Overview

Barium sulfate is an inorganic compound with the chemical formula BaSO4. It consists of barium cations and sulfate anions and contains barium in the +2 oxidation state. In nature it appears as the mineral barite and as a high‑density white crystalline powder in manufactured forms. Because it is essentially insoluble in water, barium sulfate behaves differently from soluble barium salts and is commonly handled as an inert material in many applications. For general information about the compound see chemical identity and for the element itself consult barium.

Physical and chemical characteristics

Barium sulfate is notable for its high density and strong ability to attenuate X‑rays, properties that arise from the heavy barium atom. It is white, odorless and very poorly soluble in water or dilute acids under normal conditions. The sulfate ion that pairs with barium is the common tetrahedral anion SO4 2−; more on the sulfate chemistry is available via sulfate ion. The +2 oxidation state of barium in this salt is the usual state for the element: barium oxidation state.

Uses and applications

The most widely recognized use of barium sulfate is in medical imaging: as an oral or rectal contrast medium it outlines the gastrointestinal tract on radiographs and fluoroscopic studies. Medical resources covering radiographic use reference radiography and specific gastrointestinal studies are described at clinical imaging. Beyond medicine, BaSO4 is used as a filler and pigment in paints, paper, plastics and rubber, and as a weighting agent in drilling fluids because it increases density without dissolving.

Safety and environmental notes

  • Barium sulfate is much less hazardous than soluble barium compounds because it does not dissolve readily; however, inhalation of fine dust or improper industrial exposure can present risks.
  • In medical use the compound is formulated to be safe when given by trained professionals; it should not be introduced into body cavities where perforation is suspected without clinical judgment.
  • Disposal and handling follow industrial and environmental regulations to limit dust and contamination.

History and notable distinctions

The natural mineral barite has been used historically as a pigment and in early industrial processes. Modern production yields highly pure, finely milled barium sulfate tailored to medical or industrial specifications. A key distinction is between BaSO4 and soluble barium salts: the former is used deliberately because of its inert, radiopaque character, while the latter are toxic and handled with strict controls.