If we went on turning the pages of chemical journals we should come across another bit of news: the Soviet chemist Nikitin prepared a much less fantastic compound of xenon and radon with water, phenol and some other organic liquids: Xe·6H₂O, and Rn·6H₂O. They are stable under ordinary conditions, can be readily obtained, but as before, chemical bonding has nothing to do with these compounds. The xenon and radon atoms abide piously by the perfection of their outermost shell: 8 electrons there were and 8 electrons remained. More than fifty years had passed since the inert gases were discovered, but "the cart had not budged."

   The twentieth century, the stormiest and most unforgettable of all the centuries of human history, will come to a close. And scientists will sum up the achievements of scientific thought during the past hundred years. The endless list of outstanding discoveries will include in a prominent plate "the production of chemical compounds of the inert gases." And some enthusiastic commentator will add: one of the most sensational discoveries. Sensational? Hardly! Rather a romantic story. Or even a story of how simple sometimes can be the solution of a problem which for dozens of years tormented the minds of numerous scientists with its insolvability.

   In our days chemistry resembles a mighty tree with an immense ever-spreading crown. It is no longer possible for anyone person to study even a whole branch in full. An investigator mostly has to spend years to become acquainted in detail with a small twig, a bud, or a hardly visible shoot. Knowledge of the branch as a whole adds up from thousands of such investigations.

   The "twig" studied by the Canadian chemist Neil Bartlett was a compound called platinum hexafluoride in the language of chemists, and having the formula: PtF₆. It was not by accident that he devoted so much time and effort to this substance. Compounds of fluorine with the heavy metals are very interesting substances, of great importance to science and practice. One of their uses is in the separation of the uranium isotopes uranium-235 and uranium-238 for nuclear engineering. The separation of one isotope from another: is a very complicated process, but it can be accomplished with the aid of uranium hexafluoride, UF₆. Besides, heavy metal fluorides are very active chemical substances.

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