Lithium bromide

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Lithium bromide

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Template:Longitem	LiBr
Molar mass	86.845 g/mol
Appearance	White hygroscopic solid
Density	3.464 g/cm3
Melting point	Template:Chembox CalcTemperatures
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Solubility	soluble in methanol, ethanol, ether, acetone slightly soluble in pyridine
Template:Longitem	−34.3·10−6 cm3/mol
Template:Longitem	1.7843 (589 nm)
Template:Longitem	Cubic, Pearson symbol cF8, No. 225
Template:Longitem	Fm3m
Template:Longitem	a = 0.5496 nm
Template:Longitem	74.3 J/mol K
Template:Longitem	−351.2 kJ/mol
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Template:Longitem	Lithium fluoride Lithium chloride Lithium iodide
Template:Longitem	Sodium bromide Potassium bromide Rubidium bromide Caesium bromide

Lithium bromide (LiBr) is a chemical compound of lithium and bromine. Its extreme hygroscopic character makes LiBr useful as a desiccant in certain air conditioning systems.

Production and properties

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Solubility of LiBr in water as a function of temperature

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Phase diagram of LiBr

LiBr is prepared by treating an aqueous suspension of lithium carbonate with hydrobromic acid or by reacting lithium hydroxide with bromine. It forms several crystalline hydrates, unlike the other alkali metal bromides.

Lithium hydroxide and hydrobromic acid (aqueous solution of hydrogen bromide) will precipitate lithium bromide in the presence of water.

LiOH + HBr → LiBr + H₂O

Uses

A 50–60% aqueous solution of lithium bromide is used in air-conditioning systems as desiccant. It is also used in absorption chilling along with water (see absorption refrigerator). Solid LiBr is a useful reagent in organic synthesis. It is included into oxidation and hydroformylation catalysts; it is also used for deprotonation and dehydration of organic compounds containing acidic protons, and for the purification of steroids and prostaglandins.

Medical applications

Lithium bromide was used as a sedative beginning in the early 1900s, but it fell into disfavor in the 1940s as newer sedatives became available and when some heart patients died after using the salt substitute lithium chloride. Like lithium carbonate and lithium chloride, it was used as treatment for bipolar disorder.

Hazards

Lithium salts are psychoactive and somewhat corrosive. Heat is quickly generated when lithium bromide is dissolved into water because it has a negative enthalpy of solution.