Editing Mercury(II) fulminate

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477000105
| ImageFile = <chem>{}^{-}O-\overset{+}{N}#C-Hg-C#\overset{+}{N}-O^{-}</chem>
| ImageFile1 = Mercury-fulminate-3D-vdW.png
| ImageFile2 = Mercury-fulminate-xtal-3D-vdW.png
| ImageFile3 = Mercuryfulminate puryfied.jpg
| IUPACName = Mercury(II) fulminate
|SystematicName=Dioxycyanomercury
| OtherNames = Fulminated Mercury
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 9197626
| InChI = 1/2CNO.Hg/c2*1-2-3;/rC2HgN2O2/c6-4-1-3-2-5-7
| InChIKey = MHWLNQBTOIYJJP-HZIBCBEIAJ
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2CNO.Hg/c2*1-2-3;
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = MHWLNQBTOIYJJP-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 628-86-4
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = O8H2ZFF76L
| PubChem = 11022444
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 39152
| SMILES = [O-][N+]#C[Hg]C#[N+][O-]
}}
|Section2={{Chembox Properties
| Formula = 	C<sub>2</sub>N<sub>2</sub>O<sub>2</sub>Hg
| MolarMass = 284.624 g/mol
| Appearance = Grey, pale brown, or white crystalline solid
| Density = 4.42 g/cm<sup>3</sup>
| MeltingPtC = 160
| BoilingPtC = 356.6
| Solubility = slightly soluble
| SolubleOther = soluble in [[ethanol]], [[ammonia]]
  }}
|Section3={{Chembox Explosive
| ShockSens = High
| FrictionSens = High
| DetonationV = 4250 m/s
| REFactor = 
}}
|Section4={{Chembox Hazards
| MainHazards = Highly toxic, shock sensitive explosive
| NFPA-H = 4
| NFPA-F = 1
| NFPA-R = 4
| AutoignitionPtC = 170
| AutoignitionPt_notes = 
  }}
}}

'''Mercury(II) fulminate''', or '''Hg(CNO)<sub>2</sub>''', is a [[primary explosive]]. It is highly sensitive to [[friction]], heat and [[shock (mechanics)|shock]] and is mainly used as a trigger for other explosives in [[percussion cap]]s and [[detonator]]s. Mercury(II) cyanate, though its chemical formula is identical, has a different atomic arrangement, making the [[cyanate]] and [[fulminate]] [[Ion#Anions and cations|anionic]] [[isomer]]s.

First used as a [[priming composition]] in small copper caps beginning in the 1820s, mercury fulminate quickly replaced [[flint]]s as a means to ignite [[black powder]] charges in [[Muzzleloader|muzzle-loading]] [[firearm]]s. Later, during the late 19th century and most of the 20th century, mercury fulminate  became widely used in [[Primer (firearms)|primers]] for [[Cartridge (firearms)|self-contained rifle and pistol ammunition]]; it was the only practical detonator for firing projectiles until the early 20th century.<ref name=wisniak/> 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 explosive|tetrazene]] derivatives. In addition, none of these compounds requires [[Mercury (element)|mercury]] for manufacture, supplies of which can be unreliable in wartime.

==Preparation==
Mercury(II) fulminate is prepared by dissolving [[mercury (element)|mercury]] in [[nitric acid]] and adding [[ethanol]] to the solution. [[Edward Charles Howard]] is credited with first preparing it in 1800.<ref>{{cite journal
| title = On a New Fulminating Mercury
| author = Edward Howard
| journal = [[Philosophical Transactions of the Royal Society of London]]
| year = 1800
| volume = 90
| issue = 1
| pages = 204–238
| doi = 10.1098/rstl.1800.0012
| s2cid = 138658702
| doi-access = 
}}</ref><ref name=wisniak>{{cite journal | last=Wisniak | first=Jaime | title=Edward Charles Howard. Explosives, meteorites, and sugar | journal=Educación Química | publisher=Universidad Nacional Autonoma de Mexico | volume=23 | issue=2 | year=2012 |language=en| issn=0187-893X | doi=10.1016/s0187-893x(17)30114-3 | pages=230–239| doi-access=free }}</ref> However, [[Johann Kunckel]] had discovered the compound more than a century before in the [[17th century]].<ref>{{cite web |title=300 years after discovery, structure of mercury fulminate finally determined |url=https://phys.org/news/2007-08-years-discovery-mercury-fulminate.html |website=Phys.org |access-date=19 February 2025 |date=August 24, 2007}}</ref> The [[crystal structure]] of this compound was determined only in 2007.<ref>{{cite journal |author1=W. Beck |author2=J. Evers |author3=M. Göbel |author4=G. Oehlinger |author5=T. M. Klapötke | title = The Crystal and Molecular Structure of Mercury Fulminate (Knallquecksilber) | year = 2007 | journal = [[Zeitschrift für anorganische und allgemeine Chemie]] | volume = 633 | issue = 9 | pages = 1417–1422 | doi = 10.1002/zaac.200700176| doi-access = free }}</ref>

[[Silver fulminate]] can be prepared in a similar way, but this [[salt (chemistry)|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.<ref>{{Cite web |title=The Sciences - Fulminating Substances |author= |website=Scientific American |date=11 June 1853 |url= https://www.scientificamerican.com/article/fulminating-substances-1853-06-11/}}</ref>

==Decomposition==
The thermal decomposition of mercury(II) fulminate can begin at temperatures as low as 100&nbsp;°C, though it proceeds at a much higher rate with increasing temperature.<ref>{{cite journal|doi=10.1098/rspa.1933.0040|title=Thermal decomposition and detonation of mercury fulminate|author1=W. E. Garner|author2=H. R. Hailes|name-list-style=amp|journal=Proceedings of the Royal Society of London|volume=139|issue=1–3|year=1933|pages=1–40|bibcode=1933CP....334..128S|doi-access=free}}</ref>

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)<sub>2</sub> → 2 CO<sub>2</sub> +  N<sub>2</sub> +  HgO + 3 Hg(OCN)CN
:Hg(CNO)<sub>2</sub> → 2 CO +  N<sub>2</sub> +   Hg  
:Hg(CNO)<sub>2</sub> → :Hg(OCN)<sub>2</sub> ([[cyanate]] or / and [[isocyanate]])
:2 Hg(CNO)<sub>2</sub> → 2 CO<sub>2</sub> +  N<sub>2</sub> +  Hg + Hg(CN)<sub>2</sub> ([[mercury(II) cyanide]])

==See also==
* [[Fulminic acid]]
* [[Potassium fulminate]]

==References==
{{reflist}}

==External links==
{{Commons category|Mercury(II) fulminate}}
*[https://web.archive.org/web/20060425193836/http://www.npi.gov.au/database/substance-info/profiles/53.html National Pollutant Inventory - Mercury and compounds Fact Sheet]
*{{cite news | title = 300 years after discovery, structure of mercury fulminate finally determined | publisher = physorg.com | url = http://www.physorg.com/news107176552.html | date = 24 August 2007}}
{{Mercury compounds}}

[[Category:Mercury(II) compounds]]
[[Category:Fulminates]]
[[Category:Explosive chemicals]]