Why does my nitric acid not condense?

[blindreeper]

After making a still I tried to distill some nitric acid. But I got no acid!
I used a 500ml Pyrex brand Erlenmeyer flask as the distilling flask and a 250ml Pyrex brand long necked flat bottom balloon flask as the reciver.




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HEAT


Ignore the * its just to get the pic half decent!

Ok thats my crappy picture. The condenser was on an angle downwards. Tube was just a flourecent tube (light) that was bent and had a 40cm PVC water jacket around it which had a constant water supply from the bottom of the "condeser" out of the top of it. I put in 32g sulfuric acid (boiled from a batter, I know it was conc. cause I left which was very stupid and came back to find the lab full of sulfuric acid gas and a beaker billowing of the gas.) and 68g of 13-00-46 KNO3 (put the prills in water and boiled the water off and dried them). Then I put the KNO3 in the flask. Turned the water on and left that running for 5 minutes to check from problems before I started. The tube was arounf 1 inch round and was sealed in the 500ml flask with teflon tape. I added the sulfuric acid and gave it a swirl (the acid was at 20 C as that was the outside temp and it was boiled down weeks ago and stored ina sealed container) Then I connected the flask and put it on my hotplate at 85 C.

There was some red NOx in the flask. IAfter about 10 min of heating there was visible HNO3 vapor in the round botton flask. Note: the RB flask was not sealed in there the end was just placed over the end of the condener.

What I want to know is why the HNO3 didn't condense? The condenser was 400mm long!
Some reasons I think why the distillation didn't work is that I didn't let the nitrate and sulfuric react (I found this out today, I attempted this 2 days ago)

[Arthis]

First, nobody especially likes those crapy pictures. So you should an account on 50megs.com or anywhere to host some decent mspaint made pictures.

Second, starting a new thread about a distillation problem instead of replying into the topic about HNO3 distillation is not what a (especially new) member should do.

Then let's see the problem.

There is no real reaction between HNO3 and sulfuric acid. (same and same explanations again) . HNO3 forms an azeotrope with water, which mean the max conc. you can get while distilling HNO3 alone is 70% (azeotrope point). At this concentration, the mix comports like a new compound, with special ebullition point, etc. Adding sulfuric acid just breaks the azeotrope as H2SO4 is very hygroscopic (high conc., say ~90-100%). Once the azeotrope is broken, you can distill your nitric acid as its ebullition point is low (~64-67°C if I remember).
In your case, with KNO3, you need to make it well dissolve in the sulfuric acid for the nitrate ions to be dissolved in acid.

About your distillation system, the HNO3 fumes will condense in contact with the surface of the condenser, so maybe your condenser radius is too wide, even if it's long. The water in a condenser should go from down to up. Maybe the flush of water is not high enough, then the inside part of the condeser is not well cooled down, and the gas get out of the condenser with a higher temp. than 64°C.

[blindreeper]

I apprehsiate the help arthis but I am not that new a member. Secondly this is about the HNO3 not condensing even thought there was ample space for condensation. Sorry for posting a new topic delete if neccesary.

[vulture]

There's way too much KNO3 to H2SO4 here.

What temperature did you distill at?
Not the temperature in the flask, but the temperature just before the condenser intake.
If you put the hotplate on 85C that wouldn't evaporate much HNO3 as it's boiling point is somewhere around 80C (for pure HNO3 gas).