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Author: Subject: Formation of Unusual Ammonium Chloride Double Salt?
crestind
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[*] posted on 17-7-2015 at 14:22
Formation of Unusual Ammonium Chloride Double Salt?


I found a while ago that sublimating ammonium chloride with iron chloride seemingly causes a double salt of the two to form. In the photo below you can see how the sublimate has deposited around the top of the beaker (I had a loose lid over the beaker).

NH4Cl + FeCl2 combined sublimation photo
SAfwQ4t.png - 750kB

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When the same process is carried out with common iron oxide instead of iron chloride, the result is somewhat similar in that it takes on a yellowish orange color. So my question is, in this second instance, is the resulting double salt NH4Cl plus iron oxide, or is it also NH4Cl plus iron chloride due to the HCl from NH4Cl?

(Unrelated, but if you sublimate NH4Cl with silver chloride, a lot of the silver chloride is carried away by the NH4Cl similarly, but some of the silver chloride changes to a brilliant red color.)

[Edited on 17-7-2015 by crestind]

[Edited on 17-7-2015 by crestind]
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Zyklon-A
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[*] posted on 17-7-2015 at 15:06


How'd you find out it forms a double salt?



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crestind
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[*] posted on 17-7-2015 at 17:13


Someone told me that was the cause of the orange coloration, the formation of a double salt. It seems to make sense since the resulting product does contain iron, and neither iron chloride boils at under 1,000f.

It's hard to tell from the photo, but that's a 1,000mL beaker with orange tinted ammonium chloride near the top, so that's almost 6" rise from the bottom of a beaker.

My guess is that since NH4Cl (decomposition) -> NH3 + HCl, the NH3 somehow forms a temporary iron chloride amine to volatilize it, before reacting with the HCl gas and condensing again.

[Edited on 18-7-2015 by crestind]
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Boffis
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[*] posted on 18-7-2015 at 06:33


I am not sure about the product ofthis reaction but the use of ammonium halides particularly the iodide and bromide was a standard procedure for taking Sn4+ oxide (ie cassiterite) into soultion for analysis. Fused ammonium halides are very corrosive and aggressive and it is very likely that the sublimate contains a chloroferrate complex but I'll bet there is a large excess of ammonium chloride.
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blogfast25
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[*] posted on 18-7-2015 at 09:05


Quote: Originally posted by Boffis  
I am not sure about the product ofthis reaction but the use of ammonium halides particularly the iodide and bromide was a standard procedure for taking Sn4+ oxide (ie cassiterite) into soultion for analysis. Fused ammonium halides are very corrosive and aggressive and it is very likely that the sublimate contains a chloroferrate complex but I'll bet there is a large excess of ammonium chloride.


That would be my guess too. But the colour does point to Fe(+3) (yellow ferrous compounds are rare) and oxidation of Fe(+2) to Fe(+3) in these conditions is likely.




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