Potassium azide explained

Potassium azide is the inorganic compound having the formula . It is a white, water-soluble salt. It is used as a reagent in the laboratory.

It has been found to act as a nitrification inhibitor in soil.^[1]

Structure

,,, and adopt the same structures. They crystallize in a tetragonal habit.^[2] The azide is bound to eight cations in an eclipsed orientation. The cations are bound to eight terminal N centers.^[3]

Synthesis and reactions

is prepared by treating potassium carbonate with hydrazoic acid, which is generated in situ.^[4] In contrast, the analogous sodium azide is prepared (industrially) by the "Wislicenus process," which proceeds via the reaction sodium amide with nitrous oxide.^[5]

Upon heating or upon irradiation with ultraviolet light, it decomposes into potassium metal and nitrogen gas.^[6] The decomposition temperatures of the alkali metal azides are: (275 °C), (355 °C), (395 °C), (390 °C).^[7]

Under high pressures and high temperatures, potassium azide was found to transform into the K₂N₆ and K₉N₅₆ compounds, both containing hexazine rings: N and N₆^4-, respectively.^{[8] [9]}

Health hazards

Like sodium azide, potassium azide is very toxic. The threshold limit value of the related sodium azide is 0.07 ppm. The toxicity of azides arise from their ability to inhibit cytochrome c oxidase.^[5]

Notes and References

1. Potassium Azide as a Nitrification Inhibitor . T. D. Hughes . L. F. Welch . Agronomy Journal . 62 . 595–599 . 1970 . 5 . American Society of Agronomy . 10.2134/agronj1970.00021962006200050013x.
2. M. Y.. Khilji. Sherman . W. F. . G. R. . Wilkinson. Variable temperature and pressure Raman spectra of potassium azide. Journal of Raman Spectroscopy. 12. 3. 300–303. 1982 . 10.1002/jrs.1250120319. 1982JRSp...12..300K .
3. Ulrich Müller "Verfeinerung der Kristallstrukturen von KN₃, RbN₃, CsN₃ und TIN₃" Zeitschrift für anorganische und allgemeine Chemie 1972, Volume 392, 159–166.
4. P. W. Schenk "Alkali Azides from Carbonates" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 475.
5. Horst H. Jobelius, Hans-Dieter Scharff "Hydrazoic Acid and Azides" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim.
6. Tompkins, F. C. . Young, D. A. . The Photochemical and Thermal Formation of Colour Centres in Potassium Azide Crystals . Proceedings of the Royal Society of London . Series A, Mathematical and Physical Sciences . 236 . 1204 . 10–23 . 1982 .
7. E. Dönges "Alkali Metals" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 475
8. Wang . Yu . Bykov . Maxim . Chepkasov . Ilya . Samtsevich . Artem . Bykova . Elena . Zhang . Xiao . Jiang . Shu-qing . Greenberg . Eran . Chariton . Stella . Prakapenka . Vitali B. . Oganov . Artem R. . Goncharov . Alexander F. . Stabilization of hexazine rings in potassium polynitride at high pressure . Nature Chemistry . 21 April 2022 . 14 . 7 . 794–800 . 10.1038/s41557-022-00925-0. 35449217 . 2010.15995 . 2022NatCh..14..794W . 226222305.
9. Laniel . Dominique . Trybel . Florian . Yin . Yuqing . Fedotenko . Timofey . Khandarkhaeva . Saiana . Aslandukov . Andrey . Aprilis . Georgios . Abrikosov . Alexei I. . Bin Masood . Talha . Giacobbe . Carlotta . Bright . Eleanor Lawrence . Glazyrin . Konstantin . Hanfland . Michael . Wright . Jonathan . Hotz . Ingrid . 2023-03-06. Aromatic hexazine [N6]4− anion featured in the complex structure of the high-pressure potassium nitrogen compound K9N56 ]. Nature Chemistry . 15 . 5 . 641–646 . en . 10.1038/s41557-023-01148-7 . 36879075 . 2023NatCh..15..641L . 257377020 . 1755-4330.