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Author: Subject: Tin orange iodine / chlorine compound with stable color
Lion850
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[*] posted on 7-6-2021 at 16:38
Tin orange iodine / chlorine compound with stable color


In this post I reported how I got an orange compound after dissolving tin granules in a solution of iodine in concentrated hydrochloric acid:

http://www.sciencemadness.org/talk/viewthread.php?tid=156987...

I assumed the product was SnI4, which I made a few times by reacting tin with iodine in DCM. But this product that I got from doing the reaction in HCl behaves differently on the shelf.

I store my salts in clear glass vials because I want to see the colors. This means that over time many of my metal iodides darken, some more and some less. Each time I made SnI4 and SnI2 they darkened over time. But the orange salt made from the tin - iodine - HCl reaction is keeping its color.

SnI2 and SnI4 made 8 months ago:
10.jpg - 583kB

The salt made by reacting tin and iodine in HCl some 4 months ago:
11.jpg - 601kB

The 3 salts as they look now:
12.jpg - 611kB

This leads me to wonder why the 'acid salt' apparently do not loose iodine. Is it maybe indeed not SnI4 but a tin-iodine-chlorine complex?

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garphield
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[*] posted on 7-6-2021 at 18:47


Was this an aqueous solution of HCl or was it dissolved in something else? If it was the former, this is probably some kind of oxychloride(+iodide) which would explain why it's more air-stable.
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Lion850
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[*] posted on 13-6-2021 at 23:19


Hi Garphield yes it was 'swimming pool' hydrochloric acid which is around 32% (it fumes in air).
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Amos
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[*] posted on 14-6-2021 at 05:33


I have made tin iodide before that forms large, shiny, dichromate-colored crystals, much more intense in color than your solid. If you want to follow my method, I simply left tin metal and iodine dissolved in benzene together in a closed and sealed vial, and used a hot water bath to speed up the reaction sometimes, but not consistently. After several days the benzene was deep orange in color, and upon leaving the vial open outdoor it evaporated to yield beautiful crystals. Keep it out of sunlight! I hope you'll give it a shot. Toluene might work too but I believe iodine is more soluble in benzene.
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Lion850
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[*] posted on 12-2-2022 at 00:51


Hi Amos sorry for much delayed reply but I do not have benzene so never tried.

What still intrigues me is that now, 8 months later, the above mentioned "Sn + I2 + HCl" is still exactly the same orange color, while the SnI2 and SnI4 are by now both very dark (they are exposed to indirect sunlight).

Online is mentioned a compound Tin (iv) chloride iodide Cl2I2Sn, but unfortunately none of the suppliers I could find mentions the color and I also could not find a photo. In the next days I will repeat the experiment and follow the stoichiometry this equation:
Sn + I2 + 2HCl = SnCl2I2 + H2
and I will use reasonable amounts (few grams) so that the final product weight will hopefully give an indication of what could have formed, what apparently is so much more stable than the other 2.
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MidLifeChemist
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[*] posted on 12-2-2022 at 20:00


Perhaps you can test this compound and see if you can release elemental iodine or chlorine from it. That may shed some light on its composition, or at least run in/out SnCl2I2
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Lion850
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[*] posted on 6-6-2023 at 04:15


I stumbled across the Wikipedia page for SnI2

https://en.wikipedia.org/wiki/Tin(II)_iodide

which mentions reacting tin and iodine in hydrochloric acid to make SnI2. So I think that is what I got. And now, 2 years after making it with the vial standing unshielded on the shelf, the orange color is still exactly the same. Seems to be a very stable iodine salt.
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