# Separating flake from grey mud



## shel8483 (Jun 10, 2012)

After doing hcl/peroxide stripping method and getting all the big gold stuff out I have a ton of very fine gold flake floating around in the hcl solution. Also there is a grey sediment that will not dissolve in hcl so i can filter the small flake out. I have tried to rinse but the mud stays with the gold. Is there a way to seperate this stuff without losing all the small gold flake floating around. Anytime I decant after settling this grey material comes right up and out when I pour off to the gold. This greymud is a sediment very light and swirls easily. so its very hard to seperate anything out of it. Tried dissolving it into solution and filtering but no dice. Any help would be appreciated


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## spiderman (Jun 10, 2012)

have you tried nitric, nitric will not desolve the gold, but before you use nitric rinse the mud and gold with water just incase there is any hcl left that may desolve the gold


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## martyn111 (Jun 10, 2012)

spiderman said:


> have you tried nitric, nitric will not desolve the gold, but before you use nitric rinse the mud and gold with water just incase there is any hcl left that may desolve the gold



Rinsing with water will not remove all traces of HCl, therefore by using nitric acid you will be producing AR which will dissolve a portion of your values.


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## butcher (Jun 10, 2012)

If you did happen to change from HCl and went to nitric with the hope of washing powder without dissolving gold, you would have to incinerate between these, rinsing will not remove the chlorides, water may remove some table salt and if it was boiling hot may remove some lead chloride, but you could still have enough chloride salts to make aqua regia, and dissolve some gold, neutralizing and washing then incineration would prevent the gold from dissolving.

I do not see a reason to change to nitric at this stage, and some of these white salts it is very possible they would not be soluble in nitric acid any way (like AgCl).

Let salt and foils settle well and decant solution, then wash out the chloride salts with boiling hot water keeping it hot while letting foils settle before decanting the wash from the foils, filtering may be needed at some stage but I would avoid filtering if not necessary, if you do use filtering you can wash the foils into a jar with a spray water bottle and a funnel.

Some types of white salt:
NaCl, soluble in water,
CuCl is soluble in HCl, 
PbCl2, soluble in boiling hot water,
AgCl, soluble in ammonium hydroxide, 

(Caution make sure to acidify any liquid, or solution you decant from this ammonia solution, also acidify any powder or foils with HCl acid which come into contact with ammonia compounds (which will precipitate AgCl again), so as not to form a dangerous possibly explosive compound when dry), I also keep ammonia solutions out of my regular stockpots or waste stream. (If I had no plans for reusing the ammonium chloride), the waste is treated separate, so as not to cause any trouble later.


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## shel8483 (Jun 10, 2012)

nitric not available will try boiling water thanks. hcl will not dissolve the stuff nor will cold water. tried ammonia but it really dose not put the mud into solution


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## lazersteve (Jun 10, 2012)

Gray powder in foils after AP is copper I chloride. This will require repeated washings with HCl. If all of the gray does not dissolve completely try another wash. If the HCl does not darken then you may be dealing with an organic compound or silver chloride depending on the source scrap.

Steve


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## Geo (Jun 11, 2012)

if it were mine, i would deal with it like i would a dirty solution. dissolve all that will dissolve from the mass in hcl/Cl. filter out any solids and warm the solution to a steam for an hour. allow it to cool and see if any more material precipitated. filter again and precipitate gold. you can be sure this is contaminated. wash powder with a hard boil in hcl, decant and replace the hcl wash and boil. repeat until boil remains clear. decant and add fresh hcl and dissolve powder again. allow chlorine to evaporate and precipitate gold. follow this with Harolds washes and rinses.


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## shel8483 (Jun 11, 2012)

I have tried pulling the gold flake out with hcl and cl. This is a grey area as I know there is quite a bit of gold in it . Usually I cannot get all the gold to disolve no matter how muh I swirl the solution around. When I filter I get a emerald green solution .Then drop with smb. The results are poor. I feel that some element in the solution is preventing a full drop. The solution still tests pos with stannous. Still adding more smb gives me false test results.So not really sure whats left in there. Is there a way to ensure all the gold drops/disolves. Like said I did that a couple of times before. But the results are poor. I have read copperas are a better option when dropping in a multiple metals solution. Would try it again if I had a better method to ensure all the gold comes down


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## lazersteve (Jun 11, 2012)

The gray powder is cause the green color. It dissolves in warm HCl. Once it's gone your gold foils should remain.

If you have already dissolved the gold foils with HCl-Cl then add a solid piece of copper to cement out the gold as a black powder, collect, incinierate and redissolve.

Steve


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## shel8483 (Jun 12, 2012)

Trying constant heating in a crock pot then rinse with water get it hot and repeat. now to the point where water is clear after setteling. Put hcl on it now and heat and decant,repeat process. Went through lots of acit still have solids in it so now I have completely dried it all to powder.. Should I hit it with a torch and then disolve it in hcl/cl Drop and redisolve a couple times to see if I can separate the gold. I have never had this happen before with this mystery substance. maybe nitric would dissolve it but as I stated I do not have the option to use it.


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## butcher (Jun 12, 2012)

Incineration is a good idea, (I do not like to incinerate acidic chloride powders as silver and gold chloride can be volatile in high heat, so I neutralize the powders and rinse them well before putting the heat to them), after dry get the glowing powder red hot but do not melt it, and expose to lots of air or oxygen.
This will burn off any organic materials, I do not know what your starting material was, but if it was electronic scrap and incineration was not part of you pretreatment then organic material from oils, heat sink grease, even some types of plastics can break down in these acids, and other materials is likely, the incineration will also help to oxidize any remaining base metal including the very troublesome tin, incineration will never hurt but almost always helps.

After the incineration a wash in boiling HCl, and very hot water washes is what I would use before, dissolving the gold, this will remove any soluble chloride metals, but will not dissolve the gold or silver (if any), this should put your gold powder in good enough condition to dissolve the gold, the colors of these wash's can indicate that you are removing contaminates.

(I see no reason for using nitric acid at this point, I doubt you have that much silver involved and if you did have tin involved it could just create other troubles).


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