Radium sulfate (or radium sulphate) is an inorganic compound with the formula RaSO₄ and an average molecular mass of 322.088 g/mol. This white salt is the least soluble of all known

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

salts. It was formerly used in

radiotherapy Radiation therapy or radiotherapy (RT, RTx, or XRT) is a treatment using ionizing radiation, generally provided as part of cancer therapy to either kill or control the growth of malignant cells. It is normally delivered by a linear particle ...

and

smoke detectors A smoke detector is a device that senses smoke, typically as an indicator of fire. Smoke detectors/alarms are usually housed in plastic enclosures, typically shaped like a disk about in diameter and thick, but shape and size vary. Smoke can be ...

, 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 In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...

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. 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. Radium sulfate can form

solid solution A solid solution, a term popularly used for metals, is a homogeneous mixture of two compounds in solid state and having a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solutio ...

s with the sulfates of strontium, barium or lead.

References

{{radium compounds Radium compounds Sulfates