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Silver iodide

 
Silver Iodide

 
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Silver iodide
 
 
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Silver iodide (Ag
Silver

Silver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal....
I
Iodine

Iodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
) is an inorganic compound
Inorganic compound

Traditionally, inorganic compounds are considered to be of a mineral, not biological, origin. Complementarily, most organic compounds are traditionally viewed as being of biological origin....
. This yellow photosensitive solid is used in photography
Photography

Photography is the process, activity and art of creating still or moving by recording radiation on a sensitive medium, such as a photographic film, or an ....
, as an antiseptic
Antiseptic

Antiseptics are antimicrobials that are applied to living biological tissue/skin to reduce the possibility of infection, sepsis, or putrefaction....
 in medicine, and in rainmaking
Rainmaking

Rainmaking refers to the act of attempting to artificially induce or increase precipitation , usually to stave off drought. It takes two basic forms:...
. Silver iodide is highly insoluble in water.

The crystalline structure adopted by silver iodide changes with temperature. The following phases are known:

crystalline structure of AgI is similar to that of ice, allowing it to induce freezing
Freezing

In physical science, freezing or solidification is the process in which a liquid turns into a solid when cold enough. The Melting point is the temperature at which this happens....
 (heterogeneous nucleation
Nucleation

Nucleation is the onset of a crystal in a small region. The phase transition can be the formation of a bubble or of a crystal from a liquid. Creation of liquid droplets in saturated vapor or the creation of gaseous bubbles in a saturated liquid is also characterized by nucleation ....
) in cloud seeding
Cloud seeding

Cloud seeding, a form of weather control, is the attempt to change the amount or type of Precipitation that falls from clouds, by dispersing substances into the air that serve as Cloud condensation nuclei or ice nucleus, which alter the microphysical processes within the cloud....
 for the purpose of rainmaking
Rainmaking

Rainmaking refers to the act of attempting to artificially induce or increase precipitation , usually to stave off drought. It takes two basic forms:...
.






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Encyclopedia


Silver iodide (Ag
Silver

Silver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal....
I
Iodine

Iodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
) is an inorganic compound
Inorganic compound

Traditionally, inorganic compounds are considered to be of a mineral, not biological, origin. Complementarily, most organic compounds are traditionally viewed as being of biological origin....
. This yellow photosensitive solid is used in photography
Photography

Photography is the process, activity and art of creating still or moving by recording radiation on a sensitive medium, such as a photographic film, or an ....
, as an antiseptic
Antiseptic

Antiseptics are antimicrobials that are applied to living biological tissue/skin to reduce the possibility of infection, sepsis, or putrefaction....
 in medicine, and in rainmaking
Rainmaking

Rainmaking refers to the act of attempting to artificially induce or increase precipitation , usually to stave off drought. It takes two basic forms:...
. Silver iodide is highly insoluble in water.

The crystalline structure adopted by silver iodide changes with temperature. The following phases are known:
  • Up to 420K (147 °C), AgI exists in the ß-phase, which has a wurtzite structure. It is known as the mineral iodargyrite
    Iodargyrite

    Iodyrite or iodargyrite is a natural mineral form of silver iodide.Hardness is 1.5 to 2.Related are chlorargyrite and bromargyrite....
    .
  • Above 420K (147 °C), AgI undergoes a transition to the a-phase, which has a body-centered cubic structure and has the silver ions distributed randomly between 2-, 3-, and 4-coordinate sites.
  • A metastable ?-phase also exists below 420K, which has a zinc blende structure.


Rainmaking

The crystalline structure of AgI is similar to that of ice, allowing it to induce freezing
Freezing

In physical science, freezing or solidification is the process in which a liquid turns into a solid when cold enough. The Melting point is the temperature at which this happens....
 (heterogeneous nucleation
Nucleation

Nucleation is the onset of a crystal in a small region. The phase transition can be the formation of a bubble or of a crystal from a liquid. Creation of liquid droplets in saturated vapor or the creation of gaseous bubbles in a saturated liquid is also characterized by nucleation ....
) in cloud seeding
Cloud seeding

Cloud seeding, a form of weather control, is the attempt to change the amount or type of Precipitation that falls from clouds, by dispersing substances into the air that serve as Cloud condensation nuclei or ice nucleus, which alter the microphysical processes within the cloud....
 for the purpose of rainmaking
Rainmaking

Rainmaking refers to the act of attempting to artificially induce or increase precipitation , usually to stave off drought. It takes two basic forms:...
. Approximately 50,000 kg/year are used for this purpose, each seeding experiment consuming 10-50 grams.

Silver iodide as a fast ion conductor
Fast ion conductor

Fast ion conductors, also known as solid electrolytes and superionic conductors, are solid electrical conductors which conduct due to the movement of ions through voids in their crystal lattice....

The transition between the ß and a forms represents the melting of the silver (cation) sublattice. The entropy of fusion (melting) for a-AgI is approximately half that for sodium chloride
Sodium chloride

Sodium chloride, also known as common salt, table salt, or halite, is a chemical compound with the chemical formula SodiumChlorine....
 (a typical ionic solid). This can be rationalised by noting that the AgI crystalline lattice has essentially already partly melted in the transition between a and ß forms. Adding the entropy of transition from a-AgI to ß-AgI to the entropy of fusion gives a value that is much closer to the entropy of fusion for sodium chloride.

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