What Is Barium Carbonate?
Barium carbonate, a barium salt of carbonic acid, naturally occurs as witherite—a poisonous mineral found in hydrothermal deposits within limestone formations. In some regions, notably the United Kingdom, witherite has been used as a raw material for barium production. In Japan, barium carbonate is classified as a “deleterious substance,” regulated by multiple laws.
Uses of Barium Carbonate
Barium carbonate serves as a raw material in the manufacture of various barium salts, crystal glass, and cathode ray tubes. It’s also used in electrodes, paints, enamels, ceramic glazes, metal heat treatment, and paper production. Recently, it has found extensive use in electronic materials, particularly as a component in ceramic capacitors, PTC thermistors, optical glass, semiconductors, and phosphor materials. Its toxicity also lends it to use in insecticides and rodenticides.
Properties of Barium Carbonate
Insoluble in water but soluble in carbon dioxide-rich water, nitric acid, hydrochloric acid, and ethanol, barium carbonate has a melting point of 811°C and decomposes at 1,450°C in air. Its solubility in water at 20°C is notably low, at 0.0024 g/100 mL.
Structure of Barium Carbonate
Barium carbonate’s structure is comparable to potassium nitrate, with barium ions and carbonate ions mirroring the arrangement of potassium ions and nitrate ions, respectively. It exists in orthorhombic, amorphous, and hexagonal forms, transitioning between these states under specific temperature and pressure conditions. Its chemical formula is BaCO3, with a molar mass of 197.34 g/mol and a density of 4.286 g/cm3.
Other Information on Barium Carbonate
1. Synthesis of Barium Carbonate
Barium carbonate can be synthesized by passing carbon dioxide through barium hydroxide or by adding alkali carbonate to an aqueous barium salt solution. Industrially, it’s produced from baryte through carbon reduction and carbon dioxide processing.
2. Hazards of Barium Carbonate
While barium carbonate can form toxic barium ions when dissolved in hydrochloric acid, it’s crucial in radiography to distinguish it from barium sulfate (BaSO4), a non-toxic contrast agent. Misuse or misidentification can lead to serious health risks due to its toxicity.