Sciencemadness Discussion Board

Shit RDX yields without acetic anhydride

nitropyrotech - 26-6-2025 at 17:16

I always used (in this case for example 10g hexamine:
1 mol hexamin
3 mol Ammoniumnitrate
8.6x nitric acid 100% by weight of the hexamine
I kept tempertures below 15C and added hexamine slow after the addition I let the mixture cool to roomp temp for 30 min and thanheated the mixture up to 80C (85) and kept it for 30 min like this, after crashing it into ice water I got a bit more than 2g... :D. After recrystallisation with hot acetone still the same but Idk what I did wrong, I ve done rdx synthesis without acetic anhydride and like in dugs videos. Normally you would get for 1 mol of hexamine 1 mol or rdx, idk what I am doing wrong but anyone could help me fix the yields?

ManyInterests - 26-6-2025 at 19:03

Didn't you make a thread similar to this? It's pretty active and recent...

Microtek - 26-6-2025 at 23:57

For one mol hexamine with at least two mol AN, 100% yield would be two mol of RDX, not one. So, in theory, you should have gotten about 23 gram at 75% yield.
How sure are you that the nitric was 100% and free of NOx, and that the AN was completely dry.

Axt - 27-6-2025 at 07:38

The Bachmann acetic anhydride process is predated by a patent by Trojan Powder Co. which uses just hexamine, 98% HNO3 and an ammonium salt. Interestingly the highest yield is reported from the addition of ammonium sulphate, not nitrate. 101g RDX from 70g hexamine (91% 1:1 molar eq.). It is quite heavy on the HNO3 use though.

I've never attempted to use ammonium sulphate, nor have I seen reports of anyone else trying. The process is copied below.

Mix 858g 98% nitric acid and 50g ammonium sulphate and cool to 7C.
Add 70g hexamine in portions letting temp jump 7-22C with each addition over 45min.
Stir for 5min after final addition then drown in 3L of ice water and filter.





Attachment: US2395773 RDX via HNO3 and NH4 salts.pdf (237kB)
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ManyInterests - 27-6-2025 at 22:41

Quote:
Mix 858g 98% nitric acid and 50g ammonium sulphate and cool to 7C.
Add 70g hexamine in portions letting temp jump 7-22C with each addition over 45min.
Stir for 5min after final addition then drown in 3L of ice water and filter.


Wait you can use ammonium sulphate for this and not nitrate? I am going to try that. I have a 1lb unopened bag of ammonium sulphate, but I will put them in the oven to dry out at 150C for several hours anyway. Given ammonium sulphate's far higher melting point, this should be much easier to keep dry than ammonium nitrate. Also it means I need to use less ammonium nitrate!

Edit: You are correct on it being heavier on the nitric acid than other methods, but if it gives good results, there is no arguing that. What about heating it after all addition has been done and it is allowed to rise to ambient temperature for a while? Would it require heating for better yield/purity or would simply crashing it after the final addition suffice?

And afterward would simply recrystallizing be enough, or would it need to be dissolved in azeotropic nitric acid and heated again for further purity beforehand? I am asking because every RDX synthesis involves some kind of heating to destroy impurities that cannot be removed by recrystallization.

[Edited on 28-6-2025 by ManyInterests]

Axt - 28-6-2025 at 11:38

I wouldn't conflate acetic anhydride processes with the others since it's running a different path with differing acetylated side products.

The patent mentions cold water but usually purification by destruction of side products is done after nitrolysis, by crystallising into hot water (75C, 1.5mL per g of nitric acid used). This is then cooled, filtered and recrystalised from acetone. Check MP ~204C.

[Edited on 28-6-2025 by Axt]

ManyInterests - 28-6-2025 at 16:34

Quote: Originally posted by Axt  
I wouldn't conflate acetic anhydride processes with the others since it's running a different path with differing acetylated side products.

The patent mentions cold water but usually purification by destruction of side products is done after nitrolysis, by crystallising into hot water (75C, 1.5mL per g of nitric acid used). This is then cooled, filtered and recrystalised from acetone. Check MP ~204C.

[Edited on 28-6-2025 by Axt]


That sounds even easier!

nitropyrotech - 30-6-2025 at 18:52

Quote: Originally posted by Microtek  
For one mol hexamine with at least two mol AN, 100% yield would be two mol of RDX, not one. So, in theory, you should have gotten about 23 gram at 75% yield.
How sure are you that the nitric was 100% and free of NOx, and that the AN was completely dry.

I didnt make my AN on my own, I ve bought 100kg or so in bulk a few months ago, from a east european supplier, the nitric acid was made by 1.1 mol ammoniumnitrate and 98% distilled sulfuric acid, than the collected distillate was vacuum distilled again to obtain WFNA, the hexamine was also obtained from an east european supplier, and every chemcial was sealed and stored properly so that shouldnt be a problem. and yes in theroy I should get 2 mols rdx but I didnt even got close to 1 mol. but thats maybe because I needed to let the end product crash longer I only letted it crash 1 min or so after the synthesis to crash in the ice water

Microtek - 1-7-2025 at 00:51

In my experience, water content in the AN can dramatically lower your yield, and will practically guarantee that your AN is not anhydrous. Try heating it at 120 C in the oven. If it "melts", that means that the is significant amounts of water in the crystals. If this is the case, you need to dry it at lower temps for many hours, 50 C for 12-24 hours is a decent starting point. It will be advantageous if you can ventilate it while you heat.
A more efficient way to dry it may be to ramp up the heat during the drying cycle.

ManyInterests - 1-7-2025 at 16:45

Yeah, I think I will absolutely need to super dry my AN the next time I use it for anything. I will go slightly above the melting point, since AN is a fairly fragile material.

But I think the next time I will use ammonium sulfate instead. It seems better. Once I distill more nitric acid, I will not use more than 100ml of NO2 purged 98%. I know RDX can tolerate a little less concentrate, but I will do my best to reach that much. No more runaways!

Microtek - 2-7-2025 at 23:30

When drying AN, you wan't to avoid making it liquify. The water has a much harder time escaping from the much smaller surface area that way. That is the reason you need the lengthy low-temp drying; at just 80-100 C the solubility of the AN rises enough that it dissolves in the small amount of water in the crystals.

ManyInterests - 3-7-2025 at 16:26

Understood.

BTW, In terms of the nitric acid. I will be going on a bender making nitric acid again, but this time, I will bubble dry air through it to purge all NO2 from it first, and if I need to redistill it to make it 99%... well, I have some magnesium nitrate ordered, around 500 grams of it. I know that magnesium nitrate can be reused when used to further concentrate nitric acid, but can you tell me how it is done? I'd greatly appreciate that.

nitropyrotech - 3-7-2025 at 21:39

Quote: Originally posted by ManyInterests  
Understood.

BTW, In terms of the nitric acid. I will be going on a bender making nitric acid again, but this time, I will bubble dry air through it to purge all NO2 from it first, and if I need to redistill it to make it 99%... well, I have some magnesium nitrate ordered, around 500 grams of it. I know that magnesium nitrate can be reused when used to further concentrate nitric acid, but can you tell me how it is done? I'd greatly appreciate that.


I never done it that way I cant really tell, sorry. But I always vacuum distilled RFNA with an simple destillation setup and dont forget to use ice water as the cooling liquid for the liebig condenser the colder the better, I never use any other additives this method also doesnt require heating so just turn on the vacuumpump and wait till a clear or maybe with an light yellowish touch drops

Microtek - 4-7-2025 at 00:18

Magnesium nitrate works a lot like sulfuric acid, and is indeed reuseable (as is sulfuric acid). You just heat it to drive off the water, but be aware that a lot of residual nitric acid will be driven off as well.
IMO, the best way to use it is for the first distillation, taking the nitric from 60 % to around 85 %. Then the receiving flask is changed and the heat turned way up to get the Mg(NO3)2*xH2O as water free as possible to get it ready for reuse. I have a dedicated flask with it that I'll just dehydrate before use when I need it.
The collected ~85 % nittric is then redistilled (I prefer doing this from sulfuric acid) to get it above 95 %.

ManyInterests - 4-7-2025 at 04:28

Quote: Originally posted by Microtek  
Magnesium nitrate works a lot like sulfuric acid, and is indeed reuseable (as is sulfuric acid). You just heat it to drive off the water, but be aware that a lot of residual nitric acid will be driven off as well.
IMO, the best way to use it is for the first distillation, taking the nitric from 60 % to around 85 %. Then the receiving flask is changed and the heat turned way up to get the Mg(NO3)2*xH2O as water free as possible to get it ready for reuse. I have a dedicated flask with it that I'll just dehydrate before use when I need it.
The collected ~85 % nittric is then redistilled (I prefer doing this from sulfuric acid) to get it above 95 %.


I think that can work. My starting concentration will probably be higher...

and I hate to say this, but can we have a moment of silence for my heating mantle? It appears to have decided to stop working. I will need to have it replaced... Good thing Joanlab (a much better brand that the bullshit one I got) is having a big offer on 2000ml heating mantles, so I will get that one. This will make it my THIRD heating mantle so far... damn this is an expensive hobby.

ManyInterests - 31-12-2025 at 21:52

I am bumping this up because I finally got around to doing a proper RDX synthesis that didn't result in a runaway... during the addition of the hexamine.

I used around 91% HNO3 that was fully purged from all NO2 contamination (it was water white). I had around 188ml and to that I added 33.5g of ammonium nitrate, and after mixing I let it cool to -5C before I slowly added 29.5g of hexamine over a period of 4 hours and 30 minutes. The addition temperature never went about 6C. After this I allowed it to rise up to room temperature (my room was cold, so it was 16C) over a course of an hour and then I began the heating step by using hot water baths to allow for it to rise. At the 60C mark I did hear fizzing and some gas formation, but after I took it off heating that stopped. I let it rest for a bit before putting it back on heat, but when it hit the 65C mark the fizzing was much louder and I saw red gas forming and I immediately dunked the entire thing in my crash bucket.

The milky white solution of the crash water tells me I have RDX, and I proud of that since RDX is my biggest challenge in energetics and my last two synthesizes were runaways with no yield (due to NO2 formation) but this one worked at least to get me some yield. My main question is this: I didn't heat it to the 80C point to let the intermediaries be destroyed. Does this mean I will need to acid wash my RDX at a later date or was my heating and the runaway kinda sufficient for that?

Waffles SS - 2-1-2026 at 23:16

Urbanski in Chemistry and Technology of Explosives book on page 107 mentioned for make 1000kg RDX by K-method(nitric acid + ammonium nitrate)480-500 kg hexamine +4800 kg ammonium nitrate +8600 kg nitric acid needed

This means that 1 mole of hexamine requires much more than 2 moles of ammonium nitrate.

[Edited on 3-1-2026 by Waffles SS]

Microtek - 2-1-2026 at 23:26

Yes, just as it requires more than three moles of nitric acid...

Huahuang - 3-1-2026 at 05:31

Quote: Originally posted by ManyInterests  
I am bumping this up because I finally got around to doing a proper RDX synthesis that didn't result in a runaway... during the addition of the hexamine.

I used around 91% HNO3 that was fully purged from all NO2 contamination (it was water white). I had around 188ml and to that I added 33.5g of ammonium nitrate, and after mixing I let it cool to -5C before I slowly added 29.5g of hexamine over a period of 4 hours and 30 minutes. The addition temperature never went about 6C. After this I allowed it to rise up to room temperature (my room was cold, so it was 16C) over a course of an hour and then I began the heating step by using hot water baths to allow for it to rise. At the 60C mark I did hear fizzing and some gas formation, but after I took it off heating that stopped. I let it rest for a bit before putting it back on heat, but when it hit the 65C mark the fizzing was much louder and I saw red gas forming and I immediately dunked the entire thing in my crash bucket.

The milky white solution of the crash water tells me I have RDX, and I proud of that since RDX is my biggest challenge in energetics and my last two synthesizes were runaways with no yield (due to NO2 formation) but this one worked at least to get me some yield. My main question is this: I didn't heat it to the 80C point to let the intermediaries be destroyed. Does this mean I will need to acid wash my RDX at a later date or was my heating and the runaway kinda sufficient for that?

Can 91% nitric acid really give a noticeable yield? Although it’s true that even 88% nitric acid can achieve a decent yield for nitration when used in sufficient excess, 91% nitric acid is still using the ammonium nitrate method, which actually requires an even larger excess of nitric acid. Under such limited excess, being able to obtain any yield at all honestly surprises me. Your nitric acid usage is only about half of the industrial standard (98%), so I suspect the yield might be rather disappointing

Huahuang - 3-1-2026 at 05:42

Quote: Originally posted by Axt  
The Bachmann acetic anhydride process is predated by a patent by Trojan Powder Co. which uses just hexamine, 98% HNO3 and an ammonium salt. Interestingly the highest yield is reported from the addition of ammonium sulphate, not nitrate. 101g RDX from 70g hexamine (91% 1:1 molar eq.). It is quite heavy on the HNO3 use though.

I've never attempted to use ammonium sulphate, nor have I seen reports of anyone else trying. The process is copied below.

Mix 858g 98% nitric acid and 50g ammonium sulphate and cool to 7C.
Add 70g hexamine in portions letting temp jump 7-22C with each addition over 45min.
Stir for 5min after final addition then drown in 3L of ice water and filter.




I find the underlying mechanism here quite interesting. I speculate that the sulfate ion acts as an acid scavenger in this system, which prevents excessive decomposition of the intermediates under strongly acidic conditions, while at the same time having little to no detrimental effect on the activity of the nitronium ion. In fact, it may even associate with it in a way that effectively increases the equivalent concentration of the nitronium ion.

greenlight - 3-1-2026 at 08:43

Quote: Originally posted by Huahuang  
Quote: Originally posted by Axt  
The Bachmann acetic anhydride process is predated by a patent by Trojan Powder Co. which uses just hexamine, 98% HNO3 and an ammonium salt. Interestingly the highest yield is reported from the addition of ammonium sulphate, not nitrate. 101g RDX from 70g hexamine (91% 1:1 molar eq.). It is quite heavy on the HNO3 use though.

I've never attempted to use ammonium sulphate, nor have I seen reports of anyone else trying. The process is copied below.

Mix 858g 98% nitric acid and 50g ammonium sulphate and cool to 7C.
Add 70g hexamine in portions letting temp jump 7-22C with each addition over 45min.
Stir for 5min after final addition then drown in 3L of ice water and filter.




I find the underlying mechanism here quite interesting. I speculate that the sulfate ion acts as an acid scavenger in this system, which prevents excessive decomposition of the intermediates under strongly acidic conditions, while at the same time having little to no detrimental effect on the activity of the nitronium ion. In fact, it may even associate with it in a way that effectively increases the equivalent concentration of the nitronium ion.


I remember reading a paper on how the ammonium cation and its different salts affect nitrolysis reactions and yields years ago. I can't find it anywhere on the net, but I have most of it written down in one of my workbooks. It was quite interesting.

ManyInterests - 3-1-2026 at 22:00

Quote: Originally posted by Waffles SS  
Urbanski in Chemistry and Technology of Explosives book on page 107 mentioned for make 1000kg RDX by K-method(nitric acid + ammonium nitrate)480-500 kg hexamine +4800 kg ammonium nitrate +8600 kg nitric acid needed

This means that 1 mole of hexamine requires much more than 2 moles of ammonium nitrate.

[Edited on 3-1-2026 by Waffles SS]


Urbanski is one of the best authorities on energetics manufacturing, but I have to keep reminding myself that he talking about large scale industrial processes and not lab scale, hence the mentions of many tons of material.

But that being said, the method I used was the Knoffler method that was documented by Dugan Ashley. The only thing that I think I did wrong was simply not allowing it enough time at 50C or so before moving up to 60+C, which is why a runaway happened. Still the result is almost dry and it is snow white. I am not sure if it will need an acid purification or it is good to go for simple recrystalization at this point. I made RDX a long time ago with just nitric acid and no heating step, but I spent over a year observing the batches before dissolving them in azeotropic nitric acid for purification, and they had no noticeable change.

I made more nitric acid and I bubbled out most of the NO2 and it is a very pale yellow. I plan on using this one to turn my DNT to TNT, but I wonder if the yellow will cause problems if I were to use it for another synthesis of RDX.