Barium sulfate

Barium Sulfate



CAS number ^*	ATC code V08BA01
Chemical formula	BaSO₄
Molecular weight	233.43
Specific gravity	4.5
Bioavailability	negligible orally
Melting point	1580°C
Density	4.5 g/cm³
Solubility in water	0.00115 g/L (18°C)
RTECS number	CR0600000

Barium sulfate (or barium sulphate) is the white crystalline solid with the formula BaSO₄. It is very insoluble in water and other potential solvents. The mineral barite is composed largely of barium sulfate and is a common ore of barium.

Uses

Radiocontrast agent

Barium sulfate is frequently used clinically as a radiocontrast agent for X-ray imaging and other diagnostic procedures. It is most often used in imaging of the GI tract during what is colloquially known as a 'Barium meal'.

It is administered, orally or by enema, as a suspension of fine particles in an aqueous solution (often with sweetening agents added). Although barium is a heavy metal, and its water soluble compounds are often highly toxic, the extremely low solubility of barium sulfate protects the patient from absorbing harmful amounts of the metal. Barium sulfate is also readily removed from the body, unlike Thorotrast, which it replaced. The compound works due to barium's relatively high atomic number (Z = 56), since large nuclei absorb X-rays much better than smaller nuclei.

Pigment

Barium sulfate mixtures are used as white pigment for paints, when combined with zinc oxide (ZnO) it is called lithopone, when combined with sodium sulfate (Na₂SO₄) it is called blanc fixe. It replaced white lead due to the latter's toxicity.

Pyrotechnics

Barium sulfate is also used as a high temperature oxidizer in certain pyrotechnic formulas, as it produces a green colored light while it burns. Barium nitrate is more common in green pyrotechnic formulas, as it is a more amiable oxidizer while still producing green colored light.

Other uses

Barium sulfate is used as a filler in plastics and as a component of oil well drilling fluid to increase the density.

External sources