elementcollector1
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Rhodium plating?
I recently decided to extract some rhodium metal from a plated object I had found years before. I was pretty sure this was rhodium, and thus basically
immune to corrosion, and I found that the metal underneath the plating appeared to be pure copper. So, I immersed the piece of jewelry in a bath of
sulfuric acid and hydrogen peroxide. Roughly an hour later, the plating is gone entirely, leaving shiny copper and a lemon-yellow solution. Was this
rhodium after all? How do I separate it back out if it is?
[Edited on 11-9-2013 by elementcollector1]
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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elementcollector1
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A rather curious update: I checked back on that solution. The yellow-green color appears to have diminished, if not vanished entirely. Additionally,
there is quite a bit of white precipitate covering the bottom of the flask. What on earth could this be? The only things that were dissolved were
copper, what was presumably rhodium, and possibly a plastic foil that I discovered on there for some reason. The precipitate is quite voluminous, but
also very crystalline, and a pure white (ruling out copper salts). So what could this be? There are no alkali metals or any other such in solution,
and I highly doubt it's a rhodium compound due to it's volume (compared to the volume of the rhodium plating).
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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softbeard
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The most general way to reduce platinum-group to the metal I found is good old hydrazine. I'm speculating a bit but, preferably in alkaline medium,
hydrazine should kick out a metal like rhodium as a black powder. Depending on conditions, copper may kicked out as the metal too so this could get
tricky, but any copper metal can be dissolved away with a bit of nitric acid later.
As to mysterious deposits, I haven't a clue. I know I'm always dealing with with mysterious gunk in my reactions .
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watson.fawkes
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I'd guess some zinc compound, since it's unlikely that the base metal of the plated object is pure copper,
but rather an alloy, and zinc is by far the most common alloying material, particularly for plated objects. See the term of art "gilding metal", whose
meaning is originally that metal over which gold was layered.
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