241 PLATINA. 



osmium. When pure, it is the heaviest of all known substances. 

 Its colour is steel-grey, and its specific gravity from 16"0 to 20 0. 



Spec. 1. Native Platina. — Pl. XXXI. fig. 5. Gediegen Platin, 

 Werner; Platina aurum album, 1Vallerius,\\. p. 365 ; Platine natif, 

 Bnmg.il. p. 275 ; Hauij, iii. p. 365 ; Jameson, Syst. 2d ed. iii. p. 2. 

 — Its colour is between steel-grey and silver- white. Externally it is 

 shining or glistening, and the lustre is metallic. It is nearly as hard 

 as iron, very malleable and ductile. Its specific gravity is 17'7. It 

 is infusible by the common blow- pipe, and is soluble in the nitro- 

 muriatic acid. It is never obtained pure, being always alloyed with 

 small portions of other metals, more especially palladium and gold. 

 Native platina occurs in irregular flatted grains, and in masses as 

 large as a pigeon's egg. It was supposed till lately to be the exclusive 

 product of South America, where it is met with in various places, 

 particularly in Choco, one of the provinces of New Granada, in 

 the province of Barbacoas, between the 2° and 6° of north latitude, 

 and in the gold mines of Brazil. In these situations it occurs 

 only in alluvial deposits, generally accompanied by grains and 

 loose crystals of chrome ore, magnetic iron ore, copper pyrites, 

 zircon, spinel, quartz, and native gold, with fragments of green- 

 stone and sienite. M. Boussingault is said to have discovered 

 native platina in situ, in decomposed sienitic rocks at Santa Rosa, 

 about thirty miles north east from Medellin, in the province o 

 Antioquia, in north latitude 6° 37 43", situated 7462 feet above 

 the level of the sea.* About the year 1820 it was discovered on 

 the east side of the Oural mountains, between Nyne-Tajibskoiand 

 Kuschtunskoi, in Siberia. According to Vauquelin, the grey silver 

 ore of Guadalcanal, in Spain, contains from 1 to 10 per cent, of 

 platina. f It is distinguished from silver by its colour, external 

 shape, hardness, great specific gravity, its infusibility, and insolu- 

 bility in nitric acid. 



The process for obtaining Platina in a pure state was first pointed 

 out by Dr. Wollaston. It consists in dissolving the grains of 

 crude platina in nitro-muriatic acid, and adding a solution of 

 mutiate of ammonia in excess ; a yellow powder falls down, which 



* Ann. dr. Chan. r7 Phys. xxxii. p. 204. f Id. \\..l\T. 



