Mercury(II) fulminate

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Mercury(II) fulminate
Mercury fulminate.svg
Mercury-fulminate-3D-vdW.png
Mercury-fulminate-xtal-3D-vdW.png
Mercuryfulminate puryfied.jpg
Identifiers
CAS number628-86-4 N
PubChem11022444
ChemSpider9197626 YesY
ChEBICHEBI:39152 YesY
Jmol-3D imagesImage 1
Properties
Molecular formulaC2N2O2Hg
Molar mass284.624 g/mol
AppearanceGrey, Pale Brown, or White Crystalline solid
Density4.42 g/cm3
Melting point160°C
Boiling point356.6°C
Solubility in waterslightly soluble
Solubilitysoluble in ethanol, ammonia
Explosive data
Shock sensitivityHigh
Friction sensitivityHigh
Explosive velocity4250 m/s
Hazards
Main hazardsHighly Toxic, Shock Sensitive Explosive
Autoignition temperature170 °C
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references
 
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Mercury(II) fulminate
Mercury fulminate.svg
Mercury-fulminate-3D-vdW.png
Mercury-fulminate-xtal-3D-vdW.png
Mercuryfulminate puryfied.jpg
Identifiers
CAS number628-86-4 N
PubChem11022444
ChemSpider9197626 YesY
ChEBICHEBI:39152 YesY
Jmol-3D imagesImage 1
Properties
Molecular formulaC2N2O2Hg
Molar mass284.624 g/mol
AppearanceGrey, Pale Brown, or White Crystalline solid
Density4.42 g/cm3
Melting point160°C
Boiling point356.6°C
Solubility in waterslightly soluble
Solubilitysoluble in ethanol, ammonia
Explosive data
Shock sensitivityHigh
Friction sensitivityHigh
Explosive velocity4250 m/s
Hazards
Main hazardsHighly Toxic, Shock Sensitive Explosive
Autoignition temperature170 °C
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
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.[citation needed]

Preparation[edit]

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[edit]

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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References[edit]

  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". 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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