NonEthicalPyrotechnics
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100% Nitric acid?
So the original method I used to produce nitric acid was the sulfuric acid and nitrate salt method but I just found a video on how to produce it with
a nitrate salt and molten sodium bisulfate. Now I have a bit of a theory. If both the nitrate salt and sodium bisulfate were completely anhydrous
would you distill over 100% nitric acid? Would this be a possible way to obtain anhydrous nitric acid?
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Dr.Bob
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Not easily without special care and following a real route. Doing it by the seat of your pants will likely end in failure or disater. There are
several threads on here about making fuming nitroc acid, try searching carefully.
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PirateDocBrown
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How is 98% sulfuric and dry sodium or potassium nitrate not working for you to produce near-anhydrous nitric acid?
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For all your phlogiston needs.
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PirateDocBrown
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If you are not using liquid sulfuric acid, you are gonna get the molten salts to foam up quite a bit, from released NO2 gas, which will also
contaminate your distillate.
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mackolol
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I doubt that the acid will be 100%, but it may be somewhere around 90%<. During distillation some of the acid will decompose into NO2 leaving
water in the mixture that will dilute it somewhat. Note, that acids' molecules are based on water, so it is hard to make it totally anhydrous, and to
be honest I don't either know why would one need exactly 100% one.
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Refinery
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I suppose using 98% H2SO4 or oleum, and drying the nitrate before distillation can result very pure HNO3.
The old Roguesci sources cited that RFNA could be turned into WFNA with adding a bit of urea, although eventually it will turn reddish due to
decomposition.
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Chemetix
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I've recently played with preparing some conc nitric from various methods and have to say Sulphuric is a strong candidate for preparing Nitric at
close to 100%.
Calcium Nitrate anhydrous was used to bring the azeotrope from an SG of 1.43 to 1.48. Which wasn't bad, maybe I could redistill with more CaNO3 and
push it over 1.5. But the sludge of Calnitrate mixed with nitric poses a problem. What do you do with it and not lose precious nitric? Distilling
further and ending up with a crystalline mess in a flask only to add more work to get it out and then dry it for reuse is a huge pain in the arse.
It's the same with the nitrate salt-sulphuric technique, the residue salts are a waste of time to process, and makes the effort to reclaim the excess
sulphuric un-economic.
But a simple technique of heating the sulphuric to the point of generating fumes, which is about 280C, means the acid is very dry, 98-99%. Even dirty
acid can be used it seems.
I then added 1.43 SG nitric to this and distilled. The nitric that comes over ( using cuts for heads and tails, the center fraction being collected
for use) comes to 1.5 SG.
The sulphuric can then be re heated to drive of the water and reused over and over for this purpose. The thing is that the sulphuric, if it has
organic contamination, it actually clears up as the NO2 burns off any residues, so using drain cleaner acid can become a reagent grade acid after
being used several times.
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Refinery
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And if you do these things repeatedly, you can just simply keep the reagents in their mid-state. For example, CaNO3 with HNO3 could be left just
sitting while it's still sludge, and added more HNO3 later. I have used these types of contiunous processes a couple of times, having a "seed" process
reagent where stuff is added and other is removed. Some catalytic solvent processes are an example.
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greenlight
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Quote: Originally posted by Refinery  | I suppose using 98% H2SO4 or oleum, and drying the nitrate before distillation can result very pure HNO3.
The old Roguesci sources cited that RFNA could be turned into WFNA with adding a bit of urea, although eventually it will turn reddish due to
decomposition. |
Ahhh yes, the old forum, reminds me of being a teenager . I believe you had to
bubble dry air from an aquarium pump through it for an extended period of time as well if I remember correctly or was that a different method?
If you have a vacuum pump and a good wahing trap so as to spare the pumps life, you can get some beautiful crystal clear, water white 99% nitric as it
just jumps straight over into the receiver with no decomposition.
[Edited on 12-5-2020 by greenlight]
Be good, otherwise be good at it 
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Chemetix
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"For example, CaNO3 with HNO3 could be left just sitting while it's still sludge, and added more HNO3 later."
Unfortunately the Ca Nitrate needs to be anhydrous to work, so evaporating the acid residue or processing it somehow to get the Ca nitrate dry then
anhydrous needs to be done. It took me a bit of work using the microwave to drive off the water from the hydrated crystals. I starting from a liquid
mass and dried it to a sticky lumpy mess in a pan first, as my container was not sealed it had liquefied with exposure to atmospheric moisture.
Using urea, just dilutes the acid as the reaction produces water I wanted to avoid that step.
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