Burning NH4Cr2O7 with HgSCN seems to open a black hole ...

While watching a video like this one even those who have never been fond of chemistry cannot help being intrigued.

A professor demonstrates to his students what happens when you put a mixture of ammonium dichromate (NH4)2Cr2O7 and thiocyanate of mercury Hg(SCN)2 on a sheet of aluminum foil and . . . set it on fire. 

The result causes a reaction that seems to open a sort of black hole from which impressive incandescent snake-like figures emerge creating a famous effect that is called "Pharaoh's Serpent".