radium sulfate
{{Chembox
| ImageFile = Radium sulfate.jpg
| Section1 = {{Chembox Identifiers
| CASNo = 7446-16-4
| CASNo_Ref = {{cite web |last1=Chambers |first1=Michael |title=ChemIDplus - 7446-16-4 - MXQFUMUIEZBICJ-UHFFFAOYSA-L - Sulfuric acid, radium salt (1:1) - Similar structures search, synonyms, formulas, resource links, and other chemical information. |url=https://chem.nlm.nih.gov/chemidplus/rn/7446-16-4 |website=chem.nlm.nih.gov |language=en}}{{Cascite|changed|CAS}}
| PubChem = 6365199
| ChemSpiderID = 10745681
| StdInChI=1S/H2O4S.Ra/c1-5(2,3)4;/h(H2,1,2,3,4);/p-2
| StdInChIKey = XOROGAYSRYIXBN-UHFFFAOYSA-L
| SMILES = [O-]S(=O)(=O)[O-].[Ra]
}}
| Section2 = {{Chembox Properties
| Ra=1|S=1|O=4
| SolubilityProduct = 3.66{{e|−11}}{{cite book |author1=John Rumble |title=CRC Handbook of Chemistry and Physics |date=June 18, 2018 |publisher=CRC Press |isbn=978-1138561632 |pages=5–189|edition=99 |language=English}}
| Appearance = White solid
}}
| Section8 = {{Chembox Related
|OtherCations=strontium sulfate, barium sulfate, lead(II) sulfate
}}
}}
Radium sulfate (or radium sulphate) is an inorganic compound with the formula RaSO4 and an average molecular mass of 322.088 g/mol.{{Cite web|url=http://www.chemspider.com/Chemical-Structure.10745681.html|title = Radium sulfate | O4RaS | ChemSpider}} This white salt is the least soluble of all known sulfate salts.{{cite book | url = http://library.lanl.gov/cgi-bin/getfile?rc000041.pdf| title = The Radiochemistry of Radium|ref=Kirby | last1 = Kirby | first1 = H. W. | last2 = Salutsky | first2 = Murrell L. | date = 1964 | page= 12|publisher=National Academies Press}} It was formerly used in radiotherapy and smoke detectors, but this has been phased out in favor of less hazardous alternatives.
Properties
Radium sulfate crystallizes in a solid in the same structure as barium sulfate. It forms crystals in the orthorhombic crystal system, with a unit cell of dimensions a = 9.13 b=5.54 and c = 7.31 Å. The unit cell volume is 369.7 Å3.{{Cite journal |last=Matyskin, Artem V.; Ylmen, Rikard; Lagerkvist, Petra; Ramebäck, Henrik; Ekberg, Christian |title=Crystal structure of radium sulfate: An X-ray powder diffraction and density functional theory study |url=https://www.sciencedirect.com/science/article/pii/S0022459617301925 |journal=Journal of Solid State Chemistry |date= 2017|volume=253 |pages=15–20|doi= 10.1016/j.jssc.2017.05.024|bibcode= 2017JSSCh.253...15M|url-access=subscription }} Distance from the radium ion to oxygen is 2.96 Å and the sulfur to oxygen bond length in the sulfate ion is 1.485 Å. In this compound the ionic radius of the radium ion is 1.66 Å, and it is in ten coordination.{{cite journal |last1=Hedström |first1=Hanna |last2=Persson |first2=Ingmar |last3=Skarnemark |first3=Gunnar |last4=Ekberg |first4=Christian |title=Characterization of Radium Sulphate |journal=Journal of Nuclear Chemistry |date=2013-05-22 |volume=2013 |pages=1–4 |doi=10.1155/2013/940701|doi-access=free }}
Radium sulfate can form solid solutions with the sulfates of strontium, barium or lead.