Chemical Reaction Issue

ollievon

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Mar 9, 2006
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814
Location
Upstate NY
Had a strange find in my drawer this morning where I have some of my found coins together, just your random assortment of Wheaties, War Nickel's etc. But this morning I noticed that a Barber dime I found earlier this year was discolored (or at least was turning blackish) and noticed it was on top of a Wheatie; when I lifted the Barber it was wet and looked as if there was a chemical reaction taking place between the silver and copper - ultimately discoloring both coins.

Actually, the wheat was losing it's patina and was being polished by the reaction.

Anyone experience reactions between coins before?
 
They were a bit corroded upon initially finding them and lightly cleaned with just warm soapy water, but dried long ago before heading to the drawer, the discoloration is what tipped me off as some type of oxidation or chemical reaction taking place, but it may not be the metals themselves, but perhaps the corrosion between the coins, very strange.
 
Chemical reaction Issue

We in the construction business all refer to that as oxidation when two dissimilar metals lay in contact with each other. Like attaching a copper pipe to a galvanized pipe.
 
RedOx Reaction

In solution this can happen... or high humidity.

Copper atoms, the more easily oxidized metal, lose electrons and silver ions gain electrons.

In this reaction we can think of copper being oxidized by silver ion, so silver ion is the oxidizing agent. Alternatively we can think of silver ion being reduced by copper metal, so copper is the reducing agent.

http://www.chem.memphis.edu/bridson/FundChem/T19a1100.htm
 
In solution this can happen... or high humidity.

Copper atoms, the more easily oxidized metal, lose electrons and silver ions gain electrons.

In this reaction we can think of copper being oxidized by silver ion, so silver ion is the oxidizing agent. Alternatively we can think of silver ion being reduced by copper metal, so copper is the reducing agent.

http://www.chem.memphis.edu/bridson/FundChem/T19a1100.htm

I like the way you think. Is this reaction known as "galvanic reaction"?
 
Yes, its just natural electrolysis (or oxidation)... add current and/or solution and the process can accelerate.
 
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