If we were to burn NH4Cr2O7 with HgSCN in the Dark Ages in Europe and show it to anyone, it is us who would be burning next on a fiery cross of Inquisition. And it’s no wonder, since this experiment produces a truly marvelous result. At first, as you ignite the mixture of NH4Cr2O7 and HgSCN, all you can see is that it is slowly burning with a reddish flame. After a while, however, a crater is formed in the middle of the burning pile, and then, suddenly, tentacle-like appendages start sprouting from the burning mixture. And you can almost hear the scream of the mad occultist – “Come forth, Kraken! Come forth!” But of course, this is simply a chemical reaction that is called the "Pharoah's Serpent". It was also often sold in firework stores until people realized that it was toxic.

A hillside erupts in flame as a raging wildfire fire burns in Placerita Canyon in Santa Clarita, Calif., Monday, July 25, 2016. A raging wildfire that forced thousands from their homes on the edge of Los Angeles continued to burn out of control Monday as frustrated fire officials said residents reluctant to heed evacuation orders made conditions more dangerous and destructive for their neighbors. (Photo by Nick Ut/AP Photo)

Bill Moreau watches as the Black Forest fire burns near his house near Black Forest Road Tuesday afternoon, June 11, 2013, near Colorado Springs, Colo. The Black Forest Fire was one of at least three significant wildfires burning in Colorado amid gusty winds and record-breaking hot, dry weather. (Photo by Christian Murdock/AP Photo/The Colorado Springs Gazette)

An Iraqi soldier stands guard as a pipeline burns in the background after an explosion 30 kilometers (20 miles) northeast of Tikrit, Iraq, Monday, February 11, 2008. (Photo by Bassem Daham/AP Photo)

A burning tree is seen during a fire in an area of the Amazon rainforest in Itapua do Oeste, Rondonia State, Brazil, September 11, 2019. (Photo by Bruno Kelly/Reuters)

A man takes a selfie next to a burning barricade during a protest against the government in the streets of Port-au-Prince, Haiti, February 10, 2019. (Photo by Jeanty Junior Augustin/Reuters)

Demonstrators dance around a burning an effigy of the Russian President Vladimir Putin during an anti-war action in Tbilisi, Georgia, Sunday, March 27, 2022. (Photo by AP Photo/Stringer)

Light painting on the beach at Walton-on-the-Naze in Essex, United Kingdom on April 25, 2023 using burning steel wool spun around on a rope sending sparks flying. (Photo by Kevin Jay/Picture Exclusive)