Mercury(II) fulminate
Chemical compound
From Wikipedia, the free encyclopedia
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.
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| Names | |
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| IUPAC name
Mercury(II) fulminate | |
| Systematic IUPAC name
Dioxycyanomercury | |
Other names
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| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.010.053 |
PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| 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) |
| slightly soluble | |
| Solubility in ethanol | soluble |
| Solubility in ammonia | soluble |
| Explosive data[1] | |
| Shock sensitivity | High
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| Friction sensitivity | High (explodes with fiber & steel shoe tests) |
| RE factor | 37% to 50% (Trauzl lead block) |
| Hazards[2] | |
| GHS labelling: | |
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| Danger | |
| H200, H301, H311, H331, H373, H410 | |
| 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) | |
| 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) |
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REL (Recommended) |
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IDLH (Immediate danger) |
2 mg/m3 (as Hg) |
| Related compounds | |
Other anions |
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Other cations |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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![{\displaystyle {{\mkern {2mu}}{\vphantom {A}}_{\hphantom {}}^{\hphantom {-}}{\mkern {-1.5mu}}{\vphantom {A}}_{{\vphantom {2}}{\llap {\smash[{t}]{}}}}^{{\smash[{t}]{\vphantom {2}}}{\llap {-}}}\mathrm {O} {-}{\overset {+}{\mathrm {N} }}{\equiv }\mathrm {C} {-}\mathrm {Hg} {-}\mathrm {C} {\equiv }{\overset {+}{\mathrm {N} }}{-}\mathrm {O} {\vphantom {A}}^{-}}}](http://wikimedia.org/api/rest_v1/media/math/render/svg/e5b4c737194efea9f10f5a66166db4e708455571)
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]
