Cold Dilute Nitric vs Hot Dilute Nitric for Recovery

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Marvinm4u

Member
Joined
Oct 10, 2020
Messages
13
I used a 1 nitric to 4 distilled water mix on two batches of gold-filled at about 60F.

Side Note: I did this in two beakers that were inside a 5 gallon bucket outside. I left the lid on, but not sealed. On of my solutions turned orangish brown and the other was blue. I poured off the brown solution (saved), rinsed with distilled water, then started that one again and ended up with blue solution. When opened to check the first time, I had LOTS of orange/red NOx that was released from the bucket.

Now in both, I have a VERY dark blue solution. Is this normal? I don't seem to be dropping any silver out of solution with clean copper after pouring some off and diluting 50% with distilled water.

I understand that "cold nitric" and "hot nitric" act differently, but I don't know exactly how.

Any thoughts, comments, information, advice, or criticism is appreciated.

Thanks,
MarvinM
 
Metals have a reactivity table and what you are seeing is all the highly reactive metals going into solution first, it may well dissolve some silver but that will cement back out as the acid finds more reactive metals to dissolve, you will probably find silver at the very end of the process once the copper and all other base metals are dissolved, as the silver is likely to alloyed into the gold you may need to heat your solutions to remove it.
 
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