Nitric acid help

[Azmirth]

* i know there is a thread for this but my question is more specific and need hard chemistry for this....

i want to make nitric acid above 70% ( which i have 2.5 litres of) but since its at an azeotrope im screwed. I also have 5 litres of H2SO4 so that is not a big factor either.

The KNO3 method works, but uses up costly KNO3 so i came up with using Cu(II) nitrate. But after researching i found that that no one has ever attemped to make nitric acid via this way:
This way is very efficent comparing that 1 mole of Cu(NO3)2 makes 2 moles HNO3 and 1 mole of Cu(NO3)2 = 187.56 grams compared to 1 mole of KNO3 which only makes 1 mole of HNO3 and weighs at 101.103 grams per mole, thus being a lot more effeiciant.

Cu(NO3)2 + H2SO4 --> 2HNO3 + CuSO4
KNO3 + H2SO4 ---> HNO3 + KHSO4
which makes up 2 moles of HNO3 without having to use cotsly potassium nitrate. The only problem is, since no reactions have been recoreded i cant tell if this will not work, and if the 2 end products will react. SO, i need your help to decide wheter or not his will work...

[X-ray Cat]

Any nitrate salt should work. Slight problem might be in dissolving the salts but even then it should work fine..

[[Lt]]

You can purify 70% nitric acid by distilling it with sulfuric acid which dehydrates the water off.

And yes copper nitrate may be used but the moles of copper weigh more, but the question is do you have an easy access to copper nitrate, it would help it being anhydrous.

[willi-wurm]

im suprised that your using copper nitrate, expected it to be more expensive. id suggest calcium nitrate, which is dirt cheap.

[[Lt]]

I'm having trouble with my distill set up as my retort doesn't seem to promote the condensing process, does anybody else use a retort and have these problems, I can post a couple pictures if that helps.

[X-ray Cat]

Cool the retord with ice.

[[Lt]]

I added a ice pack around the neck but a fair bit of it was forming around the sides of the sphere and dripping back into the acid/nitrate mix.

[X-ray Cat]

That always happens.. Might considder filling the sphere less and tilting the retord a bit to favor the outflow into your collecting beaker.
Still the refluxing of the nitric doesn't matter that much.. in time it will always distill over to your beaker..

[[Lt]]

Ok I finally had the time to upload these, so any help?

I have about 8 more on different angles if that helps.

[X-ray Cat]

Like i said, cool the tube connecting the two flasks with sacks of ice.
Plus it looks like your setup is closed.. Don't close it unless you're using vacuum. If you'll heat your setup when it is closed you'll build up pressure. Thereby you'll also increase boilingpoints and nothing will happen. open the setup

[[Lt]]

I did that, and it isn't closed the retort just rests inside the flask with about a 1 cm gap all around it.

[X-ray Cat]

try higher heating.. i usually heat to about 120-140 degrees celsius without vacuum. And maybe more cooling also have an icebath where your recieving flask is standing in.. You might already have that by I can't really see if you do or don't. You might also need to have more cooling sacks round the connection tube..

[[Lt]]

I thought It wasn't smart to distill Nitric acid over its boiling point cause that is what I've been doing, keeping it below 80 degrees celsius.

[X-ray Cat]

And thats where it's going wrong , breaking nitric down is inevitable, so you might aswell crank up the temperature. If your thermometer is submersed under fluid level and you're keeping that temperature at 80 degrees celsius nothing will happen.

A. Because the boiling point of nitric is (depending on local atmospheric pressure) 83 degrees celsius.

B. Because the gastemperature where your adapter or connection tube is is even lower than 83 degrees. Therefor all the nitric acid gass will have been condensed before reaching your retort exit.

C. If you want a bit of a decent distilling speed you need higher temperatures (or lower pressures ofcourse)

What you should do is not hanging your thermometer in the fluid mixture but hanging it at the same height of the exit of your distilling flask/retort instead. This will measure the gass temperature (and this temperature SHOULD indd be kept as close to 83 degrees celsius as possible).

Turn up the fluid temperature gradually till you see temperature rise in your thermometer which is measuring the gasstemperature and see it climbing up to 83 degrees.. At this temperature your condensation will also start and nitric will start dribling into you reciever flask. Take it slowly, gently and just keep it at a gentle distill. The nitric tends to rapidly start evaporating and make a gass temp rise out of the blue from 60 degrees to 83 degrees. The higher the gasstemp gets btw, the more water you're also distilling over. Keep it at 83.

[[Lt]]

Well from 2 hours I got like 10mls, but I get what your saying I was trying to reduce the amount of acid that decomposed seeing I don't have a condenser.

Thank you for the input.

[MurderSkillz]

More ice packs all the way around the tube would help condense it better.

[X-ray Cat]

Condensor doesn't reduce the amount of nitric that is being decomposed.. It'll just fasten up the condensing of your nitric gass thereby preventing nitric acid from evaporating out of your setup.. Those icepacks should do a fairly good job though...