DrScrabs - 14-5-2019 at 08:26
Hello everyone!
Today I found 2NH4NO3·(NH4)2SO4 25kg for 30 bucks. If there is any cheap way to get the nitrate salt from the double salt my stock is safe for far
more than a decade!
The expensive way I do expect would be to grind the salt as fine as possible and dissolve in a minimum amount of boiling dH2O and add a stoichiometric
amount of H2SO4 [edit: or NaHSO4] to the cooled soln. to distill of dil. HNO3 to proceed with whatever.
The cheap way I do hope for is to grind it not as fine as possible fill the mass in a long pvc pipe and slowly run dH2O through. I´d expect the
nitrate salt to be the main component in solution at the bottom of the coloumn and the remaining solid to be cruedly purified ammonium sulfate.
Solubility sulfate salt 754/L@20°C, nitrate salt 2089 g/@25°C according to wikipedia. [edited, thanks to Ubya for pointing out my stupid error]
Has anybody ever tried this?
How do you expect it to happen?
DrScrabs
[Edited on 14-5-2019 by DrScrabs]
Ubya - 14-5-2019 at 08:42
Ammonium nitrate has a solubility of 1500g/L at 20°C per Wikipedia, don't know where you picked up that number.
Ammonium nitrate at 100°C is 10 times more soluble in water than ammonium sulphate, you could try your tube idea using RT water but the biggest
difference is at 100°C, i guess the best option is still a boring recrystalization
DrScrabs - 14-5-2019 at 09:13
Thanks for pointing out my error, I looket at the data per 100ml, I corrected it in the original post.
As far as I know it always crystalizes as the double salt so it has to be a little bit more than a rex.
But the difference in solubility @100°C would make it much more attractive for a day of hot vac filtration, great!
hissingnoise - 14-5-2019 at 12:14
If you know the quantity of sulphate in the mix, you could add a stoichiometric quantity of slaked lime to precipitate sulphate as gypsum,
leaving NH4NO3 and NH4OH. 
Prolonged heating and stirring of the soln. is required to complete the metathesis... 