Caesium bromide or cesium bromide is an ionic
compound of
caesium
Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...
and
bromine
Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...
with the
chemical formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...
CsBr. It is a white or transparent solid with melting point at 636 °C that readily dissolves in water. Its bulk crystals have the cubic CsCl structure, but the structure changes to the
rocksalt
Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...
type in nanometer-thin film grown on
mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
, LiF, KBr or NaCl substrates.
Synthesis
Caesium bromide can be prepared via following reactions:
*
Neutralization:
: CsOH (aq) + HBr (aq) → CsBr (aq) + H
2O (l)
: Cs
2(CO
3) (aq) + 2 HBr (aq) → 2 CsBr (aq) + H
2O (l) + CO
2 (g)
* Direct synthesis:
: 2 Cs (s) + Br
2 (g) → 2 CsBr (s)
The direct synthesis is a vigorous reaction of caesium with other halogens. Due to its high cost, it is not used for preparation.
Uses
Caesium bromide is sometimes used in optics as a
beamsplitter component in wide-band
spectrophotometers
Spectrophotometry is a branch of electromagnetic spectroscopy concerned with the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. Spectrophotometry uses photometers, known as sp ...
.
References
Crystran Ltd experimental data July 2021
Cited sources
*
External links
Ultra-violet photoabsorption measurements in alkali iodide and caesium bromide evaporated films
{{Authority control
Caesium compounds
Alkali metal bromides
Caesium chloride crystal structure