Description
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Cadmium is a rare transition metal that has a bright silvery grey appearance in its natural solid state. It is a highly toxic metal, and it is known to cause cancer. Cadmium has an atomic weight of 112.411, a melting point of 609.93 °F. and a boiling point of 1413 °F. Cadmium is commonly used as a component in batteries, for yellow pigment coloring, as a component in some special alloys, and as a component in television phosphors.
Isolation
The isolation of cadmium is never performed privately on a small scale laboratory basis; the toxicity and health hazards of this element make small isolation experiments hazardous.
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Cadmium is most often found in nature in zinc compounds. These zinc compounds commonly occur in sulfide ores. Cadmium is collected, and isolated, as a by product of zinc processing. The first step of cadmium isolation is to remove the zinc and cadmium compound from the ores. The compounds are isolated by smelting zinc oxide with carbon, through electrolysis, or through treatment with sulfuric acid. The cadmium ‘contaminant’ can then be removed from the zinc metal through the process of vacuum distillation. During this process the distillation procedure uses pressure above the liquid mixture, and the volatile liquids are evaporated. The principle of vacuum distillation is based on the fact that when the vapor pressure of a liquid exceeds the ambient pressure, the liquid will begin to boil. If the zinc has undergone smelting, and cadmium sulfate is formed, then the cadmium is precipitated out of the solution through electrolysis.