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| Identifiers | |
|---|---|
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.030.020 |
| EC Number |
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| UNII | |
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| Properties | |
| RaCl2 | |
| Molar mass | 296.094 g/mol |
| Appearance | Colorless solid, glows blue-green[1]: 5 |
| Density | 4.9 g/cm3[1]: 5 |
| Melting point | 900 °C (1,650 °F; 1,170 K)[1]: 5 |
| 245 g/L (20 °C)[1]: 6 | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | radioactive, highly toxic, corrosive |
| GHS labelling: | |
   | |
| H300,H310,H330,H350,H370,H373,H410 | |
| NFPA 704 (fire diamond) | |
| Related compounds | |
Otheranions | Radium bromide |
Othercations | Beryllium chloride Magnesium chloride Calcium chloride Strontium chloride Barium chloride |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Radium chloride is aninorganic compound with thechemical formulaRaCl2. It is aradium salt ofhydrogen chloride. It was the firstradiumcompound isolated in a pure state.Marie Curie andAndré-Louis Debierne used it in their original separation of radium frombarium. The first preparation of radium metal was by theelectrolysis of a solution of this salt using a mercury cathode.[2][1]: 3
Radium chloride crystallises from aqueous solution as thedihydrate. The dihydrate is dehydrated by heating to 100 °C in air for one hour followed by 5.5 hours at 520 °C underargon.[3] If the presence of other anions is suspected, the dehydration may be effectuated by fusion underhydrogen chloride.[4]
Radium chloride can also be prepared by heating radium bromide in a flow of dryhydrogen chloride gas. It can be produced by treating radium carbonate with hydrochloric acid.
Radium chloride is a colorless salt with a blue-greenluminescence, 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 otheralkaline earth metal chlorides – at 25 °C its solubility is 245 g/L whereas that ofbarium 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 frombarium byfractional crystallization.[1]: 6 Radium chloride is only sparingly soluble inazeotropichydrochloric acid and virtually insoluble in concentrated hydrochloric acid.[5]
GaseousRaCl2 shows strong absorptions in the visible spectrum at 676.3 nm and 649.8 nm (red): thedissociation energy of the radium–chlorine bond is estimated as 2.9 eV,[6] and itslength as 292 pm.[7]
Contrary to diamagnetic barium chloride, radium chloride is weaklyparamagnetic with amagnetic susceptibility of 1.05×106. Itsflame color is red.[1]: 5
Radium chloride is still used for the initial stages of the separation of radium from barium during the extraction of radium frompitchblende. 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 onradium bromide orradium chromate (used for the later stages of the separation).
It was also used inmedicine to produceradon gas which in turn was used as abrachytheraputiccancer treatment.[8][9]
Radium-223 dichloride (USP, radium chloride Ra 223), tradename Xofigo (formerly Alpharadin), is an alpha-emittingradiopharmaceutical.Bayer received FDA approval for this drug to treatprostate 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).
