Lithium bromide

Cubic

Fm3m

Li, Br

  • 7550-35-8 ( pure substance)
  • 13453-70-8 ( hydrate)

Bitter-tasting, colorless, hygroscopic solid

Fixed

3.46 g · cm -3

550 ° C

1265 ° C

1,450 g · l -1 ( 20 ° C)

1,783

Attention

1800 mg · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

Lithium bromide, LiBr, the lithium salt is the hydrobromic acid which forms a colorless highly hygroscopic crystals having 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 are also various hydrates, are known LiBr · H2O n with n = 1, 2, 3 and 5 The monohydrate LiBr · H2O has a density of 2.51 g · cm -3.

Production

The preparation of lithium is effected by reaction of an aqueous lithium hydroxide or lithium carbonate with hydrogen bromide.

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

Anhydrous lithium bromide may also be prepared by the reaction of lithium hydride with bromine.

Properties

Lithium bromide is hygroscopic, concentrated solutions at 50% LiBr reduce the vapor pressure of water by about 80%. It is very soluble in water at 20 ° C 60 % solutions can be produced. Also in ethanol and ethylene glycol is soluble. The solubility is low on pressure, but strongly dependent on the temperature. Depending on the temperature, there are various hydrates of lithium bromide: below 4 ° C, the trihydrate LiBr · 3 H 2 O, 4-44 ° C, the dihydrate LiBr · 2 H2O and 44-159 ° C, the monohydrate LiBr · H2O. At still higher temperatures, the anhydrate is stable. The solubility diagram has at the transition point from the monohydrate to the anhydrate at a kink.

The standard enthalpy of lithium bromide is ΔHf0 = -351 kJ / mol.

Use

  • As a solution of lithium bromide in water for absorption chillers (> 50 % of the produced lithium bromide ).
  • Because of the strongly hygroscopic effect as a drying agent, also to dehumidify closed rooms.
  • Organic syntheses. As catalyst and reactant.
  • Flux when soldering.
  • As the electrolyte in some lithium batteries.
  • Up in the 1950s as an anticonvulsant, sedative and anti- bipolar disorders ( no longer in use due to severe side effects )
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