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Author Topic: Separate Cu from Ag?  (Read 5303 times)

Offline Bill.D.Katt.

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Separate Cu from Ag?
« on: 29/07/2010 02:45:26 »
I have a mix of Cu and Ag powder. Any idea on how to separate them? Ideally I would like to remove the Cu however I can, and just leave the Ag powder.


 

Offline lightarrow

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Separate Cu from Ag?
« Reply #1 on: 29/07/2010 12:47:22 »
An old way is Cupellation:
http://en.wikipedia.org/wiki/Cupellation

Another way, but just an idea because I don't know if it works, is to use melted NaOH in presence of air oxygen: Cu should go in solution as Na2Cu(OH)4 while Ag is unchanged.

A more complex way is to oxide both to chlorides/chlorides complexes with aqua regia or Cl2 (generated from HCl + MnO2 or chromate or chlorate, ecc) or H2O2 + HCl. Then you melt the solid chlorides, at high temperature, with a greater amount of Na2CO3; silver metal will form, while copper remain as CuO - CuCO3 - CuCl2 and you can easily dissolve it with an acid which doesn't dissolve Ag (HCl, CH3COOH, diluted H2SO4, ecc).
« Last Edit: 29/07/2010 12:56:55 by lightarrow »
 

Offline Bill.D.Katt.

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Separate Cu from Ag?
« Reply #2 on: 11/08/2010 06:39:01 »
Wow,thanks lightarrow. Although I could do two of the mentioned procedures, that is a lot more work than I ever meant it to be. But since I have a limited supply of NaOH, and I would need to make the Na2CO3 from NaHCO3, I just went with a very dilute HNO3 and stomached the slight loss of Ag.
 

Offline lightarrow

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Separate Cu from Ag?
« Reply #3 on: 12/08/2010 12:36:52 »
Which conc. of HNO3 you approximately used?
 

Offline Bored chemist

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Separate Cu from Ag?
« Reply #4 on: 12/08/2010 20:23:56 »
Incidentally, if you still have the mixed Cu and Ag nitrates you can precipitate the silver as AgCl by adding salt and convert it to silver by heating it with sodium carbonate or by treating it with Zn and HCl.
I'm also curious that you can get nitric acid, but not washing soda.
 

Offline Bill.D.Katt.

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Separate Cu from Ag?
« Reply #5 on: 14/08/2010 07:16:41 »
About 5%. Bored chemist, yes that was another method I used. As you probably guessed, I had bought a little bit of AgNO3 to see what all the rage was about Ag precipitation. I figured I would get a faster reaction with some Zn pellets instead of Cu wire, plus I would be able to purify it with HCl. That worked pretty well, but I had a slight discoloration. I've done the synthesis for dilute HNO3 many times. I though washing soda was a NaHCO3 mix with other slightly basic compounds?
 

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Separate Cu from Ag?
« Reply #5 on: 14/08/2010 07:16:41 »

 

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