Zinc iodide

Zinc ( II) iodide

White odorless solid

Fixed

4.74 g · cm -3

446 ° C

625 ° C.

• Very soluble in water ( 4500 g · l-1 at 20 ° C)
• Readily soluble in ethanol and diethyl ether

Attention

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Zinc iodide is a chemical compound of zinc and iodine from the group of halides. The white hygroscopic powder takes in moist air to water and melts ( dissolves ). In air, it reacts with the liberation of iodine, so that the compound or its solution turns yellowish.

Production and representation

Can be obtained by reaction of zinc iodide with iodine addition of water.

Properties

Zinc ( II) iodide is a colorless solid which is soluble in water, ethanol, ether, acetone and dioxane. Below 0 ° C crystallizes out of solution the dihydrate. When heated in air is decomposition.

The crystalline structure of the zinc ( II) iodide is unusual. To form ( with the exception of zinc fluoride ), but no ionic bonding of a covalent bond, such as other zinc halides and is therefore no salt in the strict sense. While the zinc atoms are tetrahedrally coordinated as in zinc chloride, in contrast to this form of four connected at three corners of a tetrahedron " Super - tetrahedron " of the composition ( Zn4I10 ) and a corresponding three-dimensional structure. These "super - tetrahedra " are similar to the structure of phosphorus pentoxide P4O10. Molecular zinc (II ) iodide has loud VSEPR model a Zn - I distance 238 pm linear.

Use

Since the compound X-ray radiation is absorbed well, it is often used as contrast agents in diagnostic radiology of materials ( penetration in damaged material ). Furthermore it is used as a school chemical in attempts to electrolysis.

Through this exploitation of this reaction and its reversal, the construction of a zinc -iodine battery is possible.