Cadmium oxide
- Cadmium (II ) oxide
- Cadmiummonoxid
Red-brown, odorless solid
Fixed
- 6.95 g · cm -3 ( amorphous)
- 8.15 g · cm -3 ( crystalline)
- 700 ° C ( sublimation crystalline)
- > 1230 ° C ( amorphous)
1559 ° C ( sublimation amorphous)
Insoluble in water ( 49 mg · l-1 at 20 ° C)
Risk
Repealed as carcinogenic
72 mg · kg -1 ( LD50, rat, oral)
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Cadmium oxide is a chemical compound of cadmium and one of the oxides. It comes in two different forms in front of an amorphous powder or crystalline compound, which differ markedly in their properties.
Occurrence
Cadmium oxide occurs in nature in the form of the rare mineral Monteponit.
Production and representation
Cadmium can be recovered with oxygen or of cadmium melts with other oxidants by the oxidation of cadmium vapor.
Alternatives are the thermal decomposition of cadmium carbonate or cadmium nitrate. Also in the roasting of cadmium sulfide, cadmium oxide is produced.
Properties
Amorphous cadmium oxide is a yellow, depending on the particle size and brown to black powder with a density of 6.95 g · cm -3. It is insoluble in water and readily reducible and bases. Soluble it is in dilute acids, ammonia, ammonium salt solutions and sodium cyanide. When strong heating in an oxygen atmosphere, it transforms into the crystalline cadmium oxide. This is dark, when heated, however, the color changes to black.
Cadmium oxide crystallizes in the cubic crystal system in the space group with the lattice parameters a = 4.695 Å and four formula units per unit cell. The structure corresponds to the sodium chloride structure. Is as zinc oxide, cadmium oxide in a non-stoichiometric oxide, in which a low deficiency of oxide ions in comparison with the cadmium ions there. This is - in contrast to zinc oxide, present in the additional zinc ions in tetrahedral interstitial sites are - by causing defects in the oxide lattice. Through different number of defects depending on the temperature and the typical color change is caused.
Cadmium oxide is a semiconductor having a low resistivity for a salt of 5.5 × 10-3 Ω · cm at 0 ° C, and a band gap of 2.16 eV.
Use
Cadmium oxide is used as a glass additive for starting glass, special color glasses that their coloration after annealing (heat treatment) assume, and as hydrogenation and dehydrogenation catalyst in synthetic organic chemistry.