Description
Cadmium iodide (chemical formula: CdI2) is a chemical compound consisting of cadmium and iodine element. It appears as a green-yellow solid, being soluble in water, alcohol, ether, acetone, ammonia, and acid. It is a compound with the typical crystal structure of the form MX2, exhibiting strong polarization effects. It has many applications such as being used in lithography, photography, electroplating, process engraving, analytical chemistry, electrodeposition of cadium as well as the manufacturing of phosphor and lubricants. It is manufactured through the reaction between cadmium metal, or its oxide, hydroxide or carbonate and hydroiodic acid.
References
https://en.wikipedia.org/wiki/Cadmium_iodide
https://us.vwr.com/store/product/7485761/cadmium-iodide-99-5-metals-basis
Chemical Properties
Pearly white flakes or a crystalline powder
Physical properties
White, hexagonal flakes or crystals; slowly turns yellow upon exposure to air or light; occurs in two allotropic forms, the alpha and beta forms; density 5.67 g/cm
3; melts at 387°C (alpha form) and 404°C (beta form); vaporizes at 742°C; vapor pressures 1 and 5 torr at 416 and 481°C, respectively; soluble in water (86 g/100 mL at 25°C), ethanol, acetone, ether, and ammonia.
Uses
Made by the action of hydriodic acid on cadmium oxide and
crystallization. The colorless, flaky crystals are soluble in
water, alcohol, and ether. This halide was a common iodizer
for collodion formulas, particularly for negatives.
Uses
Used in photography, analytical chemistry, manufacturing of phosphors, lubricants
Uses
Cadmium iodide is used in lithography, photography, electroplating and the manufacturing of phosphors, in engraving process, and was used as an antiseptic and astringent.
Uses
In electrodeposition of Cd; as nematocide; in manufacture of phosphors; as lubricant; in photoconductors; in photography, process engraving; lithography; in analytical chemistry.
Preparation
Cadmium iodide is prepared by the addition of cadmium metal, or its oxide, hydroxide, nitrate or carbonate to hydriodic acid:
CdO + 2HI → CdI
2 + H
2O
Also, the compound can be made by heating cadmium with iodine:
Cd +I
2 → CdI
2
A brownish crystalline β-form of the salt may be obtained by slow crystallization from solutions or fused salt mixtures.
Purification Methods
Crystallise it from ethanol (2mL/g) by partial evaporation. [Wagenknecht & Juza in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II p 1096 1965.]
