Cadmium iodide
- Cadmium ( II) iodide
- Cadmiumdiiodid
Colorless to dark brown, shiny, odorless hexagonal platelets
Fixed
5.67 g · cm -3 ( 30 ° C)
387 ° C
796 ° C
13 Pa (402 ° C)
1850 g · l-1 in water (20 ° C)
Risk
Repealed as carcinogenic
Template: Infobox chemical / molecular formula search available
Cadmium, CdI2, is a chemical compound of cadmium with iodine. It crystallizes in a sheet structure in the hexagonal crystal system. The cadmium iodide structure is eponymous for a number of other compounds which crystallize in the same structure.
Production and representation
Cadmium is possible from the appearance of the elements at elevated temperatures.
Furthermore, it can also be represented by dissolving cadmium or cadmium in hydroiodic acid, followed by crystallization. The result is a hydrate, which can be dehydrated with thionyl chloride and then converted to the anhydrous cadmium iodide.
Also possible is the production by the reaction of cadmium sulfate with potassium iodide.
Properties
Cadmium forms of air -stable, white shiny, hexagonal platelets, which are caused readily cleaved by the layer structure.
Cadmium crystallizes in a hexagonal crystal structure in the space group P63mc with the lattice parameters a = 425 pm and c = 1367 pm and two formula units per unit cell. The iodide ions form a hexagonal closest packing of spheres, in which every other Oktaederlückenschicht is fully staffed with cadmium ions Cd2 . The cadmium ions are octahedrally surrounded by six iodide ions, each iodide ion the top of a trigonal pyramid with three cadmium ions as basal surface (coordination = 6:3 ). This results in individual Cadmiumiodidschichten that are held together only by weak van der Waals forces. In Cadmiumiodidstruktur crystallize especially bromides and iodides, as well as some of sulfides, selenides and tellurides, such as magnesium bromide, calcium iodide, iron ( II) iodide, tin (IV) sulfide, and titanium (IV ) sulfide.
A relatively newly discovered modification of Cadmiumiodids are the well-characterized nanoparticles, the CdI2 forms upon irradiation with electrons, nanotubes and fullerene-like structures.
Compounds of the CdI2 - type
Cadmium is one like many other halides and hydroxides of divalent metals or sulfides and tellurides of tetravalent metals for CdI2 structure type, all of which have the same crystal structure:
Members
- CdI2, MgI2, TiI2
- MgBr2, TiBr2, CdBr2
- TiCl2, VCL2
- Mg (OH) 2, Ni (OH) 2, Ca ( OH) 2
- TiS2, RV2, TiSe2, Site2
- Ag2F and W2C are part of the anti - CdI2 - type with large metal cations on the iodide positions, while the anions occupy the octahedral sites.
Use
Cadmium is used as a reagent for the detection of alkaloids and nitrous acid, as well as in the production of fluorescent colors and electrolysis using cadmium. It is also used in photographic processes such as the tintype.
Safety
Cadmium is toxic by inhalation and if swallowed, has chronic toxicity and carcinogenic effect in animal experiments. The lethal dose LD50 is 166 mg / kg in mice. The lowest known lethal dose in oral ingestion by humans ( LDLO ) 81 mg / kg are given. In addition, the eco - toxicity of cadmium iodide is very high, especially for aquatic organisms, especially since it can cause long term damage in the aquatic environment.