Caesium bromide

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Caesium bromide
CsCl polyhedra.png
IUPAC name
Caesium bromide
Other names
Cesium bromide,
Caesium(I) bromide
3D model (JSmol)
ECHA InfoCard 100.029.209
EC Number 232-130-0
Molar mass 212.809 g/mol[1]
Appearance White solid
Density 4.43 g/cm3[1]
Melting point 636 °C (1,177 °F; 909 K)[1]
Boiling point 1,300 °C (2,370 °F; 1,570 K)[1]
1230 g/L (25 °C)[1]
-67.2·10−6 cm3/mol[2]
1.8047 (0.3 µm)
1.6974 (0.59 µm)
1.6861 (0.75 µm)
1.6784 (1 µm)
1.6678 (5 µm)
1.6439 (20 µm)[3]
CsCl, cP2
Pm3m, No. 221[4]
a = 0.4291 nm
0.0790 nm3
Cubic (Cs+)
Cubic (Br)
GHS pictograms The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Warning
H302, H315, H319, H335
P261, P264, P270, P271, P280, P301+312, P302+352, P304+340, P305+351+338, P312, P321, P330, P332+313, P337+313
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
1400 mg/kg (oral, rat)[5]
Related compounds
Other anions
Caesium fluoride
Caesium chloride
Caesium iodide
Caesium astatide
Other cations
Sodium bromide
Potassium bromide
Rubidium bromide
Francium bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Caesium bromide is an ionic compound of caesium and bromine with the chemical formula CsBr. It is a white or transparent solid with a melting point a 636 °C that readily dissolves in water. Its bulk crystals have the cubic CsCl structure, but the structure changes to the rocksalt type in nanometer-thin film grown on mica, LiF, KBr or NaCl substrates.[6]


Caesium bromide can be prepared via following reactions:

CsOH (aq) + HBr (aq) → CsBr (aq) + H2O (l)
Cs2(CO3) (aq) + 2 HBr (aq) → 2 CsBr (aq) + H2O (l) + CO2 (g)
  • Direct synthesis:
2 Cs (s) + Br2 (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.


Caesium bromide is sometimes used in optics as a beamsplitter component in wide-band spectrophotometers.


  1. ^ a b c d e Haynes, p. 4.57
  2. ^ Haynes, p. 4.132
  3. ^ Haynes, p. 10.240
  4. ^ Vallin, J.; Beckman, O.; Salama, K. (1964). "Elastic Constants of CsBr and CsI from 4.2°K to Room Temperature". Journal of Applied Physics. 35 (4): 1222. doi:10.1063/1.1713597. 
  5. ^ Caesium bromide.
  6. ^ Schulz, L. G. (1951). "Polymorphism of cesium and thallium halides". Acta Crystallographica. 4 (6): 487. doi:10.1107/S0365110X51001641. 

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