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| {{Chembox new
| | #REDIRECT [[Radium-223 chloride]] |
| | Name = Radium chloride
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| | Section1 = {{Chembox Identifiers
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| | CASNo = 10025-66-8
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| }}
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| | Section2 = {{Chembox Properties
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| | Formula = RaCl<sub>2</sub>
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| | MolarMass = 296.94 g/mol
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| | MeltingPt = }}
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| '''Radium chloride''', RaCl<sub>2</sub>, was the first [[radium]] [[Chemical compound|compound]] to be prepared in a pure state and was the basis of [[Marie Curie]]'s original separation of radium from [[barium]].<ref>[[Marie Curie|Curie, M.]]; [[Andre Debierne|Debierne, A.]] (1910). ''C. R. Hebd. Acad. Sci. Paris'' '''151''':523–25.</ref> The first preparation of radium metal was by the [[electrolysis]] of a solution of radium chloride using a mercury cathode.
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| ==Preparation==
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| Radium chloride crystallises from solution as the di[[hydrate]]. It may be dehydrated by heating to 100 °C in air for one hour followed by 5½ hours at 520 °C under [[argon]].<ref>Weigel, F.; Trinkl, A. (1968). ''Radiochim. Acta'' '''9''':36–41.</ref> If the presence of other anions is suspected, the dehydration may be effectuated by fusion under [[hydrogen chloride]].<ref>Hönigschmid, O.; Sachtleben, R. (1934). ''Z. Anorg. Allg. Chem.'' '''221''':65–82.</ref>
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| ==Properties==
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| Radium chloride is a white solid with a blue-green [[luminescence]], especially when heated. It is less soluble in water than other [[alkaline earth metal]] chlorides, a fact which is used in the first stages of the separation of radium from [[barium]] by [[fractional crystallization]]. It is only sparingly soluble in [[Azeotrope|azeotropic]] [[hydrochloric acid]] and virtually insoluble in concentrated hydrochloric acid.<ref>Erbacher, O. (1930). ''[[Ber. Dtsch. Chem. Ges.]]'' '''63''':141–56.</ref> | |
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| Gaseous radium chloride exists as RaCl<sub>2</sub> molecules, as with other alkaline earth metal [[halide]]s. The gas shows strong absorptions in the visible spectrum at 676.3 [[nanometre|nm]] and 649.8 nm (red): the [[Bond dissociation energy|dissociation energy]] of the radium–chlorine bond is estimated as 2.9 [[electronvolt|eV]],<ref>Lagerqvist, A. (1953). ''Arkiv Fisik'' '''6''':141–42.</ref> and its [[Bond length|length]] as 292 [[picometre|pm]].<ref>Karapet'yants, M. Kh.; Ch'ing, Ling-T'ing (1960). ''Zh. Strukt. Khim.'' '''1''':277–85; ''J. Struct. Chem. (USSR)'' '''1''':255–63.</ref>
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| ==Uses==
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| Radium chloride is still used for the initial stages of the separation of radium from barium during the extraction of radium from [[pitchblende]]. The large quantities of material involved ([[tonne]]s of ore for [[milligram]]s of radium) favour this less costly (but less efficient) method over those based on [[radium bromide]] or [[radium chromate]] (used for the later stages of the separation).
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| ==Sources==
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| *''Gmelins Handbuch der anorganischen Chemie (8. Aufl.)'', Berlin:Verlag Chemie, 1928, pp. 60–61.
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| *''Gmelin Handbuch der anorganischen Chemie (8. Aufl. 2. Erg.-Bd.)'', Berlin:Springer, 1977, pp. 362–64.
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| ==References==
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| {{reflist|2}}
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| [[Category:Radium compounds]]
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| [[Category:Chlorides]]
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| [[Category:Metal halides]]
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