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|Section2= |Section3= |Section4= |Section7= }} Silver iodide is an inorganic compound with the formula AgI. 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. ==Structure== The structure adopted by silver iodide is temperature dependent: *Below 420 K, the β-phase of AgI, with the wurtzite structure, is most stable. This phase is encountered in nature as the mineral iodargyrite. *Above 420 K, the α-phase becomes more stable. This motif is a body-centered cubic structure which has the silver centers distributed randomly between 2-, 3-, and 4-coordinate sites. At this temperature, Ag+ ions can move rapidly through the solid, allowing fast ion conduction. The transition between the β and α forms represents the melting of the silver (cation) sublattice. The entropy of fusion for α-AgI is approximately half that for sodium chloride (a typical ionic solid). This can be rationalized by considering the AgI crystalline lattice to have already "partly melted" in the transition between α and β polymorphs. *A metastable γ-phase also exists below 420 K with the zinc blende structure. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「silver iodide」の詳細全文を読む スポンサード リンク
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