Zinc iodide is the
inorganic compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...
with the formula ZnI
2. It exists both in anhydrous form and as a dihydrate. Both are white and readily absorb water from the atmosphere. It has no major application.
Preparation
It can be prepared by the direct reaction of zinc and iodine in water
or in refluxing
ether
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be c ...
. or by treating zinc with iodine in aqueous solution:
: Zn + I
2 → ZnI
2
Structure as solid, gas, and in solution
The structure of solid ZnI
2 is unusual relative to the dichloride. While zinc centers are tetrahedrally coordinated, as in
ZnCl2, groups of four of these tetrahedra share three vertices to form “super-tetrahedra” of composition , which are linked by their vertices to form a three-dimensional structure.
These "super-tetrahedra" are similar to the
P4O10 structure.
Molecular ZnI
2 is linear as predicted by
VSEPR
Valence shell electron pair repulsion (VSEPR) theory ( , ), is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theo ...
theory with a Zn-I bond length of 238 pm.
In aqueous solution the following have been detected: Zn(H
2O)
62+,
2O)5">nI(H2O)5sup>+, tetrahedral ZnI
2(H
2O)
2, ZnI
3(H
2O)
−, and ZnI
42−.
Applications
*Zinc iodide is often used as an
x-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
opaque
Opacity or opaque may refer to:
* Impediments to (especially, visible) light:
** Opacities, absorption coefficients
** Opacity (optics), property or degree of blocking the transmission of light
* Metaphors derived from literal optics:
** In lingu ...
penetrant in
industrial radiography
Industrial radiography is a modality of non-destructive testing that uses ionizing radiation to inspect materials and components with the objective of locating and quantifying defects and degradation in material properties that would lead to the f ...
to improve the contrast between the damage and intact composite.
*United States
patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...
4,109,065 describes a rechargeable aqueous zinc-halogen
cell
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...
that includes an aqueous electrolytic solution containing a zinc salt selected from the class consisting of
zinc bromide
Zinc bromide ( Zn Br2) is an inorganic compound with the chemical formula Zn Br2. It is a colourless salt that shares many properties with zinc chloride (ZnCl2), namely a high solubility in water forming acidic solutions, and good solubility in o ...
, zinc iodide, and mixtures thereof, in both positive and negative
electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
compartments.
*In combination with
osmium tetroxide
Osmium tetroxide (also osmium(VIII) oxide) is the chemical compound with the formula OsO4. The compound is noteworthy for its many uses, despite its toxicity and the rarity of osmium. It also has a number of unusual properties, one being that the ...
, ZnI
2 is used as a stain in electron microscopy.
*As a Lewis acid, zinc iodide catalyzes for the conversion of
methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...
to
triptane
Triptane, or 2,2,3-trimethylbutane, is an organic chemical compound with the molecular formula C7 H16 or (H3C-)3C-C(-CH3)2H. It is therefore an alkane, specifically the most compact and heavily branched of the heptane isomers, the only one with a ...
and
hexamethylbenzene
Hexamethylbenzene, also known as mellitene, is a hydrocarbon with the molecular formula C12H18 and the condensed structural formula C6(CH3)6. It is an aromatic compound and a derivative of benzene, where benzene's six hydrogen atoms have each ...
.
References
{{Iodides
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
Metal halides
iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine defic ...