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Rosco Bodine
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Quote: Originally posted by hissingnoise  | Al(NO3)3, hygroscopic, normally containing considerable water of hydration and decomposing below 140*C doesn't IMO, look very promising as a source of
HNO3.
If it was a viable method, I think it would be fairly common knowledge. . .
If it can be dehydrated without the salt decomposing it might have interest. |
I fail to understand your logic for why Al(NO3)3 does not look promising as a source for HNO3. The 135C decomposition point is well above the
distillation temperature for both azeotropic and pure HNO3, and dehydration of the Al(NO3)3
is not the proposed reaction, double decomposition is the proposed reaction.
As for the conditional supposition that if it was a viable method then it would be common knowledge, that seems to be excessively
presumptuous in being dismissive of a reaction which would not seem at first glance to be so far fetched. Don't misunderstand me because I don't
know if it will work or not, but nothing you just said is sufficient for actually dismissing the idea. I still think the idea may be a possibly valid
approach for improving a very old reaction. And it may not be a new idea at all. It may already be a described method for which the description is
obscure enough that it is not easily found.
MSDS for the Fisher reagent nonahydrate of Al(NO3)3 shows the hydrate melts at 73.9C and has a B.P. with decomposition at 150C.
Byproduct Al2(SO4)3 - 18H2O has a melting point of 86.5C
It would appear that it would be better to in advance break the nonahydrate some way, such as by possible mixture with another nitrate perhaps zinc
nitrate ? To further develop the idea I will see what I can find about that, but really that has more bearing upon concentration of the anticipated
HNO3 which may be produced, than would it have bearing upon whether or not the contemplated reaction occurs. The greater concern I have is that an
unfavorable equilibrium may exist for an actual acid sulfate
of aluminum to occur which would then stop the reaction in the same way as occurs for the classical and well known reaction.
[Edited on 8-9-2010 by Rosco Bodine]
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hissingnoise
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| Quote: | | I fail to understand your logic for why Al(NO3)3 does not look promising as a source for HNO3. |
It's just an opinion based on a hunch - but I think the tradition of using Na or K salts is based on experience. . .
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Rosco Bodine
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Your hunch is probably incorrect. Some further reading is revealing that extraction of aluminum ore using nitric acid is the common purification
method as the preliminary purification and isolation of alumina via thermal decomposition of the nonahydrate, with recovery of the nitric acid for
recycling in the process. The aluminum nitrate readily gives up its nitric acid by heating alone, and the first
30% of the acid comes off as a 48-50% concentration. However, by thermal decomposition the byproduct is alumina intended for electrolytic cell
feedstock.
But in the process to which my idea applies, the end product desired is not alumina nor aluminum, but the desired product is the nitric acid itself.
In the presence of H2SO4, the HNO3 should be given up even more readily than by thermal decomposition alone, while producing Al2(SO4)3 as the
byproduct instead of Al2O3. Everything looks favorable for the reaction which I am thinking should work. So the heck with your opinion based on a
hunch on this one  as the reaction kinetics seem to be there in favor for the
reaction I am hypothesizing should occur. 
[Edited on 8-9-2010 by Rosco Bodine]
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hissingnoise
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| Quote: | | So the heck with your opinion |
Gee Rosco, I'm sorry you find my lack of enthusiasm upsetting. . .
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Rosco Bodine
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There you go again with the negative waves 
http://www.youtube.com/watch?v=AhKnEo9ZyEs&feature=relat...
Think positive when you are on the way to the bank
http://www.youtube.com/watch?v=WBr2Xh599ZI&fmt=18
The process or at least the distillation part of the process where H2SO4 is used for conversion of Al(NO3)3 to HNO3 and Al2(SO4)3 is described in the
English language summary of a couple of Japanese patents. So it would seem my hypothesis does have some validity and has partly been described in
what would be an understandably obscure source to an English speaking person.
Fortunately the chemicals and reactions involved will likely not be rendered inert
in protest for my inability to speak Japanese, but who can be certain ?
Abstract of JP 6001603
PURPOSE:To improve recovery efficiency by adding sulfuric acid to spent nitric acid contg. phosphoric acid and Al so as to have not less than the
specified SO4/Al molar ratio before concentrating the mixture by distillation to the specified free sulfuric acid concentration to recover nitric
acid. CONSTITUTION:Sulfuric acid is added to spent nitric acid contg. phosphoric acid and Al so as to have >=3 molar SO4/Al ratio to convert
nitrate to nitric acid and the mixture is concentrated by distillation until the free sulfturic acid concentration becomes 25-50wt.% to recover nitric
acid in the spent acid by >=90%. Then, after warm water is added to the remained liquid to adjust it so that it may become supersatrated solution
of Al2(SO4)3, a seed crystal is added to it to cool it and after a crystal of Al2(SO4)2 is deposited, it is separated from the mother liquor by
filtration.; In another treatment of the remained liquid after nitric acid recovery, after Fe content is added to the liquid by the specified quantity
to make the ratio of free sulfuric acid to FeSO4 be <0.5, it is heat treated and brought into contact with air to oxidize it and the formed
insoluble content is filtered and removed to prepare and use a solution essentially consisting of Al2(SO4)3, Fe2(SO4)3 and phosphoric acid.
Abstract of KR 20020051204
PURPOSE: A method for reusing a waste etching solution containing nitric acid with an etching solution and an aluminum sulfate water treatment
coagulant is provided to reduce a cost required to the treatment of waste acid, and to solve a problem of sludge reclamation. CONSTITUTION: The method
for reusing a waste etching solution containing nitric acid comprises: a first step for manufacturing an aluminum sulfate solution by dissolving an
aluminum component such that the density of aluminum in sulfuric acid is 10 to 60g/l; a second step for separating the waste etching solution
containing aluminum and nitric acid generated from an etching process of an aluminum foil into a nitric acid solution and an aluminum nitrate waste
solution by using a diffusion dialysis method; a third step for mixing the aluminum sulfate solution and the aluminum nitrate waste solution, heating
the mixture at 100 to 200deg.C to evaporate the nitric acid, and cooling them to withdraw the nitric acid and to transpose the aluminum nitrate into
the aluminum sulfate; and a fourth step for adjusting a density of the nitric acid into a range of 130 to 150g/l so as to use it as an etching
solution, and adjusting a density of the aluminum sulfate solution into a range of 35 to 45g/l so as to use it as an aluminum sulfate water treatment
coagulant.
Abstract of JP 10310427
PROBLEM TO BE SOLVED: To provide a method for treating spent nitric acid by separating aluminum from a processing soln. contaminated by the aluminum
generated in the electrolysis of aluminum foil as an aluminum nitrate crystal, then removing aluminum sulfate by further treatment and controlling the
composition of the separated mother liquor to make it recyclable. SOLUTION: A spent nitric acid contg. dissolved aluminum is evaporated and
concentrated, then mixed with concd. nitric acid and cooled to separate an aluminum nitrate crystal, the separated aluminum nitrate crystal is
dissolved in water (dil. nitric acid), sulfuric acid is mixed with the soln., and the mixture is evaporated and concentrated. Water is added to the
liq. concentrate to form liq. aluminum sulfate, or the liq. concentrate is cooled to obtain crystallized aluminum sulfate.
Abstract of JP 2001054988
PROBLEM TO BE SOLVED: To provide an efficient method for treating waste nitric acid liquid for recovering high purity nitric acid from waste nitric
acid liquid containing aluminum generated in a lithographic printing production process for recycling with energy consumption reduced. SOLUTION: A
reaction process in which waste nitric acid liquid containing aluminum which is generated in a lithographic printing production process is added with
sulfuric acid in an amount 1.0-1.5 times in mole ratio as large as the amount of aluminum in the waste liquid to produce aluminum sulfate and a
distillation process in which nitric acid separated in the reaction process is separated/recovered by distillation are provided. Preferably, the
distillation process has an aluminum sulfate recovery process in which liquid containing aluminum sulfate is transferred from the bottom part of a
distillation still to a crystallization tank, in which aluminum sulfate is deposited and separated/ recovered from the nitric acid solution.
[Edited on 9-9-2010 by Rosco Bodine]
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hissingnoise
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I don't doubt that you can distill usable amounts of HNO3 from your Al(NO3)3 but the level of convenience or otherwise remains to be seen. . .
[Edited on 9-9-2010 by hissingnoise]
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Rosco Bodine
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What I was considering is using NH4NO3 as the source nitrate and using scrap aluminum electrical cable which is very pure aluminum wire as the source
of aluminum, amalgamating it to faciltiate the reaction with NH4NO3 solution.
The NH3 which evolves can be salvaged and sequestered as hexamine by
dispersion of the ammonia into a second jug of water and paraformaldehyde
(mildewcide) crystals, so I have no waste by venting the ammonia nitrogen but obtain a useful byproduct. These reactions should proceed slowly
unattended
and go to completion. The few globules of mercury separate at the end when all the aluminum is consumed and can be recycled also. I end up with one
jug of
Al(NO3)3 solution and another jug of hexamine solution. Hmmmmmm.....
This sounds increasingly interesting huh ?
Alternately, Calcium Hydroxide and NH4NO3 solution can be reacted and the resulting Calcium Nitrate solution can be reacted with Aluminum Sulfate,
precipitating Calcium Sulfate and filtering off the Aluminum Nitrate solution which is evaporated to obtain the Al(NO3)3 - 9 H2O
From the proposed variation upon the classic nitrate distillation, twice the yield of HNO3 should be produced
from the same amount of H2SO4 consumed.
It will probably be a low concentration HNO3 unless the 9 hydrate Al(NO3)3 can be broken in advance. But no big deal if the HNO3 has to be
redistilled to concentrate it using a mixed anhydrous nitrate salt for breaking the azeotrope.
Everything is recycled, except the H2SO4 and Ca(OH)2, and there is twice as much HNO3 produced for the effort. If a significant amount of acid is
desired at low cost, the effort could be worthwhile.
[Edited on 9-9-2010 by Rosco Bodine]
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White Yeti
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You can make ammonium nitrate from ammonia and ozone, and then you can turn the ammonium nitrate into nitric acid by heating it with sulphuric acid
and distilling. It's probably not worth the trouble though.
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AndersHoveland
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Aluminium trinitrate is probably not a good route. Thermal decomposition of the hydrate results in the compound losing losing its nitrate groups
before all the H2O molecules of hydration have been removed. So this does not seem like a feasible route to obtaining concentrated nitric acid.
http://www.sciencedirect.com/science/article/pii/S0040603101...
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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