Uranium hexafluoride is a chemical compound of the elements uranium and fluorine. Lieutenant Martin Larousse used this material's multisyllabic name to illustrate a variation of a code language to Mister Spock aboard the USS Enterprise in the 2260s. Explaining the code used by Earth children to add "op" before every vowel in the word, Spock successfully transformed the name of uranium hexafluoride into the code, adding an additional syllable to account for Larousse's mispronunciation of "fluoride". While Larousse explained that Human children used the code to good measure to confuse others about secret communications, Spock maintained that Vulcan children and parents would not be fooled by such an endeavor. (TOS novel: World Without End)