Barium carbonate
Names Other names Identifiers ChEBI ChemSpider ECHA InfoCard 100.007.426 EC Number RTECS number UNII UN number 1564 Properties BaCO3 Molar mass 197.335 g·mol−1 Appearance white crystals Odor odorless Density 4.286 g/cm3 Melting point 811 °C (1,492 °F; 1,084 K) polymorphic transformation Boiling point 1,450 °C (2,640 °F; 1,720 K) decomposes[1] from 1,360 °C (2,480 °F; 1,630 K) 2.58×10−9 Solubility in acid decomposes −58.9×10−6 cm3/mol 1.676 Structure orthorhombic Thermochemistry 85.35 J/mol·K[1] 112 J/mol·K[2] −1219 kJ/mol[2] −1139 kJ/mol[1] Hazards GHS labelling:[3] Warning H302 P264, P270, P301+P312+P330, P501 NFPA 704 (fire diamond) Flash point Non-flammable Lethal dose or concentration (LD, LC): 418 mg/kg, oral (rat)[3] NIOSH (US health exposure limits):[3] 0.5 mg/m3 Safety data sheet (SDS) Sigma-Aldrich[3] Related compounds
Barium carbonate is the inorganic compound with the formula BaCO3. Like most alkaline earth metal carbonates, it is a white salt that is poorly soluble in water. It occurs as the mineral known as witherite. In a commercial sense, it is one of the most important barium compounds.[5]
Barium carbonate is made commercially from barium sulfide by treatment with sodium carbonate at 60 to 70 °C (140 to 158 °F) (soda ash method) or, more commonly carbon dioxide at 40 to 90 °C (104 to 194 °F):[5]
BaS + H2O + CO2 → BaCO3 + H2S
Barium carbonate reacts with acids such as hydrochloric acid to form soluble barium salts, such as barium chloride:
BaCO3 + 2 HCl → BaCl2 + CO2 + H2O
Pyrolysis of barium carbonate gives barium oxide.[6]
Barium carbonate is mainly used to remove sulfate impurities from feedstock of the chlor-alkali process. Otherwise it is a common precursor to barium-containing compounds such as ferrites.[5]
Barium carbonate is widely used in the ceramics industry as an ingredient in glazes. It acts as a flux, a matting and crystallizing agent and combines with certain colouring oxides to produce unique colours not easily attainable by other means. Its use is somewhat controversial since it can leach from glazes into food and drink. To reduce toxicity concerns, it is often substituted with strontium carbonate, which behaves in a similar way in glazes but is of lower toxicity.[7]
In the brick, tile, earthenware and pottery industries barium carbonate is added to clays to precipitate soluble salts (calcium sulfate and magnesium sulfate) that cause efflorescence.
It is sometimes used as an “energiser” in the Case-hardening process.
