Silver iodide

Last updated
Silver iodide
AgI sample.jpg
Silver-iodide-3D-balls.png
Names
Other names
Silver(I) iodide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.125
EC Number
  • 232-038-0
PubChem CID
UNII
Properties
AgI
Molar mass 234.77 g/mol
Appearanceyellow, crystalline solid
Odor odorless
Density 5.675 g/cm3, solid
Melting point 558 °C (1,036 °F; 831 K)
Boiling point 1,506 °C (2,743 °F; 1,779 K)
3×107g/100mL (20 °C)
8.52 × 10 −17
80.0·10−6 cm3/mol
Structure
hexagonal (β-phase, < 147 °C)
cubic (α-phase, > 147 °C)
Thermochemistry
115 J·mol−1·K−1 [1]
−62 kJ·mol−1 [1]
Hazards
Safety data sheet Sigma-Aldrich
not listed
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeSilver iodide
0
2
0
Flash point Non-flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Silver iodide is an inorganic compound with the formula Ag I. The compound is a bright yellow solid, but samples almost always contain impurities of metallic silver that give a gray coloration. The silver contamination arises because AgI is highly photosensitive. This property is exploited in silver-based photography. Silver iodide is also used as an antiseptic and in cloud seeding.

Contents

Structure

The structure adopted by silver iodide is temperature dependent: [2]

The golden-yellow crystals on this mineral sample are iodargyrite, a naturally occurring form of b-AgI. Iodargyrite-263859.jpg
The golden-yellow crystals on this mineral sample are iodargyrite, a naturally occurring form of β-AgI.

Preparation and properties

Silver iodide is prepared by reaction of an iodide solution (e.g., potassium iodide) with a solution of silver ions (e.g., silver nitrate). A yellowish solid quickly precipitates. The solid is a mixture of the two principal phases. Dissolution of the AgI in hydroiodic acid, followed by dilution with water precipitates β-AgI. Alternatively, dissolution of AgI in a solution of concentrated silver nitrate followed by dilution affords α-AgI. [4] If the preparation is not conducted in the absence of sunlight, the solid darkens rapidly, the light causing the reduction of ionic silver to metallic. The photosensitivity varies with sample purity.

Cloud seeding

Cessna 210 equipped with a silver iodide generator for cloud seeding Cessna 210 Hagelflieger Detail.jpg
Cessna 210 equipped with a silver iodide generator for cloud seeding

The crystalline structure of β-AgI is similar to that of ice, allowing it to induce freezing by the process known as heterogeneous nucleation. Approximately 50,000 kg are used for cloud seeding annually, each seeding experiment consuming 10–50 grams. [5] (see also Project Stormfury)

Safety

Extreme exposure can lead to argyria, characterized by localized discoloration of body tissue. [6]

Related Research Articles

Solubility equilibrium is a type of dynamic equilibrium that exists when a chemical compound in the solid state is in chemical equilibrium with a solution of that compound. The solid may dissolve unchanged, with dissociation or with chemical reaction with another constituent of the solvent, such as acid or alkali. Each type of equilibrium is characterized by a temperature-dependent equilibrium constant. Solubility equilibria are important in pharmaceutical, environmental and many other scenarios.

Silver nitrate Chemical compound

Silver nitrate is an inorganic compound with chemical formula AgNO
3
. This compound 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 because silver was called luna by the ancient alchemists, who associated silver with the moon.

A halide is a binary phase, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a, e.g., fluoride, chloride, or theoretically tennesside compound. The alkali metals combine directly with halogens under appropriate conditions forming halides of the general formula, MX. Many salts are halides; the hal- syllable in halide and halite reflects this correlation. All Group 1 metals form halides that are white solids at room temperature.

Precipitation (chemistry) Chemical process

Precipitation is the creation of a solid from a solution. When the reaction occurs in a liquid solution, the solid formed is called the 'precipitate'. The chemical that causes the solid to form is called the 'precipitant'. Without sufficient force of gravity (settling) to bring the solid particles together, the precipitate remains in suspension. After sedimentation, especially when using a centrifuge to press it into a compact mass, the precipitate may be referred to as a 'pellet'. Precipitation can be used as a medium. The precipitate-free liquid remaining above the solid is called the 'supernate' or 'supernatant'. Powders derived from precipitation have also historically been known as 'flowers'. When the solid appears in the form of cellulose fibers which have been through chemical processing, the process is often referred to as regeneration.

An iodide ion is the ion I. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts, not organoiodine compounds. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine deficiency affects two billion people and is the leading preventable cause of intellectual disability.

A silver halide is one of the chemical compounds that can form between the element silver and one of the halogens. In particular, bromine, chlorine, iodine and fluorine may each combine with silver to produce silver bromide (AgBr), silver chloride (AgCl), silver iodide (AgI), and three forms of silver fluoride, respectively.

Silver chloride chemical compound

Silver chloride is a chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water (this behavior being reminiscent of the chlorides of Tl+ and Pb2+). Upon illumination or heating, silver chloride converts to silver (and chlorine), which is signaled by grey to black or purplish coloration to some samples. AgCl occurs naturally as a mineral chlorargyrite.

Bismuth(III) oxide chemical compound

Bismuth(III) oxide is perhaps the most industrially important compound of bismuth. It is also a common starting point for bismuth chemistry. It is found naturally as the mineral bismite (monoclinic) and sphaerobismoite, but it is usually obtained as a by-product of the smelting of copper and lead ores. Dibismuth trioxide is commonly used to produce the "Dragon's eggs" effect in fireworks, as a replacement of red lead.

Copper(I) iodide chemical compound

Copper(I) iodide is the inorganic compound with the formula CuI. It is also known as cuprous iodide. It is useful in a variety of applications ranging from organic synthesis to cloud seeding.

Potassium chromate chemical compound

Potassium chromate is the inorganic compound with the formula (K2CrO4). This yellow solid is the potassium salt of the chromate anion. It is a common laboratory chemical, whereas sodium chromate is important industrially.

Silver acetate chemical compound

Silver acetate is an inorganic compound with the empirical formula CH3CO2Ag (or AgC2H3O2). It is a photosensitive, white, crystalline solid. It is a useful reagent in the laboratory as a source of silver ions lacking an oxidizing anion. It has been used in some antismoking drugs.

Gallium(III) oxide chemical compound

Gallium(III) trioxide is an inorganic compound with the formula Ga2O3. It exists as several polymorphs, all of which are white, water-insoluble solids. Although no commercial applications exist, Ga2O3 is an intermediate in the purification of gallium, which is consumed almost exclusively as gallium arsenide.

In materials science, fast ion conductors are solids with highly mobile ions. These materials are important in the area of solid-state ionics, and are also known as solid electrolytes and superionic conductors. These materials are useful in batteries and various sensors. Fast ion conductors are used primarily in solid oxide fuel cells. As solid electrolytes they allow the movement of ions without the need for a liquid or soft membrane separating the electrodes. The phenomenon relies on the hopping of ions through an otherwise rigid crystal structure.

Ionic conductivity is a measure of a substance's tendency towards ionic conduction. This involves the movement of an ion from one site to another through defects in the crystal lattice of a solid or aqueous solution.

An advanced superionic conductor (AdSIC) is fast ion conductor that has a crystal structure close to optimal for fast ion transport (FIT).

Rubidium silver iodide is a ternary inorganic compound with the formula RbAg4I5. Its conductivity involves the movement of silver ions within the crystal lattice. It was discovered while searching for chemicals which had the ionic conductivity properties of alpha-phase silver iodide at temperatures below 146 °C for AgI.

Cobalt(II) iodide chemical compound

Cobalt(II) iodide or cobaltous iodide are the inorganic compounds with the formula CoI2 and the hexahydrate CoI2(H2O)6. These salts are the principal iodides of cobalt.

Solid state ionics

Solid-state ionics is the study of ionic-electronic mixed conductor and fully ionic conductors and their uses. Some materials that fall into this category include inorganic crystalline and polycrystalline solids, ceramics, glasses, polymers, and composites. Solid-state ionic devices, such as solid oxide fuel cells, can be much more reliable and long-lasting, especially under harsh conditions, than comparable devices with fluid electrolytes.

Cobalt(II) hydroxide chemical compound

Cobalt(II) hydroxide or cobaltous hydroxide is the inorganic compound with the formula Co(OH)
2
, consisting of divalent cobalt cations Co2+
and hydroxide anions HO
. The pure compound, often called the "beta form" is a pink solid insoluble in water.

Tellurium iodide is an inorganic compound with the formula TeI. Two forms are known. Their structures differ from the other monohalides of tellurium. There are three subiodides of tellurium, α-TeI, β-TeI, and Te2I, and one tellurium tetraiodide.

References

  1. 1 2 Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN   978-0-618-94690-7.
  2. Binner, J. G. P.; Dimitrakis, G.; Price, D. M.; Reading, M.; Vaidhyanathan, B. (2006). "Hysteresis in the β–α Phase Transition in Silver Iodine" (PDF). Journal of Thermal Analysis and Calorimetry. 84 (2): 409–412. CiteSeerX   10.1.1.368.2816 . doi:10.1007/s10973-005-7154-1.
  3. Hull, Stephen (2007). "Superionics: crystal structures and conduction processes". Rep. Prog. Phys. 67 (7): 1233–1314. doi:10.1088/0034-4885/67/7/R05.
  4. O. Glemser, H. Saur "Silver Iodide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1036-7.
  5. Phyllis A. Lyday "Iodine and Iodine Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi : 10.1002/14356007.a14_381
  6. "Silver Iodide". TOXNET: Toxicogy Data Network. U.S. National Library of Medicine. Retrieved 9 March 2016.
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