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greenlight
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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.
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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.
Be good, otherwise be good at it 
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ManyInterests
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| 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]
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Sir_Gawain
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| 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.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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ManyInterests
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| 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%?
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greenlight
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| 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?
Be good, otherwise be good at it
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ManyInterests
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| 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.
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greenlight
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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]
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DennyDevHE77
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| 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]
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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.
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greenlight
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| 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]
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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.
Be good, otherwise be good at it
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DennyDevHE77
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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.
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DennyDevHE77
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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]
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Microtek
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Is that observations from an experiment, or from research? I have never experimented with ketene, but my understanding is that it is very toxic.
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DennyDevHE77
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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.
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Microtek
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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).
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DennyDevHE77
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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.
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Microtek
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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.
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Alkoholvergiftung
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Funny thing Chemistry book from 1913 wrote Ketene is poisonous and has an very acidic smell. So you can smell it bevore you die.
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B(a)P
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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.
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Microtek
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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.
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B(a)P
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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.
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