Ag and NaOCl - or what happened to my silver spoons?

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Offline Alandriel

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I just mistakenly soaked some of my silver spoons in a weak household bleach solution.... [::)]

Some of those spoons *) are now decidedly dark grey while some only show a few tarnishes along scratch lines and some don't seem to be effected at all?

What's going on? And how can I turn the tarnished once shiny again.
My normal silver polish does not work at all



*) not entirely sure they're solid silver. I rather suspect they are plated, though perhaps not electroplated (not that I'm exactly sure what that is either)



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Offline Alandriel

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Ag and NaOCl - or what happened to my silver spoons?
« Reply #2 on: 09/12/2007 19:11:29 »


thanks paul, but no luck  [:(] ~ any other suggestions?

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Offline DrDick

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Ag and NaOCl - or what happened to my silver spoons?
« Reply #3 on: 11/12/2007 18:29:00 »
The most likely answer is that you've oxidized Ag --> Ag+, and reduced the ClO- in the bleach into Cl- (chloride), resulting in the formation of insoluble AgCl on the silver surface.  There are several ways to dissolve AgCl:
 
1) use ~6+ M HCl solution - pool (muriatic) acid should be concentrated enough
2) use 2+ M ammonia solution - household ammonia should be concentrated enough
3) use sodium thiosulfate solution - often used in photographic developing solutions

None of these should harm the underlying silver.

Dick

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Ag and NaOCl - or what happened to my silver spoons?
« Reply #4 on: 11/12/2007 19:38:40 »
I suspect that part of what's happened is that the cutlery is silver plate and the bleach has attacked the base metal under the silver coating. I might try this  with some pure silver and see if the bleach damages it.

Since silver chloride is white I don't see it being responsible for the dark grey colour. OTOH AgCl goes dark on exposure to light.
The 3 mixtures above would dissolve AgCl, but it might be better to try to reuce (some of) it back to silver. The trick with putting the spoons on Al foil in a plastic bowl and adding hot water and washing soda mighhth be worth a try.
Since this won't put the silver back as a nice even coating the stuff will need polishing afterwards.

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