Magnesium iodide

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Crystal structure
Crystal structure of magnesium iodide
__ Mg 2+      __ I -
General
Surname Magnesium iodide
other names
  • Magnesium (II) iodide
  • Magnesium diiodide
Ratio formula MgI 2
Brief description

white, odorless solid

External identifiers / databases
CAS number
  • 10377-58-9
  • 75535-11-4 (hexahydrate)
  • 7790-31-0 (octahydrate)
EC number 233-825-1
ECHA InfoCard 100.030.738
PubChem 5462737
ChemSpider 59700
Wikidata Q416265
properties
Molar mass 278.11 g mol −1
Physical state

firmly

density

4.43 g cm −3

Melting point

637 ° C ( decomposition )

solubility

very good in water (1480 g l −1 at 18 ° C)

safety instructions
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
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

  1. a b c d e data sheet magnesium iodide at AlfaAesar, accessed on December 26, 2019 ( PDF )(JavaScript required) .
  2. a b data sheet on web elements .
  3. 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.