Hokutolite

Barium sulfate

Identifiers
CAS Number	7727-43-7 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:133326 N
ChemSpider	22823 Y
ECHA InfoCard	100.028.896
EC Number	231-784-4
PubChem CID	24414
RTECS number	CR060000
UNII	25BB7EKE2E Y
InChI InChI=1S/Ba.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 Y Key: TZCXTZWJZNENPQ-UHFFFAOYSA-L Y InChI=1/Ba.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 Key: TZCXTZWJZNENPQ-NUQVWONBAD
SMILES [Ba+2].[O-]S([O-])(=O)=O
Properties
Chemical formula	BaSO4
Molar mass	233.38 g/mol
Appearance	white crystalline
Odor	odorless
Density	4.49 g/cm3
Melting point	1,580 °C (2,880 °F; 1,850 K)
Boiling point	1,600 °C (2,910 °F; 1,870 K) (decomposes)
Solubility in water	0.0002448 g/100 mL (20 °C) 0.000285 g/100 mL (30 °C)
Solubility product (Ksp)	1.0842 × 10−10 (25 °C)
Solubility	insoluble in alcohol, soluble in concentrated, hot sulfuric acid
Magnetic susceptibility (χ)	-71.3·10−6 cm3/mol
Refractive index (nD)	1.636 (alpha)
Structure
Crystal structure	orthorhombic
Thermochemistry
Std molar entropy (So298)	132 J·mol−1·K−1
Std enthalpy of formation (ΔfHo298)	−1465 kJ·mol−1
Pharmacology
ATC code	V08BA01 (WHO)
Routes of administration	by mouth, rectal
Pharmacokinetics:
Bioavailability	negligible by mouth
Excretion	rectal
Legal status	US: ℞-only
Hazards
EU classification (DSD) (outdated)	not listed
NFPA 704	0 0 0
Flash point	noncombustible
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)
REL (Recommended)	TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
IDLH (Immediate danger)	N.D.
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Barium sulfate (or sulphate) is the inorganic compound with the chemical formula BaSO₄. It is a white crystalline solid that is odorless and insoluble in water. It occurs as the mineral barite, which is the main commercial source of barium and materials prepared from it. The white opaque appearance and its high density are exploited in its main applications.

About 80% of the world's barium sulfate production, mostly purified mineral, is consumed as a component of oil well drilling fluid. It increases the density of the fluid, increasing the hydrostatic pressure in the well and reducing the chance of a blowout.

Barium sulfate in suspension is frequently used medically 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 a thick milk like solution (often with sweetening and flavoring agents added). Although barium is a heavy metal, and its water-soluble compounds are often highly toxic, the 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. Due to the relatively high atomic number (Z = 56) of barium, its compounds absorb X-rays more strongly than compounds derived from lighter nuclei.

The majority of synthetic barium sulfate is used as a component of white pigment for paints. In oil paint, barium sulfate is almost transparent, and is used as a filler or to modify consistency. One major manufacturer of artists' oil paint sells "permanent white" that contains a mixture of titanium white pigment (TiO₂) and barium sulfate. The combination of barium sulfate and zinc sulfide (ZnS) is the inorganic pigment called lithopone. In photography it is used as a coating for certain photographic papers.