JulieLeung.com: a life told in tidepools

This week the girls and I did ye old penny-cleaning-with-vinegar experiment. We tried a number of permutations including adding ketchup and/or salt to the solution with water as a control. The picture above is a penny Abigail held halfway in her mix of ketchup, vinegar and salt for ten seconds.

Ketchup seemed to help clean the pennies well, although salt was also necessary for the formation of the blue-green compound later seen on unrinsed coins left to dry on paper towels. The instructions for the experiment explained that the blue-green compound contained copper, oxygen and chloride.

The next step was to incubate nails in each solution, after the pennies were removed. I don’t remember trying this part before. Only the vinegar and salt solution had the clear result below of changing nails into a coppery color. Perhaps this transfer of copper ions also happened in the ketchup-containing solutions, but the additional acid or darker color of ketchup affected the ability to observe it. In the picture below see an untreated nail, a penny, and between the two, a nail from the vinegar and salt solution.