- Lithium bromide (LiBr) is a highly hygroscopic inorganic salt composed of lithium (Li⁺) and bromide (Br⁻) ions. It appears as a white to colorless crystalline solid that is highly soluble in water and various polar organic solvents.
- Like other lithium halides, LiBr exhibits strong ionic bonding due to the small size and high charge density of the lithium ion, resulting in significant electrostatic attraction between the ions. It crystallizes in a cubic structure, similar to sodium chloride, and its aqueous solutions are clear and strongly conductive.
- One of the most prominent characteristics of lithium bromide is its hygroscopic nature, which allows it to absorb large amounts of moisture from the air. This property underpins one of its most important industrial applications: absorption refrigeration systems. In these systems, LiBr acts as a liquid desiccant and is commonly used in combination with water, where water serves as the refrigerant and LiBr as the absorbent. When water vapor is absorbed by a concentrated LiBr solution, heat is released, enabling efficient thermal energy management. Such systems are particularly valued in large-scale HVAC applications, especially where waste heat or solar thermal energy is available.
- In organic synthesis, lithium bromide is used as a catalyst or reaction additive. It can enhance the rate and selectivity of certain reactions, including nucleophilic substitution, peptide coupling, and deprotection reactions. Because of its solubility in polar solvents and ability to stabilize charged intermediates, LiBr is often used in organolithium chemistry and polymer science. It also finds use in photographic processing, although its role has diminished with the advent of digital technologies.
- In pharmacology and psychiatry, lithium bromide was once used as a sedative and mood stabilizer in the late 19th and early 20th centuries. Like other lithium salts, it was believed to calm the central nervous system and was employed in the treatment of conditions such as epilepsy and manic depression. However, it fell out of clinical use due to concerns about toxicity and the availability of safer alternatives. Lithium carbonate and lithium citrate eventually replaced LiBr in psychiatric practice due to better pharmacokinetic profiles.
- From a safety perspective, lithium bromide should be handled with care. While it is not as hazardous as some other bromine compounds, exposure to concentrated LiBr can cause irritation to the skin, eyes, and respiratory system. Ingestion or prolonged exposure can lead to symptoms associated with lithium toxicity, including gastrointestinal distress, tremors, confusion, or even renal complications. Therefore, proper protective equipment, such as gloves and goggles, should be used when handling the substance, especially in industrial concentrations or laboratory environments.
- Environmentally, LiBr is not considered a major pollutant, but disposal should be controlled to avoid unnecessary lithium or bromide accumulation in ecosystems. Both lithium and bromide ions can disrupt aquatic environments at high concentrations, although lithium bromide itself is not acutely toxic in most settings.
