308 METALS. 



2. NOBLE METALS. 

 I. PLATINUM.— IRIDIUM.— PALLADIUM. 



NATIVE PLATINUM. 



In flattened or angular grains or irregular masses, the 

 masses occasionally large. Crystalline form cubic, but sel- 

 dom observed. Cleavage none 



Color and streak pale or dark steel-gray. Luster metallic, 

 shining. Ductile and malleable. H=4 — 4*5. Gr = 16 — 

 19. 



Composition. Platinum is usually combined with more or 

 less of the rare metals Iridium, Rhodium, Palladium, and 

 Osmium, besides copper and iron, which give it a darker 

 color than belongs to the pure metal, and increase its hard- 

 ness. A Russian specimen afforded, platinum 78*9, iridium 

 5*0, osmium and iridium 1*9, rhodium 0*9, palladium 0*3, 

 copper 0-7, iron 11-0 = 98-75. 



Platinum is soluble in heated aqua regia. It is one of 

 the most infusible substances known, being wholly unaltered 

 before the blowpipe. It is very slightly magnetic, and this 

 quality is increased by the iron it may contain. 



Dif. Platinum is at once distinguished by its malleabil- 

 ity and extreme infusibility. 



Obs. Platinum was first detected in grains in the alluvial 

 deposits of Choco and Barbagoa in South America, where it 

 received the name platina, derived from the word plata, 

 meaning silver. Although before known, an account by 

 Ulloa, a Spanish traveller in America in 1735, directed at- 

 tention in Europe, in 1748, to the metal. It has since been 

 found in the Urals, on Borneo, in the sands of the Rhine, and 

 in those of the river Jocky, St. Domingo ; and recently traces 

 have been observed in the United States, in North Carolina. 



The Ural localities of Nischne Tagilsk, and Goroblagodat, 

 have afforded much the larger part of the platinum of com- 

 merce. It occurs, as elsewhere, in alluvial beds ; but the 

 courses of platiniferous alluvium have been traced to a great 

 extent up Mount La Martiane, which consists of crystalline 



What is the condition and appearance of native platinum 1 What 

 fe said of its crystallization ? What is its specific gravity ? With what 

 is it usually combined ? Where and when was it first found ? Where 

 else does it occur ? 



