Caesium hydroxide
Identifiers
CAS number	21351-79-1 Y
EC-number	244-344-1
UN number	2682
RTECS number	FK9800000
SMILES	[Cs+].[OH-]
InChI	1/Cs.H2O/h;1H2/q+1;/p-1
InChI key	HUCVOHYBFXVBRW-REWHXWOFAG
ChemSpider ID	56494
Properties
Molecular formula	CsOH
Molar mass	149.912 g/mol
Appearance	whitish-yellow deliquescent crystals
Density	3.675 g/cm3, solid
Melting point	342.3°C
Solubility in water	300 g/100 ml at 30°C
Solubility	soluble in ethanol[1]
Basicity (pKb)	1.76
Thermochemistry
Std enthalpy of formation ΔfHo298	−416.2 kJ·mol-1
Standard molar entropy So298	104.2 J·K−1·mol−1
Specific heat capacity, C	69.9 J·mol-1·K-1[2]
Hazards
MSDS	ICSC 1592
EU Index	Not listed
Flash point	Non flammable
Related compounds
Other anions	Caesium oxide Caesium fluoride
Other cations	Lithium hydroxide Sodium hydroxide Potassium hydroxide Rubidium hydroxide
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Caesium hydroxide (CsOH) is a chemical compound consisting of an atom of caesium and a hydroxide group (also known as hydroxyl). It is a powerful base, much like other alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In fact, caesium hydroxide is powerful enough to quickly corrode through glass.

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

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

However, this compound is not usually used in experiments as the extraction of caesium is very expensive and the fact that it behaves very much like rubidium hydroxide and potassium hydroxide but reacts chemically stronger than they do.

Caesium hydroxide can be obtained by the following chemical reaction:

2 Cs + 2 H₂O → 2 CsOH + H₂

The above reaction occurs explosively with enough force to shatter a Pyrex beaker. Caesium metal will react with ice above −116 °C.

[edit] References

[edit] External links

• NIOSH Pocket Guide to Chemical Hazards
• NIST Standard Reference Database