If one wanted to further concentrate the acid to 70%, is it possible to simply boil off about a third of the liquid? I have read that the water will
come over first before the azeotrope. Is this correct?
Runningbear
woelen - 8-2-2010 at 01:41
You indeed can concentrate nitric acid in this way, but you will have quite some losses though near the end of the process. Initially, mainly water
will come over, but when the concentration of the acid rises, more and more HNO3 will come over as well. The border between pure water going over and
azeotrope going over is not sharp.
If you plan to do this, use a thermometer and monitor the temperature of the vapor, escaping from the liquid. As long as this is around 100 C, you can
go on, but as soon as it rises several degrees above 100 C then stop boiling. I expect that you can increase the concentration to 60% without too much
loss of HNO3. If you continue boiling, then you'll loose a lot of HNO3 and do not expect to go much beyond 60% in this way without excessive losses.
If you want stronger acid, then mix the 60% acid with its volume of conc. H2SO4 and then boil off. The acid will go over at well over 80 C but its
concentration then will be 90+ %. Part of the acid will decompose, so you get yellow nitric acid, containing some NO2. Beware, 90% nitric acid is
EXTREMELY corrosive and gives off dense fumes!bbartlog - 8-2-2010 at 08:22
Woelen is correct, but it is also true that if you have a Hempel column or other reflux apparatus you may be able to achieve a better separation of
the water and the azeotrope. Obviously this is not quite as simple as just boiling off water from your solution.hissingnoise - 8-2-2010 at 10:10
If you have can get 98% H2SO4 and Na/KNO3 you can distill strong HNO3 with minimal losses.
You can then dilute it as required.
Runningbear - 9-2-2010 at 19:33
thanks guys,
Measuring the temp is a great idea. I only want about 50ml so I'm not too worried about losses.
Hissingnoise, I'm aware I can distill the nitric, but to be honest, I don't like the idea of working with resulting nitric vapours. I keep thinking
if the flask happened to explode I could get hurt bad. I'd rather make a dilute solution and concentrate up to 70% which is all I need, rather than
stuff around with 95% solutions.
thanks,
Runningbearhissingnoise - 10-2-2010 at 15:15
I don't worry about flasks exploding if heating is even and isn't too rapid but I'm not too gone on the fumes myself.
At the moment, I'm trying to get an adapter so that my still will be fully enclosed.
I'll still end up inhaling some fumes when I nitrate something but that's life!
Vikascoder - 10-2-2012 at 21:22
When you mix nitric acid 60%with 98%sulphuric acid and boil the mixture at 80'c then you will get above 90& nitric acid but how ? Where will
sulphuric acid go its boiling point is very high so how you separated nitric acid from sulphuric acid Vikascoder - 10-2-2012 at 21:24
When you mix nitric acid 60%with 98%sulphuric acid and boil the mixture at 80'c then you will get above 90& nitric acid but how ? Where will
sulphuric acid go its boiling point is very high so how you separated nitric acid from sulphuric acid Mirage - 11-2-2012 at 08:18
When you mix nitric acid 60%with 98%sulphuric acid and boil the mixture at 80'c then you will get above 90& nitric acid but how ? Where will
sulphuric acid go its boiling point is very high so how you separated nitric acid from sulphuric acid
As you begin to distill this mixture, the water is absorbed by the hygroscopic H2SO4 (as long as it is in high enough concentration). Now this means
that all the water in the dilute HNO3 will have migrated to the concentrated H2SO4, leaving you with pure(ish) nitric acid gas. This condenses in you
condenser and you are left with conc. HNO3. Be sure to store in an airtight bottle, preferably somewhere dark and cold(lab freezer)
Hope this clarifies things
MirageVikascoder - 12-2-2012 at 06:08
Ya this is clear i was thinking without distillation how can it be done
