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Facts About Cadmium

Cadmium
Electron configuration and elemental properties of cadmium.
Credit: Greg Robson/Creative Commons, Andrei Marincas | Shutterstock
Atomic Number: 48
Atomic Symbol: Cd
Atomic Weight: 112.411
Melting Point: 609.92 F (321.07 C)
Boiling Point: 1,412.6 F (767 C)

Word origin: Cadmium comes from the Latin word cadmia, Greek kadmeia. This is the ancient name for calamine, or zinc carbonate. Cadmium is so named because of its similarities to zinc.

Discovery: Friedrich Stromeyer, a German chemist, discovered cadmium in 1817 while he was analyzing an impurity of zinc carbonate (ZnCO3).

Properties of cadmium

Cadmium is a soft, bluish-white metal that can be easily cut with a knife. It is similar to zinc in many aspects. [See Periodic Table of the Elements]

Cadmium and solutions of its compounds are toxic.Failure to take care when handling cadmium can cause exposure to dangerous fumes. Cadmium poisoning is a serious health problem that can occur from long-term exposure and work with cadmium-plating baths.

Silver solder also contains cadmium and should be handled with care.

Cadmium toxicity

Exposure to cadmium dust should not exceed 0.01 milligrams per cubic meter per 40-hour workweek. The maximum concentration for a period of 15 minutes should not exceed 0.14 mg/m3. Cadmium oxide fume exposure should not exceed 0.05 mg/m3, and the maximum concentration should not exceed 0.05 mg/m3per eight-hour day, 40-hour workweek. These values are currently being restudied and recommendations have been made to reduce the exposure.

Cadmium sulfide, seen here, is one of the two compounds used to make zinc cadmium sulfide. It's commonly used as a pigment.
Cadmium sulfide, seen here, is one of the two compounds used to make zinc cadmium sulfide. It's commonly used as a pigment.
Credit: Creative Commons Attribution-Share Alike 3.0 Unported | W. Oelen

Sources of cadmium

Cadmium does not abundantly occur natively. Greenockite is the only mineral of any consequence that bears cadmium. It is most often found in small quantities in zinc ores, such as sphalerite (ZnS). Cadmium mineral deposits are found in Colorado, Illinois, Missouri, Washington and Utah, as well as Bolivia, Guatemala, Hungary and Kazakhstan. Almost all cadmium in use is a by-product of treating zinc, copper and lead ores.

Uses of cadmium

In 1927, the International Conference on Weights and Measures redefined the meter in terms of the wavelength of the red cadmium spectral line. This definition has since been changed.

Cadmium is used in many types of solder, including for standard E.M.F. cells, for nickel-cadmium (Ni-Cd) batteries, and as a barrier to control nuclear fission. It is a component in low-melting alloys, including bearing alloys that have low coefficients of friction and great resistance to fatigue.

Cadmium's greatest use — about 60 percent — is electroplating.

Cadmium compounds are used in black-and-white television phosphors and in blue and green phosphors for color TV tubes.

Cadmium forms several salts, of which sulfate is the most common. Cadmium sulfide is used as a yellow pigment in oil painting.

(Source: Los Alamos National Laboratory)

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