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|Atomic Number:||48||Atomic Symbol:||Cd|
|Atomic Weight:||112.40||Electron Configuration:||2-8-18-18-2|
|Melting Point:||320.9oC||Boiling Point:||765oC|
|Description:||Silvery White Metal|
|Uses:||Obtained as a byproduct of Zinc Refining|
History(L. cadmia; Gr. kadmeia - ancient name for calamine, zinc
carbonate) Discovered by Stromeyer in 1817 from an impurity in zinc carbonate.
SourcesCadmium most often occurs in small quantities associated with
zinc ores, such as sphalerite (ZnS). Greenockite (CdS) is the only mineral of
any consequence bearing cadmium. Almost all cadmium is obtained as a by-product
in the treatment of zinc, copper, and lead ores.
- It is a soft, bluish-white metal which is easily cut with a knife.
- It is similar in many respects to zinc.
- It is a component of some of the lowest melting alloys; it is used in
bearing alloys with low coefficients of friction and great resistance to
fatigue; it is used extensively in electroplating, which accounts for about 60%
of its use.
- It is also used in many types of solder, for standard E.M.F. cells, for
Ni-Cd batteries, and as a barrier to control nuclear fission. Cadmium compounds
are used in black and white television phospros and in blue and green phosphors
for color TV tubes.
- It forms a number of salts, of which the sulfate is most common; the sulfide
is used as a yellow pigment.
HandlingCadmium and solutions of its compounds are toxic.
appreciate the toxic properties of cadmium may cause workers to be unwittingly
exposed to dangerous fumes.
Silver solder, for example, which contains
cadmium, should be handled with care.
Serious toxicity problems have been
found from long-term exposure and work with cadmium plating baths.
to cadmium dust should not exceed 0.01 mg/m^3 (8-hour time-weighted average,
The ceiling concentration (maximum), for a period of 15 min,
should not exceed 0.14 mg/m^3.
Cadmium oxide fume exposure (8-hour, 40-hour
week) should not exceed 0.05 mg/m^3, and the maximum concentration should not
exceed 0.05 mg/m^3.
These values are presently being restudied and
recommendations have been made to reduce the exposure.
In 1927 the
Interanational Conference on Weights and Measures redefined the meter in terms
of the wavelength of the red cadmium spectral line (i.e. 1m = 1.553,164.13
This definition has since been changed (see under Krypton).
CostsThe current price of cadmium is about $12/lb.
It is available
in high purity form.