vertexrocketry
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freebasing hydroxylamine
i have some hydroxylamine sulfate and i need to freebase it to make pure hydroxylamine
sciencemaddness wiki says that you can make hydroxylamine from the sulfate by adding liquid ammonia
do you think i could just freebase it with hydroxide like in nilered's video
or even better a double displacement with calcium nitrate
Ca(NO3)2+(NH3OH)2SO4→CaSO4↓+2NH3OHNO3
https://www.youtube.com/watch?v=IaTGCMixxKU&t=210s
or is liquid ammonia or butoxide(wikipedia) the only way?????
[Edited on 17-2-2025 by vertexrocketry]
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Texium
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Hydroxylamine’s conjugate acid pKa is only ~6 so hydroxide should be more than sufficient if you are trying to make an aqueous solution. Even
carbonate should work fine. The liquid ammonia procedure is for isolating pure hydroxylamine rather than an aqueous solution.
Read up on pKa. It'll save you a lot of questions and frustration in the future.
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vertexrocketry
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ok thanks
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Dr.Bob
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Pure hydroxylamine is not stable, as I recollect. In 30 years of chemistry I have never isolated it, and been told not to. For almost every
reaction, I have used a salt and then added it to a reaction (such as an organic acid to make an amide), then added the reagent (amide coupling
reagent) and then carefully added a base to free the amine slowly. Typically triethylamine, Hunig's base, pyridine, or similar are all fine. In
some the hydroxlamine salt was added to Aqueous base (NnaOH works fine), and then extracted with organic solvent, DCM is ideal, and then further
reacted, but I have never isolated the free hydroxylamine.
If you have a specific goal, we can maybe provide more ideas, but I would not try to isolate the amine.
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vertexrocketry
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i am converting hydroxylamine sulfate to hydroxylammonium nitrate to make hipep microthrusters
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woelen
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The free base NH2OH only is stable at low concentration in aqueous solution.
If you want hydroxylammonium nitrate, you do not need to first create free hydroxylamine.
You could dissolve your hydroxylammonium sulfate in water and add a solution of barium nitrate to it. Barium nitrate is easy to obtain.
Barium sulfate precipitates and a solution of hydroxylammonium nitrate remains behind.
Barium nitrate is not that well soluble in water, but the sulfate is extremely insoluble in water. So, even from the fairly dilute solutions you have
to work with, you can precipitate all barium and can get a dilute solution of hydroxyl ammonium nitrate. You should boil this down to make it more
concentrated.
Getting the dry salt from this is another challenge. I expect hydroxyl ammonium nitrate to be very very hygroscopic. The wiki page on this tells that
the pure salt is somewhat unstable. Commercially it is handled as a solution. In the past it is used for experiments with rocket fuel. Apparently
these were not really succesful, otherwise we would have heard more of it.
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Texium
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Thread Moved
6-3-2025 at 16:10 |
vertexrocketry
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i have a vacuum desiccator to dry it
i will use the barium nitrate method 
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Osmiridium
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As was already mentioned hydroxylamine is not stable, it can even lead to explosions. There were reported accidents. Trying to isolate it is never
really necessary though and its salts are safe to handle.
[Edited on 27-3-2025 by Osmiridium]
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FableP
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I had been thinking of making hydroxylamine nitrate by reacting nitric acid with nitromethane, for hipep. Its still on my to do list.
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