# First re-refined button



## Stibnut (Jan 26, 2022)

I'm a big chemistry nerd and gold refining has long been on my radar, but I was kind of intimidated by the cost and risk involved. After a brief set of experiments in 2017, I set gold refining aside and didn't go back to it until about a month ago. Lately I've gotten back into it in a big way and have been devouring as much as I can on the subject while refining some karat and gold-filled scrap from eBay. I know I won't turn a profit from eBay purchases, but for now it's all about learning the process, while trying to keep losses as small as possible.

My first drops were kind of unimpressive - my first button of 5 g was pretty heavily contaminated and I had lost at least 2 g to a boil-over onto the patio after I added sulfamic too quickly, which was itself an attempt to correct excess nitric. Two of my subsequent refinings involved processing the paper towels soaked with sodium carbonate solution which were used to wipe up the spill, netting about 0.8 g. Then I started processing more batches of mostly karat scrap and learned the importance of washing with HCl after precipitation - that made a pretty big difference although there was still some discoloration and frostiness. I precipitated these drops with ferrous sulfate, figuring it would make sense to use that for the dirtier solutions for somewhat better separation at the expense of a little iron contamination, and then later combine the gold and do a second refining using SMB.

Yesterday I had time to do this second refining on a total of 42.8 g of impure gold from the previous batches. I cornflaked it and dissolved it in AR on a hot plate, then filtered, added a little sulfamic to deal with a slight excess of HNO3, diluted with distilled water (at which point a bunch of AgCl appeared), filtered again, and then added to a large beaker for the drop. I waited for it to cool to take advantage of the better particle size at low temps, then added an excess of SMB. The gold came crashing out quickly and had settled into a nice compact sediment within an hour, with a negative stannous test on the rest of the solution. I decanted the solution off and rinsed twice with hot HCl, which lightened the gold up considerably, then rinsed several times with distilled water, put it in a Buchner funnel and filtered, adding another HCl rinse followed by more water rinses.

I put it in a melt dish, melted with MAP gas, and poured into a round mold. Other than a little bit of spillage on the edge of the mold it went really well. Total weight is 41.738 g, just a little more than 1 g less than the original impure material, which could then have been less impure than I thought.

When I looked at it, I was stunned by how beautiful and pure it looked. Because of how impure my first attempts were, I was expecting to have to refine it again and was planning to use oxalic acid for the third drop. But I got such nice patterns around the edges when it froze, two vent pipes in the middle, and dazzling reflectance that I think it’s already highly pure. I think I’ll find somewhere to get it looked at by XRF and decide after that whether I want to go ahead with another refining or sell it as is.

I’m really glad GRF exists and has so much useful information. I certainly couldn’t have made anything like this without having spent several weeks looking through the forums absorbing all your insight!


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## butcher (Jan 26, 2022)

Beautiful gold, you must also account for the education and experience which itself can be as valuable as your gold, together they are priceless, that gold is just is pretty to boot, you may have spent some in the learning process, but with your study, you have turned it into something with much more value than that beautiful gold in your hand.


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## Stibnut (Jan 26, 2022)

No doubt! I'm really in it for the chemistry and never expected to turn a profit, at least for the foreseeable future. It's really cool how much inorganic chemistry goes into refining, and I've learned a lot in the last month. A big thanks to you and everyone else here!


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## orvi (Jan 27, 2022)

Nice ! good work


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## Stibnut (Feb 3, 2022)

I had it scanned by XRF on both sides. Both scans came out to 99.99% with no impurities detected despite increasing the scan time to find them. Couldn't have asked for a better result!


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## orvi (Feb 3, 2022)

Stibnut said:


> I had it scanned by XRF on both sides. Both scans came out to 99.99% with no impurities detected despite increasing the scan time to find them. Couldn't have asked for a better result!


Be aware of the error given by the machine. Value of 0,50 % isn´t big, and indeed it is a quite pure gold. But if you want to call it 99,99% gold, the error limit should be less than 0,01 %. And I am affraid that XRF machines aren´t sensitive and accurate enough for calling gold 4N reliably.
Below two measurements from one refining I did few months ago  first measurement for 10 s, second for 25s.


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## Stibnut (Feb 3, 2022)

orvi said:


> Be aware of the error given by the machine. Value of 0,50 % isn´t big, and indeed it is a quite pure gold. But if you want to call it 99,99% gold, the error limit should be less than 0,01 %. And I am affraid that XRF machines aren´t sensitive and accurate enough for calling gold 4N reliably.
> Below two measurements from one refining I did few months ago  first measurement for 10 s, second for 25s.


Right, yeah - I'm aware there could still be enough impurities to throw the purity significantly below 4N, although I suspect (but cannot definitively prove) that I'm above 3N. It seems that truly verifying 4N or higher depends on ICP methods, with gravimetric fire assay also not being reliable enough barring very good technique on multiple samples using a 5+ place balance. I'm just happy that I got the purity high enough to not detect anything else with two scans using 30s of scan time.


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## Stibnut (Feb 3, 2022)

Also, it turns out the person offering XRF scans also buys gold, and he gave me an offer for 95% of spot because of its purity. That's a pretty good deal for someone who doesn't have a business license, so i took him up on it. Now I've not only gotten a good result on purity but also found a good and honest buyer. I'm pretty happy about that!

He offers XRF on eBay as Metallodge. I spoke with him by PM and he said he'd be interested in buying from other forum members too. So for anyone out there who does this as a hobby and is looking for someone to sell to, I highly recommend him!


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## tlgero4699 (Feb 5, 2022)

Nice to know thankyou


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## notehunter494 (Jul 8, 2022)

Excellent results Stibnut! I am embarking on the same path. Hey as an aside and being a chemistry nurd myself I am wondering if your name has anything to do with the mineral stibnite? I am an old rockhound and pyrotech-guy. Antimony sulfide was a must for titanium salutes. 

When you dropped the gold and did the final hot HCl rinse did you start with 50/50 HCl, and did you boil it with the magnetic stir rod or just add it hot and let it sit and do its work?

Prior to this did you use sulfuric acid to rid any lead that might be present before the drop?

Many thanks, Tom


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