Nitrous Oxide Synthesis

From: lewis@aera8700.mitre.org (Keith Lewis) Date: Wed, 23 Jun 1993 17:25:48 GMT
In article <1993Jun21.181707.4285@unislc.slc.unisys.com>, dale@unislc.slc.unisys.com (Dale Clark) writes:
>CREATION PROCESS
>----------------
>Nitrous Oxide (laughing gas) is most commonly made by the thermal 
>decomposition of ammonium nitrate (NH4NO3).  The chief impurity 
>of the product is N2, although, NO2, N, O2, and CO2 may also be present, 
>however, usually not in any quantity to approach toxcity.  The resulting 
>mixture is passed through water for purification.  
  

You left out NO (nitric oxide), NH3 (ammonia), and H2O (water -- the other product of the successful reaction). Laughing Gas also states that the temperature (optimum or self-regulating, I don't know) for the reaction is 240 C. But they caution against trying it at home:

Occaionally, following in the footsteps of Priestly and Davy, individuals attempt to synthesize N2O. This is definitely not recommended, for several reasons. First, the synthetic process frequently employed (heating ammonium nitrate) may lead to an explosion, and has been the cause of major accidents and numerous injuries in the industrial synthesis of N2O. Second, other oxides of nitrogen may be obtained as byproducts of the synthetic process. One of these, nitrogen dioxide, is extremely toxic, and can lead to rapid destruction of lung tissue, even if inhaled in small quantities.
From what I read on rec.pyrotechnics, nitrogen dioxide lung damage is permanant and cumulative.

Laughing Gas also states that the boiling point of N2O is -88.44 C and that the partial pressure at 27.4 C is 60 atm (!). Does that mean those little whippits can withstand 60 atm??

I tend to think the danger of explosion is low if you keep the pressure down. The "Dr. Atomic" cartoon instructions even go so far as to make it an open system -- the end is a plastic bag loosely held over the last hose. The good doctor says that you should only synthesize it if you are a professional chemist working under controlled laboratory conditions, but in the picture there is a home setup using three flasks. The first one contains the NH4NO3 and is heated. The third is a "bong" type device which bubbles the gas through water. The second is a trap to prevent the "bong" water from reaching the heated flask under negative pressure.

I wouldn't really worry about inhaling small quantities of ammonia, but I'd like to figure out a way to neutralize the NO and NO2. Would they react with baking soda (in the bubble flask)?

The PYRO file from rec.pyrotechnics lists two sources of ammonium nitrate. One is fertilizer, the other is "instant cold packs." I wonder how pure it is...

--Keith Lewis
lewis@mitre.org





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