PALLADIUM. 311 



The metal iridium is extremely hard, ani is used as well as rhodium 

 for nibs to gold pens. Its specific gravity is 21-8. Rhodium (1 to 2 yet 

 cent.) gives great hardness to steel, and would be a useful metal were 

 it more abundant. 



NATIVE PALLADIUM. 



In regular octahedrons. Als>o in hexagonal tables. Occurs 

 mostly in grains, apparently composed of divergent fibers. 

 Color steel-gray, inclining to silver-white. Ductile and 

 malleable. H. above 4*5. Gr=l 1-8— 12-2. 



Consists of palladium, with some platinum and iridium 

 Fuses with sulphur, but not alone. 



Obs. Occurs in Brazil with gold, and is distinguished 

 from platinum with which it is associated by the divergent 

 structure of its grains. Selenpalladite is nothing but the 

 native palladium. 



Uses. This metal is malleable, and when polished has a 

 splendid steel-like luster which does not tarnish. A cup 

 weighing '6\ pounds was made by M. Breant in the mint at 

 Paris, and is now in the garde-meuble of the French crown. 

 In hardness it is equal to fine steel. 1 part fused with 6 of 

 gold forms a white alloy ; and this compound was employed, 

 at the suggestion of Dr. Wollaston, for the graduated part of 

 the mural circle, constructed by Troughton for the Royal 

 Observatory at Greenwich. Palladium has been employed 

 also for certain surgical intruments. 



Quite large masses of the metal palladium are brought 

 from Brazil. It is extracted from the auriferous sands by 

 first fusing it with silver, and consequently forming a quater- 

 nary alloy of gold, palladium, silver and copper, which is 

 granulated by projecting it into water. By means of nitric 

 acid all but the gold is dissolved ; and from the solution, the 

 silver is first precipitated by common salt as an insoluble 

 chlorid, and then, after separating the chlorid, the palladium 

 and copper are precipitated by plates of zinc. This pre- 

 cipitate is redissolved in nitric acid, an excess of ammonia 

 added, and then hydrochloric acid sufficient to saturate ; a 

 double chlorid of palladium and ammonia is deposited as 

 a crystalline yellow powder, which on calcination produces 

 spongy palladium. 



Describe native palladium 1 Where and how does it occur 1 How i 

 it used ? 



