Black snake (firework)

"Black snake" is a type of consumer firework consisting of a chemical that when set on fire burns with an intumescent reaction, exuding a long twisting string of ash resembling a snake. They are sold as pellets which are placed on a noncombustible surface and ignited with a match, burning slowly with little or no flame. Two earlier traditional formulas are now banned in retail fireworks because of the toxic chemicals they contain: the Pharaoh's Serpent which contains mercury (II) thiocyanate and the sugar snake which contains potassium dichromate. Sometimes these are performed as do-it-yourself amateur chemistry demonstrations.