Mercury(II) fulminate

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

Mercury(II) fulminate
Names
Other names
Fulminated Mercury
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.010.053
UNII
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
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 4: Very short exposure could cause death or major residual injury. E.g. VX gasReactivity code 4: Readily capable of detonation or explosive decomposition at normal temperatures and pressures. E.g. nitroglycerinSpecial hazards (white): no code
1
4
4
170 °C (338 °F; 443 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

First used as a priming composition in small copper caps beginning in the 1820s, 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, by decomposing into its constituent elements. The reduced mercury which results forms amalgams with cartridge brass, weakening it, as well. 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 require 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 determined only in 2007.[2]

Silver fulminate can be prepared in a similar way, but this salt is even more unstable than mercury fulminate; it can explode even 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)

In the 1955 comedy film Mister Roberts, Ensign Frank Pulver test fires a fulminate of mercury firecracker and blows up the ship's laundry, spreading soap suds across three decks.

In the TV Western series Have Gun - Will Travel, Season 4 Episode 10 "Crowbait", Russell Collins plays prospector Crowbait, who is carrying fulminated mercury. Paladin worries about being blown up while taking a pack sack off.

In the episode of Breaking Bad titled "Crazy Handful of Nothin'", Walter White used mercury (II) fulminate (Mythbusters found that a little silver fulminate was added in) to blow up Tuco Salamanca's headquarters.

In the 1972 episode of Mannix, called "A Walk in the Shadows", fulminated mercury is determined by police to be the explosive material used in a murder, by blowing up a boat.

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; 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.
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