Korazic acid was a red, non-terrestrial chemical. Commandar Kaagh had one bottle containing korazic acid in his space pod.
Luke Smith knew korazic acid from chemistry lessons with Mr Smith. He mixed dylixium chloride, korazic acid and lyzirium phosphate to create a knock out gas. He filled the gas into a Sontaran gas canister. The gas would disable a human for two hours and a Sontaran for several minutes. Luke wanted to use the gas on Commander Kaagh. However it was later used on Chrissie Jackson, by Maria and Alan Jackson because they did not want Chrissie to know that aliens existed. Chrissie passed out in the building of the Tycho Project. She woke up at 36 Bannerman Road and was told that all her experiences with Kaagh were just a dream. Chrissie, however, knew her experiences were real. (TV: The Last Sontaran)