Zinc iodide is the inorganic compound with the formula ZnI₂. 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 ...

. or by treating zinc with iodine in aqueous solution: : Zn + I₂ → ZnI₂

Structure as solid, gas, and in solution

The structure of solid ZnI₂ 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 ZnI₂ 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 the ...

theory with a Zn-I bond length of 238 pm. In aqueous solution the following have been detected: Zn(H₂O)₆²⁺, nI(H₂O)₅sup>+, tetrahedral ZnI₂(H₂O)₂, ZnI₃(H₂O)⁻, and ZnI₄²⁻.

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 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 ...

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 ...

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 d ...

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 ...

, ZnI₂ is used as a stain in electron microscopy. *As a Lewis acid, zinc iodide catalyzes for the conversion of methanol 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 de ...