distilling nitric

[Anonymous]

I have been reading on distilling nitric, and I think I got it figured out.
Just want confirmation on 1 or 2 Facts? that I just got wind of.

If I make a dilute nitric with KNO3 and H2SO4 then try and distill it, that water will for the most part distill off until the azeotrope(spelling) cocentration of 68 percent is achieved, then the azeotrope will distill over.
I think this would cause me to lose acid unless I distill to dry KHSO4.
Also, does the acid itself degrade as the azeotrope distills? does the heat
at this temp decompose some of it?

thanks\
Jim

 

[Noxx]

No, the water won't distill off...
The solution will distill, whatever the concentration of the acid is. If you have 15% nitric acid, and you use simple distillation, you will end with 15% nitric acid. My recommendation would be to make a higher concentration nitric acid. You should add just enough water to make 68% nitric acid.

Also, you will loose some acid because it decomposes when you distill it, unless you distill in vacuum.

 

[Anonymous]

Steve, thanks,
I do not anticipate using a lot of acid and think that I would dilute it anyways, so I could work with the hopefully less reactive diluted stuff and only make enough for the task at hand.

I google search the distillation and the comments are from that, I have distilled other stuff and was suprized that the info provided stated that the water would distill off until the azeotrope was reached.

I got a distilling rig, all glass, do you just run water from the tap into the condenser, or does it need to be distilled to keep the gunk from building up?

jim

 

[butcher]

If the concentration of acid is high in solution boiling, you will first distill the almost pure nitric first and very little water will distill out, the solution boiling will lower in concentration untill Azeotrope (68%) is reached, then you will start to distill out the 68% solution till done.

On the other hand if your starting solution was a week solution (weak nitric) the soution would distill mostly water until boiling solution reaches 68% then you would distill 68% off.

I collect 90% nitric in lil water from the NOX gas , then change the reciever to collect azeotrope (68%), but you can just collect 68% by alowing solutions to mix. see my other post for little more detail they are lil hard reading.

 

[OMG]

I read that anhydrous magnesium nitrate is used to concentrate nitric. The anhydrous magnesium nitrate apparently sucks up the available water to make a hydrated form of magnesium nitrate (hexahydrate). I'm not sure if it would be possible to then just filter out the hydrated magnesium nitrate, but I'm sure you'd be able to at least boil off just the concentrated nitric (wiki says magnesium nitrate doesn't decompose until about 330 C).
If you can't get any anhydrous magnesium nitrate and were willing to sacrifice some nitric(as magnesium nitrate) you could probably just add some magnesium oxide.

 

[Noxx]

Sorry I was wrong,

As butcher said, water will distill off first (with little nitric) if you have diluted nitric acid.

For example,
The firsts mL I got was 2% nitric
after 50mL I had 10% nitric
and my last mL are 50% nitric

Concentration has been measured with specific gravity.

 

[Shecker]

George Gajda's Book on gold refining refers to a system where nitric acid can be recovered from AR by using a refluxing condenser and bringing the solution of Ar to a boil. Nitric acid boils at a lower temperature than hydrochloric acid, allowing for a separation and recovery of the nitric acid.
Normally when I sit at my desk my copy of Gajda is over my right shoulder, but for some inexplicible reason it isn't there today. When I find it I will report on further details.

Randy in Gunnison

 

[butcher]

Strong sulfuric acid acts as a dehydrator, using it can improve strength of nitric acid produced, but on downside it causes stains on your lab equiptment (Glass) when distilling. NOTE IF you try Distilling nitrate study it first make sure you understand process and safety, tools to use, dangers, poor mans nitric or Aqua regia works plenty good, easy and much safer.

 

[Lou]

You're thinking of phosphoric. Concentrated sulfuric acid doesn't affect borosilicate glass up to its max working temperature of 400C.

 

[butcher]

Lou when I distill I wasn't using lab glass, and the strong sulfuric salts stains my jar.probably attacking silicon in the glass? or maybe just leaving hard salt deposits?(of coarse I used sand bath) I have very limited supply of lab equiptment so far and save it where I can.

 

[viacin]

NOTE IF you try Distilling nitrate study it first make sure you understand process and safety, tools to use, dangers, poor mans nitric or Aqua regia works plenty good, easy and much safer.

I can only find two good posts on distilling nitric acid. I wish there was a tutorial on it. I have actually learned more on the subject from a youtube video and a 1950's chemistry book, than the forum. Am I missing a post somewhere, or has the whole process never been explained in full?

 

[Noxx]

I think you are right viacin. I should make one, I distill nitric acid every two weeks.

 

[butcher]

yes a post on distilling would be great maybe not just nitric, with data, principles ect,

 

[Lou]

Go for it Noxx! I haven't distilled nitric in a long time, not since I ran out and only had KNO3!


Lou

 

[viacin]

Noxx, I believe it would be appreciated not only by me, but by hundreds, if not thousands of members over time. Keep up the good work.

 

[Anonymous]

since nitric passivates stainless could I just make my condenser from SS tubing? I have that stuff.

thanks

Jim

 

[Harold_V]

300 series stainless is commonly used in packaging and distributing nitric acid. Unless Lou has an interesting comment, I see no reason why you can't use the material for distilling. Be certain that your choice is non-magnetic. You likely know that not all stainless is.

Harold

Edit:

A question via PM from one of the readers gave me cause to add an additional comment.

The use of stainless in this instance is restricted to the condensing unit only-----I would not endorse the use of stainless for the flask.

 

[Platdigger]

So what will your boiling flask be made of?

If glass, how will you connect your tubing to the glass?

If stainless, think it will stand up to the sulfuric nitrate mix?

I hope this will work, it would definately cut some cost.
Randy

 

[Harold_V]

If stainless, think it will stand up to the sulfuric nitrate mix?

That was the one thing I wondered about, too. Given the stainless is not in direct contact with the mix, it may work. Connecting, as you alluded, could prove to be interesting, but a Teflon stopper would solve the riddle. Easy enough to make if one has access to a lathe.

Harold

 

[Anonymous]

glass for the boiler, connected to stainless. I have access to many sized, sheet, etc. I was going to use glass (a flask of one type or another) then fit with a condenser with teflon o-rings to seal.

Jim