My oldest daughter brought this home today from school. They dropped these Zincolns in an acid that completely dissolved the zinc, while leaving the very thin layer of copper unaffected. Pretty cool.
At least when they show up in the Error Coin section we will know what happened. What else did they drop in the acid?
Ha, ha, ha!!! You beat me to the punch. I wonder if there is something strange going on here we should know about. Then again, maybe not.
Cool experiment. I did not know children still do that in school. Then again, I have no children, so I would not know.
Not to be pedantic, but the acid (probably hydrochloric HCl) dissolved the zinc core and left the copper plating. In order to get to the zinc, you have to scrape or file away the copper plating either in one place, or all the way around the coin.
Cool experiment, I might try that sometime. Today I had some crusty pennies that I put in apple cider vinegar. First 2 pics are before pics and 3 &4 are after. First 2 pics are before pics and 3 &4 are after.
After the hydrochloric acid eats the zinc, why doesn't it leave an empty "shell"? It looks like the two sides (copper) of the coin fused together?
So the acid didnt break down the plating? Cool. Didnt know zinc was weaker like that, but ive seen old ww1 and 2 zinc coinage and it tends to seem very brittle or almost powdery when corroded.
Actually zinc isn't necessarily "weak", it just reacts with acids to give hydrogen gas and a "salt" of zinc. With hydrochloric acid it would be zinc chloride and hydrogen gas. To get two neat plates like this, I would normally file the coin all around the edge. The copper doesn't react as fast with the acid.
It also depends on what acid you use. There are other acids that will strip away the copper and leave the zinc relatively unharmed. I believe Nitric acid will attack the copper much faster than the zinc.
Upon looking at a reduction potential table, it seems that copper could react with nitric acid and perchloric acid. Under standard conditions, copper won't oxidize (and thus dissolve) itself to reduce H+ ions from an acid into hydrogen gas. The nitrate ion in nitric acid and the perchlorate ion in perchloric acid can react in ways that theoretically could be enough to oxidize and dissolve copper. [Disclaimer: this doesn't come from any personal experience other than reading a reduction potential table, so I'd happily defer to any chemist's experiences with the subject] Really cool experiment!
I'm skeptical. Zinc is more reactive than copper. So, I'd expect anything that reacts with copper should MORE aggressively react with zinc.
I'm a retired high school chem teacher. And I did the same demonstration every year. But first, I'd have the students practice use a beam balance. (I imagine nowadays they use electronic balances.) I'd give them a bag of 7 U.S. cents. They'd weigh 1 cent, then record the measurement. Then do the same for 2 cents, then 3, etc. Then they'd calculate the average weight of a cent for each of the 7 measurements. Smart-a$$ lazy students wouldn't bother. They'd weigh one cent, then calculate a result for 2, 3, 4, etc. The laziest students would simply copy the results from another group. Surprisingly, year after year, almost no students knew that pre-1982 cents are heavier than the newer copper-coated zinc cents (3.11 gm vs 2.50 gm). And of course I'd put a different mix of cents in each bag. Results would vary depending on the dates and the order they were weighed. It was easy for me to see which students did all the measurements (and which students didn't). The main purpose of the lab was to emphasize recording observed measurements. And I enjoyed teaching a little numismatics too.
