Circuit Card Fingers in Aqua Regia - VIDEO

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kadriver

kadriver

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Oct 25, 2010
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Here is my latest experiment using aqua regia to recover the gold from trimmed circuit card fingers

https://youtu.be/MITXgqMJ9h8

Thank You!

kadriver
 
Running fingers in AR I would be concerned with gold cementing onto buried conductors in the circuit board. Buried metal would mean buried cemented gold, making it harder to reach.

- If you hold up the circuit boards towards a light source, can you see any shadows from buried conductors?
- How much does the dried scrap board weigh after the metal have been dissolved?
- I didn't see any mention of denoxing and yet I never saw any signs of excess nitric when you precipitated your gold. That's quite good dosage of the nitric acid... though you used 6 ml nitric to dissolve 1.3 grams of gold, shouldn't there have been quite a lot of nitric left to fight in the final drop?
- By the way, I just love the color of the remaining solution. When you get a clear solution you know the gold was quite good even before the second refining.
- Have you tested leaching the scrap circuit boards with fresh aqua regia? It's no waste as you can use it on the next batch of fingers. Any gold or other hidden metal should give a color to the AR.

And as always, thanks for the video. 8)

Göran
 
I was surprised to see it still precipitate out of that clean A/R still black, mine is almost always brown to orange from a clean solution like that.
 
Thanks for the video! The first comment popped in my mind is about the low yield, 1.3gr out of 5 pounds seems very low.

Marco
 
Yep. Been doing it this way for a while. To me this is much better than the acid peroxide method. Must faster as well (obviously).
 
g_axelsson said:
Running fingers in AR I would be concerned with gold cementing onto buried conductors in the circuit board. Buried metal would mean buried cemented gold, making it harder to reach.

- If you hold up the circuit boards towards a light source, can you see any shadows from buried conductors?
- How much does the dried scrap board weigh after the metal have been dissolved?
- I didn't see any mention of denoxing and yet I never saw any signs of excess nitric when you precipitated your gold. That's quite good dosage of the nitric acid... though you used 6 ml nitric to dissolve 1.3 grams of gold, shouldn't there have been quite a lot of nitric left to fight in the final drop?
- By the way, I just love the color of the remaining solution. When you get a clear solution you know the gold was quite good even before the second refining.
- Have you tested leaching the scrap circuit boards with fresh aqua regia? It's no waste as you can use it on the next batch of fingers. Any gold or other hidden metal should give a color to the AR.

And as always, thanks for the video. 8)

Göran
Click to expand...

Goran to answer your points:

If you keep an excess of Nitric in the solution there's no need to worry over precipitation of the gold back onto the finger boards. It's when you allow the reaction to complete without and excess that you may see this happen.

The 6ml of Nitric - remember that there isn't just the gold to dissolve, (1.3g out of 500g of fingers does seem light though) there is also the base metals under the fingers so the excess won't be as much as you think. Incidentally, I'm not sure where it came from but doesn't always take 1ml of Nitric to dissolve 1g of gold.

This first AR isn't strictly refining it's recovery of the metals from the finger boards.
 
spaceships said:
g_axelsson said:
Running fingers in AR I would be concerned with gold cementing onto buried conductors in the circuit board. Buried metal would mean buried cemented gold, making it harder to reach.

- If you hold up the circuit boards towards a light source, can you see any shadows from buried conductors?
- How much does the dried scrap board weigh after the metal have been dissolved?
- I didn't see any mention of denoxing and yet I never saw any signs of excess nitric when you precipitated your gold. That's quite good dosage of the nitric acid... though you used 6 ml nitric to dissolve 1.3 grams of gold, shouldn't there have been quite a lot of nitric left to fight in the final drop?
- By the way, I just love the color of the remaining solution. When you get a clear solution you know the gold was quite good even before the second refining.
- Have you tested leaching the scrap circuit boards with fresh aqua regia? It's no waste as you can use it on the next batch of fingers. Any gold or other hidden metal should give a color to the AR.

And as always, thanks for the video. 8)

Göran
Click to expand...

Goran to answer your points:

If you keep an excess of Nitric in the solution there's no need to worry over precipitation of the gold back onto the finger boards. It's when you allow the reaction to complete without and excess that you may see this happen.

The 6ml of Nitric - remember that there isn't just the gold to dissolve, (1.3g out of 500g of fingers does seem light though) there is also the base metals under the fingers so the excess won't be as much as you think. Incidentally, I'm not sure where it came from but doesn't always take 1ml of Nitric to dissolve 1g of gold.

This first AR isn't strictly refining it's recovery of the metals from the finger boards.
Click to expand...
The 6 ml of nitric was for dissolving 1.3 grams of recovered gold when he did the re-refining.

My experience is that it can take a lot less than a ml per gram of gold. I used 28 ml for 53g when I refined my big button.

The only thing I can think of requiring nitric in that step is to oxidize the paper in the filter that disappeared.

Göran
 

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