Barium hydroxide, represented by the chemical formula \(\text{Ba}(\text{OH})_2\), is an alkaline earth metal hydroxide. This inorganic compound is typically encountered as a white powder in its anhydrous form or as the octahydrate (\(\text{Ba}(\text{OH})_2 \cdot 8\text{H}_2\text{O}\)), which presents as transparent crystals. Its solubility in water is central to its chemical behavior and practical utility.
Solubility Status and Context
Barium hydroxide is highly soluble in water, readily dissolving to form a clear solution at room temperature. This solubility is a direct consequence of the periodic trend observed in the Group 2 alkaline earth metal hydroxides.
The solubility of these hydroxides systematically increases as you move down the group on the periodic table (magnesium, calcium, strontium, and barium). Barium forms the most soluble hydroxide among these elements, allowing it to dissolve in concentrations of around 0.1 mol \(\text{dm}^{-3}\) at \(25^{\circ}\text{C}\). Solubility is significantly temperature-dependent, meaning a greater amount can be dissolved when the water is heated.
Chemical Dissociation in Water
Barium hydroxide is an ionic compound that undergoes dissociation when placed in water. When the solid is introduced, polar water molecules overcome the strong electrostatic attractions holding the ions together in the crystal lattice, surrounding and separating the constituent ions.
This process results in the complete separation of the solid into aqueous ions, following the reaction: \(\text{Ba}(\text{OH})_2 (s) \rightarrow \text{Ba}^{2+} (aq) + 2 \text{OH}^{-} (aq)\). The release of barium ions (\(\text{Ba}^{2+}\)) and hydroxide ions (\(\text{OH}^{-}\)) makes barium hydroxide a strong base, meaning it fully ionizes and produces a highly alkaline solution.
Common Applications
The solubility and strong basicity of barium hydroxide make it valuable for several specialized applications.
- In analytical chemistry, it is used for the titration of weak acids. Its aqueous solution is advantageous because it is free of carbonate ions, which can interfere with titration results.
- It is used in the purification of sugar, specifically to refine sucrose extracted from beet sugar.
- It is employed in the manufacturing of certain lubricants, acting as a component in barium-based greases.
- The compound serves as a precursor for synthesizing other barium compounds and as an additive in specialized glass and ceramics.
Safe Handling and Toxicity
Barium hydroxide presents a dual hazard that requires strict safety protocols for handling. The compound is a strong base, and its hydroxide ions are severely corrosive, capable of causing severe burns and permanent damage to eyes, skin, and mucous membranes upon contact. Immediate and extensive flushing with water is necessary in the event of any contact to mitigate this caustic effect.
The soluble barium ion itself is toxic if swallowed or inhaled. Ingesting barium compounds can lead to serious health issues, including gastrointestinal effects, muscle weakness, and cardiac problems, with no specific antidote available.
Proper personal protective equipment, such as gloves, eye protection, and a face shield, must be used at all times when working with the solid or its solutions. Handling should occur in a well-ventilated area or under a chemical fume hood to prevent dust inhalation. The compound should be stored in a tightly closed container to prevent it from absorbing atmospheric carbon dioxide, which converts it into insoluble barium carbonate.