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Author: Subject: erythritol tetranitrate recrystallization
Herr Haber
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[*] posted on 6-10-2020 at 11:58


Quote: Originally posted by Fyndium  
I guess it has to do with crystal size.


Yes and no

No in the sense that evaporation or cooling wont carry away the impurities that in this case are all water soluble so the more water the better.

Yeah in the sense I wouldnt want to poke or scrape those crystals off the surface where the solvent has evaporated.

There are a lot of threads on this forum dealing with recrystallizing in order to achieve specific forms.
https://www.sciencemadness.org/whisper/viewthread.php?tid=25...
Almost made me cry.




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Brightthermite
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[*] posted on 7-10-2020 at 06:00


I agree about scraping high explosives off of hard surfaces, its not the funniest thing to do. The video as well as a paper I found says slow formation is important for the crystals to exclude impurities as they form. This is why I don't understand how crashing the solvent (that still contains acid) into cold water rapidly producing crystals is able to purified them. Does the acid immediately disperse in the water?

Interestingly enough, allowing the solvent to evaporate did allow the crystals to form excluding the acid. When I emptied them out of the container I had them stored in there was a layer of liquid on the bottom of the container, a pH test showed it to be the left over acid. I believe if I had rinsed the crystals after the solvent had evaporated I would have had no problems the ETN degrading. I cant speak for weather or not the bi carb was trapped in the crystals or would have been simply washed away along with the acid.

I vacuum filter my ETN, its very safe.
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Herr Haber
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[*] posted on 7-10-2020 at 08:12


Ok, what did you learn from the video I posted at the end of page 4 ?





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Brightthermite
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[*] posted on 7-10-2020 at 10:43


The method most people use is reverse antisolvent according to the video. And that there are 4 methods of re-crys. Again in the video it was mentioned that the rate at which the crystals are formed is very important for crystal quality, unfortunately it does not detail what "quality" rather is this purity or just how big and pretty the crystal is that formed?
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aromaticfanatic
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[*] posted on 7-10-2020 at 10:52


Quote: Originally posted by Brightthermite  
The method most people use is reverse antisolvent according to the video. And that there are 4 methods of re-crys. Again in the video it was mentioned that the rate at which the crystals are formed is very important for crystal quality, unfortunately it does not detail what "quality" rather is this purity or just how big and pretty the crystal is that formed?


I'm not sure if I am answering your questions but the reason you don't want large crystals of ETN is because the larger the crystal, the more internal strain is in the lattice structure which can cause the explosive to be more sensitive.

So the remaining salts and acids will be trapped when dumping in water but that is why you should do around 2 recrystallizations from an organic solvent with a little bit of baking soda added to make the pH neutral and destroying any remaining acids. The acid removal is very important if you want to store the ETN for any appreciable amount of time or if you want to plasticize it. I was lazy once and didn't recrystallize my ETN before plasticizing and it began reeking of acid, turned yellow, and would not plasticize well at all.

Hope that helps.
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Herr Haber
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[*] posted on 7-10-2020 at 18:36


Quote: Originally posted by Brightthermite  
The method most people use is reverse antisolvent according to the video. And that there are 4 methods of re-crys. Again in the video it was mentioned that the rate at which the crystals are formed is very important for crystal quality, unfortunately it does not detail what "quality" rather is this purity or just how big and pretty the crystal is that formed?


It's the method that makes more sense at this point to get rid of most of the acid by dilution and neutralization after a thorough washing neutralization step. It doesnt mean you cant try different water temp, agitation, concentration of base, nature of base...
And it doesnt mean you cant further purify the product by another method such as cooling from methanol if you have special purposes for whatever you are purifying.
A second crystallization is the best moment to work on crystal shape and size, add a stabilizer etc. to have a product that suits your needs.

There are tons of threads on the forum with ideas for all sorts of compounds. If you are after big beautiful crystals there are many other more beautiful. Some of them equally useful ;)




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Brightthermite
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[*] posted on 8-10-2020 at 10:40


Quote: Originally posted by aromaticfanatic  
Quote: Originally posted by Brightthermite  

I'm not sure if I am answering your questions but the reason you don't want large crystals of ETN is because the larger the crystal, the more internal strain is in the lattice structure which can cause the explosive to be more sensitive.

So the remaining salts and acids will be trapped when dumping in water but that is why you should do around 2 recrystallizations from an organic solvent with a little bit of baking soda added to make the pH neutral and destroying any remaining acids. The acid removal is very important if you want to store the ETN for any appreciable amount of time or if you want to plasticize it. I was lazy once and didn't recrystallize my ETN before plasticizing and it began reeking of acid, turned yellow, and would not plasticize well at all.

Hope that helps.


I personally have not found larder ETN crystals to be noticeably more sensitive, however that could be the case. A smack with a hammer isn't exactly precise. I suppose I am more confused about the actual mechanism that recrystallization works off of. The method of dumping your solvent in cold water works well. I have ETN over a year old that only went through on recrys and has no noticeable changes. Its my understanding that the idea is that if the crystal forms slow enough they will naturally exclude impurities from there lattice. So I do not understand how this is able to take place when you dump the solvent in cold water and the ETN almost instantly forms crystals, does the acid also disperse in the water immediately?

Like I said earlier when I just allowed the acetone to evaporate I was left with ETN in a puddle of acid. Had I not been so foolish I believe the ETN would have been fine after a good washing with water.

@Herr Haber, when using acetone my ETN always comes out in large chunks. What amount of water, temp, ect. do you use to achieve a more free flow?

[Edited on 8-10-2020 by Brightthermite]
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Herr Haber
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[*] posted on 8-10-2020 at 15:57


The first recrystallization should be performed with ice cold water and strong agitation for maximum effect.
That gives you a flour like product. This can be good enough depending on your needs.

I believe that if you have large chunks forming at the bottom your addition rate might be too fast, the agitation too slow or the water not cold enough. But more probably a mix of these.
Also take into account the solvent / water ratio to make all the above useful especially if you cant use a large (1/20) excess of water.
If you dump a whole bunch of saturated acetone in too little water all at once without agitation you will have a problem to dissolve. With calm and acetone. Again :)




The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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