The lithium bromide it is a neutral salt of an alkali metal whose chemical formula is LiBr. The formula expresses that its crystalline solid is composed of Li ions+ and Br- in a 1: 1 ratio. Its crystals are white or light beige. It is very soluble in water and it is also a fairly hygroscopic salt..
This last property allows its use as a desiccant in air conditioning and refrigeration systems. Likewise, lithium bromide was used since the beginning of the 20th century in the treatment of certain mental health disorders, its use being abandoned due to an inappropriate use of salt.
LiBr is produced by treating lithium carbonate, LitwoCO3, with hydrobromic acid. After heating the medium, it precipitates out of the aqueous solution as a hydrate..
This salt irritates the skin and eyes on contact, while it causes irritation of the respiratory passages by inhalation. The ingestion of lithium salts can cause nausea, vomiting, diarrhea and dizziness.
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The LiBr formula makes it clear that the Li / Br ratio is equal to 1; for each Li cation+ there must be a Br anion- counterpart. Therefore, this ratio must be kept constant in all corners of the LiBr crystal..
Li ions+ and Br- they attract each other, decreasing the repulsions between equal charges, to in this way originate a cubic crystal like gem salt; this is isomorphic to NaCl (top image). Note that by itself the whole set has a cubic geometry.
In this crystal, the Li+ they are smaller and have a light purple color; while the Br- they are more voluminous and of a deep brown color. It is observed that each ion has six neighbors, which is the same as saying that they present an octahedral coordination: LiBr6 or Li6Br; however, if the unit cell is considered, the Li / Br ratio remains 1.
This is the crystal structure preferably adopted by LiBr. However, it can also form other types of crystals: wurzite, if it crystallizes at low temperatures (-50 ° C) on a substrate; or body-centered cubic, or CsCl type, if the cubic gem salt crystal is subjected under high pressure.
The foregoing is applicable for anhydrous LiBr. This salt is hygroscopic, and can therefore absorb moisture from the environment, inserting water molecules within its own crystals. Thus, the hydrates LiBrnH arisetwoO (n = 1, 2, 3…, 10). For each hydrate, the crystal structure is different.
For example, crystallographic studies determined that LiBrHtwoOr adopt a perovskite-like structure.
When these hydrates are in aqueous solution, they can supercool and vitrify; that is, they adopt an apparently crystalline but molecularly disordered structure. Under such conditions, hydrogen bonds in water become quite important..
88.845 g / mol.
White or light beige crystalline solid.
Toilet.
552 ºC (1,026 ºF, 825 K).
1,256 ºC (2,309 ºF, 1,538 K).
166.7 g / 100 mL at 20 ° C. Note its high solubility.
Soluble in methanol, ethanol, ether, and acetone. Slightly soluble in pyridine, an aromatic compound and less polar than the previous ones.
1,784.
51.88 J / mol K.
66.9 J / mol K.
1,265 ° C. It is considered non-flammable.
Stable. The anhydrous form, however, is extremely hygroscopic.
When decomposed by heating, it produces lithium oxide.
Between pH 6 and 7 in aqueous solution (100 g / L, 20 ºC).
Lithium Bromide is not reactive under normal environmental conditions. However, you can experience strong reactions with strong acids as the temperature increases..
When dissolved in water, there is an increase in temperature, caused by a negative enthalpy of hydration.
LiBr is produced by reacting lithium hydroxide or lithium carbonate with hydrobromic acid in a neutralization reaction:
LitwoCO3 + HBr => LiBr + COtwo + HtwoOR
Lithium bromide is obtained as a hydrate. To obtain the anhydrous form, it is necessary to heat the hydrated salt under vacuum..
The name 'lithium bromide' derives from the fact that it is a metal halide, so named according to the stock nomenclature. Other names, equally valid but less used, are lithium monobromide, according to the systematic nomenclature; and lithic bromide (the unique valence of +1 for lithium), according to the traditional nomenclature.
LiBr is a hygroscopic salt, forming a concentrated brine capable of absorbing moisture from the air over a wide range of temperatures. This brine is used as a desiccant in air conditioning and refrigeration systems..
It is used to increase the volume of wool, hair and other organic fibers.
LiBr forms adducts with some pharmaceutical compounds, modulating their action. An adduct is the combination by coordination of two or more molecules, without producing a structural alteration of any of the joined molecules.
Lithium bromide was first used as a sedative in certain mental disorders, and it was discontinued in 1940. Currently, lithium carbonate is used; but in any case, lithium is the element that exerts the therapeutic action in both compounds.
Lithium is used in the treatment of bipolar disorder, having been useful in the control of manic episodes of the disorder. Lithium is thought to inhibit the activity of excitatory neurotransmitters, such as dopamine and glutamic acid.
On the other hand, it increases the activity of the inhibitory system mediated by the neurotransmitter gamma-amino-butyric acid (GABA). These actions could form part of the basis of the therapeutic action of lithium.
Skin irritation and sensitization, allergies. Serious eye damage or irritation to the eyes, respiratory tract, nasal passages and throat.
The main symptoms due to ingestion of lithium bromide are: gastrointestinal disorders, vomiting and nausea. Other adverse effects of ingesting salt include agitation, spasms, and loss of consciousness..
The condition known as "bromism" can occur with lithium bromide doses greater than 225 mg / day..
Some of the following signs and symptoms may occur in jokes: acne exacerbation and loss of appetite, tremors, speech problems, apathy, weakness, and maniacal agitation.
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