Aqua Regia Precipitating Gold Issues Help Needed Please

Hello everyone. New member. Long time visitor of the site. I recently did a small batch of about 3 grams of gold into an Aqua Regia solution. My gold was a combination of RAM foils and recovered particles from plated material. My solution was crystal clear green when I tried to drop the gold with SMB, but I did dilute quite a bit and for some reason am not able to get the gold to drop. I left it over night with the SMB and all that was dropped was a cream colored sludge that was next to impossible to recover. I saved the solution and am just wondering if there is a way to recover the gold back from the solution or did I waste it? I was thinking of maybe boiling off the solution, but I'm new to the whole gold refining and am turning to the professionals on this forum for any insights where I went wrong and how to fix the problem. Thanks everybody.

Did you test with stannous chloride at any time to see if you had gold in solution and/or if you still have gold in solution?

How much AR, and how much was HCl vs HNO₃?

How much SMB?

Dave

FrugalRefiner said:

Did you test with stannous chloride at any time to see if you had gold in solution and/or if you still have gold in solution?

How much AR, and how much was HCl vs HNO₃?

How much SMB?

Dave

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Hey Dave, thanks for replying. I used a 3:1 HCL/Nitric Acid. I didn't have any stannous chloride to test the solution at the time, problems with the shipping. And I'm not sure exactly how much of the SMB I used but I used a little at first and didn't see the brown reaction I was hoping for so I just kept adding more until I gave up and let it sit overnight. This was my first attempt at Aqua Regia method and am still learning. So I appreciate any of your experienced input. Thanks. - Matt

Did the solution fizz as you added the SMB ? If it did you probably have free nitric still in your solution so add sulphamic acid slowly until all reaction stops, if not try adding a little Hcl and see if you get any reaction.

If you used 3:1 I think the first question would be how much liquid did you use overall?

With out the stannous to test your solution you are basically working with your eyes shut. It can "see" your gold when you can't. Would you have started without the hydrochloric acid? Most likely not as everyone knows it is a key chemical, just like stannous.

Using a ratio of chemicals will leave you with excess nitric quite often. That would be my next suspect.

Alpha!
Go to Walmart and buy a package of tin fishing weights. put a weight in a test tube, cover with a little hydrochloric acid and gently heat the tube. as it fizzes, the tin is dissolving and forming SnCl. you have a small amount of stannous chloride solution to test with.
Art.

Thanks everyone for the input. I need to test with stannous, but I've been having a hard time ordering it for some reason, so I will go to Wal-Mart and make my own as you have suggested and test my solution for gold. I had used about 30ml of HCL and 10ml of nitric to dissolve a few grams of gold. It was a test run since I'm new to this method. I just want to get it right before using larger amounts of gold. I will see if I can get results with the tests. Thanks all.

If you can't find the tin sinkers, check some thrift shops and such maybe you can find something made from pewter. It seems to work pretty well also. I use sinkers about 1/4 inch in diameter and add three usually. I then add them to about 1/3 water to hydrochloric acid and heat very gently, I let hot tap water run over the bottled mixture (with a loose cap) until I see some tiny bubbles. It can be used within minutes when done right. Also add a little extra of the tin and it will last a while longer, as it does have a limited life.

Thanks again for all the help from everyone. So I was able to get a few fishing sinkers and made some SnCl and my solution tested positive so I took someones other advice on here and added HCL to my solution. Which after a certain amount reacted immediately and turned brown and started to precipitate the gold within half hour, so I just left it for now and will check it tomorrow when I get some more time and hopefully recover my gold content. Thanks for the guidance everyone, this has been a huge help. Can someone explain why the HCL was able to precipitate the gold in this situation? Thanks again everyone. -Matt

AlphaBaby said:

Thanks again for all the help from everyone. So I was able to get a few fishing sinkers and made some SnCl and my solution tested positive so I took someones other advice on here and added HCL to my solution. Which after a certain amount reacted immediately and turned brown and started to precipitate the gold within half hour, so I just left it for now and will check it tomorrow when I get some more time and hopefully recover my gold content. Thanks for the guidance everyone, this has been a huge help. Can someone explain why the HCL was able to precipitate the gold in this situation? Thanks again everyone. -Matt

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Simple you need the Hcl to create the gas to precipitate your gold.

HCl and SMB mixed creates the SO₂ that precipitate the gold.

I've seen it once when I used water to dissolve a dried out solution of gold chloride. The gold finally precipitated when I added HCl.
That is the reason I'm always adds more HCl than is needed (within reason). I've never had any problem with gold not dropping since then.

Göran