Sciencemadness Discussion Board

ETN synthesis issue

Chill - 1-7-2013 at 20:26

In preparation for the 4th, I decided to try synthesizing erythritol tetranitrate. The following is my experience with the attempt, including a paraphrasing of my lab notes. Maybe someone can offer up some assistance.

The quantity and type of materials Is as follows

*100ml H2S04 (Battery Acid boiled close to azeotrope)
* 60g KNO3 (Spectracide Stump Remover)
* 15g Erythritol

I dissolved 60g agriculture grade KNO3 into 100ml of the H2S04. The yellowed (due to acid) solution was cooled down to ~18c, there was expected precipitation of KNO3 that led to a slushy mixture. White fumes indicated that my beaker contained nitric acid.

I started my addition of erythritol and mixed the slush very frequently. Every 5 minutes I added about half a gram of E and checked the temperature, it never went over 20 Celcius. After about half an hour I had finished adding erythritol and the concoction was very thick.

I waited a few minutes before adding some cold water to the solution in preparation for filtering. by now the solution was back to room temperature. I mixed the solution a bit and noticed that the slush was dissapearing.

I was left with nothing, all the slush that I assumed would contain some ETN was dissolved back in the acid. One can guess that this was because the slush was never ETN to begin with, but just precipitated KNO3.

I don't know where I went wrong, but I had obviously not created any ETN. Any feedback from the sciencemadness community would be greatly appreciated.

Ral123 - 1-7-2013 at 21:46

KNO3 is the worst for that reaction, NaNO3 is better, NH4NO3 better, WFNA very nice. Also I ball mill my eritrithol with this: http://www.youtube.com/watch?v=58PBInYuJWU
Also, if the nitrate is cheap, you can recrystalise it.

Chill - 1-7-2013 at 22:31

Quote: Originally posted by Ral123  
KNO3 is the worst for that reaction, NaNO3 is better, NH4NO3 better, WFNA very nice. Also I ball mill my eritrithol with this: http://www.youtube.com/watch?v=58PBInYuJWU
Also, if the nitrate is cheap, you can recrystalise it.


Interesting ball mill, personally I used the ol' pestle and mortar to grind up my sugar and potassium nitrate.

I do have quite a large load of medical grade NH4NO3, I'll have to try that eventually. I did not know that KNO3 was considered "shit tier" in ETN synthesis. I was thinking my problem might've been the crappy Sulfuric.

Stump remover KNO3 isn't exactly the cheapest ($3 a lb), but I don't know of any other local sources.

golfpro - 2-7-2013 at 05:22

I think ETN yeilds is mostly a matter of reagents.

You want decent H2SO4, I'd say at least 95%, and pure, dry AN, I don't know what medical grade is??? Erythritol should be powderd, I used mortar and pestle.

This sounds crazy, and probably wouldn't do it again, but I actually used a warm water bath to get the temp up to 25* C about.

hyfalcon - 2-7-2013 at 05:28

Greenhouse grade KNO3 can be had at most farm stores in the US. It's usually pure enough for pyrotechnic uses, but I would still do a recrystallization before I would use it for anything else.

Chill - 2-7-2013 at 06:00

Quote: Originally posted by golfpro  
I think ETN yeilds is mostly a matter of reagents.

You want decent H2SO4, I'd say at least 95%, and pure, dry AN, I don't know what medical grade is??? Erythritol should be powderd, I used mortar and pestle.

This sounds crazy, and probably wouldn't do it again, but I actually used a warm water bath to get the temp up to 25* C about.


I believe my sulfuric was 95% if not very close, but I'd have to do titration to figure out for sure. All my reagents were powdered, so no worries there.

I don't think there is anything wrong with 25* C. As far as my knowledge goes, you can increase the temps just a little if the slurry gets to thick to stir. Infact, I remember reading people here getting higher yields with slightly higher temps around 20* C, which is why I attempted my first synthesis there. I can vouch for the ease of stirring at such temperatures.

golfpro - 2-7-2013 at 06:20

Dry your AN a few hours before it is used, it will get moist, and it clumps up.

You don't add water to acid solution pour the acid into a larger volume of cold water.

Chill - 2-7-2013 at 06:33

Quote: Originally posted by hyfalcon  
Greenhouse grade KNO3 can be had at most farm stores in the US. It's usually pure enough for pyrotechnic uses, but I would still do a recrystallization before I would use it for anything else.


Not any farm stores near me as far as I can see. Spectracide is decently pure, and can be improved like you said. I should've done that in the first place, but I figured the nitrate wasn't the problem considering I had pretty heavy white fumes when adding it to H2S04.

Personally, I thought my misfortune was caused due to missing some important step. I read the dupont patent before attempting ETN just to be sure that I was going to do things properly, but since the result yielded no ETN, I have doubts that I had the technique down.

If you've had success with ETN, would you say that my process looks the way it should?

Chill - 2-7-2013 at 06:40

Quote: Originally posted by golfpro  
Dry your AN a few hours before it is used, it will get moist, and it clumps up.

You don't add water to acid solution pour the acid into a larger volume of cold water.


Would adding cold water slowly like I did effect the yield though? What you are suggesting sounds more like a safety precaution. "Do what you outa, add acid to water."

I remember watching the acid change a very light (white) color temporarily when I DID add water. With the way things turned out, i'm not sure if that is a normally expected reaction.

[Edited on 7/2/2013 by Chill]

golfpro - 2-7-2013 at 17:40

Ok, my sulfuric acid is purplish 95% around, no I haven't done titration.. My yield was 12g ETN for 10g Erythritol. I probably could have let the nitration go a bit longer but I was anxious to see the stuff. I also probably left 1-3g out there in the filtration/recrystalization etc. PM me if you want to know exactly what I did, all I can say is find the pdf of quicksilver's procedure (at least I think it is), I would say that is the best one to go off of, I saw no temp rise (maybe half a degree C) during the whole time of adding Erythritol, infact it cooled a bit more than I wanted. Expect the worse, keep a nice bucket of cool water nearby.



dangerous amateur - 4-7-2013 at 02:09


Quote:

boiled close to azeotrope


How do you know?
My guess would be your acid is not strong enough.

Whats the exact weight of your stuff per 100ml?

Chill - 4-7-2013 at 12:33

I forgot to mention, the erythritol I'm using is the food grade sugar substitute that I bought at a health food store. Should this be recrystallized? I looked up a solubility graph and it looks like it's doable, but there will be some loss as I don't have the tools to reach -20*c.

Pulverulescent - 4-7-2013 at 12:51

Most freezers will go below -20°C!

Chill - 4-7-2013 at 17:31

Quote: Originally posted by Pulverulescent  
Most freezers will go below -20°C!


Maybe an empty freezer... I stuck a thermometer in my full freezer and it measured just a tad below 0*c. Around -2*c

[Edited on 7/5/2013 by Chill]

Chill - 4-7-2013 at 22:24

Quote: Originally posted by dangerous amateur  

Quote:

boiled close to azeotrope


How do you know?
My guess would be your acid is not strong enough.

Whats the exact weight of your stuff per 100ml?


Alright, I finally got to weighing it. 50ml is 86g.

86x2=172g/mol which is damn close to 184g/mol (pure H2S04)
So my sulfuric acid is around 94% which should be alright for this experiment. Correct?

Motherload - 4-7-2013 at 23:31

H2SO4 is definately strong enough.
Are you sure that the spectracide is KNO3 ?
I have only made ETN with 68% HNO3 and boiled drain cleaner.
I can see ETN ppt even before I dunk it in water.

I wonder if one was to filter the ice cold KNO3 H2SO4 mix through sintered glass and remove pptd K2SO4 .... Would it help with stirring ?

Any one know solubility data on K2SO4 in HNO3 ?

Chill - 4-7-2013 at 23:57

Quote: Originally posted by Motherload  
H2SO4 is definately strong enough.
Are you sure that the spectracide is KNO3 ?
I have only made ETN with 68% HNO3 and boiled drain cleaner.
I can see ETN ppt even before I dunk it in water.

I wonder if one was to filter the ice cold KNO3 H2SO4 mix through sintered glass and remove pptd K2SO4 .... Would it help with stirring ?

Any one know solubility data on K2SO4 in HNO3 ?


100% sure that spectracide is KNO3. I recrystallized it today and I'm going to try using it to make ETN tomorrow. If that doesn't work, I'm going to try using recrystallized ammonium nitrate.

Can I get a play-by-play of your method to compare it to my own? Doing just one step incorrectly could've screwed my yield up.

I believe I read somewhere that letting the erythritol nitrate for "too long" can lead it to have an extra hydroxyl group or something like that, and it causes it to be soluble in water, which would explain why I didn't see any yield.

I'll have to try looking for it again, it might be related.

Motherload - 5-7-2013 at 17:34

1 gm Erythritol for 4ml 68% HNO3 + 6ml 95% H2SO4
Erythritol was ground with mortar pestle.
Acid mix cooled to 10*C
Magnetic stirrer was used 240 rpm. And a thermometer dipped in the flask.
Flask was placed in cold water with a few ice cubes.
A 5 gal runnaway pail was near by.
The erythritol was trickled in with a powder trickler, I use for reloading ammunition, fairly constantly.
Temp was monitored and didn't exceed 18*C.
After the addition it was stirred for additional 20 mins.
The contents were poured into ice water, filtered and washed multiple times with water and neutralized with bicarbonate soln and re washed with water
Dried on a Teflon cookie tray and re crystallized.

Chill - 5-7-2013 at 18:36

Quote: Originally posted by Motherload  
1 gm Erythritol for 4ml 68% HNO3 + 6ml 95% H2SO4
Erythritol was ground with mortar pestle.
Acid mix cooled to 10*C
Magnetic stirrer was used 240 rpm. And a thermometer dipped in the flask.
Flask was placed in cold water with a few ice cubes.
A 5 gal runnaway pail was near by.
The erythritol was trickled in with a powder trickler, I use for reloading ammunition, fairly constantly.
Temp was monitored and didn't exceed 18*C.
After the addition it was stirred for additional 20 mins.
The contents were poured into ice water, filtered and washed multiple times with water and neutralized with bicarbonate soln and re washed with water
Dried on a Teflon cookie tray and re crystallized.


I thought it was necessary (or heavily suggested) that you recrystallize the ETN in methanol or ethanol. You just washed yours?

Motherload - 5-7-2013 at 22:36

I said dried on a Teflon cookie tray and recrystalized.
Except I did it with acetone. It gave me a high density non fluffy crystals.

If you are going to use it as soon as the crude product has dried .... Recrystallization is unnesscesarry. But definately recrystalise if you are going to store it for even a week.

[Edited on 6-7-2013 by Motherload]

Chill - 5-7-2013 at 22:39

Quote: Originally posted by Motherload  
I said dried on a Teflon cookie tray and re crystalized.
Except I did it with acetone. It gave me a high density non fluffy crystals.


Dammit, I was reading in such a rush that I missed that part, sorry about that.

Some threads suggested not using acetone because it is too good at dissolving ETN, and it becomes a PITA to get it back out of solution. Glad you were able to get it to work. I had a few bottle of pure methanol lying around collecting dust so I plan on using those.

Motherload - 5-7-2013 at 22:44

Acetone solution of ETN phase separates in water with bicarbonate and urea.
I evaporated/boiled off the acetone with stirring at 50*C.
Adding water alone with bicarbonate and urea won't ppt the ETN.

The only reason I figured this out is because I was out of methanol and you use way too much compared to acetone.

[Edited on 6-7-2013 by Motherload]

golfpro - 6-7-2013 at 07:18

I don't think there's anything wrong with fluffy crystals, except that if you have 20grams, it looks like a lot, you press it and 3 grams is a small amount

scottjm - 6-7-2013 at 08:12

Quote: Originally posted by Motherload  
Acetone solution of ETN phase separates in water with bicarbonate and urea.
I evaporated/boiled off the acetone with stirring at 50*C.
Adding water alone with bicarbonate and urea won't ppt the ETN.

The only reason I figured this out is because I was out of methanol and you use way too much compared to acetone.

[Edited on 6-7-2013 by Motherload]


Just wondering what does the urea do? The bicarbonate neutralizes the acid, but what does the urea do?

Motherload - 6-7-2013 at 11:53

Urea serves as a stabilizer which is necessary for every nitric esters longer shelf life.
There are other better stabilizers out there .... Urea is cheap and available.
You don't need if if you don't plan on storing it.

Antiswat - 6-7-2013 at 14:51

Quote: Originally posted by Ral123  
KNO3 is the worst for that reaction, NaNO3 is better, NH4NO3 better, WFNA very nice. Also I ball mill my eritrithol with this: http://www.youtube.com/watch?v=58PBInYuJWU
Also, if the nitrate is cheap, you can recrystalise it.


i did however hear from somewhere that KNO3 happens to yield the best results with this exact synthesis

also did see a few posting that KNO3 should yield the best on this forum
i would understand the logic in that the mixture is more liquid'ish and it doesnt block itself in the already very thick sludge of K2SO4

i could ask the guy to try out NaNO3 which he happens to have some laying around, hes had terrible yields in which upped abit when he tried KNO3 rather than 62% HNO3 or NH4NO3

NeonPulse - 6-7-2013 at 19:11

Quote: Originally posted by Antiswat  
Quote: Originally posted by Ral123  
KNO3 is the worst for that reaction, NaNO3 is better, NH4NO3 better, WFNA very nice. Also I ball mill my eritrithol with this: http://www.youtube.com/watch?v=58PBInYuJWU
Also, if the nitrate is cheap, you can recrystalise it.


i did however hear from somewhere that KNO3 happens to yield the best results with this exact synthesis

also did see a few posting that KNO3 should yield the best on this forum
i would understand the logic in that the mixture is more liquid'ish and it doesnt block itself in the already very thick sludge of K2SO4

i could ask the guy to try out NaNO3 which he happens to have some laying around, hes had terrible yields in which upped abit when he tried KNO3 rather than 62% HNO3 or NH4NO3
I actually get pretty decent yeilds also using KNO3 over NH4NO3 it also seems that the bigger the synth with the AN the worse the yeilds. KNO3 has worked very well for me with this type of synth although it gets pretty tough to stir. HNO3 so far has given the best yeilds (as expected)i am yet to try to have the temp higher with the AN process but i am going to give it a try i see that can improve results.

Chill - 6-7-2013 at 20:14

Quote: Originally posted by NeonPulse  
Quote: Originally posted by Antiswat  
Quote: Originally posted by Ral123  
KNO3 is the worst for that reaction, NaNO3 is better, NH4NO3 better, WFNA very nice. Also I ball mill my eritrithol with this: http://www.youtube.com/watch?v=58PBInYuJWU
Also, if the nitrate is cheap, you can recrystalise it.


i did however hear from somewhere that KNO3 happens to yield the best results with this exact synthesis

also did see a few posting that KNO3 should yield the best on this forum
i would understand the logic in that the mixture is more liquid'ish and it doesnt block itself in the already very thick sludge of K2SO4

i could ask the guy to try out NaNO3 which he happens to have some laying around, hes had terrible yields in which upped abit when he tried KNO3 rather than 62% HNO3 or NH4NO3
I actually get pretty decent yeilds also using KNO3 over NH4NO3 it also seems that the bigger the synth with the AN the worse the yeilds. KNO3 has worked very well for me with this type of synth although it gets pretty tough to stir. HNO3 so far has given the best yeilds (as expected)i am yet to try to have the temp higher with the AN process but i am going to give it a try i see that can improve results.


It might not be the AN that makes larger synths have low yields. As far as I've read, the ETN making processes DOES NOT scale well.

If you used 15/60/100 and got a good yield, you may not get a good yield by tripling the reagents to 45/180/300. Common sense would tell you that the synth would result in around x3 yield, but that's not the case.

You'd have to experiment to find what works best, but like I said, ETN synthesis doesn't scale. (Or so I've read from people on the forum)

Intergalactic_Captain - 4-9-2013 at 04:07

Don't want to start a new thread, so with the discussion of reagent quality I figure this fits in here...

I'm not sure anyone has brought up the idea of sourcing erythritol from artificial sweeteners - In this case I mean those based on stevia. At work tonight, I managed to snag a couple boxes of a new product that's about to be released for sale - And the way we do things, I guarantee you it's a near-identical knockoff of the name-brands...

That said, it can be assumed that stevia-based artificial sweeteners are 50-98% erythritol (couldn't say without the batch-mixing orders), the remainder being "flavorings"...

So, my thought is that although not nearly economical, it may be worthwhile to experiment with for those that cannot find raw erythritol over the counter, while fake sugar packets are literally everywhere... My only curiosity on the matter would be whether it would be more feasible to attempt to recrystalize the erythritol beforehand or nitrate the unknown mixture and purify the product from there - My gut feeling is that it would be more prone to runaway, but a simpler purification afterwards than beforehand...

Motherload - 4-9-2013 at 07:31

I wouldn't be using that brand of erythritol if it could be less than 98%.
Especially since the pure stuff is available online.
Also consider .... If your KNO3 isn't pure .... It's most likely just gonna have some other nitrates or sulphates etc mixed in which are not going to interfere with the reaction.
On the other hand if you had some unknown nitrate-able sugar mixed in with the Erythritol .... Now you could have problems .... Any where from temperature sensitive runaways to separation of the final product being a pain.

Xfactor - 28-9-2013 at 08:53

I made a video on synthesizing ETN with nitric, sulfuric acid and erythritol.

What do you think?
So far I know that I should not have used a thermometer to stir and that I should have added more info on the recrystallization (methanol at 50C)

Chill - 9-10-2013 at 18:19

Quote: Originally posted by Motherload  
I wouldn't be using that brand of erythritol if it could be less than 98%.
Especially since the pure stuff is available online.
Also consider .... If your KNO3 isn't pure .... It's most likely just gonna have some other nitrates or sulphates etc mixed in which are not going to interfere with the reaction.
On the other hand if you had some unknown nitrate-able sugar mixed in with the Erythritol .... Now you could have problems .... Any where from temperature sensitive runaways to separation of the final product being a pain.


This got me thinking about the purity of my erythritol. I believe it's pure, even though I get it as sugar substitute. The actual product is just named "Erythritol" and claims "100% pure" on the packaging. Ingredient list on the back only states "Pure Erythritol Crystalline Powder".

If you want to check it out for your self, google "Now Real Food Erythritol". I still don't know what could've went wrong with my first synth, and I've yet to try again. I'll try again this weekend.

nux vomica - 13-10-2013 at 02:00

I have used the little packets of sweetener you get from the supermarket containing erythritol and get same yealds as posted I use drain cleaner and ammonium nitrate as the nitration mix the sweetener packets must be almost pure erythritol.
nux

Chill - 13-10-2013 at 20:19

Bollucks, I tried the synth again and got the same results (kinda). Just to preface this long note, I'd like to reiterate a few parts of my procedure. I used 25ml more sulfuric acid this time to help dissolve the nitrate. After cooling my acid down to 10 degrees Celsius, I added my recrystallized potassium nitrate and stirred. Just like before, I was left with a cloudy acid mixture that emitted white fumes, and hard almost rock solid lumps of what I can only assume is potassium sulfate. That's what it's supposed to be, right?

Sulfuric acid+Potassium Nitrate ----> Nitric acid+Potassium sulfate

Isn't that how it works? anyways, the sulfate was very hard, almost like a rock! I proceeded with the experiment.

After an hour of nitrating, I sampled the concoction by pipetting a few ml into a test tube of cold water. I saw (what I definitely thought was) precipitation. Huzzah! The precipitate was insoluble in the water, and just to make sure that it could be ETN, I filled the rest of the test tube up with methanol. Sure enough, the precipitate had dissolved and I was left with a greyish solution.

I was convinced I had ETN, so I decided to crash my entire beaker into double it's volume in cold distilled water. I saw a little bit of precipitation as I was taking my time pouring. For whatever reason, I finish the crash and all that is out of solution are the rock like clumps that I began with. I filtered the (potassium sulfate?) clumps out and was left with a pretty clear liquid. No ETN?!

The weird thing is, for those hard rocks to be K2SO4, it would be extremely soluble in water, but they're not. So what are they? This is absolutely bonkers. How could the clumps that formed when adding the KNO3 to H2SO4 at the beginning of the experiment be the only thing out of solution once the procedure was done? And further more, WHAT are they?

Does anyone have an explanation for what happened? I swear I had some ETN by the results of my test, but I ended up getting shafted.

If anyone needs a more verbose or clear understanding and what happened, let me know. I really want to get to the bottom of this.


[Edited on 10/14/2013 by Chill]

[Edited on 10/14/2013 by Chill]

hyfalcon - 14-10-2013 at 05:45

I would just use an excess of KNO3 and H2SO4. Make sure all of your reagents are as finely ground as you can get them. Good stirring is a must.

[Edited on 14-10-2013 by hyfalcon]

[Edited on 14-10-2013 by hyfalcon]

Chill - 14-10-2013 at 06:53

Quote: Originally posted by hyfalcon  
I would just use an excess of KNO3 and H2SO4. Make sure all of your reagents are as finely ground as you can get them. Good stirring is a must.


This doesn't answer any of my questions :(

What are the clumps that are left over? What was in my test tube that wasn't soluble in water, but soluble in methanol?

If anything, I should use an extreme excess of H2SO4 to dissolve (assume that it even will dissolve) those clumps that I had in the beginning. I've seen videos of people making ETN and they don't have the clump problem, so i'm really confused.

I've played around with the sulfuric acid and nitrate some more and determined that if heated, the clumps dissolve, but as soon as the H2SO4 is chilled (like you're supposed to in ETN synth) the clumps form again as whatever they are made of comes out of solution.

EDIT:

Well, i'm convinced the clumps could be K2SO4 (or KHSO4) after I ran some tests and did some math. Since my concoction was so heavily diluted with water after last nights crashing, I was able to boil a small sample of the (mostly water) solution and was left with some solid heavily resembling the rock hard chunks mentioned previously. Obviously the solid had to be soluble in water/H2SO4 (which K2SO4 is). I also massed the Clumps that I filtered out and did some math and everything looks like it should. Without going into too much detail on the math stuff, I compared the approximate volume of water I used for crashing, and potassium sulfates solubility in water and ended up with a number only a few grams off from the measured mass of my clumps.

Anyways, The problem still remains about my apparent precipitation that turned out bunk when I crashed my entire nitration mix. The nitration mix was very milky colored, as it should be, and when I dropped a few mL into the test tube of cold water, there was definitely a significant amount of solid at the bottom which also turned out to be soluble in methanol. I'm pretty damn sure this was ETN. I figured out that K2SO4 wouldn't be that soluble (if at all) in methanol, so I don't think it's possible that I had just pipetted K2SO4.

I must say, this entire experience has left me with my brain in a knot. Where the heck could I have gone wrong? :(



[Edited on 10/14/2013 by Chill]

underground - 15-10-2013 at 21:52

Try some AN in case of KNO3 to see what is going to happen.
Also if you would like some ETN and not a big amount, try to produce some nitric acid from sulfuric acid and nitrate salt (kno3 in your case) by the distillation process, and then use the distillated nitric acid to make your ETN, It would be surely much more better ;)

Chill - 16-10-2013 at 06:36

Unfortunately, I won't be able to get a good distillation apparatus until Christmas (if I eve decide to get one). I plan on buying an organic chem set which should serve me excellently.

I suppose I'll try AN this weekend. I was really hoping someone who did the KNO3 method could chime in and let me know if what I saw was to be expected or not.

underground - 16-10-2013 at 07:14

Quote: Originally posted by Chill  
Unfortunately, I won't be able to get a good distillation apparatus until Christmas (if I eve decide to get one). I plan on buying an organic chem set which should serve me excellently.

I suppose I'll try AN this weekend. I was really hoping someone who did the KNO3 method could chime in and let me know if what I saw was to be expected or not.


Try to distill some nitric acid with to bottles connected together with Teflon. In the one bottle add the kno3/h2so4 mixture and the other bottle try to kip it cool by dipping it into an ice bath or whatever you can imagine

Chill - 16-10-2013 at 07:44

I suppose I could do that if I really needed nitric, but I really shouldn't. KNO3 should work, but it just won't for me. If the AN method turns out bunk, I suppose that means there is a problem with something else (not my choice of nitrate). I'm going to wait until I get results on the AN method before I think about trying to make nitric.

Thanks for the idea though, I'll keep it in mind.

underground - 21-10-2013 at 01:52

Try to make some HNO3 from H2SO4/ KNO3
KNO3 + H2SO4 -> HNO3 + KHSO4
You are going to need 1mole of kno3 (101.1gr) and 1mole of H2SO4 (98.1gr)
Mix well both of them and then let it to react overnight.
At the next day you are going to have some HNO3 and K2SO4
Place a funnel into a bottle, and into the funnel place a coffee filter.
Put the mixture into the funnel and collect the pretty pure HNO3 ;)

[Edited on 21-10-2013 by underground]

Pyrotrons - 22-10-2013 at 01:29

Has anyone experienced "freezing" of Ammonium Nitrate on the sides of their beakers during a synthesis? I've destroyed quite a good quantity of reagents at this point... this has happened to me three times, and seems to happen randomly. When it occurs, it has always resulted in zero yield of ETN. I remember doing two things to try and get the precipitated NH4NO3 back into solution, neither of which has ever worked. They are 1). Allowing the temperature to rise 30C and 2). Adding an excess of H2SO4.

I speculate that the thermal properties of my setup are possibly TOO good. Could very cold temperatures (near 0C) at the reaction beaker sides be reducing the NH4NO3's solubility within the mixed acids, causing it to precipitate out?

NOTE: I HAVE scaled this up from the original numbers, by a factor of about three IIRC.

The synthesis I use:

1). 240 grams of Ammonium Nitrate is slowly added to 175 mL Conc. Sulfuric Acid while keeping
the temp below 25 Celsius. (Note: I use a LOT of ice around the reaction beaker sides and bottom, with only a little water to fill.)

2). 75 grams of Erythritol is slowly added to the acid/nitrate mix while keeping the temp
10-15. This is stirred vigorously.

3). While still keeping the temp between 10 and 15 degrees Celsius, 330 mL Sulfuric Acid
is added while stirring vigorously

4). This is allowed to react for 30 minutes, then crashed into 4 liters of ice water and
filtered

(IF the synth works, I then recrystallize the ETN via Ethanol)

[Edited on 22-10-2013 by Pyrotrons]

Chill - 23-10-2013 at 14:11

Yeah, definitely sounds like you're having things coming out of solution. It shouldn't be ammonium nitrate though, it's ammonium sulfate.

(NH4)2SO4 has pretty good solubility at low temp (70.6 g/100 mL at 0c) which is why people suggest using NH4NO3 over KNO3.

K2SO4 (the product of adding KNO3 to sulfuric acid H2SO4) is BARELY soluble (only 11.1g/100ml at 20c!!!) , which is why I seem to be getting large amounts of those hard chunks of undissolved material.

I didn't suspect that they are the cause of my failed nitration, but you seem to think you've found a correlation between the presence of solids and the yield of the nitration.

I don't know what to say other than try to replicate the experiment user "Swede" on this forum did. He put the absolute minimum amount of nitrate into the mix so that there would be no sulfates out of solution. Personally, this is what I'm going to try if using ammonium nitrate doesn't work out for me.

Here's a thought, not necessarily pertaining to the failure of our synths. I know we're supposed to use a large excess of acid in this synthesis, but I never thought about how much. Using the ratio of reagents that you say you used, I calculated that you use almost exactly 2x the amount of acid as the reaction calls for. I'm wondering if anyone can explain why there is such an excess of acid.

Here's a little bit of the math I did to come to this conclusion just in case anyone wants to confirm for themselves/double check my work:

Balanced reaction:
2NH4NO3 + H2SO4 ----> (NH4)2SO4 + 2HNO3

Conversions of amounts of reagents to moles:
240g NH4NO3 / 80.05g(MM) = 3mol NH4NO3

175mL (assuming 98%) H2SO4 * 1.83g/mL (Density) = 320.25g H2SO4
320.25g H2SO4 / 98.08g(MM) = 3.27mol H2SO4

According the the balanced equation, only 1 H2SO4 molecule is used in the reaction while there are 2 molecules of NH4NO3 used. Using this information you can see that since the moles of each reagent are nearly the same, the excess of H2SO4 is ~2x.


Rosco Bodine - 23-10-2013 at 14:45

The acid sulfate not the normal sulfate is the byproduct in this reaction scenario.

There are cases where the nitrate used does have a cation which corresponds with formation of the normal sulfate under the reaction conditions for this nitration, but not for the ammonium or potassium or sodium cation, all of which nitrates will form the acid sulfate as the byproduct produced at this low temperature range for the nitration.

Therefore your equation, although the stoichiometry works on paper just fine, is not in reality what occurs in the beaker.

To be precise what actually occurs, predominately is the following reaction

NH4NO3 + H2SO4 ---> NH4HSO4 + HNO3

However, there is another simultaneous and inevitable formation to some extent of nitrosylsulfuric acid which also is a nitrating agent, and how much of it is present will depend upon the temperature and the level of H2O present in the reaction mixture. The nitrosylsulfuric acid is unstable and has a decomposition trigger point that is aggravated by increasing moisture, and many "runaways" are actually the triggering of the decomposition of the nitrosylsulfuric acid which hydrolyses to an oxidizing nitrous acid and a self-accellerating cascade or avalanche decomposition sets in which is the runaway. Staying away from that inherent danger requires keeping the water content even in the completed nitration low enough so that the effect is avoided.
Ignoring the effect or striving for too great of an acid usage economy brings danger to the nitration.

[Edited on 23-10-2013 by Rosco Bodine]

Chill - 23-10-2013 at 16:00

This explains so much for me, thank you for your response Rosco.
So you're actually just getting a bisulfate instead of a sulfate, interesting.

This is a really silly question, but I can't find any good solubility charts/tables for potassium or ammonium bisulfate. Would you happen to know where I can get this information? My google-fu is weak.

There are a ton of ways for moisture to be introduced into the nitration mix, so the fact that the acid you mentioned is aggravated by moisture is a little worrying.

As far as I know, the sulfuric acid is bound to contribute the most H2O to the mix since it's won't be 100% concentrated. The hygroscopic nature of all the compounds involved would also increase moisture. I believe I've also read that when erythritol is added to the nitration mix, H2O is a byproduct of one of the reactions that form ETN. Overall, there is quite a bit of moisture in the solution.

When you say "Ignoring the effect or striving for too great of an acid usage economy brings danger to the nitration.", do you mean trying to use the least amount of acid possible in order to save on reagent use? I'm assuming this is because using an excess of sulfuric acid acts as a buffer between the "safe zone" and runaway reaction?

[Edited on 10/24/2013 by Chill]

Rosco Bodine - 23-10-2013 at 19:58

Yes it is exactly true that striving for the greatest economy in the use of acid necessarily increases the relative water content in the starting and especially in the completed or spent reaction mixture, and you need to take into account the water content increase that is the byproduct water from the esterfication, as a percentage of the mixture of acids remaining at the completion of the nitration. If you start out with too little acid then you have a more highly hydrated spent nitration acid that is unstable and the nitrated product is already present as fuel for the fire if decomposition sets in due to the decomposition of nitrosylsulfuric acid which is self accellerating in avalanche once it begins. It is the same effect as positive feedback in an amplifier circuit, so it is the opposite effect of regulation, meaning thermal runaway and once begun it cannot be stopped except by quenching the entire mix and quick if there is even time for quick to get the job done. So the tipping point for runaway is to be avoided by providing a calculated safety margin being mindful of the spent acid composition and allowing some extra margin for safety. Sunlight aggravates the decomposition more than most people understand, and so does moisture and heat, and the effects of the three are synergistic, so it isn't just arithmetic that applies more than generally to nitrations but ultimately it is algebra involving those three variables for sure and other variables that can apply also, which must be taken into account.

Chill - 23-10-2013 at 20:41

You're very knowledgeable in this area, so I don't think it unwise to ask you what you think about my procedure.

I found it particularly strange that adding erythritol didn't increase the temperature, maybe I should've added it all at once. My second time around I did it much quicker, but the result was the same. I used sugar substitute that you can google called "NOW foods erythritol". As far as I know, it's pure erythritol, so I don't think anything was wrong with my reagents. The ratio I used was supposedly proven to work for multiple people.

I think the best way to see if I did anything wrong is to figure out specifically what other people have done to make them successful. For all I know, stirring the mixture too vigorously screwed it up (although I don't think that was it).

If you've done it before, would you mind cross referencing my procedure with yours? If you don't see anything wrong, then perhaps give me an in-depth look at the method you used that resulted in success? This has boggled my mind for the past few months, and I want to get to the bottom of it.

underground - 23-10-2013 at 20:48

I made a research here on this forum and i found somebody that had a very good yields of ~45-50g of ETN for every 35g of Erythritol

200 ml sulfuric acid
110g Ammonium Nitrate
35g Erythritol

So you can give it a try...


[Edited on 24-10-2013 by underground]

Pyrotrons - 23-10-2013 at 23:22

Hm, Ammonium Bisulfate. I trust that that is what it was. Thank you Rosco & Chill. It solidifies in my nitration bath during the addition of the Ammonium Nitrate. When I add it, the ROCK hard, white solid forms that is difficult to remove. I have broken more than one beaker trying to bust it off of the walls with screwdrivers. I really don't understand it, but I'm trying to fix that. I have added grotesque quantities of H2SO4 to try and get it back into solution...as I assumed...probably incorrectly...that it was important! Chill, as far as my correlation between white mass=Success and the lack thereof=Unsuccessful...it's possible that one or all of my reactions could have still worked had I not gotten frustrated and dumped them. That would be would be disappointing.

Notes for my syntheses:

* I always use continuous hand stirring with a glass stir rod

* My reactions seem to always fume proportionally with the addition of NH4NO3. Makes sense (HNO3) sure, but I mention this note because at least one other member of this site detailed a (successful) synthesis that for some reason did not fume.

Rosco and Chill, posts like yours make me want to seriously consider taking formal chemistry classes.

[Edited on 24-10-2013 by Pyrotrons]

Rosco Bodine - 24-10-2013 at 04:11

Stirring with a glass rod is not the safest manipulation for a sensitive nitroester, so you may want to rethink that one. In the alternative you can keep on rolling the dice.

https://www.youtube.com/watch?v=J1EWf6O77jE

<iframe sandbox width="640" height="480" src="//www.youtube.com/embed/J1EWf6O77jE?rel=0" frameborder="0" allowfullscreen></iframe>

http://www.youtube.com/watch?v=l55NbooeUVY

<iframe sandbox width="640" height="360" src="//www.youtube.com/embed/l55NbooeUVY?rel=0" frameborder="0" allowfullscreen></iframe>

[Edited on 24-10-2013 by Rosco Bodine]

dangerous amateur - 24-10-2013 at 06:59

Stirring with a glass rod is not the safest manipulation for a sensitive nitroester

It does not stirr very effeciently with these glass rods anyway, but I never found something better - there are spoons made from PTFE, but they cost a fortune.

Have you guys ever found something else that resists the nitration mix and stirrs better? I mean something ordinary people have at home?

underground - 24-10-2013 at 09:35

Does anybody know any ETN plasticized formula, i was thinking something about ETN/NM/FLOUR. Will that work ? Or ETN/WAX/VASELINE...

Chill - 24-10-2013 at 14:53

Okay, plenty of these replies are going off track. Underground, do you know that you can make your own threads for the questions you're asking?

Anyway... I've seen people stir their ETN mix using a kitchen mixer, so if glass rods are considered rolling the dice, then I don't want to know what that would be considered.

Would anyone happen to know if letting the bisulfate settle and harden at the bottom of the beaker has an adverse effect on the process? Or should the bisulfate be constantly agitated and broken up? Since the potassium bisulfate chunks i've experienced are too hard to break up into smaller pieces, I let them be while exclusively stirring the liquid portion of the mix. Could this have been the reason for my failed experiment?

golfpro - 24-10-2013 at 15:58

stirring with a glass rod is annoying and takes a lot of effort. I am also looking for a replacement. Maybe a regular plastic spoon?

underground, you just have to play around with mixes. I tried a rubber resin w/ solvents in a 90/10 ratio of ETN/plasticizer/binder and got good results. What's tricky is plasticizing large amounts at a time.

Pyrotrons - 24-10-2013 at 17:39

On the glass stir bars - duly noted. I have PTFE rod that will turn into a small bar tonight for stirring. This will replace those sharp hard things that "detonate" at hypersonic velocities when broken inside my ETN/Acid slurries :o

Rosco - Fear not the reaper.

Chill - looking forward to a response to your questions.

golfpro - I would advise against using "regular plastic spoons" in contact with high-concentration Nitric Acid. Look up "chemical compatibility" of different plastic types with Conc. Nitric Acid.

Rosco Bodine - 24-10-2013 at 18:47

Thinking about the properties of the reaction mixture being stirred the ideal material would be a length of teflon rod ....and an improvised substitute that possibly could work though I have never tried it would be a wooden dowel which has been soaked to saturation in molten paraffin.

Nitroester molecules are temperamental little beasties and you really don't want to piss them off by knocking them around between rock hard surfaces, because the potential reaction there could just ruin your whole day in a way that could even make it your last one in this world. Now what good is a learning experience if the student is no longer around, except perhaps as an object lesson for others who are tasked to gather up any pieces of the recently departed. It is highly presumptuos to approach a nitration carelessly with the idea that if you don't get it right this time there will be a next time, because there may not be a next time if you haven't given thought to what you are doing and that thinking has been correct or fortune has favored you for guessing right. Things can still go wrong that are the proverbial fly in the ointment and beyond your control. Some risk analysis is a good thing here with a prudent implementation of countermeasures that is mindful of the nature of the thing being done, which is serious and not trivial.

Pyrotrons - 24-10-2013 at 19:11

Thank you Rosco for everything shared. It is absolutely true that I will never again use glass rods for this.

Chill and I share a common issue - large amounts of Ammonium Bisulfate precipitating out of our mixed acids, possibly correlating with failed syntheses. What would be your recommendations on how to eliminate or deal with this problem?