Sciencemadness Discussion Board

Chemistry behind RDX

Metallus - 29-5-2019 at 02:20

Hello,
I'm interested in the chemistry behind explosives and their synthesis in general. In particular I want to know more about the synthesis of RDX from methenamine + HNO3 and the reasons behind all the temperature adjustments during its synthesis or how impurities affect the synthesis (eg NOx concentration, presence of sulfates or other salts, etc).

It's likely that there is already a thread with all this information, but looking for it proved to be difficult, considering the huge mole of forum posts on this subject. Most posts are about the procedure or cook recipes, without an in-depth explanation of the reasoning behind all those parameters or any "science" in general. So I want to know more about the "why"s rather than the "how"s.

1) Patent US2859215A on RDX synthesis gives a temperature range between -10 and +40°C. Some other recipes found in the web employ an ice-salt bath (-30°C). What changes with the temperature? The reaction is exothermic, so with lower T the theoretical yield increases at the expense of kinetics. In this sense, I assume the suggested 20-30°C operational temperature is a compromise between thermodynamics and kinetics. Is that correct? Or is it more of a safe temperature to avoid runaway or undesired reactions?

2) The addition of methenamine to WFNA has to be carried slowly. Is it because the reaction is dangerously exothermic and so it's necessary to let the mixture cool down a bit between each addition in order to easily maintain the temperature < 30°C?

3) After the two reactants are mixed, the temperature is quickly raised to 80°C. Is it to speed up the reaction? Why the temperature must be raised so quickly? What happens if it's raised gradually? Also why all that care to maintain it below 30°C in the first step if then you have to quickly raise the temperature? Or is the high temperature necessary to dissolve all the metenamine or rdx?

4) In order to precipitate the RDX crystals, the acid mixture is washed with cold water. Is it to counter the exothermic reaction between the leftover HNO3 and water? Or is it to more easily allow the precipitation of the crystals? Or both?

5) How do impurities affect the reaction? Especially NOx dissolved in HNO3 or the presence of sulfates or other salts: how do they influence the formation of unstable byproducts?

6) What is the most critical and dangerous step of this synthesis and why?

Mine is mostly scientific curiosity. Chemical reactions on the chart are often very simple but when you have to practically do it in reality, you have to take into account many things and make many adjustments, and so the actual procedure looks more complex. While for most industrial processes the reason behind each choice is justified, finding such info on topics like energetic materials production is more difficult.

It's ok even if you can redirect me to the related thread or link some textbook or paper or anything about it.

Thanks

[Edited on 29-5-2019 by Metallus]

markx - 29-5-2019 at 02:50

"Chemistry and Technology of Explosives", By T. Urbański has rather comprehensive information about the topic in nitramine related chapters. All the main production methods are discussed in satisfactory detail. It should at least give answers to some of your questions.

In general terms the cyclic nitramine formation takes place in a rather thick and complex "primordial soup" of the respective building blocks. There are countless ways these building blocks can stack themselves together forming a very wide array of products. The cyclic members are only one possible outcome from the reaction between nitration agents and the methenamine "fragments". Some of the byproducts are of linear configuration and these are sensitive end unstable.
The aim of the thermal and other control methods is to force the reaction towards the formation of the cyclic products and the breakup of the linear byproducts.
Especially the raising of temperature after the main synthesis is usually projected towards breaking up of the linear nitramine contaminants to yield a stable product. The nitration mixture is also diluted to some extent prior to rising of temperature so as to yield an oxydizing environment. In these conditions the linear nitramines are broken up and destroyed leaving the more stable cyclic products relatively unharmed as far as final yield goes.

VSEPR_VOID - 29-5-2019 at 18:01

There is so much interesting details in the post above. Explosive chemistry is wonderful.

I heard an expert once talk about how using wet nitric acid causes the final product to be unstable. I believe the reason had to do with radicals.

Microtek - 30-5-2019 at 02:05

As markx writes above, the exact mechanisms of RDX/HMX formation from the nitrolysis of hexamine is poorly understood (AFAIK). Researchers have been tinkering with the reaction conditions to give the highest yield of the purest product (some of this research has been done right here on SM), but exactly what happens at the molecular level as a consequence of altering these parameters simply isn't known to science (to the best of my knowledge).

Metallus - 31-5-2019 at 00:49

Thank you marks for the reference and thank you guys for your answers.

AndraDoria 13 - 15-6-2021 at 22:43

well these methods are valid for rdx type 1. Is it possible to produce type 2 rdx in an acetic anhydride free environment?

ManyInterests - 31-10-2022 at 22:31

Since I've finally made my first RDX synthesis. I do have some questions to ask about this as I found my yield to be really low (or is it supposed to be this low?) and I wonder if it is normal or not.

So what I did is this: The first thing I did was make HDN and use that as my starting nitration. as HDN is very hygroscopic, I first air dried it in order to remove all the acetone and any excess liquid before putting it in a container with calcium chloride to act as a dessicating agent. I did manage to successfully dry my HDN this way and using 20 grams of HDN and 98ml of WFNA (98%) that I had chilled in an icebath below -20C, I added the HDN slowly and stirred. The whole process took an hour and when the final addition of HDN was done, the temperature reached 0C, but never above. I continued to stir manually for almost 15 minutes before removing it from the ice bath and letting it rise to ambient temperature.

I then heated it in on my mantle to 50C and let it stay there for 5 minutes. I removed it from heat, but it didn't seem like the temp wanted to drop, so I placed the beaker in a room temperature water bath and the rising temp was brought under control. After this I let it cool down to room temp before dumping the liquid in ice cold distilled water and filtered off the RDX crystals and washed them with copious quantities of tap water to wash away all traces of acid. Once the water was acid free, I washed them still just in case.

After letting it dry and weighing everything, my final result was 10.38g of RDX. Is this supposed to happen? I know that it must be heated up to destroy any unwanted bits that could degrade it in long term storage (though I am unlikely to keep my RDX that long anyway. I just want to make the purest product that I can).

Was my yield really low? What is the best ratio of hexamine or HDN to WFNA? If anyone even has that ratio.

greenlight - 1-11-2022 at 08:57

I have made RDX a few times and from searching around here, these are the only details I could find:

http://www.sciencemadness.org/talk/viewthread.php?tid=63638

16 grams RDX from 25 grams dried HDN using 60 ml 99% WFNA.
Not the best but this was without adding anything else I have listed at bottom.

Your case is interesting as you have a large excess of acid which should maximise yield as the water by-product won't have as large a dilutent effect.

It is also strange that your reaction seemed like it was gaining exothermic momentum when taken off heat. The last heating step is there to push the reaction to completion but will result in a runaway if done too early. The fact that it "didn't seem like the temp wanted to drop" might be indicating that the nitrolysis wasn't entirely complete yet as heat energy is formed from making the bonds here.

I think maybe let it sit at room temperature (20-25°C) for a longer period of time after removing from ice when u attempt again. Then perform the heating step.

You could also try a small amount (a few grams) of ammonium nitrate dissolved in the nitric acid before chilling.
It works wonders for HMX yields and there is a couple of reasons. One is to do with deficiencies and the other is solely due to the ammonium ion. This has been proven in a paper where different nitrates (magnesium, copper, potassium, etc) were used in nitrolysis reactions and NH4 provided the highest product yields.

Another method is using nitric acid, ammonium nitrate, and acetic anhydride. This proves hard nowadays as the restriction status of acetic anhydride is extremely high due to illicit heroin manufacture.

ManyInterests - 1-11-2022 at 11:38

Quote: Originally posted by greenlight  
I have made RDX a few times and from searching around here, these are the only details I could find:

http://www.sciencemadness.org/talk/viewthread.php?tid=63638

16 grams RDX from 25 grams dried HDN using 60 ml 99% WFNA.
Not the best but this was without adding anything else I have listed at bottom.

Your case is interesting as you have a large excess of acid which should maximise yield as the water by-product won't have as large a dilutent effect.

It is also strange that your reaction seemed like it was gaining exothermic momentum when taken off heat. The last heating step is there to push the reaction to completion but will result in a runaway if done too early. The fact that it "didn't seem like the temp wanted to drop" might be indicating that the nitrolysis wasn't entirely complete yet as heat energy is formed from making the bonds here.

I think maybe let it sit at room temperature (20-25°C) for a longer period of time after removing from ice when u attempt again. Then perform the heating step.

You could also try a small amount (a few grams) of ammonium nitrate dissolved in the nitric acid before chilling.
It works wonders for HMX yields and there is a couple of reasons. One is to do with deficiencies and the other is solely due to the ammonium ion. This has been proven in a paper where different nitrates (magnesium, copper, potassium, etc) were used in nitrolysis reactions and NH4 provided the highest product yields.

Another method is using nitric acid, ammonium nitrate, and acetic anhydride. This proves hard nowadays as the restriction status of acetic anhydride is extremely high due to illicit heroin manufacture.


Acetic anhydride is not restricted in Canada (where I live) so I can get some but it seems like such an excess. I also have no access to ammonium nitrate (albeit I can make some with ammonia and nitric acid). I would rather use the fuming nitric and HDN method instead.

I used an excess of HNO3 because it is what Darian Ballard did. He did mention it was an excess of WFNA, but I wasn't sure how much. Since you said you put in 25g of HDN to 60ml WFNA, I will try that next time. we had similar yields, albeit you got slightly more than what I did (I got a little more than 50%, you seemed have gotten 64% of the starting HDN.
Quote:
It is also strange that your reaction seemed like it was gaining exothermic momentum when taken off heat. The last heating step is there to push the reaction to completion but will result in a runaway if done too early. The fact that it "didn't seem like the temp wanted to drop" might be indicating that the nitrolysis wasn't entirely complete yet as heat energy is formed from making the bonds here.

I think maybe let it sit at room temperature (20-25°C) for a longer period of time after removing from ice when u attempt again. Then perform the heating step.


Maybe I simply didn't let it cool on its own. This was my first real attempt at making RDX. I did make two attempts at making Keto-RDX, but the runaways I had really me think it wasn't worth it. I could have waited a few more minutes before putting the beaker in room temperature water. The fact that it started to cool down right away after I put the beaker in a cooler place very likely meant it that it was not a runaway.

I did let it stay at slightly below room temp for almost 20 minutes. Maybe the next time I will try to let it heat a little more before giving it the heat up.
Quote:
You could also try a small amount (a few grams) of ammonium nitrate dissolved in the nitric acid before chilling.
It works wonders for HMX yields and there is a couple of reasons. One is to do with deficiencies and the other is solely due to the ammonium ion. This has been proven in a paper where different nitrates (magnesium, copper, potassium, etc) were used in nitrolysis reactions and NH4 provided the highest product yields.


I can do that. As I don't have ammonium nitrate as i said, so I will use a little potassium nitrate instead. I know it won't get the highest yield, but if it can improve my RDX yields and add more HMX to the mix.

ShotBored - 11-11-2022 at 06:56

Quote: Originally posted by greenlight  


Another method is using nitric acid, ammonium nitrate, and acetic anhydride. This proves hard nowadays as the restriction status of acetic anhydride is extremely high due to illicit heroin manufacture.


I have been prepping AN/NA nitrolysis agent this way for some time, however I have found it difficult to prep the nitrolysis reagent accurately each time. This method leads to the offgassing of NOx and can have varying degrees of dissolved NOx in the final solution. The solution can vary from a light yellow to red-orange color and my final RDX purity can vary based on this. Cooling the NA down before addition leads to a messy, viscous slurry.

Has anyone explored a way to stabilize this preparation and prevent the NOx gassing during addition of the AN to the nitric?

ManyInterests - 5-1-2023 at 22:47

So I appear to be having problem with having a pure nitrate salt. My synths of sodium and potassium nitrates are always haphazard and while I have been able to make excellent azeotropic nitric acid with my stuff, fuming nitric acid has been more challenging. While I did make WFNA with my old sodium nitrate batch, my newer one is not being very cooperative with my first attempt with it to make WFNA. I ended up making an azeotropic nitric acid (around 70 to 72%. Excellent and super clean, but not WFNA). It could be because of the cooling in my condenser, but I am thinking it is due to the impurites in my sodium nitrate. Since I went through the sodium bicarbonate to turn my CAN into NaNO3, I think I might have used an excess of bicarbonate that caused this problem and partially neutralized my product. I will need to experiment further to make sure I don't add an excess of bicarbonate that could cause this problem. I used 300 grams of calcium-ammonium nitrate dissolved in 650ml of water (to remove the insolubles) and to the cooled filtered solution I added 316 grams of bicarbonate. I think 50 grams less bicarbonate might be more appropriate since that is probably how much insolubles there are in the CAN.

I know I can further purify HNO3 by a 2nd distillation with a 1:1 ratio of nitric acid and sulfuric acid, but I am curious if I can make RDX via 70% HNO3 in the presence of sulfuric acid and using HDN.

I've seen PETN successfully made not with WFNA but with 68-70% HNO3 and 95% H2SO4. Can the same be done with RDX or is WFNA strictly required here?

ShotBored - 6-1-2023 at 11:54
Quote:

I am curious if I can make RDX via 70% HNO3 in the presence of sulfuric acid and using HDN


No you cannot. When your HNO3 is below 98%, a slew of issues can arise. Low HNO3 can cause your RDX to have a heightened HMX content with a good amount of this HMX being alpha-variant, and heightened SEX/TAX impurities present. Due to the excess acetic anhydride present, the mixture will likely "gel" in your mixer. It will be a mess to clean up.

RDX's intermediates are also hydrolyzed by H2SO4. So I do not think using sulfuric acid is a good idea. WFNA or a 98% NA/NH4NO3 reagent is necessary.

ManyInterests - 6-1-2023 at 15:45

Sounds good.

Seems like my sodium nitrate synth right now is mostly not very good... I am going through a 2nd nitric acid pass and the way how the sulfuric acid I put in reacted with the sodium nitrate is telling me there is a lot of unreacted sodium bicarbonate in there. I am not sure why. But I will learn from it.

XeonTheMGPony - 7-1-2023 at 06:52

Quote: Originally posted by ManyInterests  
Quote: Originally posted by greenlight  
I have made RDX a few times and from searching around here, these are the only details I could find:

http://www.sciencemadness.org/talk/viewthread.php?tid=63638

16 grams RDX from 25 grams dried HDN using 60 ml 99% WFNA.
Not the best but this was without adding anything else I have listed at bottom.

Your case is interesting as you have a large excess of acid which should maximise yield as the water by-product won't have as large a dilutent effect.

It is also strange that your reaction seemed like it was gaining exothermic momentum when taken off heat. The last heating step is there to push the reaction to completion but will result in a runaway if done too early. The fact that it "didn't seem like the temp wanted to drop" might be indicating that the nitrolysis wasn't entirely complete yet as heat energy is formed from making the bonds here.

I think maybe let it sit at room temperature (20-25°C) for a longer period of time after removing from ice when u attempt again. Then perform the heating step.

You could also try a small amount (a few grams) of ammonium nitrate dissolved in the nitric acid before chilling.
It works wonders for HMX yields and there is a couple of reasons. One is to do with deficiencies and the other is solely due to the ammonium ion. This has been proven in a paper where different nitrates (magnesium, copper, potassium, etc) were used in nitrolysis reactions and NH4 provided the highest product yields.

Another method is using nitric acid, ammonium nitrate, and acetic anhydride. This proves hard nowadays as the restriction status of acetic anhydride is extremely high due to illicit heroin manufacture.


Acetic anhydride is not restricted in Canada (where I live) so I can get some but it seems like such an excess. I also have no access to ammonium nitrate (albeit I can make some with ammonia and nitric acid). I would rather use the fuming nitric and HDN method instead.

I used an excess of HNO3 because it is what Darian Ballard did. He did mention it was an excess of WFNA, but I wasn't sure how much. Since you said you put in 25g of HDN to 60ml WFNA, I will try that next time. we had similar yields, albeit you got slightly more than what I did (I got a little more than 50%, you seemed have gotten 64% of the starting HDN.
Quote:
It is also strange that your reaction seemed like it was gaining exothermic momentum when taken off heat. The last heating step is there to push the reaction to completion but will result in a runaway if done too early. The fact that it "didn't seem like the temp wanted to drop" might be indicating that the nitrolysis wasn't entirely complete yet as heat energy is formed from making the bonds here.

I think maybe let it sit at room temperature (20-25°C) for a longer period of time after removing from ice when u attempt again. Then perform the heating step.


Maybe I simply didn't let it cool on its own. This was my first real attempt at making RDX. I did make two attempts at making Keto-RDX, but the runaways I had really me think it wasn't worth it. I could have waited a few more minutes before putting the beaker in room temperature water. The fact that it started to cool down right away after I put the beaker in a cooler place very likely meant it that it was not a runaway.

I did let it stay at slightly below room temp for almost 20 minutes. Maybe the next time I will try to let it heat a little more before giving it the heat up.
Quote:
You could also try a small amount (a few grams) of ammonium nitrate dissolved in the nitric acid before chilling.
It works wonders for HMX yields and there is a couple of reasons. One is to do with deficiencies and the other is solely due to the ammonium ion. This has been proven in a paper where different nitrates (magnesium, copper, potassium, etc) were used in nitrolysis reactions and NH4 provided the highest product yields.


I can do that. As I don't have ammonium nitrate as i said, so I will use a little potassium nitrate instead. I know it won't get the highest yield, but if it can improve my RDX yields and add more HMX to the mix.


Magnesium Nitrate was recommended from my research.

ManyInterests - 7-1-2023 at 21:40

Well the company that formerly sold chemicals to anyone has changed their policy that they won't be shipping to residential addresses anymore. This means I would need to make my own magnesium nitrate to do that.

At any rate, I do have some ammonium nitrate now, I will be using that in my next synth. I actually forgot about that!

Pulverulescent - 8-1-2023 at 03:27

Quote: Originally posted by ManyInterests  
I would need to make my own magnesium nitrate to do that!

Making anhydrous magnesium nitrate is difficult and the normal hydrated form isn't a desiccant.

ManyInterests - 8-1-2023 at 16:22

So ammonium nitrate then.

At any rate, I am having some difficulties that I wasn't sure I had previously with making sodium nitrate (and possibly the potassium nitrate that I have made last summer. But I am more worried about the sodium nitrate). It was using them as the nitrate salt in reactions. I am making nitric acid with what I believe is highly impure sodium nitrate. I am making good nitric acid with it, albeit despite my best attempts at making WFNA, the specific gravity only 1.4954 or so despite my best attempts. I realize it does need to be at least around 1.51 for it to be WFNA (I didn't take the temperature, but it is very cold).

I am thinking of starting another thread on the whole thing, but I want to do my own research first and some other experimentation.

But just one quick question here. To further concentrate nitric acid, the less than WFNA must be added with magnesium nitrate (which I don't have) or (more cheaply and easily that I can get) sulfuric acid to redistill and distill over the nitric acid while leaving the sulfuric behind, am I correct in this assumption?

Nurdrage uses a 1:1 of azeotropic nitric acid to sulfuric acid (albeit nurdrage said that an excess of nitric acid is fine). Most of my yields are on the upper end of RFNA, would a 1:1 still be good or a less amount of sulfuric acid is acceptable?

[Edited on 9-1-2023 by ManyInterests]

greenlight - 9-1-2023 at 10:19

Quote: Originally posted by ShotBored  
Quote: Originally posted by greenlight  


Another method is using nitric acid, ammonium nitrate, and acetic anhydride. This proves hard nowadays as the restriction status of acetic anhydride is extremely high due to illicit heroin manufacture.


I have been prepping AN/NA nitrolysis agent this way for some time, however I have found it difficult to prep the nitrolysis reagent accurately each time. This method leads to the offgassing of NOx and can have varying degrees of dissolved NOx in the final solution. The solution can vary from a light yellow to red-orange color and my final RDX purity can vary based on this. Cooling the NA down before addition leads to a messy, viscous slurry.

Has anyone explored a way to stabilize this preparation and prevent the NOx gassing during addition of the AN to the nitric?



Chilling the nitric acid right down in a salt ice bath in a small round bottom flask and adding the ammonium nitrate in very small portions with stirring seems to minimise the off gassing for me.

Yes, it is quite viscous and light yellow, but still works as a nitrolysis bath. You can always thin it out a little with a small extra portion of nitric acid as this won't cause any harm.

[Edited on 9-1-2023 by greenlight]

greenlight - 9-1-2023 at 10:35

Quote: Originally posted by ManyInterests  
So ammonium nitrate then.

At any rate, I am having some difficulties that I wasn't sure I had previously with making sodium nitrate (and possibly the potassium nitrate that I have made last summer. But I am more worried about the sodium nitrate). It was using them as the nitrate salt in reactions. I am making nitric acid with what I believe is highly impure sodium nitrate. I am making good nitric acid with it, albeit despite my best attempts at making WFNA, the specific gravity only 1.4954 or so despite my best attempts. I realize it does need to be at least around 1.51 for it to be WFNA (I didn't take the temperature, but it is very cold).

I am thinking of starting another thread on the whole thing, but I want to do my own research first and some other experimentation.

But just one quick question here. To further concentrate nitric acid, the less than WFNA must be added with magnesium nitrate (which I don't have) or (more cheaply and easily that I can get) sulfuric acid to redistill and distill over the nitric acid while leaving the sulfuric behind, am I correct in this assumption?

Nurdrage uses a 1:1 of azeotropic nitric acid to sulfuric acid (albeit nurdrage said that an excess of nitric acid is fine). Most of my yields are on the upper end of RFNA, would a 1:1 still be good or a less amount of sulfuric acid is acceptable?

[Edited on 9-1-2023 by ManyInterests]


I start with 62% nitric acid and use double its volume of concentrated sulfuric acid when distilling for higher purity.

The resulting yellow ~85-90% nitric acid can then be either vacuum distilled or dry air bubbled through it.

Vacuum distilling requires very gentle heat and is definitely not the best thing to expose pumps to, even with a base trap in between the rig and pump. I have used this method before though to obtain WFNA.

A better method to WFNA is by bubbling dry air through it to remove the trapped nitrogen (di)oxides. The air must be dry though otherwise it will result in dilution.
I usually fully submerge a fish pond air pump underneath fresh calcium chloride im a small container so the air is pulled through it first. An in-line drying tube could be rigged up alternatively which would be more cost efficient.
Warming the acid on a hotplate with stirring and dry air bubbling results in some nasty fumes during the process and some water white highly fuming acid at the end.
Thankfully, it doesn't take too long to perform.

The acid is good to use for any nitrolysis after.

Make it to use soon after, cause damn that stuff is a bitch to store.
It has turned one of my schott duran GL 45 blue lids completely white around where it was contacting the fumes inside the bottle.

Herr Haber - 9-1-2023 at 13:35

The blue caps are just PP so it's not surprising ;)
It's a bitch to store even with the better PFA caps !

ManyInterests - 9-1-2023 at 19:17

Quote:

A better method to WFNA is by bubbling dry air through it to remove the trapped nitrogen (di)oxides. The air must be dry though otherwise it will result in dilution.
I usually fully submerge a fish pond air pump underneath fresh calcium chloride im a small container so the air is pulled through it first. An in-line drying tube could be rigged up alternatively which would be more cost efficient.
Warming the acid on a hotplate with stirring and dry air bubbling results in some nasty fumes during the process and some water white highly fuming acid at the end.
Thankfully, it doesn't take too long to perform.


Yes! I actually remembered that method. I don't have a strong air pump, but a very small pump (pictured below). It works for my vacuum filter and I did bubble through azeotropic nitric acid to clean it up (it worked fine) though when I did the method of putting it in calcium chloride I must have done it improperly because while it did nicely clean up my acid, it did result in a dilution.

I saw a youtube video where someone used a gas washing bottle filled with calcium chloride in order to bubble something. I tried to make my own gas washer out of a coke bottle but the pump wasn't strong enough, or my makeshift gas wash bottle was too big. I ordered a gas washing bottle (a small one) that I hope will work. I need to make sure it'll do the trick when it arrives. I will cover the pump and the gas wash bottle with calcium chloride and I hope that it will both clean everything up and dry up the 95% or so HNO3 and bring it up to 99%.
Quote:
The blue caps are just PP so it's not surprising ;)
It's a bitch to store even with the better PFA caps !


I will use the acid immediately after. Right now I am storing 255ml or so of my 95% nitric acid in a 375ml liquor bottle. The cap is made of plastic and is NOT screwed on. I put it in a plastic bag with sodium carbonate in it to neutralize the fumes coming out. It is in a corner where I cannot easily knock it down by accident.

my gas wash bottle cannot come fast enough!

370-Mini-Air-Pump-3-7V-6V-12V-Electric-Micro-Vacuum-Booster-Motor-For-Beauty-Instrument.jpg_Q90.jpg - 24kB

B(a)P - 9-1-2023 at 20:12

I use air from a cylinder to clean up my nitric acid.
I scuba dive so have access to cheap, clean and dry air, not an option for everyone obviously.

greenlight - 10-1-2023 at 10:38

Quote: Originally posted by Herr Haber  
The blue caps are just PP so it's not surprising ;)
It's a bitch to store even with the better PFA caps !


Oh wow, I thought they were made of something tougher than that haha. No wonder I've had to replace a few.

greenlight - 10-1-2023 at 10:43

Quote: Originally posted by ManyInterests  
Quote:

A better method to WFNA is by bubbling dry air through it to remove the trapped nitrogen (di)oxides. The air must be dry though otherwise it will result in dilution.
I usually fully submerge a fish pond air pump underneath fresh calcium chloride im a small container so the air is pulled through it first. An in-line drying tube could be rigged up alternatively which would be more cost efficient.
Warming the acid on a hotplate with stirring and dry air bubbling results in some nasty fumes during the process and some water white highly fuming acid at the end.
Thankfully, it doesn't take too long to perform.


Yes! I actually remembered that method. I don't have a strong air pump, but a very small pump (pictured below). It works for my vacuum filter and I did bubble through azeotropic nitric acid to clean it up (it worked fine) though when I did the method of putting it in calcium chloride I must have done it improperly because while it did nicely clean up my acid, it did result in a dilution.

I saw a youtube video where someone used a gas washing bottle filled with calcium chloride in order to bubble something. I tried to make my own gas washer out of a coke bottle but the pump wasn't strong enough, or my makeshift gas wash bottle was too big. I ordered a gas washing bottle (a small one) that I hope will work. I need to make sure it'll do the trick when it arrives. I will cover the pump and the gas wash bottle with calcium chloride and I hope that it will both clean everything up and dry up the 95% or so HNO3 and bring it up to 99%.
Quote:
The blue caps are just PP so it's not surprising ;)
It's a bitch to store even with the better PFA caps !


I will use the acid immediately after. Right now I am storing 255ml or so of my 95% nitric acid in a 375ml liquor bottle. The cap is made of plastic and is NOT screwed on. I put it in a plastic bag with sodium carbonate in it to neutralize the fumes coming out. It is in a corner where I cannot easily knock it down by accident.

my gas wash bottle cannot come fast enough!


A gas washing bottle will be even better than what I had set up. As long as the air is passing though a decent length cylinder of anhydrous calcium chloride you should be able to get away with just the bottle. You can cover the pump as well for extra measure if you want to of course. Calcium chloride is cheap and easy to get, 99% nitric acid not so much

Another way is to find the inlet of the pump and attach a tube packed with some calcium chloride to it.

ManyInterests - 10-1-2023 at 19:22

My gas wash bottle is quite small, so I will need to do extra of filling the bottle AND covering my upcoming air pump (it's an air mattress and pool/beach toy pump with both vacuum and pump. It should work very well for anything I need pumping for.). I have a 450 gram unopened bag of calcium chloride that I bought and I will be filling the bottle up as much as I can and cover the air in-take section of the pump completely with calcium chloride. I will need to make an improvised setup to make sure that I have as dry of a setup as possible.

Heat the acid to 50C (with a water bath) and keep pumping dry into it. I pray that this will succeed. I might make more nitric acid tomorrow and practice on making clean, concentrated WFNA and make it well.

greenlight - 12-1-2023 at 12:14

Quote: Originally posted by ManyInterests  
My gas wash bottle is quite small, so I will need to do extra of filling the bottle AND covering my upcoming air pump (it's an air mattress and pool/beach toy pump with both vacuum and pump. It should work very well for anything I need pumping for.). I have a 450 gram unopened bag of calcium chloride that I bought and I will be filling the bottle up as much as I can and cover the air in-take section of the pump completely with calcium chloride. I will need to make an improvised setup to make sure that I have as dry of a setup as possible.

Heat the acid to 50C (with a water bath) and keep pumping dry into it. I pray that this will succeed. I might make more nitric acid tomorrow and practice on making clean, concentrated WFNA and make it well.


If the air is dry it will definitely succeed and your setup sounds solid so don't worry about that.

The process will be more efficient if you also have the acid on stir. This will get all the molecules moving around even more and increase the number of collisions with the dry air. The heat (50°C) will also increase reaction rate and effective collisions.

Best of luck and dont forget to post your results :)

ManyInterests - 13-1-2023 at 18:52

I didn't stir, maybe I should have, but I think it is ultimately OK.

So some things to note about what I did. From a starting 325ml I ended up with just around 290 or so ml, a little less than 300. It is cloudy, but that is because a small piece of calcium chloride managed to get blown in the acid. I am not sure how, but it happened.

The specific gravity is less than what I expected. Around only 1.47 in total, but I don't think that is the end all be all of it for two reasons.

1: it fumes white as hell. I mean massive clouds of white, that is one characteristic of WFNA (hence the name, White fuming nitric acid). That haze you see in one of the pics are the fumes.

2: It burned a huge smoldering hole in a nitrile glove that I drizzled an itty bitty bit on it. Not even 0.5ml, but it let a tiny drop go and it made a huge hole burning hole. I did not see flames. But it was there. This is another characteristic of WFNA.

I think that despite the lower SG, it should still work. It is mildly cloudy due to the piece of calcium chloride, but that shouldn't be a problem.

Either way this is a huge learning experience. I will use it for RDX synthesis. Like all of it. Wish me luck.

Picture below is my setup and the final results.

IMG_20230113_205236391_-_Copy.jpg - 2.1MB IMG_20230113_205240939_-_Copy.jpg - 1.7MB IMG_20230113_205727375_-_Copy.jpg - 2.4MB

[Edited on 14-1-2023 by ManyInterests]

ManyInterests - 14-1-2023 at 22:20

On second thought (I cannot edit my message for some reason) I decided to not go for an RDX synth since I really don't think that it will work. the specific gravity is too low. Perhaps it is closer to 90%, which is not good enough

I did see Darian Ballard's video where he made PETN using 68% HNO3 and 98% H2SO4. I am going to try to use that method. I did make ETN using stronger nitric acid with sulfuric acid added, so I believe this should work.

Edit: the use of my 90% HNO3 to make PETN has been a 'good' success. I say that because when I was trying to heat the nitrating mixture I did see some mild brown fumes start to appear that indicated the start of the runaway. I realize that I could not keep the heat for longer and I needed to dump it in water. Due to the fact that I was using 98% pentaerythritol I did see a bit of yellowing as well, but over all the I find the yield to be good (haven't weighed it yet) and I was able to wash out the impurties with a ton of water and a few hot sodium bicarbonate washes.

The sodium bicarbonate wash is not something I've done previously. I think I should include it in all nitrations from now on since... wow. I thought I cleaned up all the acid with just water, but I was wrong. There was a lot of other impurities that the bicarbonate wash removed, and that is good.

[Edited on 16-1-2023 by ManyInterests]

greenlight - 16-1-2023 at 10:29

Quote: Originally posted by ManyInterests  
I didn't stir, maybe I should have, but I think it is ultimately OK.

So some things to note about what I did. From a starting 325ml I ended up with just around 290 or so ml, a little less than 300. It is cloudy, but that is because a small piece of calcium chloride managed to get blown in the acid. I am not sure how, but it happened.

The specific gravity is less than what I expected. Around only 1.47 in total, but I don't think that is the end all be all of it for two reasons.

1: it fumes white as hell. I mean massive clouds of white, that is one characteristic of WFNA (hence the name, White fuming nitric acid). That haze you see in one of the pics are the fumes.

2: It burned a huge smoldering hole in a nitrile glove that I drizzled an itty bitty bit on it. Not even 0.5ml, but it let a tiny drop go and it made a huge hole burning hole. I did not see flames. But it was there. This is another characteristic of WFNA.

I think that despite the lower SG, it should still work. It is mildly cloudy due to the piece of calcium chloride, but that shouldn't be a problem.

Either way this is a huge learning experience. I will use it for RDX synthesis. Like all of it. Wish me luck.

Picture below is my setup and the final results.



[Edited on 14-1-2023 by ManyInterests]


The loss in volume happened to me too when I used this method. I think it is due to the added temperature and agitation from the air bubbling in.

The specific gravity will read higher when the dissolved nitrogen dioxide is present in the acid so you will get a drop in density after you have removed it.

The fact that it is fuming so heavily is a good sign. The name red/white fuming is to describe the colour of the acid not the colour of the fumes (white fuming =clear colour).

The reaction with the glove is interesting. I tested with the red acid and the gloves smoked and then auto-ignited but I don't think I ever tested with the clear stuff. Maybe the dissolved NOx has an effect on reaction or you do have a bit of water or something mixed in there.

Here is an old picture of mine, looks as harmless as water in there:




Screenshot_20230114-173626_Gallery.jpg - 1.3MB

[Edited on 16-1-2023 by greenlight]

greenlight - 16-1-2023 at 10:46

Quote: Originally posted by ManyInterests  
On second thought (I cannot edit my message for some reason) I decided to not go for an RDX synth since I really don't think that it will work. the specific gravity is too low. Perhaps it is closer to 90%, which is not good enough

I did see Darian Ballard's video where he made PETN using 68% HNO3 and 98% H2SO4. I am going to try to use that method. I did make ETN using stronger nitric acid with sulfuric acid added, so I believe this should work.

Edit: the use of my 90% HNO3 to make PETN has been a 'good' success. I say that because when I was trying to heat the nitrating mixture I did see some mild brown fumes start to appear that indicated the start of the runaway. I realize that I could not keep the heat for longer and I needed to dump it in water. Due to the fact that I was using 98% pentaerythritol I did see a bit of yellowing as well, but over all the I find the yield to be good (haven't weighed it yet) and I was able to wash out the impurties with a ton of water and a few hot sodium bicarbonate washes.

The sodium bicarbonate wash is not something I've done previously. I think I should include it in all nitrations from now on since... wow. I thought I cleaned up all the acid with just water, but I was wrong. There was a lot of other impurities that the bicarbonate wash removed, and that is good.

[Edited on 16-1-2023 by ManyInterests]


I think you definitely should have gone for glory and had a go at the RDX synthesis, maybe with a bit longer heating before crashing into ice. From what you described apart from the glove reaction your acid seemed fine, you may have just got a little less yield depending on water content if that was the impurity. I'm confident you wouldn't have just ended up with nothing.

Yes, PETN is quite forgiving with acid strength l, I have used as low as 62% nitric acid before and still got decent yields but I usually use 70% and I don't notice a difference.
It is a different nitration mechanism though forming a nitrate ester bonding the nitrogen to an oxygen whereas with RDX your bonding the nitrogen to another nitrogen (nitrolysis) in simple terms. Water is your main by-product when nitrating alcohol and doesnt interfere with the nitration so it's prevention from the reaction mixture (within reason) is not required, the sulfuric acid does the job of "holding the water out of the way".


The yellowing and mild brown fumes during your synthesis are both big warning signs of a runaway. Always have a bucket of water at the ready or just turn it on its side in the ice bath if one properly starts because you can't stop it when it kicks off and not being able to quickly quench it is dangerous.

The repeated washing with weak sodium bicarbonate solution is a very important step and should never be skipped. I am glad you have done that, if done thoroughly you can store it safely til use.

I usually recrystallise my PETN by dissolving in hot acetone and then dripping into a ice water solution with heavy stirring and a small amount of bicarbonate or ammonia to mop up any excess acid stuck in there. This results in uniform grains that do not stick to things like the original dust and is storage stable. I have a sample from 2017 with no signs or degradation or acidity.



[Edited on 16-1-2023 by greenlight]

ManyInterests - 17-1-2023 at 16:22

Quote:
The loss in volume happened to me too when I used this method. I think it is due to the added temperature and agitation from the air bubbling in.

The specific gravity will read higher when the dissolved nitrogen dioxide is present in the acid so you will get a drop in density after you have removed it.

The fact that it is fuming so heavily is a good sign. The name red/white fuming is to describe the colour of the acid not the colour of the fumes (white fuming =clear colour).

The reaction with the glove is interesting. I tested with the red acid and the gloves smoked and then auto-ignited but I don't think I ever tested with the clear stuff. Maybe the dissolved NOx has an effect on reaction or you do have a bit of water or something mixed in there.

Here is an old picture of mine, looks as harmless as water in there:


Yeah, getting it water white is quite exciting when you also realize just how deadly the whole thing is!

And I will be trying again with this method in the future. Maybe it won't be the 98% minimum that I am looking for, but I actually believe that it will get RDX. I think the first time I did RDX synth (it was yellow-tinted with a specific gravity of around 1.50-something. But that was a while ago) I only got around a 50% yield from the HDN I used. While 50% is quite little, it is better than nothing. I consider making RDX to be the most challenging not because of the dangers involved, but simply that getting a good yield is so difficult. With every other nitrated stuff I've done, you always end up with more than you start, but with RDX it is the opposite.
Quote:


I think you definitely should have gone for glory and had a go at the RDX synthesis, maybe with a bit longer heating before crashing into ice. From what you described apart from the glove reaction your acid seemed fine, you may have just got a little less yield depending on water content if that was the impurity. I'm confident you wouldn't have just ended up with nothing.

Yes, PETN is quite forgiving with acid strength l, I have used as low as 62% nitric acid before and still got decent yields but I usually use 70% and I don't notice a difference.
It is a different nitration mechanism though forming a nitrate ester bonding the nitrogen to an oxygen whereas with RDX your bonding the nitrogen to another nitrogen (nitrolysis) in simple terms. Water is your main by-product when nitrating alcohol and doesnt interfere with the nitration so it's prevention from the reaction mixture (within reason) is not required, the sulfuric acid does the job of "holding the water out of the way".


The yellowing and mild brown fumes during your synthesis are both big warning signs of a runaway. Always have a bucket of water at the ready or just turn it on its side in the ice bath if one properly starts because you can't stop it when it kicks off and not being able to quickly quench it is dangerous.

The repeated washing with weak sodium bicarbonate solution is a very important step and should never be skipped. I am glad you have done that, if done thoroughly you can store it safely til use.

I usually recrystallise my PETN by dissolving in hot acetone and then dripping into a ice water solution with heavy stirring and a small amount of bicarbonate or ammonia to mop up any excess acid stuck in there. This results in uniform grains that do not stick to things like the original dust and is storage stable. I have a sample from 2017 with no signs or degradation or acidity.


I will be washing out my old ETN with hot bicarbonate water after this. This is even though I used a urea infused methanol recrystalization for the whole thing, so I believe that should have done away with all acids even if there was still a bit left. But I want to be sure.

Also I might want to do that with the RDX sample that I made. I still haven't recrystalized it since I only had 10 grams of it. I thought I would make a few more batches before I bothered. But I will give it a wash regardless.

I will be doing a recrystalization of the PETN that I made soon. I kept it drying for a day then crumbled up the chunks (there was a lot of moisture trapped there) and set it to dry again. I will be adding around 4ml of 28% ammonia to the hot acetone before crashing it out in 1% urea water. Then I will be giving it a final wash after filtering.

Edit: Yeah, I wanted to also mention that the next time I try for WFNA even after blowing it with dry air I will use it for RDX. I think I might end up with another 50% yield, but 50% is not 0%, which is fine.

Also the yellowing of the PETN mixture was happening well before that, which is why I thought it was more to do with the impurities. What I will do in my next PETN synth, however, is to maybe double the time I have in adding the PE to the mixture. I was mildly in a hurry because I did hear from Darian Ballard that yellowness means that the impurities are ruining the final product, which is why I figured I wanted to get this stuff done more quickly.

I guess my time frame was off. At any rate, the yellowness was there before I brought it on the heat. When I was bringing it up to room temperature putting it back in the ice bath certainly brought the temperature down quite readily. The temperature was rising when I got it out of the ice bath, but that is to be expected. I set my room temp around 25C, but the area near the floor is actually colder than higher up. What I should have done is obviously let it stay at room temp for a good long time (like 25 or 35 minutes) to make sure that no runaway is happening before I turn the heat up on it. But it was the yellowness that was already there that made me worried about the whole thing.

Next time I won't worry as much about the yellowness when adding the PE. Also I will try to let the addition temperature be higher than what it started. I originally tried to keep the temperature at 0C or less throughout, this became untenable as the additions went on, but I did let the whole setup cool further outside instead of putting it back in my freezer. The temperature at that time was -4C (it is snowy where I live) so the ambient temperature was going to pull the overall temp back down no matter what, and I would rather have a runaway happen outside than I would in my freezer for very obvious reasons.

Perhaps letting a lot of the addition happen more slowly and at higher temperatures will prevent temperature spikes. Just obviously don't let it go beyond 15C for obvious reasons.


Edit 2: I weighed out the dry PETN (before recrystalization) yeah I was right when I thought I was cutting my losses. The yield is far from the 2.2x the yield that others had, but still, it is a respectable yield.


Edit 3: OK an update after recrystalization... wow! This was funny! I used a large excess of acetone and I added 3.5ml of 28% ammonia water to it, and I prepared a water tub with 3000ml of ice cold water with 2.5 gram to 3 grams of urea dissolved in it for use.

When I dissolved my PETN in the acetone the whole solution turned... orange! I don't know why but it did. I've never seen that happen in any video or mentioned anywhere. There must have been a lot of impurities in my stuff. after that, it took a long time to just get the liquid on top filtered off and I needed to change filters many times since they got saturated with something or the other. I added much more water to the filtered water to see if any PETN precipitated out, but none did, so I believe I didn't lose anything. But there was a LOT of stuff I needed to get out of there. After I finally got to getting my PETN in the filters I gave the stuff a few washes with warm water and I took a pH test on the liquid. It was either 6.5 or 7, either way it was clean of pretty much all acids and it should be OK for a good long time. I wonder why it was like that when it was almost slightly basic when I washed it before recrystalization.

But the recrystalization liberated a LOT of crap that needed to go. I am so glad I did it quickly.

[Edited on 18-1-2023 by ManyInterests]

[Edited on 18-1-2023 by ManyInterests]

[Edited on 18-1-2023 by ManyInterests]

ManyInterests - 28-5-2023 at 21:59

I thought I'd bump this thread up because of one question I have regarding HDN. I made some HDN a few months ago and when I first made it, I let it dry in a box with some calcium chloride in it, and since then I put it in a sealed tupperware. I opened that tupperware recently and there didn't seem to be any change in the HDN. But I am not sure if it is still dry or has absorbed some moisture.

So I have this question regarding drying HDN... is it possible to do so in the oven? What I am thinking of doing is to preheat my oven to 120C (the melting point of HDN is 170C or so) and then turning off my oven, and then putting in a glass baking dish with the HDN I wish to use and another glass baking dish with calcium chloride. Will this work to allow it to dry quickly and completely? Would there be any danger involved?

[Edited on 29-5-2023 by ManyInterests]

Hey Buddy - 30-5-2023 at 21:01

You can dry HDN in an oven, but Im not sure about the drying temp, (120 C is high in general) water can be driven off at much lower temperatures under 100 C, usually over a longer period of time. but I would strongly recommend against using any kitchen stuff that you use for food being double dutied for chemical processing of any kind. Personally, I would never use my kitchen food stove for any lab process other than maybe boiling water or drying chlorides.

ManyInterests - 30-5-2023 at 21:22

Maybe I will use a water bath and with a slightly lower temperature?

I would also wish to ask for advice regarding on my new nitric acid setup. If you can look at the picture I posted on my thread in beginnings.

Hey Buddy - 1-6-2023 at 13:54

Quote: Originally posted by ManyInterests  
Maybe I will use a water bath and with a slightly lower temperature?


I dont know if 120 C is too high for HDN. In general 120 C is high for drying temp. Perhaps yuo could test a small amount to see how it dries and handles drying at 120 C? Then drop temp if necessary. Who knows, maybe 120 C will be a good temp to dry it quickly?

ManyInterests - 26-8-2023 at 18:30

I am a very unhappy man right now.

So here is what happened, I managed to get 232ml of excellent quality WFNA (only a little yellow, with no red) and I decided to use it to finally make some good RDX after waiting a long time for this. I decided I wanted to use it all up, so I used 93g of HDN prepared (using the 25g to 60ml ratio that others have recommended) and I froze the beaker with the nitric acid in salt water. so after that, I used my magnetic stirrer to start stirring and over a period of 1 hour and 45 minutes or so, I added 63g of the HDN, the temperature did rise from the starting -9C to 18C, but as soon as I added a bit more HDN I decided that I needed to recool the ice bath. Even though there was still a wheel of ice in it, the additions were so exothermic that a lot of the ice around it did melt.

However once the temperature rose above 20C, I felt that either a major temperature spike was happening, or it was in the early stages of a runaway. There were no red fumes or anything, but it was rising steadily from 22C all the way to 29C and I decided that it was gonna run away. So I dumped the entire thing in a large tub of water instead of taking any risks.

So the usual process is that after the final bit of hexamine or HDN is added, it is allowed to reach room temperature and sit there for 20 minutes before the temperature is made to rise to 50C to destroy the impurities within it before cooling back down to room temperature and it is then crashed in a large amount of water.

I am not happy at all. But I need to see what needs to be done to salvage what I got now. So I wasn't able to heat everything up to destroy the impurities, would the recrystalization step remove them? Or can I after filtering and washing put the crude RDX in hot water to see if that helps? I need some assistance here.

I will not allow this to happen next time... It stinks to go through all the trouble and still have issues.

DennyDevHE77 - 26-8-2023 at 19:58

Even after the filtering step, no one prevents you from loading your RDX into 50-60% nitric acid, and heating it there at 60-65°C until the brown vapors stop emitting. Recrystallization in acetone as far as I know does not remove all impurities, it is carried out to remove intracrystalline acid. Not because it is dangerous for rdx (as for example with petn), but because releasing from the crystals during storage, can cause corrosion of ammunition and destruction of polymeric binders and components in mixed explosives.

I have encountered methods of purification by boiling in distilled water and acute steam treatment, but these were usually carried out after oxidative crystallization. That is, in fact, after the main purification.

[Edited on 27-8-2023 by DennyDevHE77]

ManyInterests - 26-8-2023 at 21:06

Quote: Originally posted by DennyDevHE77  
Even after the filtering step, no one prevents you from loading your RDX into 50-60% nitric acid, and heating it there at 60-65°C until the brown vapors stop emitting. Recrystallization in acetone as far as I know does not remove all impurities, it is carried out to remove intracrystalline acid. Not because it is dangerous for rdx (as for example with petn), but because releasing from the crystals during storage, can cause corrosion of ammunition and destruction of polymeric binders and components in mixed explosives.

I have encountered methods of purification by boiling in distilled water and acute steam treatment, but these were usually carried out after oxidative crystallization. That is, in fact, after the main purification.

[Edited on 27-8-2023 by DennyDevHE77]


Thank you. Yes, I am going to make more nitric acid anyway (you can never have too much of that when you're into energetics). And if all you need to do is put it in 50 or 60% HNO3 then that is what I will do. I will do it after drying them and very carefully for obviously reasons.

RDX has been a huge challenge for me, largely in making the appropriate strength HNO3 for the task. So I plan on trying to making a few more synthesis of it until I feel like I got the hang of it... and I will not hestitate to recool and refreeze the water if needed to bring the temperature down. I want to avoid runaways, but at least I am happy that I was well prepared for one and avoided any disaster.

I will put aside the current RDX I made this time in a separate container and mark it that it needs further purification.

DennyDevHE77 - 27-8-2023 at 20:49

I would just like to point out that such aggressive purification is only needed in the nitrolysis method of RDX synthesis.

In nitration of compounds with already formed sym-triazine ring, hexogen is already obtained with high purity and in fact may not require purification at all. These are such methods as nitration of cyclotrinitrosoamine, or nitration of "white salt" potassium perhydrotriazinetrisulfonate (synthesized from sulfamic acid, usually a descaler). Note that nitration can be done with ordinary sulfur-nitrogen mixtures, but the yield will drop slightly, ideally you need phosphoric anhydride, it is legal, but may be a little more expensive than sulfuric acid, although in my opinion, the use of phosphoric anhydride is the most convenient way specifically for this method of synthesis.

[Edited on 28-8-2023 by DennyDevHE77]

ManyInterests - 28-8-2023 at 11:39

Quote: Originally posted by DennyDevHE77  
I would just like to point out that such aggressive purification is only needed in the nitrolysis method of RDX synthesis.

In nitration of compounds with already formed sym-triazine ring, hexogen is already obtained with high purity and in fact may not require purification at all. These are such methods as nitration of cyclotrinitrosoamine, or nitration of "white salt" potassium perhydrotriazinetrisulfonate (synthesized from sulfamic acid, usually a descaler). Note that nitration can be done with ordinary sulfur-nitrogen mixtures, but the yield will drop slightly, ideally you need phosphoric anhydride, it is legal, but may be a little more expensive than sulfuric acid, although in my opinion, the use of phosphoric anhydride is the most convenient way specifically for this method of synthesis.

[Edited on 28-8-2023 by DennyDevHE77]


I assume by nitrolysis you mean mean using WFNA as the nitrating agent. I am aware there are other methods of making RDX, but I only know of two methods of making RDX. The first is using WFNA, and the second is using ammonium nitrate along with formaldehyde and acetic anhydride. Making acetic anhydride is a challenge for another time for me, but I have an unopened 1 liter bottle of formaldhyde and I can probably make some ammonium nitrate (and I will) in the future. Via the double displacement reaction of aqueous solutions of pure calcium nitrate and ammonium carbonate. Ammonium carbonate is pricey, but the end product will be much easier to purify since it will result in ammonium nitrate in solution while the calcium carbonate is practically insoluble in water, so recovering the ammonium nitrate will be very easy and only evaporating the water will be needed with no further purification.

I don't have access to phosphoric acid, but that is a method I have no considered. I do remember reading about it in one of Urbanski's books, I'll need to look back at them.

DennyDevHE77 - 28-8-2023 at 23:19

Quote: Originally posted by ManyInterests  


I assume by nitrolysis you mean mean using WFNA as the nitrating agent.


What I meant by nitrolysis was a type of nitration in which the C-N bond is broken in the organic substrate during nitration.

There are many methods of producing RDX:
1) Direct nitration of urotropine (or urotropine dinitrate) with concentrated nitric acid (oxidative method)
2) Method "K". Same, but ammonium nitrate is added to the nitric acid at a certain stage to condense the formaldehyde in the nitro mixture into additional urotropine and thus into additional RDX.
3) "Method E". Preparation of hexogen by condensation of paraform with ammonium nitrate in acetic anhydride, preferably (but not necessarily) with boron trifluoride catalyst.
4) "Bachmann-Ross Method". Essentially a combination of methods. Nitrolysis of urotropine by nitric acid with glacial acetic acid, acetic anhydride, and ammonium nitrate.
5) Nitration of 3,7-derivatives of 1,3,5,7-tetraaza[3,3,1,1]bicyclononanes (Known as DAPT and DPT). But this is probably not profitable as it is easier to prepare HMX from them.
6) Nitration of compounds with already formed sym-triazine ring. Cyclotrimethylene trinitrosoamine or nitration of the "white salt" of potassium perhydrotriazinetrisulfonate.
7) Rarer methods, such as nitration of urotropine with nitric acid, with acetic or phosphoric anhydride in the presence of ammonium nitrate and lithium nitrate. Or nitration of urotropine with nitrogen pentaoxide in tetrachloromethane or dichloropropylene.

I would also add that methods with acetic anhydride produce impurities of diacetoxytetramethylnitramine (BSX). Long-term boiling in water helps to remove it.

ManyInterests - 7-9-2023 at 08:00

I had no idea there were that many methods of making RDX. So far the thing that I have a problem with this is the yield. Of all of the energetics I made, I notice that RDX is the only one that gives you less back than the others.

Would the method with ammonium nitrate, acetic anhydride, and formaldehyde have a higher yield than the others? You did mention long-term boiling in water. What does that mean exactly? Like I would put the crude RDX in a large beaker of water and boil it for a few hours?

DennyDevHE77 - 8-9-2023 at 02:19

The yield of the formaldehyde method is as high as 80% (for formaldehyde) usually 60-70% (this is considered a lot of for RDX). But it should be taken into account that it should be in the form of paraform, not formalin. However, paraform is legal and not very expensive. RDX by this method is highly contaminated and requires additional purification by boiling with water and recrystallization (before purification m.p. is 190-195°С). After purification, the nitrolysis product typically consists of 93.4% RDX, 6% HMX and 0.6% 1-acetyl-3,5,7-trinitroazacyclooctane. Typically, 1 kg of RDX by this method requires 630-635 g paraform, 1800 g ammonium nitrate, 5-5.1 kg acetic anhydride, and optionally 19 g boron fluoride (it is not required, it just makes the reaction more easily controlled, and reduces the formation of HMX and other impurities)

And yes, you read me correctly, RDX is simply poured into 9-10 amounts of water, and boiled for a few hours. Dirty raw RDX contains many substances that reduce its stability. For example, dinitrotriaminotrimethylamine, which is partially converted into trinitrotriaminotrimethylamine, it is relatively stable in the cold, but above 60°С it decomposes, also formed trinitrodiaminodimethylamine [TDA], it can sometimes be up to 10%, but at 75-80°С it decomposes into formaldehyde, nitrous oxide and water. Well linear esters of nitramines, 1,9-diacetoxy-2,4,6,8-tetranitro-2,4,6,8-tetraazanonan and 1,7-diacetoxy-2,4,6-trinitro-2,4,6-triazoheptane (BSX). The above-mentioned substances are not a complete list of impurities in the reaction mass, but all of them decompose on boiling in water, it is especially important to get rid of BSX as it is very sensitive. Although of course boiling in dilute nitric acid is more effective. With nitric acid it is possible to obtain RDX with m.p. 203.5°С. And several recrystallizations from acetic acid will give almost chemically pure RDX with m.p. 204.5-205°С. I note that it is impossible to remove the 6-7% HMX impurity without proper recrystallization, but I think a home chemist does not need this. Moreover, in industry, RDX produced by the Bachmann-Ross method contains about 10% HMX and it is still not separated in order to avoid increased production costs.

I should note that recrystallization from acetone will also make RDX purer, but rapid infusion of RDX solution into water will cause the HMX impurity to fall out in the form of a sensitive α-form, which is highly sensitive, so that RDX will be somewhat more sensitive. This is why HMX used to be regarded as harmful additives to RDX, increasing their sensitive

In general, this method is more suitable for those who have a productive ketene lamp at home. And ideally, ammonium nitrate is freely sold in kilograms.
As an alternative, if you have formaldehyde, you can buy acetaldehyde and make pentaerythritol. Of course, this is worth doing if pentaerythritol cannot be purchased.
Sorry for the many letters, I just wanted to tell you as much as possible.

[Edited on 8-9-2023 by DennyDevHE77]

ManyInterests - 8-9-2023 at 12:02

Quote: Originally posted by DennyDevHE77  
The yield of the formaldehyde method is as high as 80% (for formaldehyde) usually 60-70% (this is considered a lot of for RDX). But it should be taken into account that it should be in the form of paraform, not formalin. However, paraform is legal and not very expensive. RDX by this method is highly contaminated and requires additional purification by boiling with water and recrystallization (before purification m.p. is 190-195°С). After purification, the nitrolysis product typically consists of 93.4% RDX, 6% HMX and 0.6% 1-acetyl-3,5,7-trinitroazacyclooctane. Typically, 1 kg of RDX by this method requires 630-635 g paraform, 1800 g ammonium nitrate, 5-5.1 kg acetic anhydride, and optionally 19 g boron fluoride (it is not required, it just makes the reaction more easily controlled, and reduces the formation of HMX and other impurities)

And yes, you read me correctly, RDX is simply poured into 9-10 amounts of water, and boiled for a few hours. Dirty raw RDX contains many substances that reduce its stability. For example, dinitrotriaminotrimethylamine, which is partially converted into trinitrotriaminotrimethylamine, it is relatively stable in the cold, but above 60°С it decomposes, also formed trinitrodiaminodimethylamine [TDA], it can sometimes be up to 10%, but at 75-80°С it decomposes into formaldehyde, nitrous oxide and water. Well linear esters of nitramines, 1,9-diacetoxy-2,4,6,8-tetranitro-2,4,6,8-tetraazanonan and 1,7-diacetoxy-2,4,6-trinitro-2,4,6-triazoheptane (BSX). The above-mentioned substances are not a complete list of impurities in the reaction mass, but all of them decompose on boiling in water, it is especially important to get rid of BSX as it is very sensitive. Although of course boiling in dilute nitric acid is more effective. With nitric acid it is possible to obtain RDX with m.p. 203.5°С. And several recrystallizations from acetic acid will give almost chemically pure RDX with m.p. 204.5-205°С. I note that it is impossible to remove the 6-7% HMX impurity without proper recrystallization, but I think a home chemist does not need this. Moreover, in industry, RDX produced by the Bachmann-Ross method contains about 10% HMX and it is still not separated in order to avoid increased production costs.

I should note that recrystallization from acetone will also make RDX purer, but rapid infusion of RDX solution into water will cause the HMX impurity to fall out in the form of a sensitive α-form, which is highly sensitive, so that RDX will be somewhat more sensitive. This is why HMX used to be regarded as harmful additives to RDX, increasing their sensitive

In general, this method is more suitable for those who have a productive ketene lamp at home. And ideally, ammonium nitrate is freely sold in kilograms.
As an alternative, if you have formaldehyde, you can buy acetaldehyde and make pentaerythritol. Of course, this is worth doing if pentaerythritol cannot be purchased.
Sorry for the many letters, I just wanted to tell you as much as possible.

[Edited on 8-9-2023 by DennyDevHE77]


My knowledge on making it via the formaldehyde/AN/acetic anhydride method comes from one of those Paladin press books. I know it is covered in better and more scientific detail elsewhere, but that is the first thing that comes to mind.

I only have 37% formaldehyde solution. I did find a seller for paraform on amazon.ca (I live in Canada) but it is quite expensive. Acetic Anhydride was sold by westlab.ca, but they stopped selling to individuals. I would need to start a company and have a business address if I am to buy anything from them again. As for ammonium nitrate, I believe it is sold in Canada and may not necessarily require paperwork. I did look at the gardening section of my local hardware store, I did find one that was marked 34-0-0 and for real cheap. This is normally ammonium nitrate, but the MSDS kept the actual contents secret, so while it is nitrogen rich, I really wasn't sure if I finally would have been able to get ammonium nitrate via a big bag and not have to go through the process of making it. In the end of the day I do plan on buying a 25kg bag of calcium nitrate, which is available without restriction (and for the price at which it is sold, it would be by far the most economical way to get nitrates where I live). With that I can make potassium and sodium nitrates easily(via potassium/sodium carbonates), as well as ammonium whenever I need it.

Can I turn formalin into paraform? Because I was unable to find any information on doing that. The book did state that regular formalin can work.

I am exploring various ways of making acetic anhydride. The ketene lamp is one of them, and sulfur chloride is another (albeit a stinky one) I did read that it was possible to make acetic anhydride with only sulfuric acid, anhydrous calcium chloride, and glacial acetic acid. I will attach the document below.


But overall, the method seems that it would need a lot of reagents. Certainly it would be prohibitive. It seems that when it comes to making RDX, I'll be stuck with smaller quantities. Because if I wanted to make 1kg of picric acid or TNT or most other energetics, I will need far less reagents. Not that I would really want a whole kilogram of the stuff! That is a lot.

Edit: Thanks for the info. I really do wants lots of info since it will leave little room for error when I go about making this stuff.

Attachment: AceticAnhydridePhosphorouspentoixde.pdf (1.5MB)
This file has been downloaded 400 times

[Edited on 8-9-2023 by ManyInterests]

DennyDevHE77 - 8-9-2023 at 23:50

Quote: Originally posted by ManyInterests  
Can I turn formalin into paraform?


Yes, this is how it is usually obtained by evaporating ordinary formaline under vacuum and separating the white flaky precipitate. I believe this also works at atmospheric pressure, but for a longer time and at lower temperatures.

And by the way, thank you for this method of producing acetic anhydride. I didn't know about him. So far my main method has been S2Cl2

[Edited on 9-9-2023 by DennyDevHE77]

ManyInterests - 9-9-2023 at 21:56

Quote: Originally posted by DennyDevHE77  
Quote: Originally posted by ManyInterests  
Can I turn formalin into paraform?


Yes, this is how it is usually obtained by evaporating ordinary formaline under vacuum and separating the white flaky precipitate. I believe this also works at atmospheric pressure, but for a longer time and at lower temperatures.

And by the way, thank you for this method of producing acetic anhydride. I didn't know about him. So far my main method has been S2Cl2

[Edited on 9-9-2023 by DennyDevHE77]


Yeah, those methods are preposterously simple. Glacial acetic acid and calcium chloride + a little sulfuric acid? That sounds really stupidly simple.

The only issue that I buy my calcium chloride online (I have an unopened bag with me) and I am not sure if it is anhydrous as is, or it needs to be dried more, and if it can be rendered anhydrous via oven drying (max 230 or so Celsius) or do I need to do it via a crucible and a blow torch.

Also my acetic acid is around 95% (specific gravity is just short of anhydrous). Now that I have a better way of controlling temperature on my mantle due to the thermometer adapter I got. I can make sure it never rises above the boiling point of glacial acetic acid and no water. I hope I will be able to do that without the need for molecular sieves.

For formalin, how much temperature are we talking about for a regular distillation? not vacuum.

DennyDevHE77 - 14-9-2023 at 21:29

We are not talking about distillation, but evaporation, partial evaporation. I can’t say the exact temperature, these are just guesses, and experimentation is needed here, I would try to warm the formalin to 70-80C to begin with, in the end, even at room temperature, paraform is formed, it usually falls to the bottom of the container with formaldehyde.

Another thing is that I’m not sure about the feasibility, it’s much easier for you to make RDX using the usual nitrogen method, if you don’t have a distiller, then make it with nitrate salts through sulfamic acid.

Or switch to mannitol/pentaerythritol

And calcium chloride is dehydrated at a red-hot temperature (600-700C). So an oven won't be enough.

[Edited on 15-9-2023 by DennyDevHE77]

Microtek - 14-9-2023 at 22:47

If you manage to produce acetic anhydride by that method, I suggest you look at the patents by Lukasavage on HMX. There are a number of them, but the ones on DADN -> SOLEX -> HMX are excellent. Essentially 100% yield and 100% purity. They do require P2O5 though, but only a small amount of acetic anhydride is needed for the DADN. It's a very economical procedure, more so than producing RDX.

DennyDevHE77 - 14-9-2023 at 23:27

Quote: Originally posted by DennyDevHE77  
with nitrate salts through sulfamic acid.


In brief, I will quote the method of manufacture from one person known in narrow circles.

1. Obtaining potassium PHTS (potassium perhydrotriazinetrisulfonate). 5 ml of 37% formalin solution is mixed with 10 g of potassium sulfamate, maintain pH = 8), add a few ml of water to dissolve all the sulfamate. Then add sulphamic acid (or any other acid) while stirring in small portions until pH = 5. Keep stirring and after a few minutes the mixture will become viscous from the white powder, keep the mixture for another 2 hours until the end of the reaction and filter it in the cold. Rinse on the filter with 2-3 ml of cold water and dry at room temperature (it is better to dry under a fan, e.g. computer cooler), Grind the dried potassium PGTS into flour. Unlike ammonium PHTS, potassium salt can be stored without problems.

It should be noted that to obtain potassium sulphamate it is better to take sulphamic acid of "pure" grade or higher.
If the technical grade is used, the sulphamic acid should be neutralised with potassium alkali or potassium salt to increase stability during storage
with potassium alkali or potash to pH = 8 and heat the solution for a few minutes until the ammonia odour disappears.

2) Obtaining of RDX proper:

15g of potassium nitrate is poured in two steps to 30ml of 97% sulphuric acid, stirring until the substrate is dissolved. The heated nitro mixture is cooled in a bowl of cold water.
Add a few ice cubes to the water, cooling to 5-10°C. The mixture of 12 g of potassium PHTS with 6 g of potassium nitrate is ground into a fine powder, divided into 5-6
portions and, stirring thoroughly, pour into the nitro-mixture for 10 min. It is desirable to avoid the formation of lumps.
Stir the mixture for another 10 minutes (the mixture thickens and becomes very viscous), then stir periodically for the next 30 minutes, adding a few ice cubes to the bowl of water every 10 minutes.
Then add a few ice cubes to the nitro mixture and stir thoroughly until the ice melts, wait a few minutes until most of the foam disappears and add 200ml of water.
Filter the hex suspension, rinse with water and then with soda solution on the filter and then again with water. Drying. The yield is 3.7g (56%).
For purification it is enough to warm the RDX in 50% nitric acid for a few minutes. Then you will get very pure RDX with melting point above 204C.
Ammonium PHTS can be used, but it is more difficult to dry (decomposes above 40-50°C), and cannot be stored for long periods. This is why the Germans in WWII preferred to nitrate the more expensive potassium salt

This method is good because it doesn't require nitric acid, and would probably work for those who can't distill >90% nitric acid. But getting RDX through nitric acid is generally faster and easier

In the sulfamate preparation step, if the pH is kept below 3, a sulfo derivative of DPT can be obtained. And nitrate it with sulphuric acid and nitrates, obtaining disulpho-dinitro-tetraazacyclooctane, but I do not remember how to convert it into octogenes, although there was some patent.

[Edited on 15-9-2023 by DennyDevHE77]

ManyInterests - 30-6-2024 at 13:55

Decided to bump this up since I have been working on making nitric acid again, and I am doing it using my new mantle which is being... problematic. despite making everything as dry as possible I am ending up with azeotropic nitric acid, and nothing wants to distill under 115c. I will figure it out with a few more experiements I am sure.

At any rate, I do almost 300ml of 70% nitric acid, how much would I need to dissolve it? I don't have the solubility of it in nitric acid.

greenlight - 30-6-2024 at 18:59

Quote: Originally posted by ManyInterests  
Decided to bump this up since I have been working on making nitric acid again, and I am doing it using my new mantle which is being... problematic. despite making everything as dry as possible I am ending up with azeotropic nitric acid, and nothing wants to distill under 115c. I will figure it out with a few more experiements I am sure.

At any rate, I do almost 300ml of 70% nitric acid, how much would I need to dissolve it? I don't have the solubility of it in nitric acid.


Are you referring to distilling a mixture of 70% nitric acid and concentrated sulphuric acid?

I used to use this method to obtain +90% red nitric to further purify thereafter into 99% white nitric.

I used double the volume of 98% sulphuric acid and just set up for standard atmospheric distillation. So for 300ml 70% nitric, I would have used 600ml 98% sulphuric acid. It is a large portion of sulphuric but it always resulted in nice yellow high purity nitric.

ManyInterests - 1-7-2024 at 05:31

Quote: Originally posted by greenlight  
Quote: Originally posted by ManyInterests  
Decided to bump this up since I have been working on making nitric acid again, and I am doing it using my new mantle which is being... problematic. despite making everything as dry as possible I am ending up with azeotropic nitric acid, and nothing wants to distill under 115c. I will figure it out with a few more experiements I am sure.

At any rate, I do almost 300ml of 70% nitric acid, how much would I need to dissolve it? I don't have the solubility of it in nitric acid.


Are you referring to distilling a mixture of 70% nitric acid and concentrated sulphuric acid?

I used to use this method to obtain +90% red nitric to further purify thereafter into 99% white nitric.

I used double the volume of 98% sulphuric acid and just set up for standard atmospheric distillation. So for 300ml 70% nitric, I would have used 600ml 98% sulphuric acid. It is a large portion of sulphuric but it always resulted in nice yellow high purity nitric.


I think you did mention that to me. Though I did wonder why double the volume. Nurdrage used equal volume of sulfuric acid to nitric acid.

That being said, for purifying my RDX... how much nitric acid is needed? I will obviously do some experiments, but I'd rather get some info first before barreling in.

[Edited on 1-7-2024 by ManyInterests]

Sir_Gawain - 1-7-2024 at 21:40

Quote: Originally posted by ManyInterests  

That being said, for purifying my RDX... how much nitric acid is needed? I will obviously do some experiments, but I'd rather get some info first before barreling in.

Are you planning on purifying your RDX by recrystallization from nitric acid? Or making RDX?

By the way, you can convert yellow nitric acid to WFNA by cooling to below 0C and adding a few drops of 30% hydrogen peroxide. It works much better than bubbling air through it.

ManyInterests - 2-7-2024 at 04:14

Quote: Originally posted by Sir_Gawain  
Quote: Originally posted by ManyInterests  

That being said, for purifying my RDX... how much nitric acid is needed? I will obviously do some experiments, but I'd rather get some info first before barreling in.

Are you planning on purifying your RDX by recrystallization from nitric acid? Or making RDX?

By the way, you can convert yellow nitric acid to WFNA by cooling to below 0C and adding a few drops of 30% hydrogen peroxide. It works much better than bubbling air through it.


I am looking to purify the RDX I already have, thus why I am using weaker nitric acid. I assume it won't be an exothermic reaction, but I will do it very slowly and monitor carefully anyway.

And... really? That simple? does it have to be RFNA or can such a method work with azeotropic nitric acid around 70%?

greenlight - 9-7-2024 at 10:55

Quote: Originally posted by ManyInterests  
Quote: Originally posted by greenlight  
Quote: Originally posted by ManyInterests  
Decided to bump this up since I have been working on making nitric acid again, and I am doing it using my new mantle which is being... problematic. despite making everything as dry as possible I am ending up with azeotropic nitric acid, and nothing wants to distill under 115c. I will figure it out with a few more experiements I am sure.

At any rate, I do almost 300ml of 70% nitric acid, how much would I need to dissolve it? I don't have the solubility of it in nitric acid.


Are you referring to distilling a mixture of 70% nitric acid and concentrated sulphuric acid?

I used to use this method to obtain +90% red nitric to further purify thereafter into 99% white nitric.

I used double the volume of 98% sulphuric acid and just set up for standard atmospheric distillation. So for 300ml 70% nitric, I would have used 600ml 98% sulphuric acid. It is a large portion of sulphuric but it always resulted in nice yellow high purity nitric.


I think you did mention that to me. Though I did wonder why double the volume. Nurdrage used equal volume of sulfuric acid to nitric acid.

That being said, for purifying my RDX... how much nitric acid is needed? I will obviously do some experiments, but I'd rather get some info first before barreling in.

[Edited on 1-7-2024 by ManyInterests]


I just learned that way from an old tutorial youtube video and have used it ever since and it has always resulted in quality acid so I never tweaked it. Theoretically, the more sulphuric floating around, the more molecules available to hold onto the water to a certain extent.

Are you talking about treating already prepared RDX with another nitric acid bath? I've never heard of this. Do you believe your product isn't fully nitrated?

ManyInterests - 11-7-2024 at 15:17

Quote:
Are you talking about treating already prepared RDX with another nitric acid bath? I've never heard of this. Do you believe your product isn't fully nitrated?


It isn't the the issue. When you are making RDX, the final step involves heating up the nitrating mixture in order to destroy some of the impurities within the solution. This is something that, obviously, must be done very carefully. I made two small RDX synthesis, the first one I neglected to it as I was afraid to heat everything up, the second time I had a temperature spike that I feared was going to become a runaway, so I took the safe route and dumped it in large quantities of water to prevent a possible disaster.

The result of this is that there are very likely impurities in the RDX that cannot be removed by recrystalizing everything in methanol or acetone. If you read above you'll see that I was advised to bring lower concentration nitric acid (50% would work, but I used around 65%) and heat it until it stops producing red fumes. I saw the fumes, they weren't large or out of control, after they stopped I let the mixture cool down and I crashed everything in large quantities of water. then I filtered and washed until it was pH neutral.

greenlight - 13-7-2024 at 10:10

When I have made RDX I have always performed the nitrolysis then after addition is complete, allow it to remain in the ice bath for extended time, then move it to room temperature for 15 minutes before the final warming step in a hot water bath.
Bond forming is an exothermic process hence the main reason why the ice bath and slow additions are required for nitrations and nitrolysis. This is why I believe that you notice much larger temperature spikes upon additions, in for example PETN synthesis at the beginning of the nitration. Towards the end, when a large portion of the bonding has occurred, spatulas of pentaerythritol can be added with minimal to no temp change.

Once the addition of HDN in your RDX synthesis is complete and it has been allowed to stir and remain in ice bath, the majority of the bonding has been completed and it is fine to slowly bring the temperature up, sit ant room temperature for a period (~15 mins), and then proceed with the heating step on a hot water bath before crashing in ice water.

As for the purification by weaker nitric acid, I have no information nor have I ever read of this being performed. It gives me bad feelings of not being safe. Does the additional water content in the weaker nitric acid have any detrimental effect do you think?
What was the product like after you performed this?
Do you have a melting point apparatus to get an idea of purity?



[Edited on 13-7-2024 by greenlight]

DennyDevHE77 - 15-7-2024 at 22:56

Quote: Originally posted by greenlight  
As for the purification by weaker nitric acid, I have no information nor have I ever read of this being performed. It gives me bad feelings of not being safe. Does the additional water content in the weaker nitric acid have any detrimental effect do you think?[Edited on 13-7-2024 by greenlight]


When synthesizing RDX a lot of by-products are formed, heating in 50-60% nitric acid solution allows to destroy all these impurities (and in industry also stabilize the acid for further regeneration). RDX itself is not afraid of dilute nitric acid. It can be boiled in it, for example RDX obtained by nitrolysis has a melting point of 202°C, which corresponds to an impurity content of 1%. Boiled in dilute nitric acid, it already has a melting point of 203.5°C. And I repeat that RDX containing nitric acid inside crystals after such cleaning is stable. Yes, it will release it afterwards during storage, which should be taken into account if you have it mixed with any substances that do not tolerate nitric acid or you are afraid of corrosion of the case. But it does not affect the stability of the RDX itself. Or you can add diphenylethylenediamine or other centralites.

This is not the only method of cleaning, some factories boil RDX in water in autoclaves at 140°C for 5 hours, at 150°C it is already hydrolyzed, about 0.5% for two hours. At home, you can boil for a couple of hours and at atmospheric pressure at ~100°C, which will also make impurities saponify.

greenlight - 16-7-2024 at 06:07

Quote: Originally posted by DennyDevHE77  
Quote: Originally posted by greenlight  
As for the purification by weaker nitric acid, I have no information nor have I ever read of this being performed. It gives me bad feelings of not being safe. Does the additional water content in the weaker nitric acid have any detrimental effect do you think?[Edited on 13-7-2024 by greenlight]


When synthesizing RDX a lot of by-products are formed, heating in 50-60% nitric acid solution allows to destroy all these impurities (and in industry also stabilize the acid for further regeneration). RDX itself is not afraid of dilute nitric acid. It can be boiled in it, for example RDX obtained by nitrolysis has a melting point of 202°C, which corresponds to an impurity content of 1%. Boiled in dilute nitric acid, it already has a melting point of 203.5°C. And I repeat that RDX containing nitric acid inside crystals after such cleaning is stable. Yes, it will release it afterwards during storage, which should be taken into account if you have it mixed with any substances that do not tolerate nitric acid or you are afraid of corrosion of the case. But it does not affect the stability of the RDX itself. Or you can add diphenylethylenediamine or other centralites.

This is not the only method of cleaning, some factories boil RDX in water in autoclaves at 140°C for 5 hours, at 150°C it is already hydrolyzed, about 0.5% for two hours. At home, you can boil for a couple of hours and at atmospheric pressure at ~100°C, which will also make impurities saponify.


Very interesting!

Thankyou for that info, I wasn't aware of this process for purification, I was thinking along the lines of recrystallisation only.


DennyDevHE77 - 22-7-2024 at 22:52

By the way, does ketene interact with nitric acid? If it does not, then this is a great way to dehydrate nitric acid for RDX without any distillation. We take a ketene lamp with high conversion, and just drilling ketene through nitric acid (for example 56%). The water will gradually convert to acetic acid. We get a mixture of 100% nitric acid and 100% acetic acid. The latter does not interfere in any way with the formation of RDX. Although it does seem to slightly increase the HMX impurity. If you drill it further, you get acetic anhydride. Well, such a mixture is not only for RDX and HMX works, ETN is also obtained with high yields (>90%) and high purity on acetic anhydride.

DennyDevHE77 - 23-7-2024 at 02:43

It turned out that passing ketene through nitric acid produced tetranitromethane

4CH2=CO + 4HNO3 = C(NO2)4 + CO2 + 3CH3COOH

So I guess 56% nitric acid solution can be concentrated to ~90% and then tetranitromethane will start to flow. Besides it can be dangerous, at least the acid should be cooled.

But I think to some concentration it will be possible to dehydrate it

[Edited on 23-7-2024 by DennyDevHE77]

Microtek - 23-7-2024 at 08:14

Is that observations from an experiment, or from research? I have never experimented with ketene, but my understanding is that it is very toxic.

DennyDevHE77 - 23-7-2024 at 20:00

It turned out to be one of the industrial methods for producing tetranitromethane. Nothing secret or new here, it is described in many books on industrial production of explosives. It just kind of ruined my idea of dehydrating nitric acid.

Microtek - 25-7-2024 at 09:19

Ah, OK. But have you experimented with ketene production? A ketene lamp seems to be an easy route to acetic anhydride, but I have never dared to test one (and by now I have access to acetic anhydride by other means).

DennyDevHE77 - 25-7-2024 at 20:37

I am currently looking for materials for my ketene lamp, but it can rather be called a tubular furnace, I want to achieve a conversion rate of +90%. Many laboratory ketene lamps produce a measly 20-30 g of ketene per hour.

My task is a few hundred grams at least. I'm thinking of using a tube filled with activated alumina with a developed surface, which is wrapped with Kanthal wire.

One of these tubular furnaces with a length of only 30 cm produced up to 5 liters of acetic anhydride per hour in terms of ketene.

Microtek - 26-7-2024 at 07:43

OK, please be safe with the handling of the ketene. I couldn't find an LC50 value, but the IDLH (immediately dangerous to life and health concentration) is 5 ppm. Hydrogen cyanide is 50 ppm.

Alkoholvergiftung - 26-7-2024 at 07:49

Funny thing Chemistry book from 1913 wrote Ketene is poisonous and has an very acidic smell. So you can smell it bevore you die.

B(a)P - 26-7-2024 at 15:54

Quote: Originally posted by Alkoholvergiftung  
Funny thing Chemistry book from 1913 wrote Ketene is poisonous and has an very acidic smell. So you can smell it bevore you die.


The permissable exposure limit in a workplace for ketene in 0.5 ppm. The odour threshold is greater than 1 ppm. I am not sure I agree with your statement.

Microtek - 29-7-2024 at 08:43

The permissible limit is the max you are allowed to expose your workers to day after day, the threshold for acute symptoms is usually quite a bit higher. Still, I think it would be prudent to treat it with a lot of respect.

B(a)P - 29-7-2024 at 13:38

Yes, that limit (PEL) is based on 8 hours of exposure, 5 days per week, so would absolutely be conservative for the home scientist conducting a one off experiment. The short term exposure limit is 1.5 ppm. The immediately dangerous to life or health limit is 5 ppm. The odour threshold is somewhere between 1 and 12 ppm. I am still sticking with, you can't rely on odour to keep you alive when it comes to ketene exposure.