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  #1  
Old 11-19-2014, 10:50 AM
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Default Chemical Reaction Issue

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?

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Old 11-19-2014, 11:20 AM
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Never. Are you sure nothing else spilled on them?

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Old 11-19-2014, 11:40 AM
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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.

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  #4  
Old 11-19-2014, 04:53 PM
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Default 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.
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Old 11-19-2014, 04:57 PM
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Default 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/...m/T19a1100.htm

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Old 11-19-2014, 06:04 PM
flyguy784 flyguy784 is offline
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Originally Posted by GoldAudio View post
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/...m/T19a1100.htm
I like the way you think. Is this reaction known as "galvanic reaction"?

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Old 11-19-2014, 08:41 PM
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Yes, its just natural electrolysis (or oxidation)... add current and/or solution and the process can accelerate.

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Old 11-19-2014, 09:02 PM
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Originally Posted by GoldAudio View post
Yes, its just natural electrolysis (or oxidation)... add current and/or solution and the process can accelerate.
That^

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