Barium hydroxide is an inorganic alkaline compound widely used in analytical and biochemical laboratories. Due to its strong basicity and relatively high solubility compared with other alkaline earth hydroxides, it is particularly useful for titration of weak acids present in lipids, carbohydrates, and organic phosphates. In addition, it serves as an efficient precipitating agent for sulfate ions through the formation of highly insoluble barium sulfate (BaSO₄), enabling selective removal of sulfate from analytical mixtures.
Chemical Properties
Barium hydroxide (Ba(OH)₂, molecular weight 171.34 g/mol in its anhydrous form) typically appears as white, hygroscopic crystals. It commonly exists as the monohydrate (Ba(OH)₂·H₂O) or the octahydrate (Ba(OH)₂·8H₂O). The monohydrate has a melting point of approximately 78 °C and a density of about 3.74 g/cm³. Structurally, the Ba²⁺ ion is coordinated in a square antiprismatic geometry involving water molecules and hydroxide ligands within a layered crystal structure. Barium hydroxide is significantly more soluble in hot water (approximately 21.8 g/100 mL at 100 °C) than at room temperature (about 3.9 g/100 mL at 20 °C). In aqueous solution it dissociates completely to release Ba²⁺ and hydroxide ions, producing strongly alkaline solutions that can reach pH values close to 14. The compound readily absorbs atmospheric carbon dioxide, forming insoluble barium carbonate (BaCO₃).
Biochemical Applications
In biochemical and analytical laboratories, barium hydroxide is used in several quantitative and preparative methods. In lipid chemistry, solutions typically ranging from 0.1 to 0.5 N are applied for the saponification of triglycerides, where the resulting barium salts of fatty acids can be selectively precipitated, allowing subsequent quantification of glycerol. The compound is also employed in carbohydrate analysis to hydrolyze polysaccharides into reducing sugars under controlled alkaline conditions. In molecular biology and protein biochemistry laboratories, barium ions can facilitate nucleic acid co-precipitation with phosphate complexes, a principle used in certain DNA transfection approaches. Additionally, Ba²⁺ ions are occasionally utilized in enzymological studies to evaluate the activation or modulation of enzymes such as myosin ATPase or alkaline phosphatases.