Best way to fix a mess...

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Joined
Jan 8, 2021
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6
Hi all,

I came across about a lb of some copper/gold buttons, about 5% gold (according to the previous owner). In hindsight I realize I should have just started with nitric and kept all chlorides out of the mix but hindsight is 20/20...

Here's what I have done:

HCL/3% peroxide was added to all the buttons with a fish bubbler. There was no immediate reaction, but over the course of 3 days the solution turned green to black. Over the weekend, there were white crystals forming on all the metal and the solution was jet black.

I was impatient, and poured off all the black solution, rinsed a few times with water, and precipitated some white solids. Then I filled up the beaker with small additions of nitric, and brown gas was released as the nitric ate the copper. After about a liter of nitric, all the copper has dissolved and the resulting solution is a teal color which tests positive with stannous. There is a white precipitate at the bottom as well.

My best guess is that I have copper nitrate (blue), gold chloride (yellow), copper (i) chloirde (white salt), and copper (ii) chloride (green).

I am not sure how to proceed. I know I screwed up by mixing nitric in after the HCl, but I am not sure of the best way to remedy my mess. Looking forward to all the bright minds on here coming up with a gameplan :D
 

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Do you have anything left in the bottom of your beaker? If not you have either lost your gold or there was no gold in the first place.
 
As I've written many times, when in doubt, cement it out. It's the best way to recover from a mess.

Since you say the solution tests positive with stannous, we'll assume you have gold in solution. It may or may not be all of the gold you started with. Some of it may have been in the black solution you poured off or in the rinses.

Since the white precipitate is not likely to be gold, I would separate the solution from the precipitate. Then use copper to cement out the gold. You used a lot of nitric, so the solution will probably eat up a lot of copper before the values cement out. Do a little searching on cementing before you start.

Dave
 
nickvc said:
Do you have anything left in the bottom of your beaker? If not you have either lost your gold or there was no gold in the first place.

I have a white, fluffy precipitate in the bottom of my beaker. It runs through a coffee filter and Whatman 1 filters, but is able to be filtered out by a Whatman 5. Like I said, the stannous test suggests I have gold in solution.
 
FrugalRefiner said:
As I've written many times, when in doubt, cement it out. It's the best way to recover from a mess.

Since you say the solution tests positive with stannous, we'll assume you have gold in solution. It may or may not be all of the gold you started with. Some of it may have been in the black solution you poured off or in the rinses.

Since the white precipitate is not likely to be gold, I would separate the solution from the precipitate. Then use copper to cement out the gold. You used a lot of nitric, so the solution will probably eat up a lot of copper before the values cement out. Do a little searching on cementing before you start.

Dave

Thanks, Dave. I will filter out all the white precipitate and set aside for now (maybe go back later and confirm there was no gold particles mixed in with the white).

I attached some photos. The color is more of a teal than the photos appear. Also, I noticed when the teal solution was tested with stannous, it turned from teal to a deep blue.

I will try cementing out the clear teal solution with a copper bar and keep you updated.
 
A positive stannous test for gold will look purple not blue so I doubt you have gold in that solution, have you tested the first HCl and peroxide solution to see if that contains gold?
If as you say you rinsed the HCl solution from the solids adding nitric should not have dissolved any noticeable amount of gold.
So we have two scenarios in my opinion.
1. You had no gold to start with.
2. Your gold is in the first solution you used.
 
nickvc said:
A positive stannous test for gold will look purple not blue so I doubt you have gold in that solution, have you tested the first HCl and peroxide solution to see if that contains gold?
If as you say you rinsed the HCl solution from the solids adding nitric should not have dissolved any noticeable amount of gold.
So we have two scenarios in my opinion.
1. You had no gold to start with.
2. Your gold is in the first solution you used.

I did test the first solution and it was negative. In those photos, the blue I'm pretty certain is the copper nitrate, but what I was calling the positive was the black agglomerates within the blue. In the spots that were circled you can see dark black/purple specs.

And if I have residual copper chloride and I add nitric, won't that dissolve some gold? Having chlorides and nitrates in an acidic solution sounds like it would dissolve gold, no? Thanks for all the help.
 
Could be a false positive. Copper.. Test on a filter paper. One drop of solution and one drop of stannous.
Dilute with a drop of water if the stain is too dark.
 
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