Chemical and Physical Properties

Barium carbonate occurs naturally as the mineral witherite but is more commonly produced synthetically. Its notable properties include:

• Molecular weight: 197.34 g/mol

• Melting point: 1,360C (2,480F)

• Density: 4.286 g/cm

• Solubility:

  • Nearly insoluble in water (22 mg/L at 20C)

  • Soluble in acids (with effervescence)

  • Insoluble in alcohol

The compound exhibits rhombic crystal structure at room temperature, transforming into hexagonal crystals when heated above 811C. Its thermal stability makes it valuable in high-temperature industrial processes.

Production Methods

1. Natural Occurrence

Witherite (natural BaCO?) deposits exist in:

• England (the type locality)

• United States

• Canada

• China

However, natural sources account for less than 5% of commercial barium carbonate due to economic factors.

2. Industrial Synthesis

Modern production primarily uses two methods:

A. Carbonation Process

1. Barium sulfide (BaS) solution is prepared from barite (BaSO?)

2. Carbon dioxide is bubbled through the solution:
   BaS + CO? + H?O ? BaCO? + H?S

B. Double Decomposition
Barium chloride reacts with sodium carbonate:
BaCl? + Na?CO? ? BaCO? + 2NaCl

The resulting precipitate is filtered, washed, and dried to produce commercial-grade barium carbonate.

Industrial Applications

1. Glass Manufacturing (Primary Use)

Barium carbonate serves three critical functions in specialty glass production:

• Flux agent: Lowers melting temperature

• Refractive index modifier: Enhances optical clarity

• X-ray absorption: Used in cathode ray tubes and radiation shielding glass

2. Ceramic Industry

In tile and pottery production:

• Produces brilliant white finishes

• Prevents efflorescence (salt migration)

• Strengthens ceramic bodies

3. Barium Ferrite Production

Essential for manufacturing permanent magnets used in:

• Speakers

• Electric motors

• Magnetic recording media

4. Chemical Precursor

Used to synthesize other barium compounds:

• Barium titanate (for capacitors)

• Barium nitrate (pyrotechnics)

• Barium chloride (water treatment)

5. Rodenticides

Historically used in rat poisons (now banned in many countries):

• Causes cardiac arrest in rodents

• Being replaced by safer alternatives

6. Other Applications

• Brick and clay additive

• Electroplating solutions

• Optical lens production

• Sulfate removal in brine purification

Safety and Handling

Toxicity Profile

Barium carbonate is classified as:

• Acute oral toxicity(LD50 rat): 418 mg/kg

• Harmful if swallowed

• May cause respiratory irritation

Exposure Risks

• Inhalation: Dust can irritate respiratory tract

• Ingestion: Converts to soluble barium salts in stomach acid

• Skin contact: Generally low absorption but may cause irritation

Poisoning Symptoms

Barium ion interference with potassium channels causes:

• Muscle twitching

• Hypertension

• Cardiac arrhythmias

• Paralysis (in severe cases)

First Aid Measures

• Ingestion: Administer sodium sulfate solution to precipitate barium as insoluble sulfate

• Inhalation: Move to fresh air, provide oxygen if needed

• Skin contact: Wash thoroughly with soap and water

• Eye contact: Flush with water for 15 minutes

Regulatory Status

• OSHA PEL: 0.5 mg/m (as Ba)

• EU Classification: Toxic (T)

• WHMIS: D2B (Toxic material)

Environmental Considerations

Ecotoxicity

• Aquatic toxicity: LC50 (fish) >100 mg/L

• Soil mobility: Low due to insolubility

• Biodegradation: Not applicable (inorganic compound)

Disposal Methods

• Preferred: Conversion to insoluble barium sulfate

• Landfill: Only at approved hazardous waste facilities

• Recycling: Recover barium content when economically viable

Market and Economics

Global Production

• Annual output: ~7 million metric tons

• Major producers:

  • China (80% of supply)

  • India

  • Germany

  • United States

Price Trends

• Industrial grade: $300-$500/ton

• High purity grade: $800-$1,200/ton

• Market drivers:

  • Glass industry demand

  • Environmental regulations

  • Alternative material development

Emerging Alternatives and Future Outlook

Substitute Materials

• Glass industry: Barium-free formulations

• Ceramics: Alternative fluxes

• Magnets: Rare-earth compounds

Research Directions

• Nanostructured barium carbonatefor catalysis

• CO? sequestrationapplications

• Biomedical applications(limited due to toxicity)

Conclusion

Barium carbonate remains an industrially significant chemical despite its toxicity concerns. Its unique combination of properties - particularly in glass and ceramic applications - ensures continued demand, though environmental and health regulations are driving innovation in alternative materials. Proper handling procedures and waste management can mitigate risks associated with this useful but potentially dangerous compound. As industries evolve toward greener chemistry, barium carbonate may see reduced usage in some applications while maintaining niche roles where its specific characteristics prove irreplaceable.