Clean Coins with Vinegar

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Page ID: 128797

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Required Training	Required PPE
UC Lab Safety Fundamentals	Lab coat, safety glasses/goggles, nitrile gloves

Equipment	Chemicals
Crystalizing Dish or Beaker	White Vinegar (or ~5% acetic acid)
Coins	Sodium Chloride

Procedure:

Add salt and vinegar to coins in a beaker to clean them.

Discussion:

Older pennies (1856-1983) were between 88% and 95% copper. Even newer pennies have an outermost layer of pure copper (with a 97.5% zinc core). A crust is formed on these pennies, made of CuO Cu₂O and CuS among other things. When reacted with dilute acetic acid, the copper (II) oxide forms the water soluble copper acetate and dissolves away. Copper I oxide is not so soluble in 5% acetic acid. The salt added adjusts the ionic strength of the solution and promotes further dissolution and speeds up the reaction

Hazards:

Be careful not to spill. Spilled vinegar should be contained, absorbed, and washed down the drain with water. Please thoroughly clean any affected areas as vinegar smells strongly and sometimes causes skin irritation.

SOP:

N/A

Disposal (by Storeroom)

Return the vinegar/copper ion solution to the dispensary for proper disposal.

Acknowledgements

http://www.madsci.org/posts/archives...3842.Ch.r.html