Mercury(II) fulminate

Mercury(II) fulminate
Names
Other names
Fulminated Mercury
Identifiers
628-86-4 
ChEBI CHEBI:39152 Yes
ChemSpider 9197626 Yes
Jmol-3D images Image
PubChem 11022444
Properties
C2N2O2Hg
Molar mass 284.624 g/mol
Appearance Grey, Pale Brown, or White Crystalline solid
Density 4.42 g/cm3
Melting point 160 °C (320 °F; 433 K)
Boiling point 356.6 °C (673.9 °F; 629.8 K)
slightly soluble
Solubility soluble in ethanol, ammonia
Explosive data
Shock sensitivity High
Friction sensitivity High
Detonation velocity 4250 m/s
Hazards
Main hazards Highly Toxic, Shock Sensitive Explosive
170 °C (338 °F; 443 K)
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Mercury(II) fulminate, or Hg(CNO)2, is a primary explosive. It is highly sensitive to friction and shock and is mainly used as a trigger for other explosives in percussion caps and blasting caps. Mercury(II) cyanate, though its formula is identical, has a different atomic arrangement; the cyanate and fulminate anions are isomers.

First used as a priming composition in small copper caps after the 1830s, mercury fulminate quickly replaced flints as a means to ignite black powder charges in muzzle-loading firearms. Later, during the late 19th century and most of the 20th century, mercury fulminate or potassium chlorate became widely used in primers for self-contained rifle and pistol ammunition. Mercury fulminate has the distinct advantage over potassium chlorate of being non-corrosive, but it is known to weaken with time. Today, mercury fulminate has been replaced in primers by more efficient chemical substances. These are non-corrosive, less toxic and more stable over time; they include lead azide, lead styphnate and tetrazene derivatives. In addition, none of these compounds replacing Hg(II) fulminate requires mercury for manufacture, supplies of which can be unreliable in wartime.

Preparation

Mercury(II) fulminate is prepared by dissolving mercury in nitric acid and adding ethanol to the solution. It was first prepared by Edward Charles Howard in 1800.[1] The crystal structure of this compound was only determined in 2007.[2]

Silver fulminate can be prepared in a similar way, but this salt is even more unstable than mercury fulminate; it can even explode under water and is impossible to accumulate in large amounts because it detonates under its own weight.

Decomposition

The thermal decomposition of mercury(II) fulminate can begin at temperatures as low as 100 °C, though it proceeds at a much higher rate with increasing temperature.[3]

A possible reaction for the decomposition of mercury(II) fulminate yields carbon dioxide gas, nitrogen gas, and a combination of relatively stable mercury salts.

4 Hg(CNO)2 → 2 CO2 + N2 + HgO + 3 Hg(OCN)CN
Hg(CNO)2 → 2 CO + N2 + Hg
Hg(CNO)2 → :Hg(OCN)2 (cyanate or / and isocyanate)
2 Hg(CNO)2 → 2 CO2 + N2 + Hg + Hg(CN)2 (Mercury(II) cyanide)

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See also


References

  1. ↑ Edward Howard (1800). "On a New Fulminating Mercury". Philosophical Transactions of the Royal Society of London 90 (1): 204–238. doi:10.1098/rstl.1800.0012.
  2. ↑ W. Beck, J. Evers, M. Göbel, G. Oehlinger and T. M. Klapötke (2007). "The Crystal and Molecular Structure of Mercury Fulminate (Knallquecksilber)". Zeitschrift für anorganische und allgemeine Chemie 633 (9): 1417–1422. doi:10.1002/zaac.200700176.
  3. ↑ W. E. Garner & H. R. Hailes (1933). "Thermal decomposition and detonation of mercury fulminate" (PDF). Proceedings of the Royal Society of London 139 (1–3): 1–40. Bibcode:1933CP....334..128S. doi:10.1098/rspa.1933.0040. Retrieved 2013-03-11.
Mercury fulminate

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