Wyndham said:
of the 4 methods which works better for cost of materials and once we get to the Au chloride, could we use a plating method to retrieve the gold or would it leave too much in solution.
I have no knowledge of a reclamation process that involves plating, a process referenced as electrowining (or electrowinning). I'm of the opinion that it would be more complicated than simply precipitating with chemical reagents, however. It might be acceptable for a continuous operation, but not well suited to individual batches.
Also after perciptating out the gold from the Au CL would this be combined with the borax flux method to reduce the percipt to a button, seems logical, just need a conformation.
Properly washed after precipitation, it is not necessary to flux gold. A slight film of borax that coats your melting dish should be all that is required. If flux is necessary, it's a good sign your gold is not pure. It all depends on your objective. Some folks are pleased to recover the gold, regardless of quality. My logic is that there is no better time to bring gold pure than when it is finely divided, so I encourage folks to dissolve the fine powder, filter well, then use a selective reagent for precipitation. That way you come close to pure gold. Regardless of the reagent chosen, the resulting brown powder should be well washed with dilute HCl, rinsed well, then washed with ammonium hydroxide. The improvement in quality is nothing short of amazing. I have outlined in various posts the washing procedure I used. Inquire if you're interested and can't find one of them.
Harold, in another post you said that dissolving the e cell percipt with muratic and chlorox into AU CL was a good clean was to go. What is the black powder in the ecell, gold sulfate, Or is there copper in it as well?
As I understand the sulfuric stripping cell----gold is dissolved in the proximity of the anode (the part being stripped) by persulfuric acid, which is created by the current of the system, but only in the near proximity of the anode. As the dissolved gold migrates away from the anode, it is precipitated because it can not be in solution as a sulfide. The particles that are recovered are very finely divided bits of gold, bordering on being colloidal, thus the color. If I am wrong, I would be pleased to have a correction posted by one of the chemists on the board. . I try to not misinform readers.
I don't recall that particular post, but I hope I made it clear that I endorse any method of dissolving the resulting values from the stripping cell. What I
don't endorse is melting the values without further process, which is part of the answer to the question you posed.
It's unreasonable to assume that a stripping cell produces pure gold. They are known to recover various precious metals, so the yield will always be suspect if for no other reason. My logic tells me that it is unreasonable to assume that traces of all elements that are present won't be included in the yield, so they must be addressed. In practice, that appears to be true.
Contrary to commonly held beliefs, achieving a level of purity that exceeds industry standard (9995) isn't easy. Even when re-refining, there is no guarantee, for mechanical drag down becomes an issue. If your objective is fine gold, you should always dissolve the yield from a stripping cell, filter the solution well to eliminate any flocculence, then wash the resulting gold well, as advised above. That will bring you much closer to your target of pure gold. Leaving out any of the steps is likely to result in an inferior quality, which will be obvious when the gold is melted. Pure gold will melt with no flux, and will not leave any color behind in the flux coating of the melting dish aside from purple (colloidal gold). If, after melting, you find color in the flux coating of your melting dish, or if your end product has any discoloration, or has a frosty surface, of fails to form a pipe when allowed to cool naturally, it isn't pure.
Harold
