https://www.reddit.com/r/chemistry/comments/gyxkhw/potassium_permanganate_pills/

[Potassium permanganate pills](https://www.ic.unicamp.br/~stolfi/temp/permanganate-pills/01-pills-oview.png) for disinfecting produce.

In the 1990s there was an outbreak of giardia in the state of São Paulo, Brazil, caused by contaminated lettuce and/or other produce.   Local health authorities recommended disinfecting such vegetables by soaking them in water with small amounts of bleach or potassium permanganate (KMnO₄).  Local drugstores then sold small dropper bottles of bleach or permanganate solution, as well as these permanganate pills.

I found some of those pills at home, a couple of years ago.  They were still in their metal-plastic blister cards (of the type commonly used for medicine pills).  Maybe I should have kept them in that packaging, for the historic value.  Unfortunately I did not think of that, and transferred them to that vial.  I just found the vial again in my workshop.

The pills do seem to be mostly KMnO₄, but perhaps with a small amount of some binder.  Each pill was supposed to be dissolved in a large quantity of tap water. I forgot how much, but probably between 1 and 5 liters.  [They still dissolve](https://www.ic.unicamp.br/~stolfi/temp/permanganate-pills/03-solve.mp4) giving the characteristic reddish purple color.