just had this idea.. the fact that HNO3 doesnt react with aluminium has always interested me.. however i think i figured out an entirely new use for
this..?
uncoated aluminium added to concentrated nitric acid with NO2 in it from destillation, to remove the NO2 accordingly:
Al + 3NO2 > Al(NO3)2 + ½N2
if that wouldnt happen to be the yield, it could perhaps be Al(NO2)3
anyhow, this could be specifically useful for quick destillation of HNO3 in concentrated form for HNO3 + NM or RDX synthesis, supposing that it would
work out that simply and well
any thoughts on something that could render this impossible / not useful?Pulverulescent - 12-12-2013 at 05:22
None of your assumptions are correct ─ some protracted readings of inorganic texts is called for, I think . . . ?Zyklon-A - 12-12-2013 at 17:21
Well, have you tried this with NO2 (g)? Because I don't think a reaction will happen there either, and if it does not react there, why would it react
in solution?
I'm quite sure it will not react, because NO2 is actually stored in Al cylinders, so it clearly does not react with it.
[Edited on 13-12-2013 by Zyklonb]macckone - 13-12-2013 at 01:49
Aluminum passivates with nitric acid.
After that it isn't reacting with anything until the oxide layer is removed.
This can be used to store stuff that doesn't cause aluminum to passivate
but wouldn't destroy the oxide layer.
This is effectively making a ceramic container made of aluminum oxide
out of an ordinary aluminum container.
The ceramic layer is very thin and easily damaged.
Plus some chemicals will react with aluminum oxide at a slow rate
given the thin layer, storing anything that would react with the layer
is not recommended. Ie, sulfuric acid, sodium hydroxide, etc.
Other metals such as titanium passivate similarly.
Metals like stainless steel and hastelloy c276 have more complex chemical
resistance characteristics.
thats strange.. if NO2 doesnt react with Al, and NO2 is literally stored in Al cylinders.. what the hell is then reacting with my Al foil whenever i
cover up reactions that give off NO2?? let me just start a smaller NO2 production, thereafter i will scrape the formed solid on Al foil piece into a
solution and test for aluminium
i did before cover up fx. 500 mL flask with HNO3 and Pb standing in with Al foil, thick layers, at one point actually perfectly airtight.. i realised
that some white solid had formed on the al foil and i scraped it off, i didnt do any other tests others than just heating it, it relatively quickly
melted and decomposed giving off miniscule amounts of NOx, due to the tiny amountMetacelsus - 14-12-2013 at 15:03
[Edited on 14-12-2013 by Cheddite Cheese]Random - 14-12-2013 at 16:12
When the acid is concentrated it reacts so strongly that it passivates the metal, forming a protective layer. When it's dilute then the protective
layer dissolves into the present water and dissolution continues.macckone - 14-12-2013 at 23:54
When the acid is concentrated it reacts so strongly that it passivates the metal, forming a protective layer. When it's dilute then the protective
layer dissolves into the present water and dissolution continues.
When it is dilute the aluminum doesn't passivate very well.
The thinner layer is probably attacked by the hydronium ions, creating Al(OH)3 as an intermediate. This is pretty interesting chemistry in
itself. Without a source of hydronium ions in the concentrated nitric acid, this would not occur.
I am just speculating as to the actual mechanism.
If someone has an actual reference as to how or why this
occurs it would be quite interesting to me and possibly others.Fantasma4500 - 15-12-2013 at 08:29
+ AlO1 > Al(NO3)2
Al
2NO2 + Al2O3 > Al(NO3)2 + AlO?
supposing this might need further balancing, perhaps other reactions finish the 'AlO' as it doesnt exist..
however i put a stopper in a 250 mL flask, put in abit of copper and inserted aluminium tube, i covered it up with al foil on the top..
i lifted the al foil top off and saw this supposedly Al nitrate or whatever ill determine it to be.. but the tube seems like its not affected at all..
when i pulled out the stopper the seemingly N2O4 decided to go into a thick cloud of NO2.. quite strange because the entire thing is not airtight at
all.. seemingly there is enough pressure for the NO2 to turn into N2O4, making it seem as if reaction totally stopped, giving enough pressure to also
stop the generation of NO2?
seems weird and im quite frankly confused as im just trying to generate a bit of NO2 ^^-
