Sciencemadness Discussion Board - Nitrocellulose runaway, twice in a row

Nitrocellulose runaway, twice in a row

inspector071 - 4-3-2012 at 22:23

Tonight, I have tried twice to make some more guncotton. I have made about 20 grams of it in the last couple of weeks or so, but tonight I can't seem to get it to work without it running away!

Earlier tonight I started with 8 grams of cotton, 48 g distilled nitric acid (haven't gotten my hydrometer in yet, but it's concentrated acid distilled from sulfuric acid and potassium nitrate), and 52.4 g concentrated ~95% sulfuric acid. This is a roughly 1/12 ratio, and it worked just fine the other day with 5.5 g cotton. My acids were chilled to 5 deg. C prior to mixing, and I used a chilled water bath to regulate the temperature. I added the cotton and within seconds nitrogen dioxide started spewing from the center of my 250 mL beaker.

Just a few minutes ago I started with 6.5 g cotton, 37 g nitric acid, and 41 g sulfuric acid. Again, the acids were chilled to 5 deg. C before mixing. After mixing them, I iced them to make sure they were cold. I used an ice bath this time to try and lower the temperature. This time I added the cotton a little bit at a time. As soon as all had been added, again, nitrogen dioxide came forth from my beaker. After a few minutes it stopped, leaving a black mixture of partially oxidized cotton and acids. What am I doing wrong? I'm not changing anything that I know of from just the other day and a few weeks ago where I synthesized a bunch of the stuff with no problem at all.

On a side note, is there a method for determining nitrogen content of nitrocellulose? I'd be curious to know how nitrated I can get cotton with my acids (if they ever stop running away).

Bhaskar - 4-3-2012 at 22:48

I am not that experienced in nitrating cellulose, i once experienced a runaway when i did it on a large scale, my doubt is that you should nitrate it in different containers in smaller quantities. The nitric acid you are using is white fuming nitric acid and its quite a waste for such precious acid as nitration is successful at the azeotropic concentration of nitric acid(about 68%~). Umm....thats all.

disulfideprotein - 5-3-2012 at 00:02

Okay... First... Well... I would recommend chilling to 0C, add the cellulose, wait about ten to twenty minutes. After such neutralise the acids and wash then dry. Also use stoichiometric amounts so you have less of a chance of oxidation of the product.

caterpillar - 5-3-2012 at 01:43

OK, my experience. I've started with NC, and it was the first something more serious than black powder that I was able to make. The first: do not spend time and efforts, making distillators. There is a nice way to make mixed acid without it. H2SO4, of course, plus Ca(NO3)2. So simple. I found calcium salpeter in a simple shop with other fertilizers. it contents some water, and therefore real formulae is Ca(NO3)2.4H2O. heat it till all water goes away. Do not worry, overheating here is quite impossible. Then break obtained solid mass to small pieces (not dust- 3-4 mm would be better). Put it into conc H2SO4. I do not remember proper amount, but you may calculate it yourself. Assume all NO3 is replaced by SO4, and resulting mixed acid contents 40 % of HNO3 and 60% of H2SO4. Let it stay for one night. you may filter it or simple remove upper liquid layer, leaving mass of CaSO4. Then put cotton into it. Due to the consistence of cotton, you should put it into mixed acid for few minutes, than press (not very strong) it to remove excess of mixed acid and put wet cotton into another vessel. let it stay for one night. Than wash it with large amount of cold water WARNING: do not put large pieces into water, once when I did it such piece ignited under water! Take gloves and wash it quickly. Change water some times and use solution of NaHCO3 (few percent) to neutralize rest of acids.

Pulverulescent - 5-3-2012 at 02:23

Quote:

The first: do not spend time and efforts, making distillators. There is a nice way to make mixed acid without it. H2SO4, of course, plus Ca(NO3)2. So simple. I found calcium salpeter in a simple shop with other fertilizers. it contents some water, and therefore real formulae is Ca(NO3)2.4H2O. heat it till all water goes away. Do not worry, overheating here is quite impossible. Then break obtained solid mass to small pieces (not dust- 3-4 mm would be better). Put it into conc H2SO4. I do not remember proper amount, but you may calculate it yourself. Assume all NO3 is replaced by SO4, and resulting mixed acid contents 40 % of HNO3 and 60% of H2SO4.

If you knew anything at all about inorganic chemistry you'd know that the above scheme is rubbish!
Because CaSO4 is insoluble, very little reaction occurs when the dry salt is added to H2SO4!
To liberate HNO3 from calcium nitrate, the salt must first be dissolved in water before the addition of H2SO4 to the soln..
CaSO4 precipitates leaving a soln. of nitric acid.

Pulverulescent - 5-3-2012 at 02:38

Quote:

This time I added the cotton a little bit at a time. As soon as all had been added, again, nitrogen dioxide came forth from my beaker. After a few minutes it stopped, leaving a black mixture of partially oxidized cotton and acids. What am I doing wrong?

You're trying to nitrate a very impure cotton, or something that isn't cotton . . .

caterpillar - 5-3-2012 at 03:24

Quote: Originally posted by Pulverulescent

Quote:

I do know chemistry! Where d'you find, that I added CaSO4??? I do add Ca(NO3)2, of course. Just because CaSO4 is insoluble, this reaction goes on and at nearly all HNO3 is extracted. BTW, how d'you think the first fertilizer was made? I mean, Ca(H2PO4)2 superphosphate. Absolutely insoluble Ca3(PO4)2 reacted with H2SO4, producing much more soluble CaSO4. I realized, that similar method must work with Ca(NO3)2 too. You may dissolve Ca(NO3)2 in water, but you'll det diluted mixed acide. It is useless to argue with experiments, that I made many times.

Ral123 - 5-3-2012 at 03:44

I think the insolubility of BaSO4 is exploited in some nitric acid synthesis.

caterpillar - 5-3-2012 at 03:58

There is one problem with Ca(NO3)2- I wanted to get conc HNO3, but got mess of crystals instead. You can get mixed acid with 40% of HNO3, but 50-60 % of volume will be white mess- small cyrstals of CaSO4. Perhaps, using glass filter some more mixed acid could be obtained, but I simple threw it away. Here is a good news too- I think, that during this process concentration of mixed acid goes up- CaSO4 surely contents some water- CaSO4*xH2O. I made NG and NC in such way.

Pulverulescent - 5-3-2012 at 05:17

Look, when calcium nitrate is added to sulphuric acid, the particles are immediately coated with CaSO4, preventing further reaction.
The quantity of HNO3 released is negligible.
CaSO4.2H2O is gypsum, a plaster used in interior walls!
It is also used to make Plaster of Paris, Ca(SO4

2.H2O.

Quote:

Do not worry, overheating here is quite impossible.

FYI, calcium nitrate decomposes @~560°C!
Quicklime, NO2 and O2 are formed!
I suggest you read some basic inorganic chemistry texts!

simply RED - 5-3-2012 at 07:27

If you mix dry lead nitrate with concentrated 96-98% sulphuric acid and heat this in boiling water bath for 20-30 minutes it gives quantitive yield of insoluble PbSO4 and concentrated nitric acid that can be used for nitrating OH groups. I have done this multiple times, the problem is that much of the nitric acid gets soaked in the precipitate, so you have to add twice as much sulphuric than needed and decant. The decanted solution (decant after cooling!!!) is the ready nitrating mix. Works with barium nitarte too, no probem at all...

[Edited on 5-3-2012 by simply RED]

Pulverulescent - 5-3-2012 at 07:32

Quote:

I made NG and NC in such way.

You're lying!
Organic nitrates cannot be prepared by adding glycerine or cotton to mixtures of dry calcium nitrate in sulphuric acid!

Bot0nist - 5-3-2012 at 07:56

Quote: Originally posted by caterpillar

Than wash it with large amount of cold water WARNING: do not put large pieces into water, once when I did it such piece ignited under water! Take gloves and wash it quickly.

Your kidding me right? I have made hobby sized rockets for many years and use homemade nitrocellulose lacquer on every one. So, suffice to say I have made a lot of cellulose nitrate. Never once has it ignited during washing. Ever. The most you'll get is mild exertherm, not even sufficient to boil the cold washing water. A wet piece of cellulose nitrate wont even deflagrate when exposed to direct flame for several seconds! I call bullshit.
STOP!

[Edited on 5-3-2012 by Bot0nist]

Adas - 5-3-2012 at 08:55

As Pulverescent said before, make sure the stuff is really 100% cellulose. You can also try other nitration method - first put the cellulose into HNO3 and then slowly add H2SO4 - I heard this works very well.

inspector071 - 5-3-2012 at 11:05

I'm using "natural, 100% pure cotton" balls.

I'm pretty sure they are indeed pure cotton as I have successfully nitrated it before. The product burned very quickly and left behind little to no residue. I figured the black stuff in my runaway beaker was just charred cotton.

I'll give the cellulose + HNO3, then add H2SO4 a shot. I don't mind using my distilled concentrated nitric acid as I can always make more. I'd really like to have as nitrated a product as I can possibly get. When using concentrated nitric (90%+) can I use a bigger ratio, say 1/8 or 9 and still get a fully nitrated product? Seems as though a lot of these nitrations require empiric research since excess is often required to get decent yields.

What sources of pure cellulose do you guys use when making NC? And any way to analyze the nitrogen content of NC?

[Edited on 5-3-2012 by inspector071]

Somniferrous - 5-3-2012 at 11:57

Quote: Originally posted by inspector071

Tonight, I have tried twice to make some more guncotton. I have made about 20 grams of it in the last couple of weeks or so, but tonight I can't seem to get it to work without it running away!
(...)

In my dreams I always washed my cottonballs before nitrating, first with water, then with acetone.

I nitrated small batches with my proprietary NS (nitrating solution) in an ice bath. As I removed each cottonball from the NS with a hemostat, I squeezed each one out with some tweezers then transfer it to a small cold water bath then to a larger cold water bath. From there it goes into a long bath and finally in a slightly alkaline soln(H2O with a little bicarb).`

I also suspect that something has been added to the cottonballs may be causing that effect (assuming all other things are equal).

inspector071 - 5-3-2012 at 12:27

Quote: Originally posted by Somniferrous

Quote: Originally posted by inspector071

Tonight, I have tried twice to make some more guncotton. I have made about 20 grams of it in the last couple of weeks or so, but tonight I can't seem to get it to work without it running away!
(...)

I'll test a few of the cotton balls with some solvents to see if anything else is in them.

caterpillar - 5-3-2012 at 14:13

Quote: Originally posted by Pulverulescent

Quote:

I made NG and NC in such way.

You're lying!
Organic nitrates cannot be prepared by adding glycerine or cotton to mixtures of dry calcium nitrate in sulphuric acid!

You are insulting me. They can. Read that I wrote more closely. I added cellulose or glycerine to MIXED ACID. This acig I got by adding dry Ca(NO3)2 to conc (probably 92%) H2SO4. After 12-20 ours of exposition upper liquid is just desired mixed acid and can be easely removed. Made experiment by yourself, if you pretend that you are scientist in some way. I think, you beleive in your level of knowledge of chemistry too strong. "There are more things on the Earth, on the heaven, Horatio, than any dreamt of in our philosophy". About ignition: In fact, there was no flame. There was violent reaction, producing red smoke and leaving black coal instead of white cotton. Ant it occured just in water! I called it "ignition" only for simplisity. Oxidisation, destruction would be better terms, probably.

Pulverulescent - 5-3-2012 at 15:28

OK, I've prepared HNO3 by distillation from KNO3/H2SO4 mixtures only!
It has always, though, been my understanding that nitrate salts whose sulphates are insoluble react only to a small extent with H<sub2SO4 before the particles become coated by the insoluble sulphates.
If you, or sRED can produce pictorial proof that organic nitrates can be prepared from dry Ca, Pb or Ba nitrates in H2SO4 I will quickly lose my scepticism.
It would seem though, at best, a remarkably inefficient method for preparing HNO3, nitro or NC!

inspector071 - 5-3-2012 at 15:34

And isn't the mixed acid nitration preferred over a nitrate salt/sulfuric acid mix for NC? I would like to learn more about the different forms of nitrations, because, as I understand it, there are many different methods for different species being nitrated. RDX apparently decomposes in H2SO4 and must either be nitrated via pure HNO3 or less pure HNO3 and glacial acetic acid as a dehydrant. Picric acid and ETN both have syntheses that seem to favor the nitrate salt/H2SO4 method, while nitroglycerin uses a standard mixed acid.

I'm currently distilling more HNO3 as we speak. My cotton has been washed thoroughly and is now drying. Should be able to make some NC tonight.

[Edited on 5-3-2012 by inspector071]

caterpillar - 5-3-2012 at 16:25

Quote: Originally posted by Pulverulescent

OK, I've prepared HNO3 by distillation from KNO3/H2SO4 mixtures only!
It has always, though, been my understanding that nitrate salts whose sulphates are insoluble react only to a small extent with H<sub2SO4 before the particles become coated by the insoluble sulphates.
If you, or sRED can produce pictorial proof that organic nitrates can be prepared from dry Ca, Pb or Ba nitrates in H2SO4 I will quickly lose my scepticism.
It would seem though, at best, a remarkably inefficient method for preparing HNO3, nitro or NC!

I do not see, what "pictorial proof" means. Assume I'll show you snapshot of a bottle with some liquid and crystalline mess- is it proof or not? How could you know, what actually is in there? May be, NaCl + some water. Make your own experiment, it is very simple. You undestanding about diffusion is wrong. It goes, not very fast but goes. Find an article about superphosphate- it is made by similar way. Moreover, too thin dust makes problems- one needs to get rid of crystalline mess. It is not very efficient method, yeah, because I threw away lots of mixed acid with CaSO4. It is very efficient method, on the other hand, because I was able to bypass distillation. Moreover, I believe (only believe! I do not know) that this method increases quality of mixed acid- CaSO4 binds some H2O.

caterpillar - 5-3-2012 at 16:33

Quote: Originally posted by inspector071

And isn't the mixed acid nitration preferred over a nitrate salt/sulfuric acid mix for NC? I would like to learn more about the different forms of nitrations, because, as I understand it, there are many different methods for different species being nitrated. RDX apparently decomposes in H2SO4 and must either be nitrated via pure HNO3 or less pure HNO3 and glacial acetic acid as a dehydrant. Picric acid and ETN both have syntheses that seem to favor the nitrate salt/H2SO4 method, while nitroglycerin uses a standard mixed acid.

I'm currently distilling more HNO3 as we speak. My cotton has been washed thoroughly and is now drying. Should be able to make some NC tonight.

[Edited on 5-3-2012 by inspector071]

Distillation was always problem for me. I think, that if it can by bypassed, it must be done. Picric acid can be obtained by KNO3 (or NaNO3) + H2SO4. NC reqires liquid mixed acid, therefore method that I described (Ca(NO3)2 + H2SO4) is good here. Nitrourea can be obtained by HN4NO3, dissolved in H2SO4. But RDX and HMX, yeah, they surely require HNO3 and here distillation is a must (may be extraction by CH2Cl2, but even in this case one needs distillation)

simply RED - 5-3-2012 at 23:12

You may make the very very simple experiment: take powdered dry lead nitrate and twice the neeed amount conc H2SO4. Mix well in a small jar with screw cap, put a piece of nylon on the cap not to pass nitrous fumes. Screw the cap and transfer the jar to 100 degC water bath for 20-30 minutes. Agitate the jar by hand in every 1-2 minutes. You will see the insoluble heavy lead sulphate forming on the bottom. After this, cool the mix and decant/filter. This is perfect mixed acids for nitrating organics!
You will be left with a quantitive (more than 80% in any case) yield of lead sulphate precipitate that can not be mistaken with anything else.
Extremely simple and always works fine...
Also perfect to use lead nitrate to "add power" to a nitrating mix with commercial 60-65% HNO3. Always decant the mixed acids as the presence of lead sulphate may (and has!) lead to runway!

By the way, what is the solubility of calcium sulphate in conc. sulphuric acid? I never got quantitive (theoretic) yield with calcium nitrate (it works too but with much lower yield), lead nitrate works best.

[Edited on 6-3-2012 by simply RED]

caterpillar - 6-3-2012 at 01:46

May be, lead nitrate works too. But calcium nitrate is much cheaper and can (well, could some years ago, when I was young and made such experiments) be obtained as a fertilizer. When I first time met that wonderful shop, where I was able to buy some reagents, there was some restrictions. I couldn't buy acids (but H2SO4 92-94% was availible across the street as a liquid for accumulators!) but I was able to buy lead nitrate. I took 100 gr and wasted it during my first attempts to prepare picric acid and its salts. Some years later when I made stiphnic acid and went to aforementioned shop, all salts of nitric acid was in list of reagents not for free sale (one had to bring some paper from an organisation- a scool, laboratory and so on). I could buy lead acetate, but according one thick book I had to use only lead nitrate for preparation of lead stiphnate. Therefore I made ammonium salt of stiphnic acid and exploded it, using TATP as detonator. I do not know about the solubility of calcium sulphate in conc. sulphuric acid. It should be low- few gr per 1liter, no more. One has to wait, wanting to extract more HNO3, using Ca(NO3)2 and H2SO4. May be, exposition in hot water would help. But I simple waited for a night. After it I decanted the upper layer.

simply RED - 6-3-2012 at 02:55

ftp://ftp.igt.ethz.ch/PublicWorld/kostas.serafeimidis/solubi...
Very good article!

In discussion, the truth is born...
Maybe the sulphate covering of the crystals is penetrable by sulphuric acid without dissolving it (or through some kind of mass excahge) and the sulphuric acid can continue reacting with the nitrate, as water reacts with iron through the insoluble rust. As I said with lead nitrate the reaction goes to completion within 30 minutes at 100 degrees C. And you are left with shitload of PbSO4 at the bottom of the jar that can easily plug the drain canal (believe me

)... Just try it to see what I mean!

Maybe lead nitrate works better because the "heavy" lead sulphate falls at the bottom of the jar and separates from the mix but calcium sulphate forms small crystals suspension in the solution? Or maybe they work exactly the same only I did not wait long enough in my experiments with the calcium nitrate.

caterpillar - 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.

phlogiston - 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]

inspector071 - 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]

caterpillar - 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.

inspector071 - 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?

caterpillar - 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).

simply RED - 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]

Pulverulescent - 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 H2SO4 before distilling HNO3 from it.
At 27 cm in length it takes a bit of floating, but at density >1.80 you know the HNO3 you'll get will nitrolyse hexamine directly!
And the direct nitrolysis of hexamine @ 20°C is just about the easiest synthesis for any HE!

caterpillar - 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?

inspector071 - 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?

caterpillar - 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.

Bot0nist - 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]

ordenblitz - 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.

inspector071 - 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?

chemrox - 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.

ordenblitz - 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]

inspector071 - 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.

Pulverulescent - 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 . . .