Potassium bromide
Cubic
K, Br
- Bromide of potassium
- Bromsaures potassium
Colorless, hygroscopic crystals
Fixed
2.75 g · cm -3 ( 20 ° C)
732 ° C
1380 ° C.
1,3 hPa ( 795 ° C)
650 g · l -1 ( 20 ° C)
1.5598
Attention
3070 mg · kg -1 ( LD50, rat, oral)
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Potassium bromide is the potassium salt of hydrogen bromide which forms a colorless crystalline cubes which are soluble even better than potassium chloride in water.
Representation
The classical method for the production of KBr is done from the reaction between potassium carbonate with iron (II, III ) bromide. The Fe3Br8 is first re made of scrap iron with excess bromine and überschichtetem water:
In the laboratory, potassium bromide can be produced for example by the reaction of potassium with bromine in ammoniacal solution. Are formed here also water and nitrogen:
The bromination of potash gives potassium bromide, the less soluble potassium bromate separates itself:
The production of the elements has no technical meaning:
Properties
Potassium bromide behaves under pressure as a cold fluid and appears transparent in the infrared. It does not form hydrates.
The standard enthalpy of potassium bromide is ΔHf0 = -392 kJ / mol.
Potassium contains 0.0118 % to the isotope 40K, this provides 10242 Bq per kilogram of KBr, which are 89.28 % and 10.72 % Beta radiation Gamma radiation with 1.46083 MeV.
Use
Potassium bromide is used in the preparation of silver bromide emulsions to films and sheets for the photographic film. In photographic developers, it counteracts the fog and delayed development. In addition, it is used in infrared spectroscopy as a solvent for solids, so-called Kaliumbromidpresslinge. Because of the high optical transparency for electromagnetic waves in the range from 0.23 to 4.0 microns are single crystals of KBr for the preparation of optical components such as lenses and prisms used for infrared optics.
Potassium bromide was used as a medicine to treat seizures as well as a sedative since the mid 19th century. It is the oldest anti-epileptic drug. At the time, sometimes very high doses were used, which led to a chronic Bromvergiftung. This so-called bromism was characterized by excessive sedation, dizziness, headaches, lack of concentration, memory loss, hallucinations, or Bromschnupfen. In many cases, skin symptoms such as the Bromakne or Bromoderm occurred with painful purulent skin nodules (mostly on the limbs ) on.
Even today, potassium bromide is used as Dibro -Be mono to treat a specific type of epilepsy, early childhood grand mal epilepsy. The bromism occurs only rarely, because today, lower dosages are used. As a sedative it is no longer in use today.