Caesium hydroxide

Caesium hydroxide or cesium hydroxide (CsOH) is a chemical compound consisting of caesium ions and hydroxide ions. It is a strong base (pKb=-1.76), much like the other alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In fact, caesium hydroxide is corrosive enough to dissolve through glass quickly .

Caesium hydroxide
Names
Other names
Cesium hydrate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.040.298
EC Number
  • 244-344-1
RTECS number
  • FK9800000
UNII
UN number 2682
Properties
CsOH
Molar mass 149.912 g/mol
Appearance Whitish-yellow deliquescent crystals
Density 3.675 g/cm3
Melting point 272 °C (522 °F; 545 K)[1]
300 g/100 mL at 30 °C
Solubility Soluble in ethanol[2]
Basicity (pKb) -1.76 (CsOH(aq) = Cs+ + OH–) [3]
Thermochemistry
69.9 J·mol−1·K−1[4]
104.2 J·K−1·mol−1
Std enthalpy of
formation (ΔfH⦵298)
 −416.2 kJ·mol−1
Hazards
Safety data sheet ICSC 1592
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H302, H314, H318, H361, H373
P201, P202, P260, P264, P270, P280, P281, P301+312, P301+330+331, P303+361+353, P304+340, P305+351+338, P308+313, P310, P314, P321, P330, P363, P405, P501
NFPA 704 (fire diamond)
Flash point Not flammable
Lethal dose or concentration (LD, LC):
570 mg/kg (oral, rat)[5]
NIOSH (US health exposure limits):
PEL (Permissible)
 none[6]
REL (Recommended)
 TWA 2 mg/m3[6]
IDLH (Immediate danger)
 N.D.[6]
Related compounds
Other anions
 Caesium oxide
Caesium fluoride
Other cations
 Lithium hydroxide
Sodium hydroxide
Potassium hydroxide
Rubidium hydroxide
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

Due to its high reactivity, Caesium Hydroxide is extremely hygroscopic. Laboratory caesium hydroxide is typically a hydrate.

It is an anisotropic etchant of silicon, exposing octahedral planes. This technique can form pyramids and regularly shaped etch pits for uses such as Microelectromechanical systems. It is known to have a higher selectivity to etch highly p-doped silicon than the more commonly used potassium hydroxide.

This compound is not commonly used in experiments due to the high extraction cost of caesium and its reactive behaviour. It acts in similar fashion to the compounds rubidium hydroxide and potassium hydroxide, although more reactive.

References
  1. "ICSC 1592 - Cesium Hydroxide".
  2. Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, pp. 4–51, ISBN 0-8493-0594-2
  3. "Sortierte Liste: pKb-Werte, nach Ordnungszahl sortiert. – Das Periodensystem online".
  4. Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, pp. 5–14, ISBN 0-8493-0594-2
  5. Chambers, Michael. "ChemIDplus - 21351-79-1 - HUCVOHYBFXVBRW-UHFFFAOYSA-M - Cesium hydroxide - Similar structures search, synonyms, formulas, resource links, and other chemical information".
  6. NIOSH Pocket Guide to Chemical Hazards. "#0111". National Institute for Occupational Safety and Health (NIOSH).
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