There’s some chemicals, even in a high school setting, that you can’t just pour down the sink. Some you have to neutralise, some you have to filter…some you have to neutralise to produce a precipitate, and then filter that.

These are in the latter camp. I noticed after leaving a particularly sludgy iron chloride suspension over a weekend that the precipitate in the filter paper had dried in a pretty fractal pattern, the larger surface area at the top of the filter paper and capillary action leading to a gradient of drying and cracking. I’ve been slightly more careful with further disposal methods, trying to find pretty examples.