Chemistry

Cadmium is a chemical element in the periodic table that has the symbol "Cd" and atomic number forty-eight. It is a relatively rare, soft, bluish-white, toxic transition metal, cadmium occurs with zinc ores and is used largely in batteries.

Cadmium is a common impurity in zinc, and it is most often isolated during the production of zinc. Zinc sulfide ores are roasted in the presence of oxygen converting the zinc sulfide to the oxide. Zinc metal is produced either by smelting the oxide with carbon or by electrolysis in sulfuric acid. Cadmium is isolated from the zinc metal by vacuum distillation if the zinc is smelted, or cadmium sulfate is precipitated out of the electrolysis solution.

Cadmium is a soft, malleable, ductile, bluish-white bivalent metal which can be easily cut with a knife. It is similar in many respects to zinc but lends itself to more complex compounds.

Cadmium was discovered in Germany in 1817 by Friedrich Strohmeyer. Strohmeyer found the new element within an impurity in zinc carbonate and for 100 years Germany remained the only important producer of the metal. The metal was named after the Latin word for calamine since the metal was found in this zinc compound. Strohmeyer noted that some impure samples of calamine changed color when heated but pure calamine did not. Even though cadmium and its compounds are highly toxic, the British Pharmaceutical Codex from 1907 states that cadmium iodide was used as a medicine to treat "enlarged joints, scrofulous glands, and chilblains".

About three-fourths of cadmium is used in batteries and most of the remaining one-fourth is used mainly for pigments, coatings and plating, and as stabilizers for plastics. They are used in some of the lowest melting alloys. Due to a low coefficient of friction and very good fatigue resistance, it is used in bearing alloys. About six percent of cadmium finds use in electroplating. Many kinds of solder contain this metal. It is used as a barrier to control nuclear fission. Compounds containing cadmium are used in black and white television phosphors and also in the blue and green phosphors for color television picture tubes. Cadmium forms various salts, with cadmium sulfide being the most common. This sulfide is used as a yellow pigment. Cadmium selenide can be used as red pigment, commonly called cadmium red. They are used in some semiconductors such as cadmium sulfide, cadmium selenide, and cadmium telluride, which can be used for light detection or solar cells. HgCdTe is sensitive to infrared units. Some cadmium compounds are employed in PVC as stabilizers. It was used in the first neutrino detector. Lastly it is used to block voltage dependent calcium channels