Metacelsus
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Nitric Acid by Precipitation Reaction
I have been wondering whether it is practical to make nitric acid with calcium nitrate and sulfuric acid.
Ca(NO3)2 (aq) + H2SO4 (aq) -> 2 HNO3 (aq) + CaSO4 (s)
The reaction should work in theory, but I've never heard of it done in practice. Is there a reason for this (i.e., does it work)? Is it practical to
filter or decant the nitric acid? Does anyone have any real-life experience with this reaction?
References:
http://www.sciencemadness.org/talk/viewthread.php?tid=19524#...
http://www.sciencemadness.org/talk/viewthread.php?tid=18963&...
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blogfast25
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I haven't checked the SM links you provided.
Just a few quick comments: where will you get the calcium nitrate from?
Calcium sulphate has some limited water solubility (it isn't near as insoluble as calcium carbonate e.g.), so your nitric acid will likely be
contaminated with CaSO4...
[Edited on 9-3-2013 by blogfast25]
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violet sin
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http://www.youtube.com/watch?v=7akk5ppJjEw
this guy seems to be fairly trustworthy. has a breakdown of the rxn scheme and uses the CAN fertilizer + H2SO4. he also does some other fun vids too.
in reading on the standard CAN (calcium ammonium nitrate) reaction for nitric, there was stated some issues with the mix. IIRC something about the
distillation needing to be done quickly because the calcium, and something else were fighting back and forth swinging the ph and going round-robin to
destroy/neutralize some how. I couldn't find the reference anywhere so take that last bit with a grain of salt as it were. I hate not being able to
reference but saving every one is a pain, my bad. hope it helps
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AndersHoveland
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Calcium sulfate would likely have increased solubility under acidic conditions (because of bisulfate ions existing in the solution). In concentrated
sulfuric acid, this increased solubility usually does not manifest itself so much because of the competing common ion effect.
I think the precipitation will work, but your nitric acid will be contaminated by some CaSO4.
[Edited on 9-3-2013 by AndersHoveland]
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Metacelsus
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Nice video! I have a bag of CAN fertilizer sitting in my garage, but I need some H2SO4 (I just ran out  ). I'll try the reaction once I get some more.
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Fantasma4500
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well even in my paranoid country ive been able to find pure calcium nitrate, and ofcourse planning to buy it later on .. 
ive talked with a guy who told me that he does it with vacuum filter and using barium nitrate (BaSO4 ppt)
for AN you could very simply just mix (NH4)2CO3 with Ca(NO3)2 cheap and very pure end result
he reccomends only to do the reaction of H2SO4 with Ba(NO3)2 as little as 50 mL as you would like to filter the stuff aswell
but i guess if you could get to do this in say..... quanities as much as 200 mL then placing it in a tall beaker should add some effectivity to
decanting (:
but possibly you should consider using something else but Ca(NO3)2 due to the solubility of CaSO4, but i wouldnt see it as a huge problem, actually i
cant imagine what reactions it would be a problem in??
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blogfast25
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Nice video, very thorough treatment of stoichiometry and mass balances.
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DerAlte
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I have not tried this reaction nor watched the video, but it sounds promising. One caveat: calcium nitrate is very hygroscopic and probably exists in
fertilizer form as the 4-hydrate rather than the pure salt. However, according to CRC the tetrahydrate decomposes at 40C, assumedly just losing water
since the anhydrous nitrate does not decompose until 500+C. It should be easy to dry well.
As for the solubility of calcium sulphate in strong H2SO4, it is probably very low due to common ion effect, but re-read AH's comment. I would think
it would be a very good idea to have H2SO4 in fair excess so that the sulphate is well wetted and does not dry out into a solid mass, and also to make
sure the nitrate, as well as being dry, is finely powdered. Then the crystals would not get coated easily with insoluble sulphate. The resultant
nitric acid should be pretty free of water, but watch out for dissociation. The product will probably contain oxides of nitrogen, usually no problem
in most cases (i.e. red and fuming!).
Be careful of breakages! Hot suphuric plus nitric sounds nasty!
Der Alte
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blogfast25
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Quote: Originally posted by DerAlte  | The product will probably contain oxides of nitrogen, usually no problem in most cases (i.e. red and fuming!).
Be careful of breakages! Hot suphuric plus nitric sounds nasty!
Der Alte |
Actually, he's calculated the whole thing to get azeotropic HNO3 to come over, by adjusting the mass balances. Firstly some water comes over, then the
azeotrope, or so he claims. I didn't see any verification of acid strength but distillate temperature was azeotropic after a while.
'Amen' to the second bit. Brrr...
[Edited on 11-3-2013 by blogfast25]
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DerAlte
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I should have watched the video earlier but these days 20mins. seems to exceed my attention span! (Gets worse as you age). The guy used calcium
ammonium nitrate, decahydrate. I would be a bit careful about producing plaster of paris in an expensive 3 neck flask! Visions of a solid mass,
impossible to shift – expensive experiment.
He seemed to have a decent handle on the stoichemistry, however, and aimed to make the azeotrope. I liked his nonchalance re NO2 fumes –
refreshingly different from the average paranoia that prevails today. His yield seemed a bit low and his acid didn’t quite seem up to 68% during his
Cu reaction. Otherwise, I guess, a pretty good demo and do-able, with care.
Der Alte
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mr.crow
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CAN is NOT calcium nitrate
You can dissolve the AN in water leaving insoluble crap behind
[Edited on 11-3-2013 by mr.crow]
Double, double toil and trouble; Fire burn, and caldron bubble
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