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)

A police officer walks along a street of the burning village of Smolenka near Chita on Monday, April 13, 2015. Russian authorities say out-of-control agricultural fires have killed at least 15 people, injured hundreds more and destroyed or damaged more than 1,000 homes in Siberia. The fires were started by farmers burning the grass in their fields, but spread quickly because of strong winds. (Photo by Evgeny Yepanchintsev/AP Photo)

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)

In this July 5, 2016 photo, a tamed elephant rests in a pool of water by a road in Baduraliya, a village outside Colombo, Sri Lanka. Even as the country cracks down on illegal ownership, the enduring demand for elephants has the government planning to set up its own pool of captive animals to be hired out to temples for ceremonies and maintained with budget funds. (Photo by Eranga Jayawardena/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)

Seen in a long camera exposure, the Caldor Fire burns on Sunday, August 29, 2021, in Eldorado National Forest, Calif. (Photo by Noah Berger/AP Photo)