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Author: Subject: problem in making gun cotton
idrbur
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[*] posted on 5-11-2015 at 02:39
problem in making gun cotton


I am trying to make gun cotton from 3 days .1st time i try to make it by mixing KNO3 and H2SO4 and 2nd and 3rd time with nitric acid and sulphuric acid but every time cotton get dissolved in nitrating mix . So can somebody tell me whats going wrong and how can i seprate nitrocellulose from that mix.
And thanks in advance.

[Edited on 5-11-2015 by idrbur]
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Bert
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[*] posted on 5-11-2015 at 04:34


What is the strength of your acids?



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idrbur
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[*] posted on 5-11-2015 at 04:57


Sulphuric acid(90%-95%) and nitric acid(65%)
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[*] posted on 5-11-2015 at 05:28


Quote:
1st time i try to make it by mixing KNO3 and H2SO4 and 2nd and 3rd time with nitric acid and sulphuric acid but every time cotton get dissolved in nitrating mix.

Cotton doesn't dissolve in MA ─ it appears you're using a polymer-based 'cotton substitute'?

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idrbur
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[*] posted on 5-11-2015 at 06:35


Today cotton doesn't dissolved in mix but cotton become like a chewed chewing gum and was not looking like gun cotton.
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kecskesajt
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[*] posted on 5-11-2015 at 07:23


Temperature controll?
20 °C is fine.Leave it for only 30 mins.
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[*] posted on 5-11-2015 at 07:28


Give ratios of all your reactants- Weight, volume, etc.- along with %, molarity or density of acids when asking questions about your experimental results. Otherwise, people here can't tell you much. Full details on procedure such as temperature, dwell time in the nitrating bath too.

What is the source of the stuff you think is cotton?





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[*] posted on 5-11-2015 at 07:45


I kept the beaker into an ice bath for 2 hour. Solution was made from 4 part sulphuric acid(90-95%) and 3part nitric acid(65%)
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[*] posted on 5-11-2015 at 08:13


That's really weird, are you sure you have 100% cotton and there are no impurities in your acids?
Are there red fumes when the cotton dissolves and does the temperature of the nitrating mix rise during/after it has dissolved?

[Edited on 5-11-2015 by greenlight]




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idrbur
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[*] posted on 5-11-2015 at 09:21


Yup! The temprature has rised a bit.
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[*] posted on 5-11-2015 at 10:02


Are you using cotton balls, or cotton fabric? If you are using cotton balls, you should try using an old cut up 100% cotton t-shirt to see if you get similar results. But remember to remove any elastic first.



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[*] posted on 5-11-2015 at 10:33


I've heard people complain of this before but never had it happen, my first instinct is that you don't have pure cellulose.
Try nitrating a piece of toilet paper and see what happens.
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[*] posted on 5-11-2015 at 12:38


+1 on trying plain white UN scented toilet paper.

Also: What is the weight of alleged cotton added to what volume or weight of the mixed nitrating acid.

[Edited on 5-11-2015 by Bert]




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Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).

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[*] posted on 5-11-2015 at 16:37


+2 for a TP test.

You could be getting too hot (but you would see a red discoloration) or your Nitric isn't Nitric.

Your Sulphuric and Nitric should be clear and colourless.

I get great results with cotton wool balls or toilet paper (even blue paper towels and random industrial toilet paper).

I use 70% Nitric acid and 98% Sulphuric acid (lab grade).

I use about 30:70 nitric:sulphuric ratio.

I mix the acids in a stoppered flask and cool the flask under running cold water with swirling, the mixed acid generates a lot of heat.

I use excess acid as I work in a lab, so acid consumption isn't an issue.

I nitrate at room temperature (20 C) for at least 30 mins.

I use a large beaker with a watch glass on top during the nitrating in a fume hood. (I have done this in a stopped flask before but its much easier in a beaker).

I will mix and swirl the solution on occasion.

I use a glass rod to stir and sometimes push the cotton under the solution.

When complete, I dump the cotton balls/paper in a sink full of cold water (I have a pipe over the plug so I can keep the water running). This is done 1 at a time and I splay them open wring them out with gloves on. they can get hot and discolour (go yellow or pink) at this stage if its not done carefully as the diluting acid can generate quite a bit of heat.

(Side note things are going bad (too hot) at any step if you get those nasty red NOx fumes)

Next I boil and stir in a (Na) carbonate solution for at least 10 mins.

then I boil and stir in DI water until I get a neutral pH.

I'm a little naughty next and dry for 15mins in a 100 C oven then desiccate for a few hours.

Once I found a pile of sludge instead of gun cotton in the oven because I rushed the rinse and neutralisation steps, guess I was lucky I didn't blow the door off the oven.

If done correctly the product always burns clean fast and bright (might be the Na from the carbonate), and is stable for storage.

Wear goggles/glasses at all stages and wear gloves (2 pairs don't hurt nitrile under a thicker PVC/rubber glove) and a coat or overalls when working with acid.
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[*] posted on 5-11-2015 at 17:04


Today i will again try for this but as you suggested i will try it with toilet paper or cotton t-shirt and i will again post my result on this thread.

and Thank you guys for all the suggestions.
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[*] posted on 5-11-2015 at 21:02


Just a thought, maybe your acids are more diluted in water than you think, that would promote the acide hydrolysis of the cellulose into sugars instead of nitration.

" cotton become like a chewed chewing gum and was not looking like gun cotton." If you mean that it becomes kind of rigid it is normal (at least with the KNO3/H2SO4 way), you have to wash it thoroughly repeatedly with water and sodium bicarbonate and let it dry before use.

PS: This procedure works, I wrote it and made NC with it 3 or 4 times.
http://sciencemadness.wikia.com/wiki/Synthesis_of_nitrocellu...


[Edited on 6-11-2015 by alexleyenda]




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[*] posted on 6-11-2015 at 05:55


I just made some nitrocellulose using reagent grade 35ml 98% Sulphuric acid and 15 ml 70% Nitric acid at 20 Degrees. The cotton says on the packet that it is 100% cotton.
None of the cotton dissolved so all I can think of is that the cotton isn't what it says it is and contains something else or the temperature has gone too high. Either that or maybe too much sulphuric acid is present which is destroying the cotton.




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[*] posted on 6-11-2015 at 08:30


Ok guys this time i got a good result now i 'm going to test it after it dry .
Thanks for the help. :)
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[*] posted on 6-11-2015 at 08:35


Doesn't it feel satisfying? :D



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[*] posted on 6-11-2015 at 09:18


The results are quit satisfying . Its not burning too fast that it should, but still its satisfying. Thanks:D
Now i will try for a bigger batch

[Edited on 6-11-2015 by idrbur]
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[*] posted on 6-11-2015 at 10:02


Repeat dippings in fresh MA will yield NC with the highest possible nitrogen content . . .

Good luck in removing those acid contaminents!

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[*] posted on 6-11-2015 at 11:25


If you have DCM,try this:
Mix flour fine,dry KNO3 with the most cc. H2SO4.
Stir for 1/2hour.
Add 3 times of its volume of DCM(for example: 100ml nitrating acid + 300ml of DCM)
Stir 1/2 hour vigirously then decant the upper layer.
Evap. DCM at 50 °C(or under vacuum,distill it)
Mix with H2SO4 at a ratio of 1:1
Cool to 10 °C
Slowly add 100% cotton balls, washed, fully dried in an oven.
Let it sit for half an hour or even an hour in the nitrating bath with stirring and watching the temp,do not rise above 20 °C.
After this, pour the whole batch in ice-slush.
Stir vigirously for 2mins.
Decant,add water,stir, repeat 5x
Add sat NaHCO3,stir for 30mins,decant, repeat 2x
Wash with distilled water 4 times
Then prepare a 3% urea solution,soak in the cotton, then dry it out.
13-14% N is minimum.
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[*] posted on 6-11-2015 at 17:28


Nitrating mixtures for high nitrogen nitrocellulose in the literature have very low water contents.

If you have 60% nitric acid, it occurs to me that producing SO3 and adding to the nitric acid to make mixed acid would be one way to reduce the effective water content.

Question: is it even possible to do this safely? The exothermic nature of the SO3 hydration, and the possibility of HNO3 decomposition make this seem quite dangerous.
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[*] posted on 6-11-2015 at 19:08


I don't think that i can find DCM and also i don't have vacuum disstilation setup.
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[*] posted on 6-11-2015 at 23:38


Quote: Originally posted by kecskesajt  
If you have DCM,try this:
Mix flour fine,dry KNO3 with the most cc. H2SO4.
Stir for 1/2hour.
Add 3 times of its volume of DCM(for example: 100ml nitrating acid + 300ml of DCM)
Stir 1/2 hour vigirously then decant the upper layer.
Evap. DCM at 50 °C(or under vacuum,distill it)
Mix with H2SO4 at a ratio of 1:1
Cool to 10 °C
Slowly add 100% cotton balls, washed, fully dried in an oven.
Let it sit for half an hour or even an hour in the nitrating bath with stirring and watching the temp,do not rise above 20 °C.
After this, pour the whole batch in ice-slush.
Stir vigirously for 2mins.
Decant,add water,stir, repeat 5x
Add sat NaHCO3,stir for 30mins,decant, repeat 2x
Wash with distilled water 4 times
Then prepare a 3% urea solution,soak in the cotton, then dry it out.
13-14% N is minimum.


DCM can be used to make white fuming nitric acid without vacuum distillation.
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