Caesium bromide explained

Caesium bromide or cesium bromide is an ionic compound of caesium and bromine with the chemical formula 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 type in nanometer-thin film grown on mica, LiF, KBr or NaCl substrates.^[1]

Synthesis

Caesium bromide can be prepared via following reactions:

• Neutralization:

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 bromine. 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.

References

• Crystran Ltd experimental data July 2021

External links

• MSDS at Oxford University
• Crystran Physical data, IR transmission spectrum
• Ultra-violet photoabsorption measurements in alkali iodide and caesium bromide evaporated films

Notes and References

1. 10.1107/S0365110X51001641. Polymorphism of cesium and thallium halides. Acta Crystallographica. 4. 6. 487–489. 1951. Schulz. L. G.. 1951AcCry...4..487S .