In 12 M Hydrochloric Acid (again, do not do at home).
To my surprise the Peep did dissolve SOME in 12 M HCl this year (it did not last year) so
I do think they made some changes in their recipe. (or my acid is stronger this year??).
My memory may be failing - perhaps I did dilute the acid in previous years. I used it in
high concentrations this year. After about 2 hours - without thinking but WITH gloves
on I sort of nudged the Peep with my index finger. The acid ate through the fingertip of
my glove fairly quickly and I removed the glove even quicker! It was a "safety moment"
for the class. Again, final photo is after FOUR hours.