Sciencemadness Discussion Board

HNO3 from HCl and nitrate salt

kt5000 - 11-9-2014 at 17:38

tried the Nurdrage method of making HNO3 by combining HCl, potassium nitrate, and elemental copper. This produces NO2 gas that we bubble into distilled water or H2O2 solution to produce HNO3.

It worked pretty well. I'm sure the yield sucked. I was left with a puzzling solution in the flask that produced the gas. I ended up with a bunch of what I think was copper(ii) chloride. When I added Al metal and let it sit for hours, a bunch of copper precipitated out. I'm thinking there may have been other chlorides and am wondering where my potassium went.

Here's what I have:

2HCl + KNO3 + Cu --> NO2 (g) + CuCl2 + H2O + K ?

My best guess.. There's a lot of stuff precipitated out. It would be neat to recover potassium from that. Any insight is much appreciated.

Amos - 11-9-2014 at 17:46

If you used enough HCl to convert all of the nitrates, releasing all of the NO2, adding enough aluminum would get all of your copper back while filling the solution with aluminum chloride as well. If you wanted to go through the trouble, aluminum chloride is soluble in acetone while potassium chloride hardly is, so you could recover your potassium chloride that way.

[Edited on 9-12-2014 by No Tears Only Dreams Now]

kt5000 - 11-9-2014 at 17:54

I noticed potassium is higher on the reactivity series than Al.. So the potassium grabbed up all available Cl- ions, leaving the excess Cl- to produce CuCl2. Then adding the excess Al steals the Cl- from the less reactive copper, leaving elemental copper and AlCl3 ?

Let me know if I got that right :) I think the oxidation state for Al is +3..

kt5000 - 11-9-2014 at 18:08

I made it balance:

4HCl + 2KNO3 + Cu --> 2NO2 + 2KCl + CuCl2 + 2H2O

Does that look right?

bbartlog - 11-9-2014 at 18:12

Anhydrous AlCl3 is soluble in acetone, but you would have some kind of hydroxychloride (the water would hydrolyze the AlCl3).

(edit):
Quote: Originally posted by kt5000  
I made it balance:

4HCl + 2KNO3 + Cu --> 2NO2 + 2KCl + CuCl2 + 2H2O

Does that look right?


Yes, looks like I posted just after you did -

As for the reaction, you could think of it in several parts:

HCl + KNO3 -> KCl + HNO3 (not that this happens in the sense of producing isolated compounds, but acidifying the nitrate solution gives you something like nitric acid)

1/2Cu + 2HNO3 -> 1/2Cu(NO3)2 + NO2 + 2H2O (the primary reaction of concentrated nitric acid with copper)

Cu(NO3)2 + 2HCl -> CuCl2 + 2HNO3 (which then feeds back in to reaction #2)

... for a net reaction of

2KNO3 + Cu + 4HCl --> 2KCl + CuCl2 + 2H2O + 2NO2


But the second part is a simplification and in more dilute solutions apparently some NO can also be produced.

[Edited on 12-9-2014 by bbartlog]

kt5000 - 11-9-2014 at 18:22

That make a lot more sense, thanks. I have a bad newbie habit of trying to think of stuff as only a single reaction.

[Edited on 12-9-2014 by kt5000]

Amos - 11-9-2014 at 18:53

Aluminum chloride can be produced in solution, that solution boiled until solid, and then strongly heated and dried to produce the anhydrous form. I've got about 15-20 grams that I made this way. Unless my slightly yellow hygroscopic powder isn't the correct chemical...

kt5000 - 11-9-2014 at 19:14

I ended up with world's weakest nitric acid, then dropped some Cu in there to make Cu(NO3)2. Next time I do it, I'll measure the amount of Cu reacted to quantify the strength.

Amos - 12-9-2014 at 06:15

My first post on this site was an idea of mine to improve the efficiency of this process. I wanted to put copper into the nitrate/hydrochloric acid mix within an erlenmeyer flask, and simultaneously channel the nitrogen dioxide and steam from a boiling flask into a cold graham condenser with the output end pointing downward. This would be accomplished with two tubes leading to a two-hole stopper on the receiving end of the condenser. My reasoning was that it would encourage the formation of nitric acid as the two gases (NO2 and water vapor) cooled in the presence of one another, essentially condensing as nitric acid. I also decided to use boiling hydrogen peroxide to produce the steam, as the decomposition would yield additional oxygen to oxidize any NO produced as well. I never got around to trying the idea as I've been out of nitrates for some time now, and because it's easier to just distill your own nitric from concentrated sulfuric acid and a nitrate salt. But I would really love if someone tried this.

aga - 12-9-2014 at 08:45

If you have a pure nitrate salt, use conc Sulphuric and distill nearly pure HNO3 (also Nurdrage).

Praxichys - 12-9-2014 at 09:35

Quote: Originally posted by No Tears Only Dreams Now  
Aluminum chloride can be produced in solution, that solution boiled until solid, and then strongly heated and dried to produce the anhydrous form. I've got about 15-20 grams that I made this way. Unless my slightly yellow hygroscopic powder isn't the correct chemical...


You do not have anhydrous aluminum trichloride. Hydrated aluminum chloride decomposes into aluminum oxychloride and then aluminum oxide. http://en.wikipedia.org/wiki/Aluminium_chlorohydrate

The yellow color is likely from impurities, possibly iron.

kt5000 - 12-9-2014 at 12:33

Quote: Originally posted by aga  
If you have a pure nitrate salt, use conc Sulphuric and distill nearly pure HNO3 (also Nurdrage).


I saw this one also, but I don't think I'm ready to try it. I remember reading that hot nitric acid etches glass, so that's a concern, and I'm not comfortable yet handling/storing concentrated nitric acid. The weak stuff generated in the HCl method seems like a fairly safe way to start tinkering with less risk.

Amos - 12-9-2014 at 12:55

Quote: Originally posted by Praxichys  
Quote: Originally posted by No Tears Only Dreams Now  
Aluminum chloride can be produced in solution, that solution boiled until solid, and then strongly heated and dried to produce the anhydrous form. I've got about 15-20 grams that I made this way. Unless my slightly yellow hygroscopic powder isn't the correct chemical...


You do not have anhydrous aluminum trichloride. Hydrated aluminum chloride decomposes into aluminum oxychloride and then aluminum oxide. http://en.wikipedia.org/wiki/Aluminium_chlorohydrate

The yellow color is likely from impurities, possibly iron.


No, I didn't think that what I had was anhydrous, it's still a bit goopy. But I was wrong to suggest that it could be made anhydrous through heating. Good to know.

aga - 12-9-2014 at 13:21

Quote: Originally posted by kt5000  
I saw this one also, but I don't think I'm ready to try it. I remember reading that hot nitric acid etches glass, so that's a concern, and I'm not comfortable yet handling/storing concentrated nitric acid.

Me neither on both counts.

I did it anyway, and it is a wonderful distillation.

Being scared is Good.
Proper Natural survival response to Real Danger.

I did mine in a fume hood, and diluted the HNO3 pretty soon afterwards, purely out of Fear (=Respect) of the orange nastiness i had produced.
Not done it since, simply because i have enough nitric.

The glassware didn't care at all, although i lost a Keck clip to the acid, due to an imperfect seal at the RBF.

Boiling hot conc Sulphuric with stuff in it was more of a worry than the less hot conc Nitric.

kt5000 - 12-9-2014 at 13:34

Quote: Originally posted by No Tears Only Dreams Now  
I also decided to use boiling hydrogen peroxide to produce the steam, as the decomposition would yield additional oxygen to oxidize any NO produced as well.


I did bubble my NO2 into an H2O2 solution, at Nurdrage's suggestion. But is was 3% grochery store crap and probably didn't aid the oxidation much.

I read something a while back suggesting bubbling air though cold, weak H2O2 to increase its concentration up to 30%. Something about aiding the evaporation of water without speeding up the decomp. I have been meaning to try it. Not sure how I'd test the concentration though. The method I found requires potassium permanganate, which is a List 1 chemical, iirc. I try to avoid those in the home lab.

aga - 12-9-2014 at 14:06

All of the chemicals involved are Dangerous, in that they can All Hurt You.

Highly concentrated H2O2 can easily take your eyes out too.

Take appropriate Safety Precautions and use the best route suited to what you want.

Texium - 12-9-2014 at 14:23

Quote: Originally posted by kt5000  
I read something a while back suggesting bubbling air though cold, weak H2O2 to increase its concentration up to 30%. Something about aiding the evaporation of water without speeding up the decomp. I have been meaning to try it. Not sure how I'd test the concentration though. The method I found requires potassium permanganate, which is a List 1 chemical, iirc. I try to avoid those in the home lab.
That method of concentrating hydrogen peroxide sounds a bit sketchy... Also, potassium permanganate is extremely useful, and it's actually only list 2. It would be a good idea to get some. You shouldn't have any trouble as long as you have a good variety of other chemicals that don't imply drug making. It would be impossible to get by without using list 2 chemicals, as hydrochloric and sulfuric acids are also on that list among other things.

kt5000 - 12-9-2014 at 14:30

:) I didn't mean to imply they weren't dangerous. My concern is that I have a basic home lab and, if law enforcement ever knocks on the door, I want it to be as clear as possible that the goal isn't drug production. I read stories about law enforcement paying visits looking for listed chemicals like elemental iodine, red phosphorous, etc. I figure by avoiding the listed chemicals as much as possible, keeping a clean lab, etc., improves appearances.

kt5000 - 12-9-2014 at 14:33

Quote: Originally posted by zts16  
it's actually only list 2.


That makes me feel better :)

aga - 12-9-2014 at 14:39

Yes, good plan.

However .... having any Glassware, any Chemicals, including Table Salt, will get you into some serious discussions with LE.

Your Goals may not have any relevance if Their Goal it to have some photos of a 'Lab' to which the press prepend the word 'Drug' automatically.

Strange that Drug Companies, publicly saying that they are Drug Companies, are not raided daily.

Chemistry is becoming an Extreme Sport.

Life Lesson : Do and Learn what you can while you can.

kt5000 - 12-9-2014 at 15:25

Quote: Originally posted by aga  

Strange that Drug Companies, publicly saying that they are Drug Companies, are not raided daily.


They fund more senate campaigns than I do. *sigh*

Amos - 12-9-2014 at 18:25

Quote: Originally posted by kt5000  
:) I didn't mean to imply they weren't dangerous. My concern is that I have a basic home lab and, if law enforcement ever knocks on the door, I want it to be as clear as possible that the goal isn't drug production. I read stories about law enforcement paying visits looking for listed chemicals like elemental iodine, red phosphorous, etc. I figure by avoiding the listed chemicals as much as possible, keeping a clean lab, etc., improves appearances.


Don't go out of your way to hide the fact that you do it, and keep good lab notes on what you do. Also, it probably wouldn't hurt if you had some things in your lab that remind people that chemistry is for other things too. For example, I think that having collections of copper compounds and elements in my lab kind of makes it hard to believe that I'm making drugs; I have clear evidence of what I'm actually using the stuff for.