270 M. Stromeyer's new Details respecting Cadmium. [Oct. 



wise gives the process for procuring cadmium in a state of 

 purity. 



According to this process, we begin by dissolving in sulphuric 

 acid the substances which contain cadmium, and through the 

 solution, which must contain a sufficient excess of acid, a cur- 

 rent of sulphuretted hydrogen gas must be passed. The 

 precipitate formed is collected and well washed. It is then 

 dissolved in concentrated muriatic acid, and the excess of acid 

 driven off by evaporation. The residue is dissolved in water, 

 and precipitated by carbonate of ammonia, of which an excess 

 is added to redissolve the zinc and the copper that may have 

 been precipitated by the sulphuretted hydrogen gas. The 

 carbonate of cadmium, being well washed, is heated to drive off 

 the carbonic acid, and the remaining oxide is reduced by mixing 

 it with lamp-black, and exposing it to a moderate red heat in a 

 glass, or earthen retort. 



The colour of cadmium is a fine white, with a slight shade of 

 bluish-grey, and approaching much to that of tin. Like this 

 last metal, it has a strong lustre, and takes a good polish. Its 

 texture is perfectly compact, and its fracture hackly. It crys- 

 tallizes easily in octahedrons, and presents at its surface on 

 cooling the appearance of leaves of fern. It is soft, very flexible, 

 and yields readily to the file, or the knife. It stains pretty 

 strongly; however, it is harder than tin, and surpasses it in tena- 

 city. It is likewise very ductile, and may be reduced to fine 

 wires, or thin plates ; yet, when long hammered, it scales offin 

 -different places. Its specific gravity, without being hammered, 

 is 8*6040, at the temperature of 62* ; when hammered, it is 

 8*6944. It melts before being heated to redness, and is volati- 

 lized at a heat not much greater than what is necessary to 

 volatilize mercury. Its vapour has no peculiar odour. It 

 condenses in drops as readily as mercury, which, on congealing, 

 present distinct traces of crystallization. 



Cadmium is as little altered by exposure to the air as tin. 

 When heated in the open air, it burns as readily as this last 

 metal, and is converted into a brownish-yellow oxide, which 

 appears usually under the form of a smoke of the same colour ; 

 but which is very fixed. Nitric acid dissolves it easily cold ; 

 diluted sulphuric acid, muriatic acid, and even acetic acid, attack 

 it with disengagement of hydrogen gas ; but their action is very 

 feeble, especially that of acetic acid, even when it is assisted by 

 heat. The solutions are colourless, and are not precipitated by 

 water. 



Cadmium forms only a single oxide ; 100 parts of the metal 

 combine with 14*352 of oxygen. According to this, the equiva- 

 lent number for cadmium is 69*677, and that of the oxide 69*677 

 + 10 = 79*677. The colour of the oxide varies according to 

 the circumstances in which it is formed. It is brownish-yellow, 

 light-brown, dark-brown, and even blackish. It is quite fixed 



