# Gold and Copper in Solution



## AndreTrollip (Jun 26, 2016)

Hi Guys,

I am making my first attempt at extracting and refining gold. I have dissolved my gold in aqua regia, but I fear I may have also dissolved a lot of copper along with it because my solution is a deep green color.

So having made this mistake, I need some expert advice to try and get the gold out.

Can I still use SMB to drop the gold out? And do I still need to neutralize the solution with urea before adding the SMB?

Any help would be appreciated.


----------



## AndreTrollip (Jun 26, 2016)

I found this thread that seems to be about a similar problem.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=24074&p=254708&hilit=Copper+in+Aqua+regia#p254708

I think I will rather use copper to cement out the gold if I don't find a better solution.


----------



## 4metals (Jun 26, 2016)

Either option would work for you. It is good that you are reading. You should also read about ways to minimize your nitric usage so you will have no need to "kill" the excess. 

If you have a lot of solution, I would choose copper, if it is a small quantity, I would dilute it with cold water and add metabisulfite. 

And, as usual, always test all solutions with stannous chloride.


----------



## AndreTrollip (Jun 26, 2016)

Thank you 4metals. Appreciate the reply.


----------



## goldsilverpro (Jun 26, 2016)

It's poor procedure to try and dissolve gold away from copper with aqua regia. The copper wants to dissolve the copper first. When some gold does dissolve and there's still copper undissolved, the gold tends to precipitate (cement) back onto the copper in the form of a fine black powder. If you want to dissolve all of the gold, it's usually necessary to dissolve all of the copper.

With gold plating on copper, there are 3 basic approaches
1 - *Strip the gold away from the copper without attacking the copper*. On the forum, this is most commonly done with a strong sulfuric acid used electrolytically. Professionally, a cyanide solution is normally used
2 - *Dissolve all the copper, leaving the gold undissolved*. Then, the gold is dissolved by itself, using a small amount of aqua regia. Initially, the copper is dissolved with nitric acid/water or with the AP process, Muriatic acid/hydrogen peroxide (or, better, an air bubbler)
3 - *Dissolve everything with aqua regia* More difficult to drop the gold with SMB because of the large amounts of base metals present. For the same reason, the gold dropped will be quite dirty.


----------



## kernels (Jun 26, 2016)

I did a similar thing a while ago, evaporated down to get rid of nitric, then dropped gold out with SMB, my solution ended up a nice blue color. Then simply re-refine the gold powder at least once more. The nice thing was that because I started the second refining process with powder, it was easy to get the nitric close to spot on, and also used barely any acid.


----------

