Gold precip with SMB, HELP!

Detroit_Refined

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Aug 26, 2021
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So, i just tried to run my first batch if gold filled scrap. I dissolved out all the base metals with dilute nitric acid and recovered the foils. Put the foils into aqua regia, filtered it and attempted to precipitate it using stump out by bonide. This is only my second time refining gold and the first run was with inquarted gold. That worked out great! This current batch turned brown like normal but without any fizzing reaction, even after 4-5 spoon fulls.
This was only 200 grams of gold filled scrap. It did end up having some karat gold in it that i separated after the nitric treatments. What gives? Should i keep adding smb? Did i do some thing wrong?
 

nickvc

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Check your solution with stannous that may tell you where your gold is, you may well have precipitated it by your description, at best you are probably only looking at about 6 grams, allow the brown powder to settle, heating may well speed things up.
 

Hartbar

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May 6, 2021
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I’m no expert, but at 4% yield maybe 8 grams of gold, if you did well.
Did you neutralize the nitric with sulfamic acid before the SMB?
I believe excess nitric will stop the SMB working properly.
Like I said, I’m no expert.
 

g_axelsson

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No fizzing sounds like you maybe ran out of acid. That can put the gold in a state where it is still in solution even with adequate amount of SMB. Try to add a bit of HCl, slowly as it might react violently with all the SMB in solution.

Any brown fumes indicates that there is still nitric left in solution and dissolving the gold as fast as it is precipitated.

Adding a bit more HCl to gold chloride doesn't hurt the process, it can always be evaporated off if you need to decrease the volume.

Göran
 

Thill824

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Aug 24, 2021
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I don’t really know anything, but spoonful of smb sounds off. I dissolved my smb into distilled water then used it. Turned yellow gold solution crystal clear with brown gold settling nicely at the bottom
 
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