Mercury(II) fulminate, or Hg(CNO)₂, is a

primary explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ...

. It is highly sensitive to

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of ...

, heat and

shock Shock may refer to: Common uses Collective noun *Shock, a historic commercial term for a group of 60, see English numerals#Special names * Stook, or shock of grain, stacked sheaves Healthcare * Shock (circulatory), circulatory medical emerge ...

and is mainly used as a trigger for other explosives in

percussion cap The percussion cap or percussion primer, introduced in the early 1820s, is a type of single-use percussion ignition device for muzzle loader firearm locks enabling them to fire reliably in any weather condition. This crucial invention gave rise ...

s and

detonator A detonator, frequently a blasting cap, is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the last two being the most common. The commercial use of explosives uses electr ...

s. Mercury(II) cyanate, though its chemical formula is identical, has a different atomic arrangement; the

cyanate Cyanate is an anion with the structural formula , usually written . It also refers to any salt containing it, such as ammonium cyanate. It is an isomer of the much less stable fulminate anion .William R. Martin and David W. Ball (2019): "Sma ...

and fulminate

anions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by con ...

are

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Is ...

s. First used as a

priming composition An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...

in small copper caps beginning in the 1820s, mercury fulminate quickly replaced

flint Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and start ...

s as a means to ignite

black powder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). T ...

charges in

muzzle-loading A muzzleloader is any firearm into which the projectile and the propellant charge is loaded from the muzzle of the gun (i.e., from the forward, open end of the gun's barrel). This is distinct from the modern (higher tech and harder to make) desig ...

firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China, when bamboo tubes ...

s. 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. Mercury fulminate has the distinct advantage over

potassium chlorate Potassium chlorate is a compound containing potassium, chlorine and oxygen, with the molecular formula KClO3. In its pure form, it is a white crystalline substance. After sodium chlorate, it is the second most common chlorate in industrial use. ...

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(II) azide is an inorganic compound. More so than other azides, is explosive. It is used in detonators to initiate secondary explosives. In a commercially usable form, it is a white to buff powder. Preparation and handling Lead(II) azide i ...

, lead styphnate, and

tetrazene Tetrazene is a chemical compound with the molecular formula H2NN=NNH2. It is a colorless explosive material. An analogue is the organosilicon derivative (tms)2NN=NN(tms)2 where tms is trimethylsilyl. Isomeric with tetrazine is ammonium azide. T ...

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 Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...

and adding

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

to the solution. It was first prepared by Edward Charles Howard in 1800. The

crystal structure In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pattern ...

of this compound was determined only in 2007.

Silver fulminate Silver fulminate (AgCNO) is the highly explosive silver salt of fulminic acid. Silver fulminate is a primary explosive, but has limited use as such due to its extreme sensitivity to impact, heat, pressure, and electricity. The compound becomes ...

can be prepared in a similar way, but this

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

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. A possible reaction for the decomposition of mercury(II) fulminate yields

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

gas,

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

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 (

or / and

isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...

) :2 Hg(CNO)₂ → 2 CO₂ + N₂ + Hg + Hg(CN)₂ (

mercury(II) cyanide Mercury(II) cyanide, also known as mercuric cyanide, is a compound of mercury. It is an odorless, toxic white powder. It is highly soluble in polar solvents such as water, alcohol, and ammonia; slightly soluble in ether; and insoluble in benzene ...

)

References

External links

National Pollutant Inventory - Mercury and compounds Fact Sheet
* {{Mercury compounds Mercury(II) compounds Fulminates Explosive chemicals

Preparation

Decomposition

See also

References

External links