gold filings

[qfinej]

Hey Guys,

I'm reading hokes book at the moment and I'm reading the section about refining filings for gold and platinum metals and I'm a little confused it doesn't say to add silver to reduce carat to 6ct. Is this because you aren't melting and granulating? Also after the nitric treatment is finished this will just leave gold and platinum group metals is that correct? I know there will be trace metals

 

[nickvc]

With your gold lemel or filings with little or no silver because the material is already very small there is no need to inquart them as the acid can penetrtate well. If you incinerate the filings first and then put them into your beaker add some distilled water and slowly add a 50/50 AR water solution without heating the acid should dissolve the gold, palladium and base metals, some of the platinum may dissolve but that can be reclaimed by the stock pot. This should leave you with the platinum filings and a little silver chloride which can be easily removed and a solution with your gold, palladium, base metals and some platinum. The gold can be precipitated after filtering, it may need a second refine, and the remaining solution can be added to your stock pot to recover any PGMs.
I must admit this is an excellent method to make the recovery and refining of your platinum much easier as your starting material to refine is nearly all platinum so a concentrated solution is easy to obtain, necessary for all PGM refining, personally it's far too much for me and I just recover PGMs and melt, assay and sell but if you can get it right and you use a lot of platinum which I believe you do in your alloys it's probably well worth the extra steps to refine it, no refining charges and no premium to buy the platinum plus you get it all back!