Caesium hydroxide

Caesium hydroxide Identifiers InChI InChI=1/Cs.H2O/h;1H2/q+1;/p-1 InChIKey HUCVOHYBFXVBRW-REWHXWOFAG Standard InChI InChI=1S/Cs.H2O/h;1H2/q+1;/p-1 Standard InChIKey HUCVOHYBFXVBRW-UHFFFAOYSA-M CAS number [21351-79-1] EC number 244-344-1 UN number 2682 RTECS FK9800000 ChemSpider 56494 Properties Chemical formula CsOH Molar mass 149.91 g/mol Appearance whitish-yellow solid, deliquescent Density 3.675 g/cm3, solid Melting point 273.3 °C Solubility in water 395.5 g/100 ml at 15 °C Solubility in ethanol soluble Thermochemistry Std enthalpy of formation ΔfHo298 −416.2 kJ/mol Standard molar entropy So298 104.2 J K−1 mol−1 Specific heat capacity C 69.9 J K−1 mol−1 Hazards Material safety data sheet (MSDS) ICSC 1592 EU index number not listed GHS pictograms GHS signal word DANGER GHS hazard statements H330, H314, H318, H302 Flash point non-flammable Related compounds Other anions Caesium oxide Other cations Lithium hydroxide Sodium hydroxide Potassium hydroxide Rubidium hydroxide Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Caesium hydroxide monohydrate Identifiers InChI InChI=1/Cs.2H2O/h;2*1H2/q+1;;/p-1 InChIKey ABSOMGPQFXJESQ-REWHXWOFAC Standard InChI InChI=1S/Cs.2H2O/h;2*1H2/q+1;;/p-1 Standard InChIKey ABSOMGPQFXJESQ-UHFFFAOYSA-M CAS number [35103-79-8] EC number 244-344-1 ChemSpider 10620883 Properties Chemical formula CsOH·H2O Molar mass 167.93 g/mol Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Caesium hydroxide (CsOH) is the product of the violent reaction between caesium and water:

2Cs + 2H₂O → 2CsOH + H₂

It is a powerful base, much like other alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and will quickly corrode through glass. It is also extremely hygroscopic, and laboratory caesium hydroxide is typically a monohydrate.

Caesium hydroxide 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 has a higher selectivity to etch highly p-doped silicon than the more commonly used potassium hydroxide.

Further reading

• Corey, E. J.; Noe, Mark C. Preparation of O-Allyl-N-(9-anthracenylmethyl)cinchonidinium Bromide as a Phase Transfer Catalyst for the Enantioselective Alkylation of Glycine Benzophenone Imine tert-Butyl Ester: (4S)-2-(Benzhydrylidenamino)pentanedioic Acid, 1-tert-Butyl Ester-5-Methyl Ester. Org. Synth. 2003, 80, 38, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=v80p0038>.

External links

• International Chemical Safety Card 1592
• NIOSH Pocket Guide to Chemical Hazards 0111