Cadmium iodide is an inorganic compound with the formula CdI2. It is a white hygroscopic solid. It also can be obtained as a mono- and tetrahydrate.[2] It has few applications. It is notable for its crystal structure, which is typical for compounds of the form MX2 with strong polarization effects.
Preparation
Cadmium iodide is prepared by the addition of cadmium metal, or its oxide, hydroxide or carbonate to hydroiodic acid. Also, the compound can be made by heating cadmium with iodine.[2]
While uneconomical compared to the production of terephthalic acid from p-xylene, the Henkel method has been proposed as a potential route to produce terephthalic acid from furfural. As existing Bio-PET is still reliant on petroleum as a source of p-xylene, the Henkel process could theoretically offer a completely bioplastic route to polyethylene terephthalate.[4]
Crystal structure
The iodide anions in CdI2 form a hexagonal close-packed lattice, while the cadmium cations occupy all of the octahedral holes in alternating layers.
In cadmium iodide the iodideanions form a hexagonal closely packed arrangement while the cadmium cations fill all of the octahedral sites in alternate layers. The resultant structure consists of a layered lattice. This same basic structure is found in many other salts and minerals. Cadmium iodide is mostly ionically bonded but with partial covalent character.[5]
Cadmium iodide's crystal structure is the prototype on which the crystal structures of many other compounds can be considered to be based. Compounds with any of the following characteristics tend to adopt the CdI2 structure:[citation needed]
^ abF. Wagenknecht; R. Juza (1963). "Cadmium iodide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. p. 1096.
^Solomon, I.; Eisenberg, W. (1976). Utilization of coal conversion process by-products. Quarterly report, December 27, 1975--March 27, 1976 (Report). doi:10.2172/7186862.
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