Sciencemadness Discussion Board

Mysterious white gas from decomposing ammonium nitrate

Cou - 24-10-2013 at 13:50

I notice that when I decompose ammonium nitrate, it makes this white cloud gas. Is this a nitrogen oxide? I know it's not hydrogen because that's colorless, oxygen is colorless, nitrous oxide should be colorless, and steam would have condensed.

Metacelsus - 24-10-2013 at 14:15

Quote: Originally posted by Cou  
steam would have condensed.


Water droplets suspended in air appear white. For example, look at clouds. Also, it could be a fine suspension of ammonium nitrate dust carried by the gaseous decomposition products.

deltaH - 24-10-2013 at 14:15

Colloids in suspension.

From wiki's article on N2O:

Production section:

"Ammonium nitrate smoke, as an extremely persistent colloid, will also have to be removed. The cleanup is often done in a train of three gas washes; namely base, acid and base again. Any significant amounts of nitric oxide (NO) may not necessarily be absorbed directly by the base (sodium hydroxide) washes."

Edit: Aw snap Cheddite Cheese :)

[Edited on 24-10-2013 by deltaH]

woelen - 25-10-2013 at 04:35

@bfesser: I see no reason to move this thread to detritus. It may be a beginner's question, but I see nothing wrong with this. Hence my move of this thread from detritus to beginnings.

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The white fumes most likely are condensed water vapor. Mostly, ammonium nitrate, is somewhat humid (it is hygroscopic) and the water vapor may not collect on the vessel, because it is warm (or even hot). Such white fumes are quite common when compounds are heated.

Just another remark: A gas is never white. A gas is transparent, although it may have color (e.g. NO2, Cl2). If something looks opaque, then it either consists of very small liquid particles (fume), or it consists of solid particles (smoke).

I want to put a warning over here. Heating ammonium nitrate can be dangerous. Above a certain temperature, a runaway reaction may occur, the decomposition of ammonium nitrate to water and N2O is exothermic and may suddenly self-accelerate to nearly explosive violence! So, be careful!


[Edited on 25-10-13 by woelen]