Zur Kristallchemie des Radiums

Abstract

Radiochimica Acta einzelner Kugeln des verwendeten Dowex 50 W X 2 im Temperaturbereich von 20-90 °C untersucht. Danach ist der Einfluß so klein, daß bei lOOfacher Vergrößerung innerhalb des Beobachtungsfehlers von + 10% keine Änderung der Kugelgröße festgestellt werden konnte. Die Beeinflussung von Quelldruck, Hydratation, Dissoziation, Beweglichkeit der Ionen im Korn und Austauschenthalpie ist nur qualitativ bekannt und konnte hier nicht untersucht werden. Es ist aber anzunehmen, daß der aus allen diesen Faktoren resultierende Temperaturgang der Austauschgeschwindigkeit negativ ist und deshalb die starke Zunahme durch den positiven Temperaturkoeffizienten der Ionenbeweglichkeiten teilweise kompensiert. Diese Annahme wird durch die Versuchsergebnisse bestätigt. Wie die Abb. 7 zeigt, verläuft die experimentelle Kurve der Temperaturabhängigkeit wesentlich flacher als die theoretische Kurve, bei der nur der Temperaturgang von D berücksichtigt wurde. Wir möchten zum Schluß Herrn Prof. Dr. W. SEEL-MANN-EGGEBEET für die großzügige Unterstützung, die er uns bei der Durchführung dieser Arbeit gewährte, herzlich danken.

Radium Revisited: Revitalization of the Coordination Chemistry of Nature’s Largest 2+ Cation

“…7,8 However, the largest contributions to the structural chemistry of radium were report by Weigel and Trinkl, who using a combination of micro-scale synthesis and photographic powder X-ray diffraction techniques established the close correspondence between the structural chemistry of Ba 2+ and Ra 2+ as well as the first experimental determination of the ionic radius of Ra 2+ . [9][10][11] In addition, in the light of the fact that Ra 2+ exists in the form of hydrated ions in both environmental and medical scenarios, the hydration and dynamics of Ra 2+ have been probed to reveal Ra 2+ is more labile than Ba 2+ . 12 Further applications of modern characterization techniques are needed to provide a more precise understanding radium and will likely demonstrate that its larger atomic/ionic radius can yield chemistry that is not accessible with barium.…”

Radium Revisited: Revitalization of the Coordination Chemistry of Nature’s Largest +2 Cation

“…Given the low solubility of RaSO 4 , which renders it useful in cancer treatment, as well as its geologic and historic significance, it remains the best studied radium compound. X-ray powder diffraction and EXAFS studies of RaSO 4 with high isotopic purity have been reported. , However, the largest contributions to the structural chemistry of radium were report by Weigel and Trinkl, who, using a combination of microscale synthesis and photographic powder X-ray diffraction techniques, established the close correspondence between the structural chemistry of Ba 2+ and Ra 2+ as well as the first experimental determination of the ionic radius of Ra 2+ . − In addition, in light of the fact that Ra 2+ exists in the form of hydrated ions in both environmental and medical scenarios, the hydration and dynamics of Ra 2+ have been probed to reveal that Ra 2+ is more labile than Ba 2+ . Further applications of modern characterization techniques are needed to provide a more precise understanding of radium and will likely demonstrate that its larger atomic/ionic radius can yield chemistry that is not accessible with barium.…”

Structure and bonding of a radium coordination compound in the solid state

“…Of the few solid-state structural studies reported to date for Ra 2+ , efforts have been confined to the synthesis of simple inorganic Ra 2+ compounds and their characterization by X-ray powder diffraction (pXRD). [21][22][23][24][25][26] Although pXRD can rapidly provide data on the symmetry properties of microcrystalline samples and enable a general comparison of the structural similarities between complexes of Ra 2+ and its congeners (e.g., Ba 2+ , Sr 2+ , and Ca 2+ ), this technique is unable to provide precise information regarding metal-ligand bond distances and coordination geometries about the metal center. 27 Furthermore, the ionic salts studied to date offer limited insight into the behavior and structural organization of Ra 2+ with larger, multidentate molecular chelators used in nuclear medicine.…”