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Radium chloride
Identifiers
CAS Number	10025-66-8 ;
3D model (JSmol)	Interactive image;
ChemSpider	20138060 ;
ECHA InfoCard	100.030.020
EC Number	233-035-7;
UNII	KKO873WR2Z ;
CompTox Dashboard (EPA)	DTXSID00893671 ;
	InChI InChI=1S/2ClH.Ra/h21H;/q;;+2/p-2 Key: RWRDJVNMSZYMDV-UHFFFAOYSA-L ; InChI=1/2ClH.Ra/h21H;/q;;+2/p-2 Key: RWRDJVNMSZYMDV-NUQVWONBAG;
	SMILES Cl[Ra]Cl;
Properties
Chemical formula	RaCl2
Molar mass	296.094 g/mol
Appearance	Colorless solid, glows blue-green
Density	4.9 g/cm3
Melting point	900 °C (1,650 °F; 1,170 K)
Solubility in water	245 g/L (20 °C)
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	radioactive, highly toxic, corrosive
	GHS labelling:
Pictograms
Hazard statements	H300, H310, H330, H350, H370, H373, H410
NFPA 704 (fire diamond)	4 0 1
Related compounds
Other anions	Radium bromide
Other cations	Beryllium chloride; Magnesium chloride; Calcium chloride; Strontium chloride; Barium chloride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Radium chloride is an inorganic compound with the chemical formula Ra Cl₂. It is a radium salt of hydrogen chloride. It was the first radium compound isolated in a pure state. Marie Curie and André-Louis Debierne used it in their original separation of radium from barium. The first preparation of radium metal was by the electrolysis of a solution of this salt using a mercury cathode.^[2]^[1]^: 3

Preparation

Radium chloride crystallises from aqueous solution as the dihydrate. The dihydrate is dehydrated by heating to 100 °C in air for one hour followed by 5.5 hours at 520 °C under argon.^[3] If the presence of other anions is suspected, the dehydration may be effectuated by fusion under hydrogen chloride.^[4]

Radium chloride can also be prepared by heating radium bromide in a flow of dry hydrogen chloride gas. It can be produced by treating radium carbonate with hydrochloric acid.

Properties

Radium chloride is a colorless salt with a blue-green luminescence, especially when heated. Its color gradually changes to yellow with aging, whereas contamination by barium may impart a rose tint.^[1]^: 5 It is less soluble in water than other alkaline earth metal chlorides – at 25 °C its solubility is 245 g/L whereas that of barium chloride is 307 g/L, and the difference is even larger in hydrochloric acid solutions. This property is used in the first stages of the separation of radium from barium by fractional crystallization.^[1]^: 6 Radium chloride is only sparingly soluble in azeotropic hydrochloric acid and virtually insoluble in concentrated hydrochloric acid.^[5]

Gaseous RaCl₂ shows strong absorptions in the visible spectrum at 676.3 nm and 649.8 nm (red): the dissociation energy of the radium–chlorine bond is estimated as 2.9 eV,^[6] and its length as 292 pm.^[7]

Contrary to diamagnetic barium chloride, radium chloride is weakly paramagnetic with a magnetic susceptibility of 1.05×10⁶. Its flame color is red.^[1]^: 5

Uses

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 (to extract a gram of pure radium metal, about 7 tonnes of pitchblende is required) 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).

It was also used in medicine to produce radon gas which in turn was used as a brachytheraputic cancer treatment.^[8]^[9]

Radium-223 dichloride (USP, radium chloride Ra 223), tradename Xofigo (formerly Alpharadin), is an alpha-emitting radiopharmaceutical. Bayer received FDA approval for this drug to treat prostate cancer osteoblastic bone metastases in May 2013. Radium-223 chloride is one of the most potent ((antineoplastic drugs)) known.^{[citation needed]} One dose (50 kBq/kg) in an adult is about 60 nanograms; this amount is 1/1000 the weight of an eyelash (75 micrograms).

References

^ ^a ^b ^c ^d ^e ^f ^g ^h Kirby, H. W.; Salutsky, Murrell L. (December 1964). The Radiochemistry of Radium (PDF) (Report). Subcommittee on Radiochemistry, National Research Council, National Academy of Sciences. doi:10.2172/4560824. OSTI 4560824. NAS-NS-3057.
^ Curie, Marie; Debierne, André-Louis (5 September 1910). "RADIOACTIVITÉ. Sur le radium métallique. Note de Mme P. CURIE et M. A. DEBIERNE" [RADIOACTIVITY. On metallic radium. Note by Mrs. P. CURIE and Mr. A. DEBIERNE]. C. R. Hebd. Acad. Sci. Paris (in French). 151: 523–25. Retrieved 22 November 2024.
^ Weigel, F.; Trinkl, A. (1968). "Crystal Chemistry of Radium. I. Radium Halides". Radiochimica Acta. 9: 36–41. doi:10.1524/ract.1968.9.1.36. S2CID 201843329.
^ Hönigschmid, O.; Sachtleben, R. (1934). "Revision des Atomgewichtes des Radiums". Zeitschrift für anorganische und allgemeine Chemie. 221: 65–82. doi:10.1002/zaac.19342210113.
^ Erbacher, Otto (1930). "Löslichkeits-Bestimmungen einiger Radiumsalze". Berichte der Deutschen Chemischen Gesellschaft (A and B Series). 63: 141–156. doi:10.1002/cber.19300630120.
^ Lagerqvist, A. (1953). Arkiv Fisik 6:141–42.
^ Karapet'yants, M. Kh.; Ch'ing, Ling-T'ing (1960). Zh. Strukt. Khim. 1:277–85; J. Struct. Chem. (USSR) 1:255–63.
^ Goldstein, N. (1975). "Radon seed implants. Residual radioactivity after 33 years". Archives of Dermatology. 111 (6): 757–759. doi:10.1001/archderm.1975.01630180085013. PMID 1137421.
^ Winston, P. (June 1958). "Carcinoma of the Trachea Treated by Radon Seed Implantation". The Journal of Laryngology & Otology. 72 (6): 496–499. doi:10.1017/S0022215100054232. PMID 13564019. S2CID 36790323.