The Pharoah’s Serpent is a firework made of Mercury Thiocyanate. While this is extremely dangerous due to the release of toxic mercury fumes, it is one of the most interesting things I’ve ever seen. The snakes are made of foamed carbon. This chemical is also listed as a class 6 poison by the US DOT, and should not be handled under any circumstances, so those kids are probably already dead. It’s incredible how so much ash and debris is left behind by the chemical reaction that started with such a small amount of the chemical. Nature (or rather synthetic compounds produced with elements of nature) is spectacular.