The thing is that it has long been known that the black tarnish
that forms on silver is silver sulfide. I have noticed that most
of the unwashed masses think that anything that corrodes, or discolors
a metal is a rust, or oxide... even when it isn't.
Silver oxide is not formed easily. It doesn't happen in air under
normal circumstances, it takes ozone, or a lot of heat. Pure water
won't do it either. That is one of the reasons humans like silver
things.
Silver does tarnish quickly in the presence of air borne hydrogen
sulfide, of which humans are a major source.
Silver oxide is water soluble, and forms silver hydroxide, which
is a rather strong alkali, similar to lye.
Silver sulfide isn't a great conductor, but it is soft, and rubs
away easily, and is a whole lot better than tarnished copper...
hence the statements that tarnished silver is a good conductor.
You won't find any strict numbers on conductivity for silver sulfide
because it is a semiconductor, and as such varies all over the place
depending on impurities, past and present exposure to light, and a
host of other issues.
-Chuck Harris
Hal Murray wrote:
[email protected] said:
The reason that silver is used is that the oxide is also a very good
conductor.
That's interesting. Does anybody have numbers to back it up? I poked
around a bit but didn't find anything.
My memory (from ages ago) is that RF gear is often gold plated even though
gold is less conductive than silver because gold doesn't oxidize and it's
much more conductive than silver oxide.
How much of the crap on exposed silver is oxide vs sulfide?
Many years ago, a friend told me this story. His friend was in charge of
maintenance of microwave towers in California's central valley. He
complained a lot, and Bell Labs finally sent out a microwave engineer. They
went out to a tower and climbed up to look at things. Just then, a crop
duster came by spraying sulfur on the local grapes. They had sent the right
guy. He had grown up in German wine country and instantly recognized what
was going on. The next batch of microwave gear was gold plated rather than
silver. Problem solved.
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