BaSO4 — Barium Sulfate
Barium Sulfate (BaSO4) is a white crystalline inorganic compound used in radiology as a contrast agent and in industries for pigments, coatings, and drilling fluids due to its high density and chemical inertness.
Interactive 3D Molecular Structure — BaSO4
Properties
| Chemical Formula | BaSO4 |
|---|---|
| Molecular Mass | 233.39 g/mol |
| Physical State | Solid (crystalline) |
| Melting Point | 1,580 °C |
| Boiling Point | Decomposes before boiling |
| Density | 4.5 g/cm³ |
| Solubility | Insoluble in water, soluble in concentrated sulfuric acid |
| pH | Neutral |
| Odor | Odorless |
| Color | White |
| Taste | Tasteless |
| Polarity | Ionic |
| Type of Bond | Ionic (between Ba²⁺ and SO₄²⁻) |
| Crystal Structure | Orthorhombic |
| Stability | Stable and non-reactive under normal conditions |
Introduction to Barium Sulfate
Barium Sulfate (BaSO4) is an inorganic compound composed of barium (Ba²⁺) and sulfate (SO₄²⁻) ions. It occurs naturally as the mineral barite and is widely known for its remarkable density, chemical inertness, and radiopacity. Due to its insolubility in water and acids (except concentrated sulfuric acid), barium sulfate is used safely in medical imaging as a contrast agent for X-ray and CT scans of the digestive system. It also serves as a filler and whitening agent in paints, plastics, and paper, and as a component in drilling muds in oil and gas exploration.
Structure and Bonding
Barium Sulfate has an ionic structure consisting of barium cations (Ba²⁺) and sulfate anions (SO₄²⁻). Each barium ion is surrounded by sulfate ions in a crystalline lattice with orthorhombic geometry. The sulfate ion itself is a tetrahedral unit, with the sulfur atom at the center and four oxygen atoms symmetrically surrounding it. The electrostatic attraction between Ba²⁺ and SO₄²⁻ ions results in a highly stable, insoluble solid lattice, which is responsible for the compound’s low solubility and high melting point.
Preparation of Barium Sulfate
Barium Sulfate can be prepared in the laboratory through the precipitation reaction between a soluble barium salt and a soluble sulfate salt. A typical reaction involves barium chloride and sodium sulfate:
\( BaCl_2 + Na_2SO_4 \rightarrow BaSO_4 \downarrow + 2NaCl \)
The reaction produces an insoluble white precipitate of BaSO4, which can be filtered and purified. Industrially, barium sulfate is obtained from natural barite by beneficiation and purification to remove impurities.
Physical and Chemical Properties
- Appearance: White crystalline powder.
- Solubility: Almost insoluble in water and dilute acids.
- Density: 4.5 g/cm³, making it very heavy compared to most non-metallic compounds.
- Thermal Stability: Stable up to 1,580 °C but decomposes above this temperature to form barium oxide (BaO) and sulfur trioxide (SO₃).
- Chemical Inertness: Barium sulfate does not react with most chemicals, which makes it ideal for medical and industrial use.
Uses of Barium Sulfate
Barium Sulfate is one of the most versatile inorganic compounds. Its applications span multiple fields due to its density, whiteness, and non-reactivity.
- Medical Imaging: In medicine, a suspension of BaSO4 is used as a radiocontrast agent for X-ray and CT scans of the digestive tract. Its high atomic number blocks X-rays, helping visualize internal organs clearly.
- Paints and Coatings: Used as a pigment extender and filler in paints, giving smoothness, brightness, and resistance to corrosion.
- Plastics and Rubber Industry: Acts as a filler to improve the hardness, abrasion resistance, and whiteness of plastic and rubber products.
- Drilling Fluids: Added to oil and gas drilling muds to increase density and control pressure in boreholes.
- Paper and Ceramics: Used to enhance whiteness, smoothness, and gloss in paper coatings and ceramic glazes.
Safety and Toxicity
Barium Sulfate is considered non-toxic because of its insolubility. Unlike soluble barium compounds such as barium chloride or nitrate, which can release toxic Ba²⁺ ions, BaSO4 does not dissolve in the gastrointestinal tract and therefore passes harmlessly through the body when used in medical imaging. However, finely powdered BaSO4 should be handled with care to prevent inhalation or mechanical irritation.
Environmental Impact
Due to its chemical stability and insolubility, barium sulfate poses minimal environmental hazards. It does not leach into groundwater or react with other environmental compounds easily. However, mining of barite ore can lead to habitat disturbance and soil erosion. Sustainable mining practices and recycling of industrial BaSO4 waste can minimize environmental effects.
Interesting Facts
- The natural mineral form of barium sulfate is called barite or barytes.
- BaSO4 has a Mohs hardness of 3–3.5, similar to calcite.
- Its radiopaque property makes it essential in medical diagnostics.
- It is used in fireworks to produce green coloration due to barium content.
Key Reactions of Barium Sulfate
Precipitation Reaction
\( BaCl_2 + Na_2SO_4 \rightarrow BaSO_4 \downarrow + 2NaCl \)
This is the standard method of preparing BaSO4 in laboratories. The insoluble BaSO4 precipitates out of the solution as a white solid.
Thermal Decomposition
\( BaSO_4 \xrightarrow{>1580°C} BaO + SO_3 \)
At high temperatures, BaSO4 decomposes to form barium oxide and sulfur trioxide. This reaction occurs in a controlled industrial environment since BaSO4 is otherwise very stable.
Reaction with Concentrated Sulfuric Acid
\( BaSO_4 + H_2SO_4 \rightarrow Ba(HSO_4)_2 \)
Though BaSO4 is insoluble in dilute acids, it reacts slightly with concentrated sulfuric acid forming barium bisulfate. This reaction is mild and typically used to regenerate certain sulfate salts.