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.

Satirical sculptures burn during the traditional Fallas festival in Valencia, Spain, on March 19, 2014. Every year the city celebrates the ancient “Las Fallas” fiesta, a noisy week that is full of fireworks and processions in honor of Saint Joseph that ends on midnight of March 19, burning large satiric figures displayed around the streets of the city. (Photo by Alberto Saiz/Associated Press)

Flames burn in a field in Capaci, near Palermo, in Sicily, southern Italy, Wednesday, July 26, 2023. On the island of Sicily, two people were found dead Tuesday in a home burned by a wildfire that temporarily shut down Palermo's international airport, according to Italian news reports. Regional officials said 55 fires were active on Sicily, amid temperatures in the 40s Celsius. (Photo by Alberto Lo Bianco/LaPresse via AP Photo)

Embers remain among the debris after most of the buildings were burned to the ground in a wildfire at Gounsa Temple in Uiseong on March 26, 2025. At least 18 people have been killed in one of South Korea's worst wildfire outbreaks, with multiple blazes burning and causing “unprecedented damage”, the acting president said. (Photo by Yasuyoshi Chiba/AFP 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)

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)

Police walk past a burning car during riots in Birmingham City Centre on August 8, 2011 in Birmingham, England. After three nights of rioting and looting in and around London, the chaos is starting to spread to other cities around Britain. (Photo by Jeff J Mitchell/Getty Images)

Kurdish gunmen hold their rifles in front of the burning house of a Shi'ite militiaman during clashes in Tuz Khurmato, Iraq, April 24, 2016. (Photo by Goran Tomasevic/Reuters)