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Author: Subject: Nitrocellulose runaway, twice in a row
caterpillar
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[*] posted on 6-3-2012 at 12:33


I think, the truth must be born mostly in experiments. Discussion is very useful thing, of course, but they are only secondary. Unfortunatelly, there was no Net nor such site when I was young. Literature on explosives was only in restricted sections of libraries. It took me years to understand, how distillation can be bypassed (using nitrates and sulphuric acid). The first experiment that I made was more than stupid: I put some phenole into a jar, added KNO3 and then H2SO4. Small amount of sulphuric acid ignited phenole.



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[*] posted on 6-3-2012 at 13:31


Both lead(II)sulphate and barium sulphate are soluble in concentrated sulphuric acid (supposedly due to the formation of HSO4-). This may explain why lead and barium nitrate do seem to work for this purpose.

It also means you should keep in mind that the acid mixture contains an appreciable quantity of highly toxic lead.

[Edited on 6-3-2012 by phlogiston]




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[*] posted on 6-3-2012 at 15:02


Thanks for all the replies. I distilled some more nitric acid last night (and the hydrometer I ordered arrived today, but it is awfully large for my 50 or so mL of acid) and nitrated my nicely washed cotton. I made sure my acids were chilled to near 0°C before the addition of cotton. I added the cotton slowly and had no runaway. I kept it in an ice bath for a few minutes before putting it in just a chilled water bath. It nitrated for 30 minutes longer. I rinsed it with plenty of water and then a dilute sodium bicarb bath. No bubbling was noticed. Gave it a final water rinse and set it up to dry. I started with 6.50 grams of cotton and the final product weighed in at 9.91 grams. Does calculating the moles of cellulose used then finding the average molar mass of the NC allow me to figure out how nitrated my product is?

One more thing: I remember reading somewhere here, I believe, a book full of information on different energetics and their synthesis. I checked the library but none of them rang a bell. It was very detailed, and I remember seeing a table of different percent nitrations of cellulose. Any ideas what book this could have been? I believe the author's name was Russian or Polish.

Found it: the book I was looking for was "Chemistry and Technology of Explosives" by Tadeusz Urbanski.

[Edited on 7-3-2012 by inspector071]
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[*] posted on 6-3-2012 at 21:05


Go ahead. I could only recommend you do not waste obtained HNO3 for such simple thing like gun cotton. Use it for something more interesting like nitramines. How one can get NC with different percentage of N you may read in famous book, written by Jared Ledgard.



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[*] posted on 6-3-2012 at 21:30


Quote: Originally posted by caterpillar  
Go ahead. I could only recommend you do not waste obtained HNO3 for such simple thing like gun cotton. Use it for something more interesting like nitramines. How one can get NC with different percentage of N you may read in famous book, written by Jared Ledgard.


Yep, I'll be using some to try and synthesize RDX. Though the R-salt synthesis sounds very interesting. I suppose I can give them both a try. I wish there was a big table of people's different methods of synthesis for tricky reactions like RDX to compare yields and figure out which ones are the most efficient. Without knowing the concentration of my distilled nitric acid, is it worth it to try and straight up nitrate hexamine with it?
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[*] posted on 7-3-2012 at 00:49


R-salt is as all nirtosamines carcinogen. Oxidisation of R-salt to RDX can be performed by mixture of conc HNO3 and H2O2 at -30 C. The most simple method to prepare RDX is probably K- method. You need hexamine dinitrate (and it can be prepared without HNO3- use HN4NO3 + H2SO4, for example). K- method means treatment of hexamine (dinitrate will be better) with conc HNO3 + HN4NO3 at 80- 85 C. This method is the simplest, as I know. Direct nitration of hexamine is not as effective (and oxidization occurs- NH4NO3 suppress it).



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[*] posted on 7-3-2012 at 01:06


Indeed HDN + c.HNO3 is best! Use only fresh distilled nitric acid or you will have to purge it...

By the way, the nitrating mixture that is prepared with barium or lead nitrate and sulphuric acid gives excelent yield when nitrating NG, EG and PG.
How soluble are the sulphates in c.H2SO4?

[Edited on 7-3-2012 by simply RED]




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[*] posted on 7-3-2012 at 01:48


Quote:
I wish there was a big table of people's different methods of synthesis for tricky reactions like RDX to compare yields and figure out which ones are the most efficient. Without knowing the concentration of my distilled nitric acid, is it worth it to try and straight up nitrate hexamine with it?

I use a hydrometer for checking the density of H<sub>2</sub>SO<sub>4</sub> before distilling HNO<sub>3</sub> from it.
At 27 cm in length it takes a bit of floating, but at density >1.80 you know the HNO<sub>3</sub> you'll get will nitrolyse hexamine directly!
And the direct nitrolysis of hexamine @ 20°C is just about the easiest synthesis for any HE!




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[*] posted on 7-3-2012 at 15:00


Direct nitrolysis of hexamine may easy go wrong- an oxidisation occurs. I met it twice. If one is using hexamine didtrate, he saves large amount of conc HNO3. I do not think, that K-method is more complicated. KA really is, to say nothing about W and E methods. Direct nitrolysis of hexamine can give you one mole RDX per one mole hexamine (really not so much, of course). But such simple modification as K-method can theoretically give 2 moles of RDX per one mole of hexamine. And NH4NO3 suppresses oxidisation. This is why I think that K-method is the best. What's the problem to dissolve some ammonium nitrate in nitric acide?



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[*] posted on 7-3-2012 at 23:30


Where can I find some synthesis procedures for these different methods? The only detailed one I have so far is the original RDX patent, which is the direct nitration of hexamine via pure nitric acid.

On another note, I just synthesized some more picric acid using Roscoe's olde time country procedure, tailoring it for my reagents, namely potassium nitrate, and also cutting the amounts in thirds. So far everything looks good. Just have to dilute the picric acid/nitrating acid mix, filter, and recrystallize. Hopefully this will allow me to make some lead picrate as a primary. Does anyone do much with straight picric acid anymore, or are the metal salts the most useful?
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[*] posted on 8-3-2012 at 02:42


Look for it: Jai_Prakash_Agrawal,_Robert_Hodgson-Organic_Chemistry_of_Explosives-Wiley(2007) Nice book, but mostly theory. my recomendation- use hexamine dinitrate instead of pure hexamine. You may save some conc nitric acide. I made picric acide, kalium and ammonium salts of it. Ammonium picrate mixed with AN and Al is nice explosive. I used TATP to initiate it. Kalium salt explodes, been ignited in confinement and burns violently in open air.




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[*] posted on 8-3-2012 at 04:09


TNP is a phenomenal booster with all the brisance you could need. It is easy and cheap to prep, and isn't to sensitive, but responds to primaries well. I, personally have never used a metal picrate. Be careful if you make Pb picrate. IIRC, there is a route that employs metathesis, instead of strong heating. Do a lit search.

PS, we are getting off topic. Perhaps you all should continue discussion about RDX and TNP in the corresponding threads.


[Edited on 8-3-2012 by Bot0nist]




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[*] posted on 8-4-2012 at 13:15


What you call a runaway is localized heating from the H2SO4 dehydrating the cotton as you add it to the mixed acid. Most common mistake made is not drying your cotton before nitrating it. An hour or so in the oven at 110c does the job.
It's usually the simple things that cause the most troubles.
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[*] posted on 9-4-2012 at 20:03


Thanks for the help. My cotton could have certainly not been dried well. Next time I nitrate some, I'll be sure to dry it thoroughly.

What is the difference between a traditional runaway and the heating of the mixed acid due to dehydration? Both seem to create NO2, heat, and leave a oxidized charred mess in the bottom of the beaker. What is the accepted runaway temperature for the nitration of cellulose?
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[*] posted on 9-4-2012 at 20:24


This is a pretty ugly way to talk to another member, "If you knew anything at all about inorganic chemistry you'd know that the above scheme is rubbish!" A little civility, please.



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[*] posted on 10-4-2012 at 18:08


inspector071..

I wouldn't worry too much about a runaway as long as you dehydrate your cotton thoroughly and let it cool in a sealed bag before nitrating it. Typically I see a 5.5% loss in weight after proper drying of cotton. Use an excess of acid if in doubt since it is a good heat sink and keep the starting temperature around ~15c and it will all work out. I've made hundreds of pounds of gun cotton over the years for special effects use and never had a problem.

If you're worried about wasting your acid, you can economize the process by saving your spent acid and do a cascade nitration the next time. Simply start your fresh cotton in your old acid then move it into new acid. I did mine in three steps then tossed the well used mix. Also in this way you have far less chance of overheating. The resulting nitrogen content will be greater as well.

One last tip for best product.. You lose a lot of the nitrogen content if the quenching isn't speedy. Take your cotton out of the acid and plunge into cold clean water and wring it with a gloved hand, under the water, as fast as you can pumping out the acid. The quicker you can exchange the weak nitrating acid with clean water, the sooner you stop the inevitable de-nitration that is happening.

Enjoy.

[Edited on 11-4-2012 by ordenblitz]
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[*] posted on 10-4-2012 at 19:10


Neat stuff ordenblitz; thanks for the tips. I really should be saving my spent acid. Usually I just neutralize and dispose of it, but it certainly has a use. What do you estimate the nitrogen content of the twice nitrated cotton is? I'm still trying to understand the properties of the different types of nitrocellulose. Is it correct that less nitrated cellulose is soluble in alcohol/ether solution (collodion) while highly nitrated guncutton (13%+) is not? And that 13% can actually detonate when confined? I assume the density would have to be right, though, perhaps requiring the nitrocellulose to be compacted with the aide of some acetone to remove the fibrous nature of the original guncotton?

I'll make a note about the quenching too. Do you simply rinse well, then soak in a hot dilute sodium bicarbonate solution, followed by a final rinse? I know with nitroglycerine and energetics that are recrystallized a stabilizer such as diphenylamine and a small amount of some more neutralizer (like sodium bicarbonate) are added at the time of recrystallization to ensure stability. It doesn't seem as though there's a feasible way to do that with nitrocellulose if you wish to leave it in its fibrous form. Though I suppose if the mixed acid cannot permeate the very center of the cellulose fiber, there's not much of a need to try and stabilize the very inside of it as with liquid and crystalline energetics.
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[*] posted on 11-4-2012 at 02:33


Quote:
This is a pretty ugly way to talk to another member.

Yes it is, chemrox ─ my apologies, caterpillar . . .




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