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SCRATCHED PENNIES IN HYDROCHLORIC ACID
One Penny Floats
Pre-1982 pennies were minted from a copper alloy of 5% zinc. After 1984 pennies were copper-coated zinc. The scratches exposed the zinc disk to the HCl, reacting to form zinc chloride & hydrogen gas. The thin copper shell floated to the top.
Copyright:© 2005 Richard Megna - Fundamental Photographs
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