Hydrazinium
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Nitric acid without distillation
After thinking recently about a way to get nitric acid without having to buy a distillation set up. My thoughts run thusly;
Ca(NO<sub>3</sub> <sub>2</sub> and
H<sub>2</sub>SO<sub>4</sub> are openly available to me through the internet, and so a procedure that involved simply adding
the Ca(NO<sub>3</sub><sub>2</sub> slowly to the
H<sub>2</sub>SO<sub>4</sub> and simply filtering off the precipitated CaSO<sub>4</sub> would be simple, easy, and
would provide a fairly pure nitric acid.
Has anyone attempted this?
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BromicAcid
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People have tried this, from what I remember the precipitate is gelatinous and voluminous and that due to this yields are abysmal. I'm sure there are
examples of attempts on this site.
Mentioned here by alancj, and covered most thoroughly here, and covered here, and I'm sure in several other threads as well.
[Edited on 1/16/2011 by BromicAcid]
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Hydrazinium
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It would seem that the method can work for low concentrations (30-40%) but that at higher concentrations the sulphate is soluble in the acid. It is
suggested that using barium salts would solve the problem. I'm hoping to get a sintered glass filter funnel soon which might be able to get rid of the
precipitated barium sulphate.
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hissingnoise
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Ca(NO2)2 is dissolved in a minimum of water and is then added to a stoichiometric quantity of H2SO4.
The precipitated sulphate is separated by decanting.
If the dry salt is added to H2SO4 minimal reaction occurs on the surfaces of the Ca(NO2) granules and very little HNO3 forms.
The barium salt works too, but again, only in solution!
[edit] H2SO4 should, of course, be added to the solution rather than the other way round . . .
[Edited on 16-1-2011 by hissingnoise]
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not_important
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As already stated, the solubility of CaSO4(hydrated) is high enough to limit the usefulness of the HNO3 produced, I posted the numbers here before.
Also it must be run in solution. Using a hot nearly saturated solution of Ca(NO3)2 helps, the sulfate is less soluble in hot water than cold,
_really_ good stirring is needed to avoid the occurrence of trapped droplets of the calcium nitrate and/or sulfuric acid solutions. Filtering is
still a drag.
It is difficult to get stoichiometric quantities, you must titrate the acid with reasonable accuracy, and calcium nitrate is hygroscopic so picks up a
variable amount of water; fertiliser grade is not pure Ca(NO3)2 anyway.
Adding concentrated H2SO4 must be done quite slowly to avoid splattering and explosive boiling.
[Edited on 16-1-2011 by not_important]
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