Sciencemadness Discussion Board

erythritol tetranitrate recrystallization

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Herr Haber - 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.

Brightthermite - 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.

Herr Haber - 7-10-2020 at 08:12

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


Brightthermite - 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?

aromaticfanatic - 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.

Herr Haber - 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 ;)

Brightthermite - 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]

Herr Haber - 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 :)

Sensitivity

Brightthermite - 4-3-2021 at 16:33

The first time I made ETN I never did a recrys and just stored it as is in a plastic bottle. When I checked it several days later obviously there was lots of brown fumes. Does anyone know how much of a safety hazard this is? I understand it destroys your product but does it pose any real sensitivity issues?

Also I am still having a problem getting a neutral recrys. Using acetone to dissolve the ETN the crash into water is not working. I use to add a bit of baking soda to the acetone but was advised against this. Any tips?

[Edited on 5-3-2021 by Brightthermite]

XeonTheMGPony - 5-3-2021 at 03:40

get urea, 3% by weight to co administer to the recrystallizing water, and to the solvant

Brightthermite - 5-3-2021 at 11:31

Thanks Ill try this next time. Second question how can you check you have pure product after? I used pH paper to check the the pH of the solvent and the water after crashing my solvent. I added bicarb until neutral to the solvent. However this did not work well enough apparently.

I once again dissolved around 60 grams in acetone. Added a small amount of bicarb to the solvent. Then dumped it into quench water with bicarb. The solution has a yellow tinge to it which I have not seen before. Of course I had no pH paper to check the pH of each solution so that was nice.

I believe I may not fully understand how the recryst works. The idea is to dissolve your product into solvent which frees trapped acid. Now there is a solution of solvent, dissolved product, and acid. (Again I was advised in other post NOT to neutralize the solvent solution) Next you dump this in water which rapidly causes the product to reform and fall out of solution. How is acid not trapped back in the product when it rapidly precipitates, considering that the acid/solvent solution are literally intermixed when the rapid formation takes place?


IMG_1203.jpg - 3.3MB


XeonTheMGPony - 8-3-2021 at 03:54

When I make an ETN batch, I crash into ice water and mix, let stand for a couple hours (let all the ice melt) to ensure it is all out of solution, then I filter, then I wash with a couple liters water, tap. By this time there is no real noticeable acidity.

Crude is dried on glass frit, then weighed 3% urea is added to methanol once dissolved all the ETN is added and the methanol warmed till all ETN is dissolved (Some times a alcohol must be added drip by drip to get it fully dissolved)

All gunk is filtered out at this stage and then all the filter stuff rinsed with an aliquat of fresh heated methanol.

10 times the volume of water is prepared and again 3% urea is added to this based of the last weight of the crude, then under stirring the solvent / ETN mix is slowly poured in, then the beaker rinsed with minimal hot methanol.

Once addition is complete allow to stir for a few more minutes then allow to stand for an hour or so and test Ph, for me at this point it isn't acidic (been a while can't give a exact number but over 7 in very least)

pain and time consuming, but it can take your life, and if you plan to store it, then it is well worth the time to ensure it will keep for that time.

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