NADPH
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Silver purification
Hi!
I want to purify silver. I have some alloy with ~85% silver along with copper and other metals.
I dissolved it in nitric acid and got some bluish green mess.
Then I precipitated AgCl with NaCl solution and washed AgCl until blue color was gone.
What is easiest way to turn all AgCl into pure metalic silver (without any AgCl impurities)?
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unionised
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Melt it with sodium carbonate or treat it with zinc and dilute acid.
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bahamuth
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Hi.
Think I can help you there.
Recently I have done this a lot; take your washed AgCl and mix it with ~30% NaOH(aq), add sucrose, heat(bring to a simmer) and stir once in a while,
usually a couple hours. Vacuum filter and wash with water twice, suck dry; wash twice with acetone, suck completely dry. Store dry.
If you can leave it overnight boiling, I have observed that the silver powder clumps together and is easier to wash and handle afterward.
Any sufficiently advanced technology is indistinguishable from magic.
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dann2
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This copied from elsewhere:
Purifying sterling silver
Dissolve your sterling silver in nitric acid; a bit of heat will help if your acid is dilute. Next, precipitate the silver as the chloride, AgCl, by
adding an excess of NaCl solution. Wash your precipitate and then reduce it to metallic silver by one of the following methods:
1) Add an excess of NaOH solution and heat to boiling/ nearly boiling. Add either glucose (dextrose) or formaldehyde solution, a little at a time,
until all the AgCl is reduced to metallic silver. (The resultant silver powder is grey. not shiny) This method only takes less than an hour.
2)Add some pieces of zinc to your AgCl under water. The zinc will slowly reduce the AgCl to silver metal. The excess zinc can be dissolved in HCl.
This method takes a few days.
3) Dry your silver chloride and intimately mix it with an excess of Na2CO3 (soda ash). Heat this mixture with a propane torch (this is normally done
on a block of charcoal) until the silver melts to form a button of pure silver.
I prefer the first method as I have used it on several occasions in the past. I have never tried this, but you might be able to make your own
conductive epoxy by adding the silver powder obtained in methods (1) or (2) to some normal (not 5 minute!) epoxy. The idea is to use the epoxy to bond
some copper strip to the electrode. This will only require a small amount of epoxy. It might also work if you add graphite powder rather than silver
although I expect the resistance to be higher.
I (Dann2) have not done the above BTW.
Dann2
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densest
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Electrolysis is a very easy way to get crystals of pure-ish (>99%, 99.9% if you're careful) silver.
Use a dilute nitric acid electrolyte - as small an amount as possible, a stainless steel cathode, your impure silver as the anode, and apply enough
voltage that 20-100 milliamperes flows per square centimeter of anode. Silver crystals will form on the cathode and fall to the bottom - they don't
stick to the steel. Monitor the voltage - as soon as it starts to rise, you're starting to get copper and other more active metals into solution, so
stop. Carefully done, most of the silver is removed from the electrolyte, which can be distilled and the acid reused. If you get greedy, the last
crystals are impure. If a sludge accumulates under the anode, you may have platinum metals there.
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NADPH
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I tried to reduce AgCl with zinc metal and then dissolve excess zinc in HCl and got dark brownish powder which was still contaminated with AgCl.
I got much better results by putting copper ingot into solution of Cu(NO3)2 contaminated AgNO3. After few washing steps I got pale gray powder instead
of brownish black.
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