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Q&As since 1989


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Submerging pennies in vinegar and Nitric Acid and effect

2005

The information we have found on your website has been very helpful after daughter conducted her experiment on how different liquids affect pennies (tap water, melted snow, salt water, vinegar [in bulk on eBay or Amazon], Pepsi, Coke, Mountain Dew, hair spray, tea) has been conducted. However, analysis of results need a bit of expert help to explain.Experiment was conducted by putting 2 pennies in each liquid (dull oxidized penny and a shiny penny) in a plastic covered container, they were checked weekly and returned to the liquid and returned to refrigerator until the next week (length of experiment 4 weeks).1. One penny in the vinegar> solution developed a hole other did not. Thinking penny with a hole has a defect (hole or scratch) but is the acid level or something else strong enough with the amount of time we left pennies in the liquid?2. One penny in the 5% Nitric Acid ate the half of the pennies insides out - still has the copper plating portions (very flimsy now) but the zinc metal in the middle is gone. Maybe same answer as number 1?3. Other pennies have become darker (copper oxide) and some have become coated in white (?). What could this white film be called.We have printed a lot of information from your site to read and search through but if you have any comments on the items above that would be greatly appreciated or if you can point us to other reference materials on this matter. Thanks in advance for your assistance and time.

Mom and Stephanie
Internet Development Manager and Student - Warren, Michigan

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An often overlooked variable in this type of experiment is that the US cent went from solid copper to copper plated zinc in 1982. Since the two metals react very differently it is important to keep all coins in the experiment either pre 82 or post 82. (both types were minted in 1982 and they are difficult to tell apart so I'd advise against using any from that year)
I would bet that the holes and white coating you observed were from the newer cents while the dark patinas were from the earlier years...or perhaps from coins with undamaged plating.

James Saxon
- Hayward, California, USA
2005

Interesting, but we have conducted this same copper penny experiment and found that a penny from 1985 also turned white after soaking in Tabasco for 2 days. How do you explain that?

Jordan H.
- Beaverton, OR, USA
2006