Kalpana Kalpana (Editor)

Zinc iodide

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Formula
  
ZnI2

Melting point
  
446 °C

Boiling point
  
1,150 °C

Molar mass
  
319.22 g/mol

Density
  
4.74 g/cm³

Appearance
  
white solid

Zinc iodide httpsiytimgcomvib0hYEcacXQhqdefaultjpg

Zinc iodide lab overview


Zinc iodide is a chemical compound of zinc and iodine, ZnI2. The anhydrous form is white and readily absorbs water from the atmosphere. It can be prepared by the direct reaction of zinc and iodine in refluxing ether. or by reacting zinc with iodine in aqueous solution:

Contents

Zn + I2→ ZnI2

At 1150 °C, zinc iodide vapour dissociates into zinc and iodine.
In aqueous solution the following have been detected, octahedral Zn(H2O)62+, [ZnI(H2O)5]+ and tetrahedral ZnI2(H2O)2, ZnI3(H2O)− and ZnI42−.

The structure of crystalline ZnI2 is unusual, and while zinc atoms are tetrahedrally coordinated, as in ZnCl2, groups of four of these tetrahedra share three vertices to form “super-tetrahedra” of composition {Zn4I10}, which are linked by their vertices to form a three-dimensional structure. These "super-tetrahedra" are similar to the P4O10 structure. Molecular ZnI2 is linear as predicted by VSEPR theory with a Zn-I bond length of 238 pm.

Synthesis of zinc iodide lab overview


Applications

  • Zinc iodide is often used as an x-ray opaque penetrant in industrial radiography to improve the contrast between the damage and intact composite.
  • United States Patent 4109065 describes a rechargeable aqueous zinc-halogen cell which includes an aqueous electrolytic solution containing a zinc salt selected from the class consisting of zinc bromide, zinc iodide, and mixtures thereof, in both positive and negative electrode compartments.
  • In conjunction with osmium tetroxide ZnI2 is used as a stain in electron microscopy.

    • References

    Zinc iodide Wikipedia
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