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 ethanol.[1]: F217 [clarification needed] 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.[citation needed]

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. 1 2 3 4 5 6 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. 1 2 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.
allikas: https://en.wikipedia.org/wiki/Mercury_fulminate