nitropyrotech
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How to make white fuming nitric acid from red fuming for rdx synthesis
Hello, anyone know how to make white fuming nitric acid from red fuming with NOx gases dissolved in it, I tried to do it with 35% hydrogen peroxide
but it ended in an runaway reaction where I got to breathe the beutiful NOx gases in, even when the nitric acid was cooled down in a freezer before.
So are there any other methods, that would work, I heard that blasting air into the acid will get the NOx gases away and the yellowish color too, I
just need white fuming nitric acid for synthesis of rdx because I just got a shit yield (from 10g hexamine I got 2g RDX), I used regular RFNA and the
modified bachmann route where I added Ammonium nitrate first to the RFNA and than slowly start to add the hexamine, after all the additioin everything
was stabilized at room temp while stirring for 30 min first and than heated to 80C and kept stirring for 30min, after recrystallisation I got 2g of
RDX from hexamine, I dont know the ratios of acetic anhydride and I cant find literatures online so I just went without it, would be helpful if anyone
know the ratios, acetic anhydride is pretty diffculft to obtain and its pretty expensive for me because I live in germany so I would appreciate a
method that use less of this stuff as possible
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Sir_Gawain
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The hydrogen peroxide method works great for me, perhaps you added too much. For the RDX synthesis, I’ve had much better luck by first making
hexamine dinitrate, then reacting that with WFNA. 68% nitric acid is used to make the HDN so you save on WFNA. The reports of HDN’s hygroscopicity
are overstated imo, I found it dries quite easily. I’ve even stored some in a poorly sealed bottle for over a year with little decomposition.
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greenlight
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Second that, much better to go hexamine dinitrate first and then to RDX.
As for the dry air method, I have used it many times with success. Warmed, stirred red fuming nitric acid in a beaker on a hotplate stirrer with air
bubbled in from an aquarium pump inside a desiccator covered with fresh calcium chloride granules results in clear colourless acid every time. Do
this with proper ventilation outside of course.
[Edited on 28-5-2025 by greenlight]
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ManyInterests
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Quote: Originally posted by Sir_Gawain  | | The hydrogen peroxide method works great for me, perhaps you added too much. For the RDX synthesis, I’ve had much better luck by first making
hexamine dinitrate, then reacting that with WFNA. 68% nitric acid is used to make the HDN so you save on WFNA. The reports of HDN’s hygroscopicity
are overstated imo, I found it dries quite easily. I’ve even stored some in a poorly sealed bottle for over a year with little decomposition.
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My HDN felt quite moist even if I stored it in a tightly wrapped plastic bag in a sealed plastic tupperware for a long time (and I had dried it
previously). I got so frustrated with HDN that I burned my supply and I want to use straight hexamine going forward. This is even though hexmaine
MIGHT be mildly hygroscopic.
I tried to do an RDX synthesis recently, but it failed and ended in a runaway. Thankfully I prepared well beforehand and had a large bucket of cold
water to dump everything in. But I think in this situation it was a case of very poorly made WFNA (which I am sure at this point wasn't WFNA).
I wanted to talk about that. Since that attempt at making WFNA was my first attempt at doing a reflux distillation. What I did is I made 500ml of 83%
nitric acid using sodium nitrate and I redistilled it with 500ml of sulfuric acid. I think I messed up that redistillation and accidentally got
sulfuric acid in my stuff (I had a final yield of 355ml before stopping).
The reason why I think I had gotten sulfuric acid is because the SG of my end result was over 1.55g. This is impossible. and it was fuming red
throughout. Adding the ammonium nitrate didn't dissolve and it just didn't work correctly. When I cooled it down and started adding my HDN, there were
red fumes of NO2 throughout even if it wasn't a runaway.
One thing is that I did not end up with any RDX at all. In previous attempts I did have a runaway (or near runaway) before dumping, and I did get some
RDX (that I later dissolved in azeotropic nitric acid for purification). This tells me I seriously screwed up making WFNA with a redistillation.
One issue I had with redistilling is that I broke the only thermometer adapters that could fit in my flask. I replacements and of other thermometer
adapters of various lengths so hopefully I will have multiple ways to read my temperature next time. I really, really want to succeed at getting good
yields of RDX.
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Sir_Gawain
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Did you rinse the HDN with a little ice cold acetone and dry thoroughly on the pump?
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bariumbromate
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simply add a half gram of Urea to every 500ml of nitric acid that works fine just add very slowly to avoid a runaway reaction
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ManyInterests
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Room temperature acetone, and yes I did.
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nitropyrotech
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| Quote: Originally posted by Sir_Gawain | | The hydrogen peroxide method works great for me, perhaps you added too much. For the RDX synthesis, I’ve had much better luck by first making
hexamine dinitrate, then reacting that with WFNA. 68% nitric acid is used to make the HDN so you save on WFNA. The reports of HDN’s hygroscopicity
are overstated imo, I found it dries quite easily. I’ve even stored some in a poorly sealed bottle for over a year with little decomposition.
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I have never tried the method with hexamine dinitrate before, Ive heard it improves thermal stability so it wont take 2 hours to add everything but I
think I ll try the hexamine dinitrate route and see how it will go, I also hope it will improve my yield without use of acetic anhydride
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nitropyrotech
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| Quote: Originally posted by greenlight | Second that, much better to go hexamine dinitrate first and then to RDX.
As for the dry air method, I have used it many times with success. Warmed, stirred red fuming nitric acid in a beaker on a hotplate stirrer with air
bubbled in from an aquarium pump inside a desiccator covered with fresh calcium chloride granules results in clear colourless acid every time. Do
this with proper ventilation outside of course.
[Edited on 28-5-2025 by greenlight] |
Will it also work when I put a tube inside of the RFNA and just blast air from a aquarium pump into it because I dont have a dessicator
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nitropyrotech
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| Quote: Originally posted by greenlight | Second that, much better to go hexamine dinitrate first and then to RDX.
As for the dry air method, I have used it many times with success. Warmed, stirred red fuming nitric acid in a beaker on a hotplate stirrer with air
bubbled in from an aquarium pump inside a desiccator covered with fresh calcium chloride granules results in clear colourless acid every time. Do
this with proper ventilation outside of course.
[Edited on 28-5-2025 by greenlight] |
Will it also work when I put a tube inside of the RFNA and just blast air from a aquarium pump into it because I dont have a dessicator
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greenlight
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| Quote: Originally posted by nitropyrotech | | Quote: Originally posted by greenlight | Second that, much better to go hexamine dinitrate first and then to RDX.
As for the dry air method, I have used it many times with success. Warmed, stirred red fuming nitric acid in a beaker on a hotplate stirrer with air
bubbled in from an aquarium pump inside a desiccator covered with fresh calcium chloride granules results in clear colourless acid every time. Do
this with proper ventilation outside of course.
[Edited on 28-5-2025 by greenlight] |
Will it also work when I put a tube inside of the RFNA and just blast air from a aquarium pump into it because I dont have a dessicator
|
Ideally, the air need to dry and free of any water vapour. dDpending on the ambient weather conditions, you could introduce further water into your
acid diluting it.
You don't have to have a desiccator, just run you aquarium pump covered in damp rid or other similar hygroscopic drying agent inside any plastic
container it fits.
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FrankRizzo
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It's trivial to make an inline dessicator with a soda bottle or similar, filled with indicating silica gel or damp rid.
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nitropyrotech
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| Quote: Originally posted by greenlight | | Quote: Originally posted by nitropyrotech | | Quote: Originally posted by greenlight | Second that, much better to go hexamine dinitrate first and then to RDX.
As for the dry air method, I have used it many times with success. Warmed, stirred red fuming nitric acid in a beaker on a hotplate stirrer with air
bubbled in from an aquarium pump inside a desiccator covered with fresh calcium chloride granules results in clear colourless acid every time. Do
this with proper ventilation outside of course.
You think Ammoniumnitrate will work too? I mean I have bulk ordered it and have 300kg at home
[Edited on 28-5-2025 by greenlight] |
Will it also work when I put a tube inside of the RFNA and just blast air from a aquarium pump into it because I dont have a dessicator
|
Ideally, the air need to dry and free of any water vapour. dDpending on the ambient weather conditions, you could introduce further water into your
acid diluting it.
You don't have to have a desiccator, just run you aquarium pump covered in damp rid or other similar hygroscopic drying agent inside any plastic
container it fits. |
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nitropyrotech
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| Quote: Originally posted by greenlight | | Quote: Originally posted by nitropyrotech | | Quote: Originally posted by greenlight | Second that, much better to go hexamine dinitrate first and then to RDX.
As for the dry air method, I have used it many times with success. Warmed, stirred red fuming nitric acid in a beaker on a hotplate stirrer with air
bubbled in from an aquarium pump inside a desiccator covered with fresh calcium chloride granules results in clear colourless acid every time. Do
this with proper ventilation outside of course.
[Edited on 28-5-2025 by greenlight] |
Will it also work when I put a tube inside of the RFNA and just blast air from a aquarium pump into it because I dont have a dessicator
|
Ideally, the air need to dry and free of any water vapour. dDpending on the ambient weather conditions, you could introduce further water into your
acid diluting it.
You don't have to have a desiccator, just run you aquarium pump covered in damp rid or other similar hygroscopic drying agent inside any plastic
container it fits. |
Ammoniumnitrate will it work too I bulk orderd 300kg from my supplier from latvia
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ManyInterests
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| Quote: | | Ammoniumnitrate will it work too I bulk orderd 300kg from my supplier from latvia |
300 kg? Wow, that's dedication!
But for me right now I am trying an RDX synthesis with pure hexamine and no HDN. My usual method but holy hell are the additions HOT. I had to put my
cooling bath and the beaker in the freezer once for 90 minutes before resuming, and right now the former solid ice block has melted almost completely
(but no runaway and I stirred for 8.5 minutes before covering and putting it back in the freezer) when the nitration beaker was at 14.5C. I will wait
another 3 hours or so before everything cools... and I only added a little bit of the hexamine in comparison to how much I am making.
Man this stuff is a bitch to make. I want to make a decent amount just as a challenge.
Edit: I have a question: Since I have had runaways with RDX in the past and many failures with making it (leading to very poor yields salvaged from
crashing the acid to prevent a disaster) Would a multi-day process work? Like there is no way I can add all the stuff to my mixture in one day. It
will take far too long. I've done many nitrations before, and normally I would just do the whole thing from nitrating to crashing it and then
filtering/washing it in one session, but I simply cannot do this with RDX due to the extreme heat it produces in hexamine additions. HDN is a little
less hot, I know, but even HDN doesn't mitigate the heat that much.
so it makes me wonder... just how bad for the yield would it be to take that many breaks between additions to cool back down in the freezer?
[Edited on 24-6-2025 by ManyInterests]
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Microtek
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It sounds strange to me that you are getting that much of an exotherm. When I do it, the exotherm is quite manageable. I sounds as if your ice bath is
actually just a block of ice, is that the case? If so, you should take the advice we gave you before and replace it with a proper liquid bath,
preferably stirred. The heat transfer from forced convection is much greater that what you will get from a static block.
Also, have you tried adding two molar equivalents (relative to hexamine) of dried AN to the HNO3 before adding the hexamine? It increases the yield
and also, in my experience, makes it more well behaved. The only downside is that drying AN is not as trivial an operation as it may seem. 50 C for 18
hours has been used by Bachmann, IIRC.
[Edited on 24-6-2025 by Microtek]
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ManyInterests
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| Quote: Originally posted by Microtek | It sounds strange to me that you are getting that much of an exotherm. When I do it, the exotherm is quite manageable. I sounds as if your ice bath is
actually just a block of ice, is that the case? If so, you should take the advice we gave you before and replace it with a proper liquid bath,
preferably stirred. The heat transfer from forced convection is much greater that what you will get from a static block.
Also, have you tried adding two molar equivalents (relative to hexamine) of dried AN to the HNO3 before adding the hexamine? It increases the yield
and also, in my experience, makes it more well behaved. The only downside is that drying AN is not as trivial an operation as it may seem. 50 C for 18
hours has been used by Bachmann, IIRC.
[Edited on 24-6-2025 by Microtek] |
Yes and Yes.
Ok I didn't dry the AN that much, I wasn't aware it would take that much to dry it...
So here is what happened. I first made around 515ml of 99% (1.51 SG) nitric acid. I am proud that I got that much in one day (I did no less than 4
distillations with 2 liter flasks). It red with NO2, but after leaving it in the freezer (loosely closed cap and in a bag full of sodium bicarbonate)
for 48 hours it got a little better. I added the AN and some urea with stirring for 30 minutes to allow NO2 to escape and for it to clear up a bit. It
was still a bit red, but that couldn't have affected it that much, could it?
BTW, This time I did today was the SECOND time I did it using AN... but, just like the first time I had done earlier. It was a disaster! No joke!
Despite controlled additions, my final addition (which was larger than previous, I must admit) produced a runaway, so I had to crash it to avoid a
disaster. I had some very mild NO2 inhalation, but nothing serious. No RDX came out in solution, like the previous time.
So right now I am baffled as all hell. I worked REALLY hard to make that much nitric acid, and while I can do that again easily, it was a lot of work
and I don't want to have to do this again and still fail. BTW, I had measured out 170g of hexamine and barely 20g was added over a span of 9 hours at
least. There was NO2 gas coming out throughout, BTW. The 2 times I did it with AN added in the nitric acid and I still had it fail. Doing it with HDN
won't do any better since that is what I did last time.
I am legit baffled as to what I am doing wrong?
For the ice bath, what I did is made a salt water solution, put the beaker in the middle, then put the whole thing in the freezer (covered obviously).
until everything froze solid, around 6 or 8 hours. it was really, really cold. But despite this, in my first addition, the iceblock almost completely
melted in an hour of addition. This shit was HOT.
I thought the AN and urea (around 1g, not much) was supposed to stop runaways like this from happening? Or at least cool down the reaction?
I did do RDX two times prior without the use of AN or urea, I wasn't sure how red it was back then, but in the end I had a runaway on one of them (but
it did not resemble these at all, there was no fizzing and no foaming, but the temperature was rising steadily and uncontrollably, so I had to crash
it. Despite that, I had a 50% yield of RDX from the amount of HDN I put in. The first time I also had a similar yield. But in these cases I had no
yield.
I know I am using increasing amounts of reagents... but that is just how I work. I always keep making things bigger... and also I want to succeed! RDX
is pissing me off. I made almost everything else on my bucket list of energetics, but RDX has been an absolute bitch to make so far and it is pissing
me off.
Edit: I am just going to make RDX with plain nitric acid and no AN going forward. Since know I know it doesn't HAVE to be 99%, I can bubble air
through the acid first while heating to clear out the NO2, not necessarily super dry air, but if I get 99% acid again, it'll still work with 95% just
fine. Also one reason why I added the AN is to make the heating step safer since I did hear that it also eliminated any risk of an accidental
detonation. What I will do is after the addition is all done I will only gently heat it (using a hot water bath) to 50C before dumping, there isn't
much risk in that. To remove any impurities what I can do is simply redissolve the RDX later in 50-60% nitric acid and heat it that way. I did it
before, no risk of danger. The yield will still be not good, around 50% of the beginning material or so... but 50% is better than nothing.
[Edited on 25-6-2025 by ManyInterests]
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Microtek
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OK, I am almost certain that the NOx in your nitric is to blame for the excessive exotherm. NO2 (red/brown) is in an equilibrium with N2O4 (almost
colorless) and that equilibrium is displaced far towards the N2O4 side of the reaction at low temp. This means that when you see the colour fade when
you put the nitric in the freezer, it doesn't mean that the NOx disappears. It is still there in the form of N2O4 and will oxidize the hexamine
fragments and produce a lot of heat while also lowering your yields.
Purging the nitric at ca. 50 C with dried air is the way to go. You can just make a lidded jar with two tubes, one reaching to the bottom and one only
just going through the lid. Fill it with a drying agent such as CaCl2 (flake preferably) or silica gel, and use an aquarium pump to blow air through
it and into your nitric. A good bubbler can be made by making many piercings in the bulb of a single use plastic pipette.
The airstream will volatilize some of your nitric, so if you set up for reflux you will save some of that and also reduce the fumes.
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ManyInterests
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| Quote: Originally posted by Microtek | OK, I am almost certain that the NOx in your nitric is to blame for the excessive exotherm. NO2 (red/brown) is in an equilibrium with N2O4 (almost
colorless) and that equilibrium is displaced far towards the N2O4 side of the reaction at low temp. This means that when you see the colour fade when
you put the nitric in the freezer, it doesn't mean that the NOx disappears. It is still there in the form of N2O4 and will oxidize the hexamine
fragments and produce a lot of heat while also lowering your yields.
Purging the nitric at ca. 50 C with dried air is the way to go. You can just make a lidded jar with two tubes, one reaching to the bottom and one only
just going through the lid. Fill it with a drying agent such as CaCl2 (flake preferably) or silica gel, and use an aquarium pump to blow air through
it and into your nitric. A good bubbler can be made by making many piercings in the bulb of a single use plastic pipette.
The airstream will volatilize some of your nitric, so if you set up for reflux you will save some of that and also reduce the fumes.
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I believe you. I knew that people say that the nitric shouldn't be red, but I had no idea it would have that big of an outsized effect. Especially
since when I did do RDX without AN I am seriously questioning if if it was that red.
At any rate the next time I do this I will run a much smaller batch so that way if something goes wrong I won't lose a lot of basic reagents. I also
learned that using bisulfate to make nitric acid needs more specialized care, since I ended up losing two flasks. Making this the most expensive
experiment I ever ran.
I formerly used small inflatable pump, but I think I can spare the money for a quieter aquarium pump, since I did find some that are cheap and
effective.
For the setup. I can make it work, but I am not sure how to set it up for reflux. Previously when I did it, I did have a gas wash bottle filled with
CaCl2 (not flaked, they're spheres, however) but the end went directly to a beaker. I don't mind losing some nitric as long as I rid my HNO3 of the
stuff.
I want to succeed!
Edit: Would putting the pump itself in CaCl2 also help to dry the air some more?
[Edited on 25-6-2025 by ManyInterests]
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Microtek
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CaCl2 spheres are fine. When I said "preferably flakes", I just meant that it shouldn't be powdered, as that will clog up and make a mess. It is not
critical what kind of air pump you are using, but the airflow shouldn't be too fast, or the CaCl2 won't have time to dehydrate the airstream.
Setting up for reflux is similar to a distillation setup, but the condensed liquid runs back into the boiling flask. It is usually done simply by
inserting the condenser directly, and vertically, into the boiling flask. It is not necessary to do this, but it will reduce the amount of HNO3
vapours in your lab. I find that these fumes are quite hard on my fume hood extraction fans.
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ManyInterests
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| Quote: Originally posted by Microtek | CaCl2 spheres are fine. When I said "preferably flakes", I just meant that it shouldn't be powdered, as that will clog up and make a mess. It is not
critical what kind of air pump you are using, but the airflow shouldn't be too fast, or the CaCl2 won't have time to dehydrate the airstream.
Setting up for reflux is similar to a distillation setup, but the condensed liquid runs back into the boiling flask. It is usually done simply by
inserting the condenser directly, and vertically, into the boiling flask. It is not necessary to do this, but it will reduce the amount of HNO3
vapours in your lab. I find that these fumes are quite hard on my fume hood extraction fans. |
I can manage with that.
Oh and I forgot to mention something important. As I said, with my two RDX synthesis, the first one using redistilled nitric acid.
It was my first time concentrating RFNA (83%) into WFNA. But I am not sure if I succeeded. I ran into some problems. While setting up my distillation
apparatus I accidentally broke my thermoprobe. I have since replaced it and got other ones of smaller length, allowing me to fit it in a reflux setup.
But at that time I couldn't... meaning I had to play it all by ear. I put in a 1:1 ratio of sulfuric acid to my nitric acid. Again, I had no idea how
hot it was being, and I tried to turn the apparatus on and off as needed. But I cannot be sure if all the nitric distilled over or it got so hot that
some sulfuric got over. I just wasn't sure. It was my first time doing it.
I am pretty sure something was very off about the end batch. Because A: its SG was 1.57, which is impossible unless there were contaminants in it, and
B: It was fuming red throughout at all times. I can't be sure if I had some sulfuric acid come over or what.
But whatever it was, it had the same result of my 2nd batch, except even worse. I am not sure if even the ammonium nitrate fully dissolved in the
thing.
I ordered some magnesium nitrate (500g) from onxymet and it is currently on its way, I also have the new thermoadapters that are GREAT which worked
well for my previous distillations to make decent 99% acid.
I know Nurdrage has a video on using magnesium nitrate to concentrate azeotropic to WFNA territory... but have you done it before? And how to salvage
my magnesium nitrate for reuse and remove any left over nitric acid from it?
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