As I'm sure a lot of you know, NO2 is a nasty gas. It forms nitric acid when you inhale it, leading to pulmonary oedema that can kill you hours after exposure (LD50 is 90 ppm/4hr in rats). It also leads to desensitisation of smell, so you aren't necessarily alerted by it's acrid odour.

Formation of NO2 is something that you usually want to stop when performing chemical reactions, because you don't want to exposure yourself.

But say you wanted to deliberately form NO2?


The industrial process used is this:

Pass ammonia over a platinum catalyst at 850C, to produce NO, which is subsequently oxidised to NO2 by the oxygen in air.

4 NH3 + 5 O2 → 4 NO + 6 H2O
2 NO + O2 → 2 NO2

The platinum catalyst is needed or you just get nitrogen (N2) and water (H2O).

Although ammonia is obviously easy to obtain, the platinum catalyst and 850C temperatures are not so easy.


So, what are some other methods, using easily-obtainable materials?


1) Simply heating copper(II) nitrate:

2 Cu(NO3)2 → 2 CuO + 4 NO2 + O2


2) Nitric acid plus copper wire:

Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O

Nice pictures here (http://www.angelo.edu/faculty/kboudrea/demos/copper_HNO3/Cu_HNO3.htm).


3) Sodium nitrite + iron sulfate + sulphuric acid:

2 NaNO2 + 2 FeSO4 + 3 H2SO4 → Fe2(SO4)3 + 2 NaHSO4 + 2 H2O + 2 NO

Not sure if that one would work very well - the NO oxidises only slowly in air, and this reaction doesn't produce any extra oxygen.


Any other suggestions?

Also, what are the pros and cons of NO2 as a CW over other easily-obtained gasses?

Well, the main drawback of NO2/N2O4 is its characteristic pungeant odor in even very low concentrations and the characteristic brownish color in concentrated state.

It is relatively highly toxic, a bit more than chlorine for example, but not as toxic as phosgene, diphosgene or the very best PFIB, if considering lung irritants/choking agents. It's comparable to chloropicrin rather, and is easily detected because of it beeing a common air pollutant...all air pollution measuring stations in the vincinity would go mad alerting police/firefighters. This, combined with other properties would make a surprise attack likely to be failed.

If you want a potent choking agent, consider perfluoroisobutene. It has no odor in effective concentrations, which are very low and it penetrates in some extent regulary gas mask filters.

PFIB could also be made by pirolysis of CF2=CF2.

CCl2=CCl2 + AgF (KF, hv) (KF, crown18) = CF2=CF2 (gas)
Fluoro- chloro ethenes could be used as a wepon by itself. Like CClF=CClF.

NOx are useless as CW. I've worked many times with it without gas mask and fume hood and only once had just light pneumonia.
Maybe nox could be combined with CClxFy=CClxFy to get nitrated products, even more nasty...

Pass ammonia over a platinum catalyst at 850C, to produce NO, which is subsequently oxidised to NO2 by the oxygen in air.

That temperature is way to high for a catalytic process using platinum. Optimum temperature for a good yield is in the range 420-460 degrees C.

Although ammonia is obviously easy to obtain, the platinum catalyst and 850C temperatures are not so easy.

I have platinum from a brand new catlytic converter I bought on ebay for $20. I built a furnace that consistently gets 450C temperatures ideal for the reaction. What I can not get for love nor want of money is ammonia. Ammonia, and I don't mean the stuff at the grocery store, is used to make evil drugs, and is therefore a legislated precursor. If it is so easy to get, how do you do it?

I was working on a urea-to-ammonia (U2A) system, but now I have a new catalytic process using air I am hoping to test soon.

That temperature is way to high for a catalytic process using platinum. Optimum temperature for a good yield is in the range 420-460 degrees C.

At atmospheric concentrations that it correct. However, at the higher pressures used in the industrial process, 800-940C is the temperature generally used.

"At typical gauze temperatures of 800-940C, nitric oxide is thermodynamically unstable and slowly decomposes into nitrogen and oxygen. Decomposition losses are minimised by avoiding excessive catalyst contact time and rapidly cooling the gases as they exit the converter." (quote from Kirk-Othmer Encyclopedia of Chemical Technology 4th ed, Vol 17, p 89.)


Thankyou for pointing out that platinum catalysts can be easily obtained. However the point that >25% ammonia is difficult to obtain justifies my claim that the industrial process used for creating NO2 is not practical for my purposes.


Thanks also Meyer25 for your input. However a pungent odour and coloured gas are not necessarily drawbacks. The production of NO2 is cheap and easy enough that it can be done on a large scale, and panic reactions would likely be the primary weapon, rather than the gas itself. You would ideally use shallow dishes full of nitric acid, with quite a lot of copper, in order to rapidly create the NO2. Place a few around (for e.g.) a shopping centre during christmas rush, particularly around the entrances and emergency exits (which are usually at the end of a constricted corridor).

To obtain ammonia it is possible to produce your own using ammoinum nitrate fertilizer and sodium hydroxide, this will liberate ammonia which can be condensed to give liquid ammonia for the production of the "evil drugs" or could be passed straight into the tube furnace to produce NO2.

Is there not the problem with using NO2 or N2O4 that it will preferentially dissolve into the atmospheric water and therefore be of minimal use, unless in very large amounts, as an effect CW?

I would think that a cylinder of chlorine would be more effective, as you can purchase this relatively easily or "borrow" it from a water treatment facility in time of dire need.

Thank you for listening to a newbie