Gold Filled Scrap Trial / Results

[Marco_Brody]

Hi everyone - after studying the forum and reading the Hokes book (you all so kindly provided free of charge) my brother and I made a go at the first refining attempt and are very pleased with the result. Grazi for this fantastic site and let me know where we can make a contribution for its continued success!

We want to share how it worked out - this is specifically for refining the gold filled jewelry type of scrap. I would appreciate any insights / criticisms etc of the process as we intend to do another batch this weekend.

We only had HNO3 (tech grade 70% ) HCL (muriatic I think 32%) sulphuric 98% and sodium metabisulfate (from brewing supply) available for the process.

Process with photos: -- the photos came out in the reverse order I wanted - please count from the bottom (learning to use forum).

Started with 133 grams of gold filled jewelry - ended up with almost 5 grams of gold.

1. Thoroughly washed the jewelry
2. Incinerated to remove oils etc
3. We skipped the first sulphuric wash because we only had a little bit of sulphuric
4. We did not acquaint ourselves with the reaction of tin / lead to acid because we didn't have pure examples of either
5. We dumped the entire lot into a large pyrex bowl and added water to cover the pieces (wathc cases, earrings, chains, pendants, bracelets, rings etc)
6. Added Nitric Acid
7. Waited out reaction for about an hour. Not much was happening after the initial foam up so we added some heat by way of a hot plate
8. Nitric reaction ended with blue liquid.
9. We filtered off the blue liquid and were left with what is seen in photo 1. There were a few old round iniitaled pins that went into the mixture. They came out as half-dollar sized pieces of gold foil but still looked exactly like they were when they went in with initials and all. Very cool. Also - a watch case came out looking exactly like it went in except it was just a very thin shell of its former self. Also cool.
10. We washed what is seen in photo 1
11. The pieces in photo 2 were things we thought were G.F. that turned out to be some other plated metal and plastic
12. 50/50 sulphuric /water solution added to stuff in photo 1 (added acid to water for safety rather than water to acid - thank you Mr. Hoke)
13. Let sit for 20 mins - no heat (Hoke's reccomends heat)
14. Dillute & drain (takes a long time because you have to add a ton of water to the sulphuric or else it burns up the coffee filters)
15. Wash again

Hokes reccomends immediately dissolving the by-product in Aqua Regia. We wanted to reach as close to pure as possible so we dried the remnants out pretty good and then weighed them . We inquarted with sterling silver scrap in a porcelain crucible (matched weight of gold with silver estimating the scrap was about 12K). Melting was done with an Oxygen / MAAP brazing torch ($49.99 in home depot with the gas tanks). Once molten, we ice-cast the mixture into a stainless stock pot.

16. Inquarted gold put back into the Nitric Acid. This was a real suprise. At first, there was pretty much no reaction. We had to heat it to the point that it was almost boiling and stir it with a glass drink sitrrer. I had expected (based on what I read and videos I saw) something similar to the reaction that occurred when we first added the Nitric Acid to the G.F. material. It took almost 2 1/2 hours to get the ice-cast flakes to brake down.

17. Dillute / filter / wash again.

18. Nice brown crunchies / dust in bottom of bowl
19. Fresh Nitric Acid
20. Added HCL till reaction began - then a little sulphuric (which apparenlty gets the lead out)
21. The aqua regia turned a awesome golden yellow color --- but there were some pieces on the bottom that did not dissolve despite waiting 1/2 hour.
22. We filtered again
23. Metabisulfate --- we were not sure how to estimate how much gold we were expecting so we kept adding it until the liquid was clear.
24. Dillute, drain (no filter this time - we just kept dilluting, settling and pouring off)
26. Pour off till just cappuchino grinds in the bottom of bowl.
27. Spooned out into crucible
28. added flux and cooked it up --- it was one of the most amusing things I've seen in a long time. First the poweder dries out to a light brown and then it just reddens and balls up into gold balls. Like magic!
29. Nice molten ball was poured gently from crucible into a pan of room temp water.

30. Hammered the little ball flat like thick little coin. Weight = just under 5 grams. Tests 22K. (photo 3-4)
31. Grinning ear to ear

 

[goldenchild]

You did extremely well for your first time doing this! The only things I would change...

The sulfuric washes arent necessary. Sulfuric only be used in your final digestion to drop any lead that may have been put into solution. Also, once you had your gold foils you did not need to inquart. The foils are so thin that you could have actually dissolved the foils in AR right away. The pieces that didnt dissolve in your final digestion may have been silver chloride. If your final result tested 22k you have to work on your washing procedure unless you are ok with 22k. Again very nice job 8)

 

[Marco_Brody]

You did extremely well for your first time doing this! The only things I would change...

The sulfuric washes arent necessary. Sulfuric only be used in your final digestion to drop any lead that may have been put into solution. Also, once you had your gold foils you did not need to inquart. The foils are so thin that you could have actually dissolved the foils in AR right away. The pieces that didnt dissolve in your final digestion may have been silver chloride. If your final result tested 22k you have to work on your washing procedure unless you are ok with 22k. Again very nice job 8)

Thanks Goldenchild - I really appreciate the advice and words of encouragement. Being able to go right from the foils to the AR will be a huge time / expense saver. Not having to do the sulfuric washes is also great because that is probably the most annoying (patience demanding) part. It is so strong it just dissolves the filters to nothing unless you dillute it so much that it takes for ever to drip through.

We're going to try a smaller batch so we have more control over it and try to get the purity up. Anything special to use for washing between steps - or just water?

 

[goldenchild]

Washing your gold should be your very last steps before drying and melting. But before I get to that let me stress the importance of good filtration. When you have your gold chloride and are ready to filter it you should get it to the point that its perfectly transparent. This is whether your gold chloride is a nice yellow or a dark green. Filtration can be the difference between needing to digest your gold again after the first drop to only having to wash your gold once. 22k vs 24k.

The way to do this is after the AR digestion, while the gold chloride is still warm add ice. Add a generous amount and stir. This will push any silver chloride out of solution. Now filter the solution. I use a Buchner funnel with vacuum assist. If your chloride isn’t perfectly transparent then pour off the chloride into a catch vessel and rinse the filtering vessel very well into the catch vessel. Now filter the gold chloride once again into the filtering vessel using the same filter you just used. In the end you want your gold chloride to look like you took a cup of water and added a few drops of yellow or green food coloring to it.

Now after you precipitate your gold and let it settle, decant and rinse with water until there is no more color. Now with only the gold in your vessel add HCL. Boil the HCL. This is one of the only times you bring a reaction to an actual boil. 5 to 10 minutes should do. Let it cool. If there is color decant the solution into your catch vessel, rinse with water until there is no more color and add HCL. This should be repeated until the HCL boil produces no color. All the HCL and water from your HCL washes should all go into the same vessel and tested with stannous at the end.

Lastly you will want to do a final boil in ammonia. This will get out any silver chloride that made it through filtration. This is why it's so important to do a very good filtration. If done correctly you will have 0 silver chloride in solution. After that final boil in ammonia, and if there is no color, rinse with water. Add a small amount of HCL just to re-acidify your gold. Dried ammonia on your gold could be bad.

Because I focus so much on filtration I personally am able to actually only perform one HCL boil and skip the ammonia boil. This is from gold that is precipitated from both dirty and clean solutions. My gold consistanly XRFs at .9998. Filtration filtration filtration.

 

[maynman1751]

Your blue liquid may also contain some silver. You can either cement it with copper or add HCl and make silver chloride. It's best to cement with copper as that will give you .99 silver with no additional processing.

 

[Marco_Brody]

Washing your gold should be your very last steps before drying and melting. But before I get to that let me stress the importance of good filtration. When you have your gold chloride and are ready to filter it you should get it to the point that its perfectly transparent. This is whether your gold chloride is a nice yellow or a dark green. Filtration can be the difference between needing to digest your gold again after the first drop to only having to wash your gold once. 22k vs 24k.

The way to do this is after the AR digestion, while the gold chloride is still warm add ice. Add a generous amount and stir. This will push any silver chloride out of solution. Now filter the solution. I use a Buchner funnel with vacuum assist. If your chloride isn’t perfectly transparent then pour off the chloride into a catch vessel and rinse the filtering vessel very well into the catch vessel. Now filter the gold chloride once again into the filtering vessel using the same filter you just used. In the end you want your gold chloride to look like you took a cup of water and added a few drops of yellow or green food coloring to it.

Now after you precipitate your gold and let it settle, decant and rinse with water until there is no more color. Now with only the gold in your vessel add HCL. Boil the HCL. This is one of the only times you bring a reaction to an actual boil. 5 to 10 minutes should do. Let it cool. If there is color decant the solution into your catch vessel, rinse with water until there is no more color and add HCL. This should be repeated until the HCL boil produces no color. All the HCL and water from your HCL washes should all go into the same vessel and tested with stannous at the end.

Lastly you will want to do a final boil in ammonia. This will get out any silver chloride that made it through filtration. This is why it's so important to do a very good filtration. If done correctly you will have 0 silver chloride in solution. After that final boil in ammonia, and if there is no color, rinse with water. Add a small amount of HCL just to re-acidify your gold. Dried ammonia on your gold could be bad.

Because I focus so much on filtration I personally am able to actually only perform one HCL boil and skip the ammonia boil. This is from gold that is precipitated from both dirty and clean solutions. My gold consistanly XRFs at .9998. Filtration filtration filtration.

Thanks for this info. Much appreciated. I have ordered the Buchner filter kit and will wait until it arrives before trying another batch. Our gold chloride was definitely cloudier than water w food coloring. It was more the consistency of iced tea - which I mistakenly thought meant it was loaded with gold! I had a friend test the gold button and it is definitely contaminated -- 22K -- not 24K. Definitely want to shoot for the 24K though - so we've got to work on this filtering.

 

[Marco_Brody]

Your blue liquid may also contain some silver. You can either cement it with copper or add HCl and make silver chloride. It's best to cement with copper as that will give you .99 silver with no additional processing.

This will provide an interesting activity while waiting for the filter kit to arrive. We saved the blue liquid because in a 5 gallon bucket because our town only takes haz mat once a month. Thanks for the advice.

 

[goldenchild]

Your blue liquid may also contain some silver. You can either cement it with copper or add HCl and make silver chloride. It's best to cement with copper as that will give you .99 silver with no additional processing.

This will provide an interesting activity while waiting for the filter kit to arrive. We saved the blue liquid because in a 5 gallon bucket because our town only takes haz mat once a month. Thanks for the advice.

That's cool that your town will take hazmat but you may find that your wastes can really start to pile up. Also, you dont exactly want people to know what you're doing. If you want to go the extra mile and learn to dispose of the wastes yourself I recommend the thread below. If you're ambitious enough you may even end up with an added bonus of Cu.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=47&t=1300