CADMIUM. 577 



SECTION VI. 



CADMIUM. 

 Eg. 696.8 or 55.83; Cd. 



This metal is frequently found in small quantity with zinc, 

 and derives the name cadmium, applied to it by Stromeyer, 

 from cadmia fossilis, a denomination by which the. common ore 

 of zinc was formerly designated. In the process of reducing 

 ores of zinc, the cadmium which they contain comes over among 

 the first products of distillation, owing to the great volatility of 

 that metal. It may be separated from zinc, in an acid solution, 

 by sulphuretted hydrogen, which throws down cadmium as a 

 yellow sulphuret. This sulphuret dissolves in concentrated 

 hydrochloric acid, affording the chloride of cadmium, from which 

 the carbonate may be precipitated by an excess of carbonate of 

 ammonia. Carbonate of cadmium is converted by ignition into 

 the oxide, and the latter yields the metal when mixed with one- 

 tenth of its weight of pounded coal, and distilled in a glass or 

 porcelain retort, at a low red heat. 



Cadmium is a white metal, like tin, very ductile and mallea- 

 ble. It fuses considerably under a red heat, and is nearly as 

 volatile as mercury. The density of cadmium, cast in a mould, 

 is 8.604, after being hammered, 8.6944. Cadmium may be 

 dissolved in the more powerful acids, by substitution for hydro- 

 gen, with the aid of heat ; but nitric acid is its proper solvent. 



Oxide of cadmium, CdO ; 796.8 or 63.83. The only known 

 oxide of cadmium is obtained by the combustion of the metal, 

 or by the ignition of its carbonate, as a powder of an orange 

 colour, or as a white hydrate by precipitation from its salts by 

 an alkali. Its density, in the anhydrous condition, is 8.183, 

 (Herapath.) This oxide is soluble in ammonia, but not in its 

 carbonate, (differing in the last property from zinc and copper), 

 nor in the fixed alkalies. Its salts are white, and greatly re- 

 semble those of zinc. They are precipitated of a fine yellow by 

 sulphuretted hydrogen. 



Sulphuret of cadmium is distinguished from sulphuret of 

 arsenic, which it resembles in colour, by being insoluble in 

 potash, and by sustaining a red heat without subliming. 



p p 2 



