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Is aluminum used to get gold from black sand?

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vancouverbc:
I have some metal that seems to be 70% aluminum and 30% gold. Should I be able to disolve the aluminum away with hydrochloric acid? I know that this metal was the result of a process used to extract gold from black sand.

PlacerPal:

Might be lead and gold from an assay and sometimes smelting process of
gathering gold and silver using lead. You would need to Cupel it to remove
the lead leaving the dore gold and silver. Send it to me and I will Cupel it for you.
I'll return the lead so you will know for sure.   ;D

 :)

vancouverbc:
I was thinking aluminum because the overall specific weight of what I have is only 7.6 but what I have might be a cement with air in it.

I did a put a .23 gram sample in hcl/clorox and got a ton of white precipitate but the precipitate all disappeared when I put a bunch more clorox in. The silver piece that was left in the hcl/clorox seems to have a much higher melting temp than lead. I have a lot to learn:)

JOE S (INDY):
These are the professionals on their specialized forum:

Gold Refining Forum

Register and then read, read, read. 

Once I did that, I felt confident in asking questions. 

Let us know how you did.

Joe

PlacerPal:
Quote from: vancouverbc on January 20, 2011, 10:21:05 AM

I did a put a .23 gram sample in hcl/clorox and got a ton of white precipitate but the precipitate all disappeared when I put a bunch more clorox in. The silver piece that was left in the hcl/clorox seems to have a much higher melting temp than lead. I have a lot to learn :)


I am thinking you have some silver.
When you added the HCl/Clorox mix, the HCl lowered the pH of the caustic Clorox
driving free chlorine into the solution. Its a common method for leaching. Free chlorine
dissolves both silver and gold. BUT, the silver precipitates as silver chloride (AgCl) which
would be the white precipitate. When you added more Clorox you stopped the attack on
the silver and drove the silver chloride back into solution. Had you kept adding about
the same proportions of HCl/Clorox, you may have dissolved all the silver and given time,
the silver chloride would settle to the bottom of your container.

Silver chloride is difficult to deal with since it does not dissolve easily in common acids.
One can smelt it with a flux to get fairly pure silver. Better is to get the silver as silver nitrate
(AgNO3), which can be precipitate from a solution with a piece of iron or aluminum as
as fairly pure silver. To purify that silver, again smelting or electrolytic refining (YouTube).

The HCl/Clorox method is low toxicity and hazard if done in small volumes but can be smelly
if too much HCl is used and the chlorine generation runs on too fast. Its tedious too and very
temperature sensitive as all chemistry is. Use good ventilation.

Trivia about Clorox and Javex (Canada)
The formula is NaClO and about a 5- 6% solution. Because of the chlorine given off when
used for bleach, bathroom cleaning, etc. people sometimes think it is the chlorine that is
the agent doing the bleaching and disinfection. But it is not or at least not much. It is the
oxygen (O) that does most of the work since the oxygen is free from its partner oxygen
atom as in O2.

 :)


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