Conundrum w A/P

[Robertda]

Hi All,

First let me say that I have done my homework so to speak. I have gotten Hoke's book and read it one and a half times. I am trying to capture gold off of gold plated pens. On the gold pins I used HCl and hydrogen peroxide. A 50% 50% mixture. After about four hours all the gold was off the pins and I could see nothing but bare copper. The solution was clear as water and the Stannous test did not indicate the presence of gold. I thought that the gold would flake off and float in the container. Could someone give me an idea as to why the solution is clear and why there is no indication of gold with the stannous test.

I was not able to find it in her manuscript, but I think that's a document that needs to be read multiple times.

Thanks in advance Robert,

 

[4metals]

Are they gold plated pins or gold plated pens? Why does this matter? Well if they are pins, the gold color is likely gold plating for conductivity reasons. If they are gold pens, the reason is likely cosmetic and therefore not necessarily gold. That could explain a negative stannous result.

 

[UncleBenBen]

Could someone give me an idea as to why the solution is clear and why there is no indication of gold with the stannous test.

Welcome to the forum Robertda!

I'm going to assume you meant pins, as in electronics. You used too much H₂O₂. The peroxide oxidized the gold allowing it to be dissolved. Then it will have cemented back out of solution onto the copper in the pins. Any gold will now be in the form of a brown to black powder or mud.

What type of pins, and how much are you working with?

If it's just a small amount of lightly plated pins there may not be enough cemented powder to even see until it settles for a day or two.

Try and study up more on the forum about the copper (II) chloride leach. Also referred to as AP. It only takes a very small amount of hydrogen peroxide to get the leach started. Then an aquarium air bubbler will keep it going as it dissolves the copper in the pins.

I hope this helps you a little.
Ben

 

[Grelko]

Hi All,

First let me say that I have done my homework so to speak. I have gotten Hoke's book and read it one and a half times. I am trying to capture gold off of gold plated pens. On the gold pins I used HCl and hydrogen peroxide. A 50% 50% mixture. After about four hours all the gold was off the pins and I could see nothing but bare copper. The solution was clear as water and the Stannous test did not indicate the presence of gold. I thought that the gold would flake off and float in the container. Could someone give me an idea as to why the solution is clear and why there is no indication of gold with the stannous test.

This is when I started and the problems I had processing my pins. It answers alot of the questions you might have about it.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=22285

Did the solution start turning green or yellow, then go back to clear?

If you used a lot of pins, you might not have enough HCl to finish dissolving the brass pins. The zinc in the brass will make the solution clear or greyish "cloudy".

 

[Robertda]

Ben, et al

Thanks a lot for the reply, it is much appreciated. They were "Pins". It was a Siri typo that printed pens. I did hold the gold pins in the palm of my hand, a small mound of them. I miss placed my scale and never got to weigh them. I've use this peroxide and HCl on gold fingers and the gold just flaked off so I thought that would occur with these but it didn't. Now have a clear liquid with the copper pins in it. They were unused ones. There doesn't seem to be any gold plating on them now because all I can see is the pink copper color. I did have a out of proportion mixture of hydrogen peroxide and hcl, per your earlier comment. If I understand you and the other gentleman who responded I need to get an aquarium bubbler and place the hose underneath the pins and let it bubble until the pin are consumed. I did add one third more HCl which was about 200 mL .

Comments?

On more articles...

Robert

 

[UncleBenBen]

With no oxidizer like H₂O₂ in the solution, less reactive metals like gold will be reduced or "cemented" out of solution as elemental gold by more reactive metals like copper.

The goal of the copper (II) chloride leach is to dissolve the copper substrate, releasing the gold plate on top. An aquarium bubbler will keep oxygen in the leach(same oxygen provided by the peroxide) to oxidize and dissolve that copper.

I think you may be on a good path, just know the study never stops. This is a vast and complicated field, and the great part is, nobody will ever know all of it. Take advantage of the search function, this great forum is treasure in its own rite. Make it a habit to read here, and to read here often. You will be glad you did!!

Ben