Rubidium fluoride (RbF) is the fluoride salt of rubidium. It is a white crystalline solid with a cubic crystal structure, similar to common salt. It forms two different hydrates, a sesquihydrate with the stoichiometric composition 2RbF÷3H<sub>2</sub>O and a third hydrate with the composition 3RbF÷H<sub>2</sub>O.
There are several methods for synthesising rubidium fluoride. One involves reacting rubidium hydroxide with hydrofluoric acid:
Another method is to neutralize rubidium carbonate with hydrofluoric acid:
Another possible method is to react rubidium hydroxide with ammonium fluoride:
The least used method due to expense of rubidium metal is to react it directly with fluorine gas, as rubidium reacts violently with halogens:
The enthalpy of solution of rubidium fluoride was determined to be âÂÂ24.28 kJ/mol.
Rubidium fluoride has a purple or magenta red flame test.
In addition to simple rubidium fluoride, an acidic rubidium fluoride with the molecular formula HRbF<sub>2</sub> is also known, which can be produced by reacting rubidium fluoride and hydrogen fluoride. The compounds H<sub>2</sub>RbF<sub>3</sub> and H<sub>3</sub>RbF<sub>4</sub> were also synthesized.