Cadmium, a soft, silvery-white metallic element. It is much like zinc, but is a heavier metal with a lower melting point. It can be formed into thin sheets. Cadmium and its compounds are highly poisonous.
The major use of cadmium is as a coating on iron and steel parts to protect them against corrosion. The coating is usually applied by electroplating. Another important use is as a negative electrode in nickel-cadmium batteries. Cadmium is a component of certain alloys with a low melting point that are commonly used for soldering and for fusible parts in automatic fire sprinklers. In nuclear physics, cadmium is used in shields for stopping neutrons.
An important compound of cadmium is cadmium sulfide. It is used as a yellow pigment for paints and inks. Mixed with cadmium selenide, it forms an orange pigment. Cadmium sulfide is also used in television-tube phosphors and as a light-sensitive substance in some kinds of solar cells and copying machines.
Cadmium was discovered by Friedrich Strohmeyer of Germany in 1817. The element occurs chiefly in the mineral greenockite (cadium sulfide) and in zinc ores. Deposits of greenockite are too small to be mined commercially and almost all cadmium is obtained as a by-product during the process of smelting zinc ores.
Symbol: Cd. Atomic number: 48. Atomic weight: 112.41. Specific gravity: 8.65. Melting point: 609.6 F. (320.9 C.). Boiling point: 1,409 F. (765 C.). Cadmium has eight natural isotopes. It belongs to Group II-B of the Periodic Table and has a valence of +2.