Rubidium hydroxide

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Rubidium hydroxide
IUPAC name
Rubidium hydroxide
Molar mass 102.475 g/mol
Appearance Colorless hygroscopic solid
Odor Odorless
Density 1.74 g/cm3 (at 25 °C)
Melting point 301 °C (574 °F; 574 K)
Boiling point 1,390 °C (2,530 °F; 1,660 K)
100 g/100 ml (15 °C)
Solubility Reacts with acids
Soluble in ethanol, methanol
Insoluble in anh. ammonia, diethyl ether, THF
Vapor pressure ~0 mmHg
−413.8 kJ/mol
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Related compounds
Related compounds
Lithium hydroxide
Sodium hydroxide
Potassium hydroxide
Caesium hydroxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Rubidium hydroxide is a strong base with the formula RbOH.



Rubidium hydroxide is hygroscopic and will rapidly absorb carbon dioxide from air to form rubidium carbonate and bicarbonate.


Rubidium hydroxide is a white hygroscopic solid, which is very soluble in water.


Rubidium hydroxide is commercially available from a certain number of chemical suppliers in form of 50% or 99% aqueous solution.

Rubidium hydroxide is rarely used in chemistry because sodium and potassium hydroxide can perform nearly all the functions of rubidium hydroxide in a cheaper and safer way.


Rubidium hydroxide can be synthesized by carefully adding rubidium oxide into water:

Rb2O + H2O → 2 RbOH

Boiling a solution of rubidium carbonate with calcium hydroxide will also yield rubidium hydroxide.

While RbOH can also be made by adding rubidium metal to water, this is very dangerous as the reaction is explosive.


  • Make rubidium salts
  • Make rubidium metal



Rubidium hydroxide is highly caustic and protection must be worn at all times when handling the compound. Dissolving this compound in water will release a large amount of heat, as well as particulates of RbOH solution, which is corrosive.

Rubidium, like sodium and potassium, almost always has +1 oxidation state when dissolved in water, even in biological contexts. The human body tends to treat Rb+ ions as if they were potassium ions, and therefore concentrates rubidium in the body's intracellular fluid (i.e., inside cells). The ions are not particularly toxic; a 70 kg person contains on average 0.36 g of rubidium, and an increase in this value by 50 to 100 times did not show negative effects in test persons. The biological half-life of rubidium in humans measures 31–46 days.


Rubidium hydroxide should be kept in air-tight containers, away from acids.


Since rubidium is expensive, it's best to recycle this compound.


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