Rubidium azide

Rubidium azide is an inorganic compound with the formula RbN3. It is the rubidium salt of the azide ion (N–
3). Like most azides, it is explosive.[3]

Rubidium azide
Names
IUPAC name
rubidium(1+);azide
Other names
Rubidium azide
Identifiers
3D model (JSmol)
ChemSpider
Properties
RbN3
Molar mass 127.49 g·mol−1
Appearance Colorless needles[1]
Density 2.79 g/cm3[1][2]
Melting point 317–321 °C (603–610 °F; 590–594 K)[2][3]
Boiling point Decomposes
107.1 g/100 g (16°C)
114.1 g/100 g (17°C)[4]
Solubility 0.182 g/100 g (16°C, ethanol)[4]
Thermochemistry
-0.1 kcal·mol−1[2]
Hazards
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 4: Very short exposure could cause death or major residual injury. E.g. VX gasReactivity code 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazards (white): no code
0
4
3
Related compounds
Other anions
 Rubidium nitrate
Other cations
 Lithium azide
Sodium azide
Potassium azide
Silver azide
Ammonium azide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Preparation

Rubidium azide can be created by the reaction between rubidium sulfate and barium azide which results in formation of easily separated insoluble barium sulfate:[4]

In at least one study, rubidium azide was produced by the reaction between butyl nitrite, hydrazine monohydrate, and rubidium hydroxide:

This formula is typically used to synthesize potassium azide from caustic potash.[5]

Uses

Rubidium azide has been investigated for possible use in alkali vapor cells, which are components of atomic clocks, atomic magnetometers and atomic gyroscopes. Azides are desirable starting materials because they decompose into rubidium metal and nitrogen gas when exposed to UV light. According to one publication:

Among the different techniques used to fill microfabricated alkali vapor cell [sic], UV decomposition of rubidium azide (RbN3) into metallic Rb and nitrogen in Al2O3 coated cells is a very promising approach for low-cost wafer-level fabrication.[6]

Structure

At room temperature, rubidium azide has the same structure as potassium hydrogen fluoride; a distorted cesium chloride structure. At 315 °C and 1 atm, rubidium azide will transition to the normal cesium chloride structure. The II/I transition temperature of rubidium azide is within 2 °C of its melting point.[3]

Rubidium azide has a high pressure structure transition, which occurs at about 4.8 kilobars of pressure at 0 °C. The transition boundary of the II/III transition can be defined by the relationship , where is the pressure in kilobars and is the temperature in degrees Celsius.[3]

Reactions

As with all azides, it will decompose and release nitrogen gas when heated or severely shocked:

Hazards

At 4.1 kilobars of pressure and about 460 °C, rubidium azide will explosively decompose.[3] Under normal circumstances, it explodes at 395 °C.[2] It also decomposes upon exposure to ultraviolet light.[6]

Rubidium azide is very sensitive to mechanical shock, with an impact sensitivity comparable to that of TNT.[7]

Like all azides, rubidium azide is toxic.


References
  1. Perry, Dale (1995-05-17). Handbook of Inorganic Compounds. Online. p. 333. ISBN 9780849386718. Retrieved 31 January 2018.
  2. Hart, William; Beumel, O. F.; Whaley, Thomas (22 October 2013). The Chemistry of Lithium, Sodium, Potassium, Rubidium, Cesium and Francium: Pergamon Texts in Inorganic Chemistry. Online: Pergamon Press. p. 438. ISBN 9781483187570. Retrieved 31 January 2018.
  3. Pistorius, Carl W. F. T. (27 December 1968). "Phase Diagrams to High Pressures of the Univalent Azides Belonging to the Space Group D 4hI8-14/mcm" (PDF). Online. pp. 1, 4–5. Retrieved 1 February 2018.
  4. Hála, Jiri. "IUPAC-NIST Solubility Data Series. 79. Alkali and Alkaline Earth Metal Pseudohalides" (PDF). nist.gov. Retrieved 31 January 2018.
  5. Ogden, J. Steven; Dyke, John M.; Levason, William; Ferrante, Francesco; Gagliardi, Laura. "The Characterisation of Molecular Alkali-Metal Azides" (PDF). PMID 16491492. Retrieved 2 February 2018. Cite journal requires |journal= (help)
  6. Karlen, Sylvain; Gobet, Jean; Overstolz, Thomas; Haesler, Jacques; Lecomte, Steve (26 January 2017). "Lifetime assessment of RbN3-filled MEMS atomic vapor cells with Al2O3 coating" (PDF). Optics Express. 25 (3): 2187–2194. Bibcode:2017OExpr..25.2187K. doi:10.1364/OE.25.002187. PMID 29519066. Retrieved 17 March 2018.
  7. Babu, K. Ramesh; Vaitheeswaran, G. (2013). "Structure, elastic and dynamical properties of KN3 and RbN3: A van der Waals density functional study". Solid State Sciences. Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad. 23: 17–25. arXiv:1311.0979. Bibcode:2013SSSci..23...17R. CiteSeerX 10.1.1.768.1309. doi:10.1016/j.solidstatesciences.2013.05.017.
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