyway KI3 can be used instead.

I appreciate the response, and all the willingness of forum members to share their knowledge. However, I did not say anything about ammonium tri-iodide turning into nitrogen tri-iodide. I understand potassium iodide is another route, as is hydroiodic acid, but my interest is in the specifics of ammonium iodide. Thank you anyway.