This my third and biggest attempt at CPU metal extraction. Started with 5lbs of CPU's this batch, boiled in diluted nitric acid for 3 days switching out the solution daily and vacuum filtering. Saved the filtrate for the next step each time. After the 3rd boil the CPU's were pretty well stripped and I had about 100 grams of what I think was silver nitrate mixed with the gold flakes in 3 cakes. I added the cakes to a beaker and submerged in 37% HCL 3:1 with distilled H20. Left this to boil overnight and came back in the morning to see almost everything was dissolved, including the gold flakes. I did a stannous test and it was positive so I know it dissolved the gold. I started digging around to see if I could find an explanation for this. Here is the best I could come up with. When I added the washed silver nitrate and gold flakes to the HCL the silver dropped the nitrate and became silver chloride. The released nitrate then became nitric acid which then mixed with the HCL making aqua regia and dissolved the gold flakes. Does this sound right? If so, I now have a beaker (currently reducing to target volume of 500ml) that has dissolved gold and silver chloride. For denoxing I intend to boil a gold button until there is no more reaction. What would be the best next move in order to recovery both metals, ideally separately? I don't want to drop in SMB without knowing that its not going to cause an unwanted reaction with the silver chloride. What is a good method to recover the silver from this silver chloride state? Thanks in advance.
David
David