Caesium hydroxide

Caesium hydroxide is a crystalline solid with the formula CsOH. It is notable for being the strongest normal, aqueous base; all bases stronger than it are superbases that react with water.

Properties

Physical

Caesium hydroxide is a crystalline, hygroscopic white solid resembling potassium hydroxide.

Chemical

Caesium hydroxide is a very reactive alkali. It readily reacts with glass:

2CsOH + CaSiO₃ → Cs₂SiO₃ + Ca(OH)₂

2CsOH + SiO₂ → Cs₂SiO₃ + H₂O

The resulting salt is caesium silicate, or caesium waterglass, which is water-soluble and similar in properties to common waterglass. Because of this, it is best to keep this compound in polyethylene bottles.

Caesium hydroxide readily reacts with carbon dioxide in the air:

2CsOH + CO₂ → Cs₂CO₃ + H₂O

CsOH + CO₂ → CsHCO₃

It is known to react with excess nitric acid forming unusual acidic adducts:

CsOH + 2HNO₃ → CsHN₂O₆ + H₂O

Availability and synthesis

Caesium hydroxide can be purchased from various reagent suppliers. It can also be synthesized from elemental caesium, which is sold to element collectors. There are two methods of doing this.

Kewl method: breaking the ampoule with caesium under water, remotely, from a safe distance. The reaction results in an explosion. Make sure that the vessel in which you perform the reaction is strong enough to contain it.

Safe method: treating caesium metal with small amounts of water vapor. This requires a glovebox with an inert atmosphere. Beware of hydrogen buildup in the glovebox and make sure no oxygen is present in it!

Handling

Safety

Caesium hydroxide is a very corrosive substance. It is, however, not toxic.

Storage

Store this compound in closed polyethylene bottles with no access to air.

Disposal

Disposing of caesium compounds is not recommended because of their rarity and price. But if you absolutely want to, you should neutralize the base with any non-toxic acid.