From: fernee@newton.physics.uq.oz.au (Mark Fernee)
Subject: Re: Gun cotton
Organization: Physics Dept. The University of Queensland
Date: Wed, 2 Sep 1992 10:49:18 GMT

In article <10764860.129.715417861@eng2.eng.monash.edu.au>, 10764860@eng2.eng.monash.edu.au (PAUL WALSH) writes:
|> 
|> 	This may sound a dumb question but I am not too keen on attempting 
|> to make up some nitric acid.
|> 
|> 	Is it possible to produce gun cotton by adding KNO3 to concentrated 
|> sulphuric acid waiting a while then adding some cotton wool for a period of 
|> time and finally washing it out with water?
|> 
|> 	I realise that gun cotton is made by combining Nitric and Sulphuric 
|> acids and soaking some cellulose (spelling?) in it for a while. I also 
|> realise that Nitric acid can be made by mixing KNO3 and H2SO4. Is it 
|> possible to miss the step of making the nitric acid?
|> 
|> 	Ratios of chemicals needed would also be appreciated, as would the 
|> length of time needed in soaking the cotton wool.
|> 
|> 	Thanks...Paul!
|> 

I would not advise you try your method, unless you want either HNO3 gas or NOx or
both wafting about. Either way you will not have any guncotton. Making HNO3 from KNO3 and
H2SO4 requires an elevated temperature, which is well above the temperature required for
a successful nitration. The nitration is already exothermic, and thermal runaway is 
common when making this. It is usually not catastrophic, but can be quite messy.

The chemistry of nitration is not entirely straight forward. Often the temperatures for
such processes need to be tightly regulated, and many reactions are highly exothermic,
requiring very good thermal dissipation or great care and patience. If you want to make
some crude nitrated cellulose use 2 parts conc H2SO4 to 1 part conc HNO3 (note: you do
not necessarily need nitration grade HNO3 { > 95% pure}, although this will give a
better product and be much more reliable). Do this in a wide container with so the
acid level is very shallow. This allows more efficient thermal dissipation, which
prevents runaway. Just place small amounts of cotton wool on the acid and swirl it
around for about 3-4 mins. Only do this in very small quantities at room temp (20 deg C).
If you can cool it, all the better. Wash the product thoroughly in a sodium bicarbonate
solution (even boil it). It will not look any different, but it sure burns differently!

I have made it in a shallow glass ash tray with much success. All my other attempts
have runaway. So be careful!!! NO2 is not much fun in confined spaces.

Nitrating is serious business. Read some books !!

You can buy conc nitric acid ( approx 66% solution) from a chemical suppliers or
you could, as I did once, order it from a chemist. ( Unfortunately the chemist put
it in a glass bottle with a plastic cap. After a few months the acid destroyed the
cap,.. sad). Generally it is not too useful for nitrations, but there are a few
important exceptions.

I did make fuming nitric acid at high school once. It wasn't too hard. There were
no accidents during the manufacture, but afterwards the teacher (who was supervising
me at the time) told me to wash out the flask containing the HOT H2SO4 and KNO3 mix.
I told him that he was a loon! So he did it. He put a HOT conical flask under the tap
and turned it on. You know what they say about adding water to acid? Well try hot acid
straight off the bunsen...... Ka Boom!!! It shot a bolt of acid all the way to the 
ceiling, but luckily the flask didn't break. Chalk one up for pyrex...

By the way, he wasn't a chemistry teacher (Luckily).

Acid is dangerous! Be careful..

Mark.

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