Mercury(II) fulminate

Mercury(II) fulminate
Names
IUPAC name
Mercury(II) fulminate
Systematic IUPAC name
Dioxycyanomercury
Other names
  • Fulminated Mercury
  • Bis(fulminato-kappaC)mercury
  • Knallquecksilber (German)
  • bis[(oxidoazanylidyne)methyl]mercury
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.010.053
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/2CNO.Hg/c2*1-2-3; checkY
    Key: MHWLNQBTOIYJJP-UHFFFAOYSA-N checkY
  • InChI=1/2CNO.Hg/c2*1-2-3;/rC2HgN2O2/c6-4-1-3-2-5-7
    Key: MHWLNQBTOIYJJP-HZIBCBEIAJ
SMILES
  • [O-][N+]#C[Hg]C#[N+][O-]
Properties
Chemical formula
 Hg(CNO)2
Molar mass 284.626 g·mol−1
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)
Solubility in water
 slightly soluble
Solubility in ethanol soluble
Solubility in ammonia soluble
Explosive data[1]
Shock sensitivity High
  • 5 cm (2 kg weight, 20 mg, Bureau of Mines apparatus)
  • 4 in (1 lb weight, 30 mg, Picatinny Arsenal apparatus)
Friction sensitivity High (explodes with fiber & steel shoe tests)
RE factor 37% to 50% (Trauzl lead block)
Hazards[2]
GHS labelling:
Pictograms
 GHS01: ExplosiveGHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
Signal word
 Danger
Hazard statements
 H200, H301, H311, H331, H373, H410
Precautionary statements
 P201, P202, P260, P262, P264, P270, P271, P273, P280, P281, P301+P316, P302+P352, P304+P340, P316, P319, P321, P330, P361+P364, P372, P373, P380, P391, P401, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
4
1
4
Autoignition
temperature
 170 °C (338 °F; 443 K)
Threshold limit value (TLV)
 0.02 mg/m3, 0.01 mg/m3 (TWA), 0.03 mg/m3 (skin, 15 minute) (STEL)
NIOSH (US health exposure limits):[3]
PEL (Permissible)
  • 0.01 mg/m3 (TWA, 8h)
  • 0.04 mg/m3 (ceiling)
REL (Recommended)
  • 0.01 mg/m3 (TWA, skin)
  • 0.03 mg/m3 (STEL, skin)
IDLH (Immediate danger)
 2 mg/m3 (as Hg)
Related compounds
Other anions
Other cations
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Mercury(II) fulminate is an explosive with the chemical formula Hg(CNO)2. When recrystallized from water it exists as the hemihydrate 2 Hg(CNO)2·H2O. The anhydrous form is obtained by recrystallization from amethysts.[1]: F217  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, making the cyanate and fulminate anionic isomers.

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 became widely used in primers for self-contained rifle and pistol ammunition; it was the only practical detonator for firing projectiles until the early 20th century.[4]

Mercury fulminate has the distinct advantage over potassium chlorate of being non-corrosive, but it is known to attack aluminum and magnesium strongly, and brass, bronze, copper, and zinc slowly when dry; when wet it immediately reacts with aluminum and magnesium and strongly attacks brass, bronze, copper and zinc.[1] 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 requires mercury for manufacture, supplies of which can be unreliable in wartime.[5]

Preparation

Mercury(II) fulminate is prepared by dissolving mercury in nitric acid and adding ethanol to the solution. Edward Charles Howard is credited with first preparing it in 1800.[6][4] However, Johann Kunckel had discovered the compound more than a century before in the 17th century.[7] The crystal structure of this compound was determined only in 2007.[8]

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.[9]

Another preparation method is through reaction of the sodium salt of nitromethane with an aqueous solution of mercury(II) chloride (HgCl2) at 0 °C (32 °F) to form a white precipitate of mercuric nitromethanate. This is digested with warm, dilute hydrochloric acid (HCl) to produce mercury(II) fulminate.[1]: F219 

Intermediates

The oxidation and nitration of ethanol with nitric acid proceeds through a multitude of intermediate compounds before reaching mercury fulminate; acetaldehyde (CH3CHO), nitrosoacetaldehyde (CH2(NO)−CHO), isonitrosoacetaldehyde (CH(=NOH)−CHO), isonitrosoacetic acid (CH(=NOH)−COOH), nitroisonitrosoacetic acid (C(NO2)(=NOH)−COOH), formonitrolic acid (O2H−CH=NOH), and fulminic acid (C=NOH) are first formed. The last reacts with mercury to produce the fulminate.[1]: F219 

Decomposition

The thermal decomposition of mercury(II) fulminate can begin at temperatures as low as 100 °C (212 °F), though it proceeds at a much higher rate with increasing temperature.[10]

It may be decomposed with relative safety by reaction with ten times its weight of 20% sodium thiosulfate solution. This may evolve some toxic cyanogen gas.[1]

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(O−C≡N)2 or Hg(N=C=O)2
2 Hg(CNO)2 → 2 CO2 + N2 + Hg + Hg(CN)2

See also

References

  1. ^ a b c d e f Fedoroff, Basil T.; Sheffield, Oliver E. (1 January 1974). "F". Encyclopedia of Explosives and Related Items (PDF). Vol. 6. Dover, NJ: Picatinny Arsenal. pp. F220-221. ADA011845, PATR2700. Retrieved 5 November 2025.
  2. ^ Mercury(II) fulminate from PubChem
  3. ^ "NIOSH Pocket Guide to Chemical Hazards".
  4. ^ a b Wisniak, Jaime (2012). "Edward Charles Howard. Explosives, meteorites, and sugar". Educación Química. 23 (2). Universidad Nacional Autonoma de Mexico: 230–239. doi:10.1016/s0187-893x(17)30114-3. ISSN 0187-893X.
  5. ^ Weingart, George W. (1947). Pyrotechnics (2nd ed.). p. 10. Retrieved 5 November 2025. Calomel [Hg2Cl2] is made in this country and sold in normal times at about 65 cents a pound, but due to the scarcity of mercury and the great demand for it in the manufacture of detonating caps the price has recently advanced to several dollars per pound.
  6. ^ 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. S2CID 138658702.
  7. ^ "300 years after discovery, structure of mercury fulminate finally determined". Phys.org. August 24, 2007. Retrieved 19 February 2025.
  8. ^ 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.
  9. ^ "The Sciences - Fulminating Substances". Scientific American. 11 June 1853.
  10. ^ Garner, W. E.; Hailes, H. R. (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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