nitric recovery pounding issue

[Master Nater]

i have a question on a nitric recovery experiment. i've got quite a bit of used nitric acid, and thought i would give nitric recovery a try, as i saw a video about it and thought it would be a great way to recover nitric, if even at a dilute consistency, because the first thing i do is dilute when dissolving PMs. my used solution that i'm working with only has 4.5 liters of 70% nitric in 7 gallons of used solution, so it is fairly dilute. it is saturated with mostly copper nitrate, but there are a few other various nitrates and potential impurities. the first go around, all of the water boiled off just fine and as it was getting up to temp to begin distilling off the nitric, it began VIOLENTLY pounding inside the beaker as it was heating, and seemed like it was going to break my glass. so i shut down the heat, and let things cool. my first thought was that i didn't have enough sulfuric acid to transfer all of the nitrates to sulfates, and that the nitric hadn't been freed up enough yet. so i gave a healthy does of sulfuric acid and tried again. same pounding, right at 116 degrees C. any ideas on why this solution will not allow me to distill off the nitric acid? an impurity issue? i'm really at a loss....

 

[Shark]

Remove the salts from the bottom of your beaker and try it again.

 

[FrugalRefiner]

I agree with Shark. The salts are allowing hot spots to develop on the bottom of your flask. When it finally gets hot enough it creates a little steam explosion, throws the sediment up into solution, allowing fresh solution to hit the hot spot resulting in those boil ups. You should be using a secondary containment container in case your flask breaks.

Dave

 

[Master Nater]

i assume you're referring to the white precipitate at the bottom. any idea how those salts got in there??? i haven't used any chlorides and sure haven't put any of them into my solutions. possibly leeched out of a 5-gallon storage bucket?

 

[Master Nater]

i was using corningware secondary, but was getting really frustrated, and dropped it. thank you both for your help.

 

[Yggdrasil]

i assume you're referring to the white precipitate at the bottom. any idea how those salts got in there??? i haven't used any chlorides and sure haven't put any of them into my solutions. possibly leeched out of a 5-gallon storage bucket?

It is the salts of dissolved metals dropping out when the solution gets saturated.

 

[BGDOCK]

Can you try low heat not boiling to evaporate the solution to 6M , Lazer Steve had great post on reusing nitric ,
Sure would be nice to revisit this again ,
( haven’t heard from you LS )

Jeff