This metal occurs in calamine and zinc blende in proportions varying from 1 1/2 to 3 per cent. It is recovered during the smelting of these ores for their metallic zinc in the following manner:-The more volatile cadmium vapour passes off with the first portions of the zinc distilled, imparting a brown hue to the flame; whence the term "brown blaze" is applied to this period of the roasting. The vapours burn in the air with formation of a mixture of cadmium and zinc oxides. The powder thus deposited is separately collected, mixed with charcoal in iron tubes, and distilled again, when the first deposit from this distillation will be found still richer in cadmium. The mixture is dissolved in dilute sulphuric acid, and the cadmium is thrown down as a sulphide by introducing sulphuretted hydrogen gas; the cadmium sulphide is washed, dissolved in strong hydrochloric acid, and converted into carbonate by adding ammonia carbonate; this cadmium carbonate is washed, dried, and distilled with charcoal to afford the pure metal. (Huntington.) Or, the mixture of cadmium and zinc is re-distilled, and the second product is dissolved in hydrochloric acid, from which the cadmium is precipitated by metallic zinc. (Roscoe and Schorlemmer.) Metallic cadmium possesses the colour and appearance of tin, which it resembles also in giving a crackling noise when bent; but it is harder and more tenacious.
It can be cut with a knife, drawn into wire, and rolled into foil, but becomes brittle at 180° F. (82° C). Its sp. gr. varies from 8 546 (cast) to 8*667 (hammered). It is capable of taking a high polish.