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

sulfate The sulfate or sulphate ion is a polyatomic ion, 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 salt (chemistry), ...

salts. It was formerly used in

radiotherapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Ra ...

and

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

, but this has been phased out in favor of less hazardous alternatives.

Properties

Radium sulfate crystallises 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 lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with ...

crystal system, with a unit cell of dimensions ''a'' = 9.07 ''b''=5.52 and ''c'' = 7.28 Å. The unit cell volume is 364 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 homogenous mixture of two different kinds of atoms in solid state and have a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The wor ...

s with the sulfates of strontium, barium or lead.

References

{{radium compounds Radium compounds Sulfates