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poor man's aqua regia + copper = ?


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#1 max.yevs

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Posted 25 March 2009 - 10:33 PM

I already have this experiment running-
20.2% HCl + excess ammonium nitrate = poor man's aqua regia

It is slowly eating a piece of copper pipe (and we all know HCl could not do this by itself)...

the solution is becoming a very dark greenish, anybody know what this copper compound is?

a little bit of chlorine is being produced- you can see its distinctive color on the surface

is it really just copper chloride? then how does ammonium nitrate come into play?

Edited by max.yevs, 25 March 2009 - 11:28 PM.

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#2 UC

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Posted 25 March 2009 - 11:48 PM

I already have this experiment running-
20.2% HCl + excess ammonium nitrate = poor man's aqua regia

It is slowly eating a piece of copper pipe (and we all know HCl could not do this by itself)...

the solution is becoming a very dark greenish, anybody know what this copper compound is?

a little bit of chlorine is being produced- you can see its distinctive color on the surface

is it really just copper chloride? then how does ammonium nitrate come into play?


It's some sort of mixed valency Cu(I),(II) complex involving chlorides. It's fairly common to see this. Please do this outdoors, if you aren't already. Aqua regia evolves dangerous NOCl fumes as well as NOx.

Due to the ammonium ion, the web of reactions occuring is even odder. Here's a short rundown of some of what's going on:

 4H^+ + 2NO3^- + Cu -> Cu^+^2 + 2NO2 + 2H2O
 Cu^+^2 + Cu -> 2Cu^+ (This is aided by chloride complexation of the Cu(I) ion as soluble CuCl2^-)
 Cu^+ + 2H^+ + NO3^- -> Cu^2^+ + H2O + NO2
 3NO2 + H2O -> 2HNO3 + NO
 NO + NO2 + 2H2O <-> 2HNO2
 HNO2 + NH4^+ -> N2 + 2H2O + H+
 HNO2 + HCl <-> NOCl + H2O
 HNO3 + 3HCl -> Cl2 + 2H2O + NOCl
 Cl2 + Cu -> Cu^2^+ + 2Cl^-
 Cl2 + 2Cu^+ -> 2Cu^2^+ + 2Cl^-
 2NO + O2 -> 2NO2

I'm sure I've missed a few.

Edited by UC, 26 March 2009 - 12:13 AM.

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#3 max.yevs

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Posted 26 March 2009 - 12:06 AM

yeah, its outdoors... and i just remembered i forgot they had to be put in right proportions
and thanks, i got the idea of substituting with NH4NO3 from you on another post


ah sorry didn't see the latex equations at first, so from what i see, this is the basic idea...
a small amount of ammonium nitrate turns into nitric acid, which oxidizes copper (your first/third equation)
the NO2 released partially helps reformulate the nitrous and nitric acid (your fourth/fifth equation)
nitric and nitrous acid react with HCl to give N2, Cl2 and NOCl (and NOCl > 2NO + Cl2) (your sixth/seventh/eighth equation)
the chlorine also oxidizes copper... (your ninth/tenth equation)

here's a picture... you can definately see and smell a little chlorine
sometimes i can see little brown traces of what looks like NO2, but i can't say for sure

actually copper was not the best metal to choose for this experiment, since nitric acid by itself can eat through copper.
even vinegar + H2O2 can dissolve copper

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Edited by max.yevs, 26 March 2009 - 02:29 AM.

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#4 max.yevs

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Posted 27 March 2009 - 01:50 AM

here's a better picture...

to my surprise, the whole pipe section thingy dissolved after about 24 hours...

Its a nice clean dark green color, although i put it out in the sun to evaporate, around the edges its forming nice bluish/light bluish/cyanish crystals... i assume its copper chloride.

//Thread Closed

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#5 YT2095

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Posted 27 March 2009 - 08:56 AM

Never mix Ammonium Nitrate with Copper!
explosive TACN can be formed, which it is doesn`t go off, is certainly Plenty enough evidence to get you arrested and sent away for a VERY long time!
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#6 UC

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Posted 27 March 2009 - 05:09 PM

Never mix Ammonium Nitrate with Copper!
explosive TACN can be formed, which it is doesn`t go off, is certainly Plenty enough evidence to get you arrested and sent away for a VERY long time!


You do realize that this has been beaten to death as a subject on sciencemadness? I believe it's the anhydrous material that is truly dangerous, and I'm not sure that anyone there has been able to produce it, though I don't read energetic materials forum much.

Also, the formation of the ammine complex requires that the solution have a reasonable amount of NH3 in it. Mixed with strong HCl, this is extremely unlikely. Splash some HCl in some dark blue tetraamminecopper (II) solution. The color of the complex (and the complex itself) vanishes upon acidification.

The NOx formed will end up destroying a good portion of the ammonium ion anyway, via nitrous acid. IIRC, NH4NO2 *can* be made with ammonia and hydrogen peroxide, but is only "stable" in the cold, decomposing on heating to nitrogen and water.
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