Magnesium iodide
Crystal structure | |||||||||||||||||||
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__ Mg 2+ __ I - | |||||||||||||||||||
General | |||||||||||||||||||
Surname | Magnesium iodide | ||||||||||||||||||
other names |
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Ratio formula | MgI 2 | ||||||||||||||||||
Brief description |
white, odorless solid |
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External identifiers / databases | |||||||||||||||||||
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properties | |||||||||||||||||||
Molar mass | 278.11 g mol −1 | ||||||||||||||||||
Physical state |
firmly |
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density |
4.43 g cm −3 |
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Melting point |
637 ° C ( decomposition ) |
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solubility |
very good in water (1480 g l −1 at 18 ° C) |
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safety instructions | |||||||||||||||||||
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Magnesium iodide (MgI 2 ) is a chemical compound , the magnesium salt of hydriodic acid . In addition to being anhydrous anhydrate , it also occurs in several forms of hydrate MgI 2 · (H 2 O) x , such as hexa- and octahydrate.
Extraction and presentation
Magnesium iodide can be obtained directly from the elements magnesium and iodine by heating and excluding air or oxygen :
It is also possible to produce it by reacting magnesium with mercury (II) iodide .
properties
Magnesium iodide is a colorless, odorless, very water-soluble, trigonal crystalline solid substance which, due to its hygroscopicity and sensitivity to air , must be stored under a dry protective gas (usually argon ). With water it forms various hydrates (MgI 2 · 6 H 2 O, MgI 2 · 8 H 2 O, MgI 2 · 9 H 2 O). In the air it gradually decomposes to elemental iodine , magnesium hydroxide and water, turning brown .
Magnesium iodide, like many other halides and hydroxides of divalent metals or sulfides and tellurides of tetravalent metals, belongs to the polytype 2H of the CdI 2 structure (a = 4.14 Å, c = 6.88 Å). It is extremely hygroscopic. The octahydrate crystallizes from its aqueous solution at ordinary temperature, above 43 ° C the hexahydrate is stable.
Individual evidence
- ↑ a b c d e data sheet magnesium iodide at AlfaAesar, accessed on December 26, 2019 ( PDF )(JavaScript required) .
- ↑ a b data sheet on web elements .
- ↑ a b c Georg Brauer (ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 906.