That second episode was useful to me in a way. We tried to recreate the exploding test tube (what for? Beats me, I guess we also wanted to get expelled) but the closest we could get was by mixing KMnO4 (potasium permanganate), H2O2 (hydrogen peroxide or agua oxigenada) and HCl (hydrochloric or muriatic acid). A few months ago a girl was brought to the ER with a black to deep violet to dark pink discoloration on her hands and around her mouth. She was seen eating a black powder which the mother had the good sense of bringing with her. There was no wrapper or label but the father said he uses it to prevent algal growth and mosquito breeding for their water tank. We sent him home to get the label or canister. The discoloration of the skin reminded me of my classmates' napes and arms and I asked a nurse to give me some H2O2 and sure enough when I mixed it in a specimen bottle it started to bubble and get warm (it seems HCl wasn't necessary to produce the 'eruption' but was the cause of the acid burns. Treatment was unremarkable after that and the girl is okay. The label did say KMNO4.