Re: Recovering Silver from Precipitates


Farooq W a écrit dans le message
<1156135704.860382.284110@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>...

number6 wrote:
Farooq W wrote:

Caustic and formaldehyde to reduce the silver to metal ... wash
free of
salts and redissolve in nitric acid ...


Wouldn't just dropping a clean copper penny (pre-1983) precipitate
silver metal as well?

I did something similar in my college days - adding solid copper to
AgNO3 did the trick.

Michael


Copper penny would work when the silver salt is soluble in water. AgCl
and AgSCN are highly insoluble.

Did you try mine ??? We've recycled over a million ounces like that ...

I am trying to avoid formaldehyde (carcinogenic?), since the lab does
not have a properly working fumehood. Someone suggested that I dissolve
the ppt in ammonia, add hydrosulfite which quantitatively reduces the
ppt to silver. Have you heard of or tried this method?

Thanks.


silver chloride and thiocyanate are both soluble in NH4OH. Numerous methods
can be used to ppt the silver. Then put the silver back into solution.
Caution: Do not let the silver in solution of NH4OH dehydrate nor let
students do this.
JL










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