Lithium bromide

Crystal structure
__ Li +      __ Br -
Crystal system	cubic
Space group	Fm 3 m (No. 225)
Coordination numbers	Li [6], Br [6]
General
Surname	Lithium bromide
Ratio formula	LiBr
Brief description	bitter-tasting, colorless, hygroscopic solid
External identifiers / databases
CAS number 7550-35-8 (pure substance) 13453-70-8 (hydrate) EC number 231-439-8 ECHA InfoCard 100,028,582 PubChem 82050 ChemSpider 74049 Wikidata Q409701
properties
Molar mass	86.85 g mol −1
Physical state	firmly
density	3.46 g cm −3
Melting point	550 ° C
boiling point	1265 ° C
solubility	1450 g l −1 (20 ° C) in water 314 g l −1 (25 ° C) in DMSO
Refractive index	1,783
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 302-315-319-317 P: 280-305 + 351 + 338
Toxicological data	1800 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Lithium bromide LiBr, the lithium salt of hydrobromic acid , forms colorless, highly hygroscopic crystals with a melting point of 550 ° C, a boiling point of 1265 ° C and a density of 3.46 g · cm ⁻³ . The enthalpy of solution in water is −48.83 kJ / mol.

In addition to the anhydrous lithium bromide, there are also various hydrates , known are LiBr · n H ₂ O with n = 1, 2, 3 and 5. The monohydrate LiBr · H ₂ O has a density of 2.51 g · cm ⁻³ .

Manufacturing

Lithium bromide is produced by reacting an aqueous lithium hydroxide or lithium carbonate solution with hydrogen bromide .

${\displaystyle \mathrm {LiOH+\ HBr\longrightarrow \ LiBr+\ H_{2}O} }$

${\displaystyle \mathrm {Li_{2}CO_{3}+\ 2HBr\longrightarrow \ 2LiBr+\ H_{2}O+\ CO_{2}} }$

The lithium hypobromite formed in the reaction of elemental bromine with lithium hydroxide solution in addition to lithium bromide can be reduced to lithium bromide with formic acid or ammonia .

The anhydrous lithium bromide can also be produced by reacting lithium hydride with bromine .

${\displaystyle \mathrm {LiH+\ Br_{2}\longrightarrow \ LiBr+\ HBr} }$

properties

Solubility limits of LiBr in the T-ξ diagram

Solubility diagram of LiBr

Lithium bromide is hygroscopic, concentrated solutions with 50% LiBr reduce the vapor pressure of the water by approx. 80%. It is very soluble in water ; 60% solutions can be prepared at 20 ° C. It is also readily soluble in ethanol and ethylene glycol . The solubility is low on the pressure, but strongly dependent on the temperature. Depending on the temperature, there are different hydrates of lithium bromide: below 4 ° C the trihydrate LiBr · 3 H ₂ O, between 4 and 44 ° C the dihydrate LiBr · 2 H ₂ O and between 44 and 159 ° C the monohydrate LiBr · H ₂ O. The anhydrate is stable at even higher temperatures . The solubility diagram shows a kink at the transition point from monohydrate to anhydrate.

The standard enthalpy of formation of lithium bromide is ΔH _f ⁰  = −351 kJ / mol.

use

• As a solution of lithium bromide in water for absorption refrigeration machines (> 50% of the lithium bromide produced).
• Because of its strongly hygroscopic effect as a drying agent, also for dehumidifying closed rooms.
• Organic syntheses. As a catalyst and educt .
• Flux when soldering.
• As an electrolyte in some types of lithium batteries.
• Until the 1950s as an anticonvulsant , sedative and agent against bipolar disorders (no longer in use due to severe side effects)

Individual evidence

1. ↑ Entry on lithium bromide. In: Römpp Online . Georg Thieme Verlag, accessed on November 10, 2014.
2. ↑ ^{a b c d} data sheet lithium bromide from AlfaAesar, accessed on February 5, 2010 ( PDF )(JavaScript required) .
3. ↑ Dimethyl Sulfoxide (DMSO) Solubility Data. Gaylord Chemical Company, LLC; Bulletin 102, June 2014, p. 15. (PDF)
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Index of Refraction of Inorganic Crystals, pp. 10-246.
5. ↑ ^{a b c} Entry on lithium bromide in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
6. ↑ Entry on lithium bromide at chemicalland21.com.
7. ↑ Erich Meister: Basic practical course in physical chemistry. 2006, ISBN 3-8252-8329-1 .
8. ^ Author collective: Organikum . 21st edition. Wiley-VCH, Weinheim 2001, ISBN 3-527-29985-8 , pp. 1151-1152.
9. ↑ Herold, Keith; Radermacher, E .; Klein, Reinhard; Sanford, A .: Absorption Chillers and Heat Pumps. Boca Ration: CRC Press, 1996, ISBN 0-8493-9427-9 .
10. ^ ^{A b} R. Abegg, F. Auerbach, I. Koppel: Handbook of inorganic chemistry. Verlag S. Hirzel, 1908, Volume 2, Part 1, pp. 128-129. Full text
11. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 1170.
12. ↑ Cold air air conditioning: cold generation below 0 ° C with a water / lithium bromide resorption chiller