Barium carbonate, chemically represented as \(\text{BaCO}_3\), is a white, odorless inorganic compound that exists naturally as the mineral known as witherite. Barium carbonate is a solid at room temperature and pressure. This compound is one of the most commercially significant sources of the element barium, finding extensive use in various industrial processes. Its dual nature—being highly stable in its solid form yet chemically reactive under certain conditions—defines its industrial importance.
The Ionic Basis of its Solid State
The solid state of barium carbonate is a direct result of its composition as an ionic compound. It forms when a positively charged barium cation (\(\text{Ba}^{2+}\)) bonds with a negatively charged carbonate anion (\(\text{CO}_3^{2-}\)). These oppositely charged ions are held together by powerful electrostatic attractions, known as ionic bonds.
This intense attraction forces the ions into a highly ordered, rigid structure called a crystal lattice. The substantial energy required to disrupt this lattice translates into physical properties typical of ionic solids, such as a high melting point of around \(811\text{ °C}\). The compound’s appearance as a white crystalline solid or powder further reflects this highly organized internal structure.
Essential Chemical Behaviors
A defining characteristic of barium carbonate is its very low solubility in pure water. This limited solubility is a property it shares with other alkaline earth metal carbonates.
Despite its water-insolubility, barium carbonate readily reacts with acids. When exposed to an acid, such as hydrochloric acid, the compound decomposes. This reaction forms a more soluble barium salt, water, and carbon dioxide gas, which can be observed as effervescence. This acid-reactivity is important for both its processing and its toxicity.
Practical Applications and Handling
Barium carbonate’s unique properties make it valuable across several major industries. It is widely used in the ceramics industry, where it acts as a flux in glazes, helping to lower the firing temperature of materials. It is also added to clay bodies to prevent efflorescence, which is the unsightly white scum that can form on the surface of fired clay products.
The compound is also an important component in the manufacturing of specialty glass, where it enhances the glass’s refractive index and brilliance. Historically and in some locations, barium carbonate was used as a rodenticide, or rat poison, due to its toxicity.
The toxicity of barium carbonate is directly linked to its chemical behavior with acids. While insoluble in water, if ingested, it reacts with the hydrochloric acid present in the stomach. This reaction releases the soluble barium ion (\(\text{Ba}^{2+}\)), which is then absorbed into the bloodstream, causing poisoning.