124 Dr, Clarke on Cadmium. [Feu. 



have 111) sell succeeded in the revival ot cadmium, so as to witnea* 

 its beautiful silvery aspect ; but I have never been able to obtaitt 

 the metal in any quantity, and it is only within the last week, 

 owing to the kindness oi Dr. Wollastun, who presented me with 

 a lamina of pure cadmium. ^ as he received it from Professor 

 Stromet/er, that 1 have had the satisfaction of examining this 

 curious substance. From the appearance exhibited by this spe- 

 cimen, it has the colour and lustre of silveVy and has all the 

 pliability of a piece of tin foil. Its other characters in the 

 metallic state are known, and, therefore, need not be mentioned. 

 Before I proceed to any farther account of its ores, I will just 

 mention two experiments for its revival, which seem to be 

 attended with success. The first I have once before men- 

 tioned ; it consists in filling a glass test-tube (which con- 

 tains a portion of the oxide of cadmium adhering to the inner 

 surface) with liydvoffen gas, and then with a common blow- 

 pipe directing the name of a candle against the tube, so as 

 to give it a red heat. In this experiment, if care be used 

 so as to prevent the breaking of the glass tube, metallic cadmium 

 seems apparent in a thin cuticle upon the inner surface of the 

 glass vessel. I have said ** seems apparent,^' because the quan- 

 tity is too small to allow of any satisfactory examination after- 

 wards, and also because it may be objected that this metallic 

 appearance is owing to the revival, not of the cadmium from its 

 oxide, but of another metallic oxide used in the manufacture of 

 the glass. Another way, less liable to objection, relates to an 

 experiment by which I undoubtedly obtained a sight of this 

 metal, although in a quantity so minute as to be hardly visible 

 to the naked eye. It was accomplished in the following man- 

 ner : A small quantity of the pure oxide of cadmium was dis- 

 solved in muriatic acid, and a piece of paper being steeped in 

 the solution and dried, was made into a pellet between the 

 fingers, and supported upon a slip of platinum foil before iheblue 

 jiame of the blowpipe. Here as the muriate became concentrated by 

 the burning of the paper, and afterwards decomposed, the oxide 

 of cadmium was reduced by the carbonaceous matter both of the 

 paper and the blue fame, and as it began to burn and to exhibit 

 its reddish-broiDH protoxide upon the platinum foil, a small bead 

 of cadmium remained upon the surface of the platinum ; which, 

 being fixed into the end of a deal splinter, admitted the action of 

 the file, and exhibited the silvery aspect of the pure metal. In 

 this experiment I had no room to doubt of the nature of the 

 result ; because the oxide which I used came from Professor 

 Strof nether himself, and there was no impurity in any of the sub- 

 stances I had employed. As the temperature at which cy/Jw??/w 

 becomes volatilized is so inconsiderable, it is of course difficult 

 to attempt its reduction by means of heat; the metal burning in 

 the very instant of its revival, unless the greatest caution be 

 observed. The phsBnomena, however, attendant upon its com- 



