Silver fulminate (AgCNO) is the highly explosive
silver
Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
salt
In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
of
fulminic acid.
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 exp ...
, 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 an exa ...
, the impact of a single
water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
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. 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 in his research project to prepare a large variety of
fulminates. Along with
mercury fulminate, it is the only fulminate stable enough for commercial use.
Detonators using silver fulminate were used to initiate
picric acid in 1885, but since have been used only by the
Italian Navy
The Italian Navy (; abbreviated as MM) is one of the four branches of Italian Armed Forces and was formed in 1946 from what remained of the ''Regia Marina'' (Royal Navy) after World War II. , the Italian Navy had a strength of 30,923 active per ...
.
[ 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
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...
one and a trigonal one with a rhombohedral lattice. The trigonal polymorph consists of cyclic hexamers, (AgCNO)6.
Properties
Fulminates are toxic, about the same as cyanide
In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.
Ionic cyanides contain the cyanide anion . This a ...
s.[ When pure, silver fulminate is chemically stable, not decomposing after years of storage. Like many silver salts, it darkens with light exposure. It is 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 (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
or chlorine
Chlorine is a chemical element; it has 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 between ...
or bromine
Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...
, but not when contacting iodine
Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...
.[ It is insoluble in ]nitric acid
Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
, but dissolves in ammonia
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...
, alkali chloride
The term chloride refers to a compound or molecule that contains either a chlorine anion (), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond (). The pr ...
s, alkali cyanide
In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.
Ionic cyanides contain the cyanide anion . This a ...
s, aniline
Aniline (From , meaning ' indigo shrub', and ''-ine'' indicating a derived substance) is an organic compound with the formula . Consisting of a phenyl group () attached to an amino group (), aniline is the simplest aromatic amine. It is an in ...
, pyridine, and potassium iodide by forming complexes.[ Concentrated ]hydrochloric acid
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...
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 in nitric acid
Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
into ethanol
Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
, under careful control of the reaction conditions, to avoid an explosion. AgNO3 + HNO3 + C2H5OH → AgCNO + byproducts
The reaction is usually done at 8090 °C; at 30 °C, the precipitate may not form. Only 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 with ammonia
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...
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 comes in contact with alcohol. This is a hazard in some formulations of chemically silvering mirror
A mirror, also known as a looking glass, is an object that Reflection (physics), reflects an image. Light that bounces off a mirror forms an image of whatever is in front of it, which is then focused through the lens of the eye or a camera ...
s.
Novelty explosive
Silver fulminate, often in combination with potassium chlorate, is used in trick noise-makers known as "throw-downs", "crackers", "snappers", "whippersnappers", "pop-its", or "bang snaps", a popular type of novelty firework. They contain approximately 200 milligrams of fine gravel
Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone.
Gr ...
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 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 crackers 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 azide
Silver azide is the chemical compound with the chemical formula, formula . It is a silver(I) salt of hydrazoic acid. It forms a colorless crystals. Like most azides, it is a primary explosive.
Structure and chemistry
Silver azide can be prepared ...
, 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 precisely 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 a ...
of silver fulminate, it may also refer to the nitride or azide, the decomposition product of Tollen's reagent, or an alchemical 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 exp ...
* Justus von Liebig
Justus ''Freiherr'' von Liebig (12 May 1803 – 18 April 1873) was a Germans, German scientist who made major contributions to the theory, practice, and pedagogy of chemistry, as well as to agricultural and biology, biological chemistry; he is ...
* Friedrich Woehler
* Silver cyanate
* Isomerism
In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...
* Fulminate
* Fulminic acid
* Potassium fulminate
* Mercury(II) fulminate
* Iron picrate
References
Further reading
*
{{Silver compounds
Silver compounds
Fulminates