Barium carbonate or Witherite, has the molecular formula BaCO3. The mineral Witherite is named after an English chemist, William Withering, who recognized Witherite to be distinctive chemically from barytes in 1784. It is a white crystalline solid which melts at 1740 ˚C and decomposes at 1300 ˚C. It could be crystallized in the orthorhombic system. While it is soluble in acidic solutions, it is insoluble in water and alcohol. It is normally employed in rat poison, bricks, ceramic glazes and cement.
Barium carbonate is made from barium sulphide or black ash which is dissolved in water. The clear solution is the raw material in producing barium carbonate.
There are two ways to produce the carbonate anion:
1. Soda ash method: barium sulphide reacts with the solid form or dissolved sodium carbonate to produce barium carbonate and sodium sulphide. The resulting barium carbonate precipitate is filtered, washed and dried.
2. Straight gassing method: carbon dioxide is passed through barium sulphide to form barium carbonate and hydrogen sulphide gas. The toxic hydrogen sulphide gas would then be converted to sulphur compounds or the elemental sulphur, while the barium carbonate would undergo precipitation, washing, drying and grinding.
Due to its physical property of being a white powder form, it is used as a white pigment and paper coating agent to manufacture white paper. As a consequence, the optical and tactile characteristics are improved, in terms of whiteness, gloss and smoothness. The printability of the paper and print quality of images and texts have been improved with the help of this substance.
Barium carbonate is used in ceramic glaze, by acting as a flux, matting and crystallizing agent, and it is combined with coloring oxides to produce colors on ceramics.
In glass industry, it is added into glass as a flux for silica. In brick, tile, earthenware, pottery and clays manufacturing, it is frequently used. It serves as a brine purification chemical in the chlor-alkali industry.
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