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  for Metal Finishing since 1989
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Penny Science Project

I am doing a project on removing tarnish from pennies using coca cola, sprite and water. I can't find out what the chemical reaction is, or why it should work. Can you suggest help?

Eric N.
- Duncan B.C. Canada
1999

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The chemical reaction is acid dissolving tarnish, Eric..

There may be several different acids in soda, and the tarnish may consist of various oxides, sulfides, and carbonates, so there is not a single simple equation. But here is one balanced equation that is probably one of the reactions --

2H₃(PO₄) + 3CuO => Cu₃(PO4)₂ + 3 H₂0

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

I think that lemon juice cleans pennies the best.

Lundon G.
- California
2002

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Well Eric, I did a project on that but instead of water, I put Dr. Pepper. It was Coke that cleaned it the most and I found this out on this website: www.finishing.com/134/43.shtml It said: "Acids have power to remove copper tarnish because copper oxide dissolves in acid; the stronger the acid, the more dissolution power." Hope it helps. See ya.

Stephen M.
- El Paso, Texas, U.S.A.
2003

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