Isotope separation first attempt

As of early September, 1985, the facility is being commissioned. Carbon, nitrogen and oxygen beams from the tandem have reached the interim target locations via the bypass line, and an iodine beam has been injected into the cyclotron. First attempts to accelerate iodine in the cyclotron are imminent Some experimental equipment, including the on-line isotope separator [SCH81J, is already set up and undergoing tests with tandem beams. 

The phenomenon of isotopy refers to the fact that certain elements consist of more than one component (now called isotopes) which seemed, at the time of their discovery, to be impossible to separate. The first attempt to restore order to the situation was made by Soddy, who had discovered the phenomenon in 1911. Soddy announced the theory of isotopy which stated that "isotopes of the same species are inseparable and belong in the same place in the periodic table." However, this new notion implied that one simple substance (something that could not be further purified) would be equivalent to two or more abstract elements in violation of the one-to-one correspondence demanded by the nineteenth-century element scheme. Some argued that isotopes might eventually prove to be separable in which case each isotope would have to be regarded as an abstract element. However, for most chemical purposes, isotopy seemed to make no difference. 

Fluorine was first isolated in 1886 by the French chemist Moissan, after nearly 75 years of unsuccessful attempts by several others. For many years after its isolation, fluorine remained little more than a scientific curiosity, to be handled with extreme caution because of its toxicity. Commercial production of fluorine began during World War II, when large quantities were required in the fluorination of uranium tetrafluoride (UF4) to produce uranium hexafluoride (UF6), for the isotopic separation of U235 by gaseous diffusion in the development of the atomic bomb. Today, commercial production methods are essentially variations of the Moissan process, and safe techniques have been developed for the bulk handling of liquid fluorine. 

For most isotopes it is preferable to work with gases rather than liquids, because the higher diffusion coefficients result in higher separative capacity. The optimum pressure is usually near atmospheric. However, when was first found to be fissionable, Nier [N3] attempted to separate it by thermal diffusion of UFe vapor at low pressure without success, so that it was necessary to work with the liquid at high pressures [Al] to obtain useful separation. The optimum spacii between hot and cold surfaces is a few millimeters for gases and fraction of a millimeter for liquids. 

Element 104, the first transactinide element, is expected to have chemical properties similar to those of hafnium. It would, for example, form a relatively volatile compound with chlorine (a tetrachloride). The Soviet scientists have performed experiments aimed at chemical identification, and have attempted to show that the 0.3-s activity is more volatile than that of the relatively nonvolatile actinide trichlorides. This experiment does not fulfill the test of chemically separating the new element from all others, but it provides important evidence for evaluation. New data, reportedly issued by Soviet scientists, have reduced the half-hfe of the isotope they worked with from 0.3 to 0.15 s. The Dubna scientists suggest the name kurchatovium and symbol Ku for Element 104, in honor of Igor Vasilevich Kurchatov (1903—1960), late Head of Soviet Nuclear Research. The Dubna Group also has proposed the name for Element 104. In 1969, Ghiorso, Nurmia, Harris, K. A. Y. Eskola, and P. L. Eskolaof the University of California... 

Fermi in any case was more interested in pursuing a chain reaction in natural uranium than in attempting to separate isotopes. He was not discouraged by the small cross-section for fission in the natural [element], comments Anderson. Stay with me, he advised, we ll work with natural uranium. You ll see. We ll be the first to make the chain reaction. I stuck with Fermi. ... 

Although the idea of dynamically similar but thermodynamically different polymers seems at first to be a rather contrived and artifical model, there is one class of systems that are actually quite close realisations of it. These are pairs of isotopically substituted polymers of high relative molecular mass, approaching those relative molecular masses for which phase separation would take place. The composition dependence of the mutual diffusion coefficient for such diffusion couples has been measured directly for interfaces between polystyrene and deuterated polystyrene (Green and Doyle 1987) and the results are in excellent agreement with theory (figure 4.21). This also means that we can use equation (4.4.7) to check whether isotopic labelling is likely to perturb an attempted self-diffusion measurement. 

Another strand of development came from several attempts to separate some of these new radio-elements chemically, which ended in failure. First of all, in 1907 Herbert McCoy and WiUiam Ross concluded that, in the case of thorium and radiothorium, Our experiments strongly indicate that radiothorium is entirely inseparable from thorium by chemical processes, " a comment Soddy considered the first definitive statement of the chemical inseparability of what were soon to be called isotopes. Soddy himself wrote in the same year that there seemed to be no known method of separating thorium X from mesothorium.They were in fact two isotopes of thorium. Similar cases began to multiply. Bertram Boltwood discovered the radio-element ionium, which could not be chemically separated from thorium. In another famous case, Hevesy and Paneth were asked by Rutherford to try to separate radio-lead from ordinary lead and likewise failed to do so, in spite of using 20 different chemical methods. Their work was not entirely in vain, however, since it led to the development of the use of radioactive tracers, which have become an indispensable tool in modem chemistry and biochemistry. 

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