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Silver fulminate (AgCNO) is the highly explosive
silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
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 quantitie ...
of
fulminic acid Fulminic acid is an acid with the formula HCNO, more specifically . It is an isomer of isocyanic acid () and of its elusive tautomer, cyanic acid (), and also of isofulminic acid (). Fulminate is the anion or any of its salts. For historic ...
. Silver fulminate 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 expl ...
, but has limited use as such due to its extreme sensitivity to impact, heat, pressure, and electricity. The compound becomes progressively sensitive as it is aggregated, even in small amounts; the touch of a falling
feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and a premier ...
, the impact of a single
water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
droplet, or a small static discharge are all capable of explosively detonating an unconfined pile of silver fulminate no larger than a dime and no heavier than a few
milligrams The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. ...
. Aggregating larger quantities is impossible, due to the compound's tendency to self-detonate under its own weight. Silver fulminate was first prepared in 1800 by
Edward Charles Howard Edward Charles Howard FRS (28 May 1774 – 28 September 1816) the youngest brother of Bernard Howard, 12th Duke of Norfolk, was a British chemist who has been described as "the first chemical engineer of any eminence." Career In January 1799 h ...
in his research project to prepare a large variety of fulminates. Along with
mercury fulminate Mercury(II) fulminate, or Hg(CNO)2, is a primary explosive. 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 formu ...
, it is the only fulminate stable enough for commercial use.
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 electri ...
s using silver fulminate were used to initiate
picric acid Picric acid is an organic compound with the formula (O2N)3C6H2OH. Its IUPAC name is 2,4,6-trinitrophenol (TNP). The name "picric" comes from el, πικρός (''pikros''), meaning "bitter", due to its bitter taste. It is one of the most acidic ...
in 1885, but since have only been used by the
Italian Navy "Fatherland and Honour" , patron = , colors = , colors_label = , march = ( is the return of soldiers to their barrack, or sailors to their ship after a ...
. The current commercial use has been in producing non-damaging novelty noisemakers as children's toys.


Structure

Silver fulminate occurs in two polymorphic forms, an orthorhombic one and a trigonal one with a rhombohedral lattice. The trigonal polymorph consists of cyclic hexamers, (AgCNO)6.


Properties

Fulminates are very toxic, about the same as
cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
s. When pure, silver fulminate is chemically very stable, not decomposing after years of storage. Like many silver salts, it darkens with light exposure. It is only slightly soluble in cold water and can be recrystallized using hot water. It can also be recrystallized from a 20% solution of ammonium acetate. It is not hygroscopic and can explode when moist or under water; it was reported to remain explosive after 37 years under water. It explodes upon contact with concentrated
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
or
chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
or
bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table (halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simila ...
, but not when contacting
iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...
. It is insoluble 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 nitri ...
, but dissolves in
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
, alkali
chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
s, alkali
cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
s,
aniline Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine In organic chemistry, an aromatic amine is an organic compound consisting of an aroma ...
,
pyridine Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a d ...
, and
potassium iodide Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are u ...
by forming complexes. Concentrated
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...
decomposes it non-explosively with a hissing noise;
thiosulfate Thiosulfate ( IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, ...
also decomposes it non-explosively, and can be used for disposal.


Preparation

This compound can be prepared by pouring a solution of
silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar caustic' ...
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 nitri ...
into
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
, under careful control of the reaction conditions, to avoid an explosion. The reaction is usually done at 8090 °C; at 30 °C, the precipitate may not form. Only very tiny amounts of silver fulminate should be prepared at once, as even the weight of the crystals can cause them to self-detonate. Another way to make silver fulminate is to react
silver carbonate Silver carbonate is the chemical compound with the formula Ag2CO3. This salt is yellow but typical samples are grayish due to the presence of elemental silver. It is poorly soluble in water, like most transition metal carbonates. Preparation and ...
with
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
in solution.
:4 Ag2CO3 + 4 NH3 → 4 AgCNO + 6 H2O + 4 Ag + O2 Silver fulminate also forms when nitrogen oxide gas is passed through a solution of silver nitrate in ethanol. Silver fulminate can be prepared unintentionally, when an acidic solution of
silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar caustic' ...
comes in contact with alcohol. This is a hazard in some formulations of chemically
silvering Silvering is the chemical process of coating a non-conductive substrate such as glass with a reflective substance, to produce a mirror. While the metal is often silver, the term is used for the application of any reflective metal. Process Mos ...
mirror A mirror or looking glass is an object that Reflection (physics), reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the ...
s.


Novelty explosive

Silver fulminate, often in combination with
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. It ...
, is used in trick noise-makers known as "throw-downs", "crackers", "snappers", "whippersnappers", "pop-its", or "bang snaps", a popular type of novelty
firework Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large number of devices in ...
. They contain approximately 200 milligrams of fine
gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...
coated with a minute quantity (approximately 80 micrograms) of silver fulminate. When thrown against a hard surface, the impact is sufficient to detonate the tiny quantity of explosive, creating a small
salute A salute is usually a formal hand gesture or other action used to display respect in military situations. Salutes are primarily associated with the military and law enforcement, but many civilian organizations, such as Girl Guides, Boy Sco ...
from the supersonic detonation. Snaps are designed to be incapable of producing damage (even when detonated against skin) due to the buffering effect provided by the much greater mass of the gravel medium. It is also the chemical found in
Christmas cracker Christmas crackers are festive table decorations that make a snapping sound when pulled open, and often contain a small gift, paper hat and a joke. They are part of Christmas celebrations in the United Kingdom, Ireland and Commonwealth countri ...
s having first been used for that purpose by Tom Smith in 1860. The chemical is painted on one of two narrow strips of card, with abrasive on the second. When the cracker is pulled, the abrasive detonates the silver fulminate. A fulminate mixture with 1020% potassium chlorate is cheaper and more brisant than the fulminate alone.


Silver fulminate and "fulminating silver"

Silver fulminate is often confused with
silver nitride Silver nitride is an explosive chemical compound with symbol Ag3N. It is a black, metallic-looking solid which is formed when silver oxide or silver nitrate, is dissolved in concentrated solutions of ammonia, causing formation of the diammine silve ...
, silver azide, or fulminating silver. "Fulminating silver", though always referring to an explosive silver-containing substance, is an ambiguous term. While it may be a
synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
of silver fulminate, it may also refer to the nitride or azide, the decomposition product of Tollen's reagent, or an
alchemical Alchemy (from Arabic: ''al-kīmiyā''; from Ancient Greek: χυμεία, ''khumeía'') is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practiced in China, India, the Muslim world, ...
mixture, which does not contain the fulminate anion.


See also

*
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 expl ...
*
Justus von Liebig Justus Freiherr von Liebig (12 May 1803 – 20 April 1873) was a German scientist who made major contributions to agricultural and biological chemistry, and is considered one of the principal founders of organic chemistry. As a professor at t ...
*
Friedrich Woehler Friedrich may refer to: Names * Friedrich (surname), people with the surname ''Friedrich'' * Friedrich (given name), people with the given name ''Friedrich'' Other * Friedrich (board game), a board game about Frederick the Great and the Seven Year ...
*
Silver cyanate Silver cyanate is the cyanate salt of silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transit ...
*
Isomerism 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. Iso ...
*
Fulminate Fulminates are chemical compounds which include the fulminate ion (). The fulminate ion is a pseudohalic ion because its charge and reactivity are similar to those of the halogens. Due to the instability of the ion, fulminate salts are frictio ...
*
Fulminic acid Fulminic acid is an acid with the formula HCNO, more specifically . It is an isomer of isocyanic acid () and of its elusive tautomer, cyanic acid (), and also of isofulminic acid (). Fulminate is the anion or any of its salts. For historic ...
*
Potassium fulminate Potassium fulminate is the potassium salt (chemistry), salt of the fulminate ion. Its only use, aside from chemical demonstrations, is in the percussion caps for some early rifles. Usually prepared by reacting a potassium amalgam with mercury ful ...
*
Mercury(II) fulminate Mercury(II) fulminate, or Hg(CNO)2, is a primary explosive. 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 formul ...


References


Further reading

* {{Silver compounds Silver compounds Fulminates