# What else will dissolve in HCL-CL?



## tamerakshar (Feb 7, 2009)

Will contaminating metals dissolve in HCL-CL ?
i'm focusing in copper residues, will it dissolve in HCL-CL ?
thx


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## Lou (Feb 7, 2009)

Yes.


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## tamerakshar (Feb 7, 2009)

what if i added SMB, will copper precipitate with gold contaminating it ?


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## butcher (Feb 7, 2009)

the SMB would precipitate gold first, and if in excess Smb would then precipitate some copper, but if you are trying to precipitate the copper I would not rely on SMB, but would use a metal to drop copper (replacement reaction) then wash copper residue in a acid to purify if copper was my goal.


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## tamerakshar (Feb 7, 2009)

butcher,
after nitric bath i always find a powder of base metals with the gold foils, in your opinion what is the best way to get rid of these residues, especially tin.


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## butcher (Feb 8, 2009)

nitric should remove majority of the base metals, then what is left when moving on to chloride process ,some may stay behind not easily dis olved as chlorides,thats were filtering chlorides helps, and in solution when gold is precipitated, more base metals will stay in solution, not precipitating with the gold, then good final washes finish up purifying, and if nessasary the whole process is repeated, disolving gold the second time is much easier because most all impuritys were removed the first go around. refining is removing other impuritys at most all steps until a pure end product is achieved. recovery is concentrating the gold and removing it from the bulk of other materials, sometimes the first run of a process is more of recovery and the second time is refining the recovered gold, hope this makes sense.


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## tamerakshar (Feb 8, 2009)

butcher,
i always find that grayish powder after the nitric bath, i think its tin and its a mess to filter.
Is this familiar to find these messy residues ?
thx for help.


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## butcher (Feb 8, 2009)

if at all possible best not to introduce tin in the first place. that way it doesn't cause trouble. I cannot say for sure your gray is tin or lead, but hard to filter sounds like tin.


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## Harold_V (Feb 9, 2009)

tamerakshar said:


> butcher,
> i always find that grayish powder after the nitric bath, i think its tin and its a mess to filter.
> Is this familiar to find these messy residues ?
> thx for help.



When you are faced with this problem, incinerate the material completely, then do a hot wash in HCl. Fill the vessel with water (tap water is fine), siphon, then rinse well. You can then process for values. By doing so, the resulting solution will be easy to filter.

Harold


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## tamerakshar (Feb 10, 2009)

thx Harold, I appreciate your help.


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## tamerakshar (Feb 10, 2009)

Harold,
regarding the hot HCL wash, what turns HCL into a yellowish color?


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## tamerakshar (Feb 10, 2009)

I tested the yellowish HCL wash with S/C and there is some gold dissolved, do you think that the amount of gold dissolved, turned the solution to yellow ?


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## tamerakshar (Feb 10, 2009)

With incineration not completely done, i think there was a little traces of nitric which helped in dissolving some gold.


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## Harold_V (Feb 11, 2009)

I'm a little late getting back to this one. 

Yes, if you do a wash without doing a complete incineration, you can expect traces of gold to dissolve with the HCl wash. Incineration is very important, for more than one reason. It oxidizes the tin, which is also helpful. Incinerate until you achieve a dull red heat, if possible. Be careful to not melt anything----and insure that all carbonaceous material is ignited. 

A yellow tint can also be created by the presence of iron. Be safe----always test your solutions with stannous chloride. ALWAYS! It is the eyes of the refiner. 

Harold


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## Ignatz61 (Feb 16, 2009)

When dissolving gold plated Kovar in Nitric I get a thick yellow powder settled at the bottom of the beaker. After washing the foils as clean as I can and putting in AR the foils dissolve but the remaining powder settles again.
What would be yellow and not dissolve in AR or Nitric? A wash in HCL produces some green liquid and a fine yellow/orange powder still at the bottom?


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## arthur kierski (Feb 16, 2009)

i have the same problem as ignatz61--what is the yellow powder?


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## lazersteve (Feb 16, 2009)

If your processors had gold tops you may be seeing Tungsten Oxide:

Here's a photo of what I have seen and know is a tungsten compound, but not sure which. I think it's tungsten oxide:







The top lid is a tungsten copper alloy plated with gold.

The dark material is gold that did not dissolve. The tungsten compound is a yellow color.

Steve


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## Harold_V (Feb 17, 2009)

I agree, Steve. That's what you commonly find when processing heavy electrical silver contacts, the ones with the waffle back. 

Harold


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