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DJF90
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If theres a limited quantity (calculated of course) of P2O5 then the water will react way before the HNO3. And any HNO3 molecules that do get
dehydrated will react with the remaining water present to form HNO3 again, so theres no problem. Its only really economic if you want to make N2O5 as
a nitrating agent, using it to dry azeotropic nitric acid is not.
You may be able to break the azeotrope by using a pressure swing distillation; I'm sure if you wanted to look information can be found in the context
of distilling ethanol, perhaps check the Ethanol and Azeotrope pages on wikipedia.
gnitseretni: This wouldnt work. Like User says, you need the salt used to be hygroscopic, and generally anhydrous. Calcium sulfate may well work;
although if you can find a nitrate salt that would work it would probably be a better choice.
[Edited on 20-12-2009 by DJF90]
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gnitseretni
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Quote: Originally posted by User  |
No thats not really what i was saying.
If course it has to be a salt that 'captures' water, as far as i know AN does not have to ability to trap H20 in its structure.
I meant a substance that binds water to itself. |
Ok, uhm.. well which one would you use? I'd like to give it a try the next time i distill me some HNO3, and if i can get whatever it is you suggest
that is 
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hissingnoise
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An anhydrous salt like magnesium nitrate can only be prepared from the anhydrous acid acting on the metal. . .
The same goes for copper!
The oxide produces a hydrate!
Anhydrous HNO3 can be prepared from dilute acid by dehydration by P2O5 using the correct stoichiometry!
The advantage H2SO4 has with dilute acid is that it's reusable after being reconcentrated.
Theoretically, distilling HNO3 from anhydrous Na or K nitrate and 98% H2SO4 should give 100% HNO3 but decomposition occurs and reduces
concentration.
[Edited on 20-12-2009 by hissingnoise]
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gnitseretni
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| Quote: Originally posted by hissingnoise | An anhydrous salt like magnesium nitrate can only be prepared from the anhydrous acid acting on the metal. . .
The same goes for copper!
The oxide produces a hydrate!
Anhydrous HNO3 can be prepared from dilute acid by dehydration by P2O5 using the correct stoichiometry!
The advantage H2SO4 has with dilute acid is that it's reusable after being reconcentrated.
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I knew it sounded too simple to be true
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User
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I think Ca(NO3)2 could do the trick indeed.
It binds water
High melting point (561 degrees celsius) so I assume it can be baked to dryness..
It's hydrated form is the tetrahydrate so that means it can bind 4 water atoms per molecule.
Ca(NO3)2 =164.088 g/mol
Ca(NO3)2*4 H2O = 236.15 g/mol
1 gr Ca(NO3)2 can bind 0.4387 gr of H2O if my calculations are correct.
So if one has 10 gr of 70% HNO3 it contains 3 grams of water.
One needs to add 6.84 gr of Ca(NO3)2.
Dont know if it is practical but i think it can be done.
One could even use DCM to extract the HNO3 and distil off the dcm to obtain highly concentrated NA.
Just a mind spin.
[Edited on 20-12-2009 by User]
What a fine day for chemistry this is.
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hissingnoise
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Even here, distillation is needed as Ca(NO3)2 is soluble in HNO3.
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DetaDude
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crazyboy
Please show me where I stated that P4O10 was used to desiccate HNO3.
I think if you search the recent posts you'll find that I was refering to statements by others and nowhere did I mention P4O10.
Sorry.
Genius creates many a great works............Labor alone finishes them!
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entropy51
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[P2O5 is the empirical formula. P4O10 is the molecular formula. Same difference.
[Edited on 21-12-2009 by entropy51]
[Edited on 21-12-2009 by entropy51]
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hissingnoise
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It should be possible to distill ~98% HNO3 or better from H2SO4 consistently with an extra bit of care.
An air condenser between flask and water-cooled condenser might reconstitute some NO2 to HNO3, slightly upping concentration.
The receiver cooled below 0*C should help too.
But the main considerations are getting the nitrate salt completely anhydrous or as near it as possible and making sure H2SO4 is 98%.
Drying KNO3 by heat and popping it in a dessicator overnight would be good because what looks dry may still contain some little moisture.
Reconcentrating dilute H2SO4 is more difficult but done in dry/cold air with fume-extraction the finished conc. should be close to 98%.
Distillation then with a slight excess of H2SO4 should give near anhydrous HNO3.
Better than distilling twice. . . no?
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crazyboy
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| Quote: Originally posted by DetaDude | Please show me where I stated that P4O10 was used to desiccate HNO3.
I think if you search the recent posts you'll find that I was refering to statements by others and nowhere did I mention P4O10.
Sorry. |
http://www.fordhamprep.org/gcurran/sho/sho/lessons/lesson55....
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per.y.ohlin
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| Quote: Originally posted by User |
One could even use DCM to extract the HNO3 and distil off the dcm to obtain highly concentrated NA.
Just a mind spin.
[Edited on 20-12-2009 by User] |
To avoid decomposition, the nitric acid can actually be precipitated out of the DCM. Carbonfeind describes the process here
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hissingnoise
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That procedure was first described on this board many, many moons ago!
Evaporating the DCM is probably easier as a simple ice-cooled receiver will condense DCM.
Welcome to SciMad, per.
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User
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It comes from a patent and has been discussed a million times on the web.
Pat. US 3981975
The whole point is that DCM isn't that good at dissolving NA.
One needs quite a lot of solvent to get some decent amounts of WFNA.
What a fine day for chemistry this is.
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hissingnoise
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Yeah, and the patent makes it sound a lot easier that the cold reality. . .
If you *can* get it out though, it'll be STRAAAWNG!
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DetaDude
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Ah the DCM method
I've tried this method, with only marginal success, it is somewhat time intensive, and yields are not to great. I was able to extract a small amount
of WFNA >96% but it took awhile and plenty of DCM.
From an economic standpoint I'll stick with good ole distillation.
hissingnoise is correct about this method (DCM) it sounds a whole lot easier (from the patent) than it actually is in reality .
Genius creates many a great works............Labor alone finishes them!
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hissingnoise
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Finding a seller willing to supply oleum would simplify things somewhat. . .
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ScienceSquirrel
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Getting your mitts on oleum is well nigh impossible.
Even if you can find a vendor who stocks it they want a lot more than it is really worth.
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hissingnoise
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We're back to oxidation by O3 circuitously. . .
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hissingnoise
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And to get a good yield from the DCM method the first essential is to shake the damn mixture until your two arms fall off. . .
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ChrisWhewell
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Any good chemist can make their own oleum when necessary.
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entropy51
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Perhaps you'd like to share your favorite recipe.
As you know, members here have done it, but it's not trivial.
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hissingnoise
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Yes, preferably something with 'Sulphur In'---> 'SO3 Out'---> would suit us best?
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ScienceSquirrel
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GPR sulphuric acid 98% ca £10 a litre.
40% oleum ca £75 a litre
And if you do not like the price you can always give it a go yourself.
Take a litre of sulphuric acid, build a sulphur trioxide generator and bubble the generated gas through the acid until the the solution has gained
the requisite mass.
Easy enough
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DetaDude
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Ozone the ultimate oxidizer
Point of information:
Has anyone here actually used ozone for chemical synthesis ?
Say for example; to clean up HNO3, or to give SO2 encouragement to become SO3 et. al. etc.
If you have some experience with ozone please be so kind as to share your experiments with us.
Genius creates many a great works............Labor alone finishes them!
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hissingnoise
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I'd doubt it, DetaDude; its synthesis needs dry oxygen and its generation is woefully inefficient.
The cost of good equipment is very high, too!
A homemade generator can be cobbled together but it's unlikely to work continuously---or well!
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