CuCl2 flux to toughen gold melt

[mls26cwru]

I have been reading through Ammen's book and ran across a section that mentions using copper-2-chloride as a toughening agent to further purify gold when melting... has anyone tried this? Should it be melted with borax as well when trying this? Does anyone know the chemical mechanisms behind this? I am assuming it creates chlorides with trace metals and forms a slag that can be separated from the melt... any input would be appreciated as the book did not go into it too much (at least in the section i am reading currently).

Thanks,
Mike

 

[4metals]

While I have never used CuCl2 as a toughening agent I would suggest that if you get too hot, as is possible in an induction furnace, it can decompose and leave you with contaminated gold. Although if you feel the need to use it your gold is likely already contaminated.

Toughening is typically done with niter, potassium nitrate. It is added to a fine gold melt in very small (like a pinch) increments and it will dance around the surface and oxidize any base metals in the gold which are at the surface of the melt. The key here is at the surface of the melt. To get the impurities from what is below the surface of the melt, that's where your refining skills come in. The niter sizzles and bounces around the surface of the melt, I like to add a small (did I say small?) pinch of borax which will form a sticky spot on the crucible wall on the surface of the pool of molten gold, this sticky spot collects the oxidized impurities the niter collects and they stay on the wall of the crucible when you pour.

Remember, this is a band aid! Refine it well and it will not be needed.

 

[mls26cwru]

Thank you 4metals! I was just wondering if anyone knew anything about it.

When I read it in the book, I was intrigued about it, but it did not go into any detail. I do have a gram of gold that needs further refining, so i might give it a go with that... but im gonna try to read up on it first.

I was just looking to see if i could pick somebody's brain about the whole process.

 

[mls26cwru]

http://books.google.com/books?id=1-9GAQAAIAAJ&pg=PA357&lpg=PA357&dq=copper+chloride+flux+toughening+gold&source=bl&ots=_Ght53BTeT&sig=JRLbqI6oJb4R1GSreSDU78ZRWF0&hl=en&sa=X&ei=DKqKUsTWJoaN2gWCo4CYAw&ved=0CCwQ6AEwAQ#v=onepage&q=copper%20chloride%20flux%20toughening%20gold&f=false

interesting tidbit i found looking around for more information about this... I would like to try it, but definitely think Harold's washing procedures are far and away a safer option!

 

[Harold_V]

http://books.google.com/books?id=1-9GAQAAIAAJ&pg=PA357&lpg=PA357&dq=copper+chloride+flux+toughening+gold&source=bl&ots=_Ght53BTeT&sig=JRLbqI6oJb4R1GSreSDU78ZRWF0&hl=en&sa=X&ei=DKqKUsTWJoaN2gWCo4CYAw&ved=0CCwQ6AEwAQ#v=onepage&q=copper%20chloride%20flux%20toughening%20gold&f=false

interesting tidbit i found looking around for more information about this... I would like to try it, but definitely think Harold's washing procedures are far and away a safer option!

Even careful washing may not remove some of the contamination, is it is often bound securely within the precipitated gold, and dragged down.
I'm very narrow of mind where the purity of gold is concerned. For me, it was of upper importance for my gold to be above question, as virtually all of it was put back in use in the way of jewelry. Benchmen are not thrilled to discover that the gold they use has problems, as they often cast hand carved waxes, so their hard work is lost.

I fully understand that a guy isn't likely to produce 9999 quality, but there's little reason to settle for less than the industry standard of 9995, and it's not all that hard to achieve. You most likely would exceed that degree of purity with just a little more effort.

I tried the niter process early on, and was never pleased with the results. They may have been evident by assay, but so far as the behavior of the gold, it wasn't. I wanted to see a glistening surface n my molten gold, which I never achieved without a second refining. Even prolonged washing, alone, did not improve the gold, depending on how dirty it was. When I resorted to a second refining, the results were drastically improved, often with the contamination that was removed quite evident in the barren solution.

If you are really concerned abut purity, don't rely on a single refining, not unless your gold chloride solution is very clean, and it often is not. A second refining will do wonders, as the traces of contaminants that have the potential to be dragged down are significantly reduced.

Harold