Rubidium fluoride
Other names
Rubidium(I) Fluoride
3D model (JSmol)
ECHA InfoCard 100.033.262 Edit this at Wikidata
RTECS number
  • VL8740000
  • InChI=1S/FH.Rb/h1H;/q;+1/p-1 checkY
  • InChI=1/FH.Rb/h1H;/q;+1/p-1
  • [Rb+].[F-]
Molar mass 104.4662 g/mol
Appearance white crystalline solid
Density 3.557 g/cm3
Melting point 795 °C (1,463 °F; 1,068 K)
Boiling point 1,408 °C (2,566 °F; 1,681 K)
130.6 g/100 mL (18 °C)
−31.9·10−6 cm3/mol
Occupational safety and health (OHS/OSH):
Main hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
Flash point Non-flammable
Related compounds
Other anions
Rubidium chloride
Rubidium bromide
Rubidium iodide
Rubidium astatide
Other cations
Lithium fluoride
Sodium fluoride
Potassium fluoride
Caesium fluoride
Francium fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Rubidium fluoride (RbF) is the fluoride salt of rubidium. It is a cubic crystal with rock-salt structure.


There are several methods for synthesising rubidium fluoride. One involves reacting rubidium hydroxide with hydrofluoric acid:[1]

RbOH + HF → RbF + H2O

Another method is to neutralize rubidium carbonate with hydrofluoric acid:[1]

Rb2CO3 + 2HF → 2RbF + H2O + CO2

Another possible method is to react rubidium hydroxide with ammonium fluoride:

RbOH + NH4F → RbF + H2O + NH3

The least used method due to expense of rubidium metal is to react it directly with fluorine gas, as rubidium reacts violently with halogens:[1]

2Rb + F2 → 2RbF


Rubidium fluoride is a white crystalline substance with a cubic crystal structure that looks very similar to common salt (NaCl). The crystals belong to the space group Fm3m (space group no. 225) with the lattice parameter a = 565 pm and four formula units per unit cell.[2] The refractive index of the crystals is nD = 1.398.[2] Rubidium fluoride colors a flame (Bunsen burner flame) purple or magenta red (spectral analysis).

Rubidium fluoride forms two different hydrates, a sesquihydrate with the stoichiometric composition 2RbF·3H2O and a third hydrate with the composition 3RbF·H2O.[3]

In addition to simple rubidium fluoride, an acidic rubidium fluoride with the molecular formula HRbF2 is also known,[4] which can be produced by reacting rubidium fluoride and hydrogen fluoride.[4] The compounds H2RbF3 and H3RbF4 were also synthesized.[5][4]

The solubility in acetone is 0.0036 g/kg at 18 °C and 0.0039 g/kg at 37 °C.[6]

The standard enthalpy of formation of rubidium fluoride is ΔfH0298 = −552.2 kJ mol−1,[7] the standard free enthalpy of formation ΔG0298 = −520.4 kJ mol−1,[7] and the standard molar entropy S0298 = 113.9 J K −1 ·mol−1.[7] The enthalpy of solution of rubidium fluoride was determined to be −24.28 kJ/mol.[8]


  1. ^ a b c "WebElements". Archived from the original on 2008-04-18. Retrieved 23 February 2006.
  2. ^ a b Ans, Jean d'; Lax, Ellen (1998). Taschenbuch für Chemiker und Physiker (in German). Springer. ISBN 978-3-540-60035-0.
  3. ^ texte, Académie des sciences (France) Auteur du (1911-01-01). "Comptes rendus hebdomadaires des séances de l'Académie des sciences / publiés... par MM. les secrétaires perpétuels". Gallica. Retrieved 2023-12-24.
  4. ^ a b c Eggeling, Hans; Meyer, Jullius (1905-08-19). "Über die Fluoride des Rubidiums". Zeitschrift für anorganische Chemie. 46 (1): 174–176. doi:10.1002/zaac.19050460111. ISSN 0863-1778.
  5. ^ A Text-Book of Inorganic Chemistry. Forgotten Books. ISBN 978-1-4510-0469-4.
  6. ^ Aterton Seidell (1940). Solubilities Of Organic Compounds Vol - I. Carnegie-Mellon University Hunt Library, N.Sathyanarayanan. D.Van Nostrand Co.
  7. ^ a b c Dickerson, Richard E. (1988). Prinzipien der Chemie (in German). Walter de Gruyter. ISBN 978-3-11-009969-0.
  8. ^ texte, Académie des sciences (France) Auteur du (1911-01-01). "Comptes rendus hebdomadaires des séances de l'Académie des sciences / publiés... par MM. les secrétaires perpétuels". Gallica. Retrieved 2023-12-24.