Mercury thiocyanate is an inorganic chemical compound that makes for some pretty dramatic moving art when it's ignited. In the science world, mercury thiocyanate (typically present as a white powder) has several uses in chemical synthesis, but its real claim to fame is in pyrotechnics. When it's lit, the compound produces a long spiraling column of ash and smoke that looks like a moving snake. These used to be sold in firework stores, but now you're only likely to see them in a chemistry class because of claims of toxicity. The modern version is a nontoxic "black snake" that makes a less spectacular — albeit safer — presentation.