In the above post, there are a few things I should have mentioned but didn't as they should be understood without saying them. Nevertheless, hindsight suggests that I need to state the obvious.

The school lab experiment I've described above was both dangerous and unofficial in that it was not sanctioned or supervised by a qualified teacher and I would strongly suggest no one attempts it (or anything similar). Moreover, these days, in many jurisdictions it will likely be unlawful†. My message is do not try it both for your own safety and that in this hypersensitive, overly-political world you will draw the ire of others!

† Back then—decades ago in much simpler times—this would not have been the case for small lab quantities although it likely would have drawn the ire of the chemistry teacher—not so much because of the material's intrinsic dangers—as then, there were many dangerous chemicals that were both commonly available and easily obtainable without authority (and that are now no longer available)—but rather because he'd have deemed we'd not have had sufficient experience to do it safely.