PLATINUM 585 



ginous matters, or sometimes with small grains of magnetic oxide of iron, adhering to 

 the surface of the platinum grains. Their specific gravity is also much lower than 

 that of forged pure platinum ; varying from 15 in the small particles, to 18'94 in 

 Humboldt's large specimen. This relative likeness is owing to the presence of iron, 

 copper, lead, and chromium, besides its other metallic constituents, palladium, osmium, 

 rhodium, and iridium. 



Its main localities in the New Continent are the three following districts : 



At Choco, in the neighbourhood of Barbacoas, and generally on the coasts of the 

 South Sea, or on the western slopes of the Cordillera of the Andes, between the 2nd 

 and the 6th degrees of north latitude. The gold-washings that furnish most platinum 

 are those of Condoto, in the province of Novita ; those of Santa Rita, or Viroviro, of 

 Santa Lucia, of the ravine of Iro, and Apoto, between Novita and Taddo. The 

 deposit of gold and platinum grains is found in alluvial ground, at a depth of about 

 20 feet. The gold is separated from the platinum by picking with the hand, and also by 

 amalgamation ; formerly, when it was imagined that platinum might be used to debase 

 gold, the grains of the former metal were thrown into the rivers, through which mis- 

 taken opinion an immense quantity of it was lost. 



Platinum grains are found in Brazil, but always in the alluvial lands that contain 

 gold, particularly in those of Matto-Grosso. The ore of this country is somewhat 

 different from that of Choco. It is in grains, which seem to be fragments of a 

 spongy substance. All the particles are nearly globular, exhibiting a surface formed 

 of small spheroidal protuberances strongly cohering together, whose interstices are 

 clean, and oven brilliant. This platinum includes many small particles of gold, but 

 none of the magnetic iron-sand or of the small zircons which accompany the Peruvian 

 ore. It is mixed with small grains of native palladium, which may be recognised by 

 their fibrous or radiated structure and particularly by their chemical characters. 



Platinum grains are found in Hayti, or Saint Domingo, in the sand of the river 

 Jacky, near the mountains of Sibao. Like those of Choco, they are in small brilliant 

 grains, as if polished by friction. The sand containing them is quartzose and ferru- 

 ginous. This native platinum contains, like that of Choco, chromium, copper, osmium, 

 iridium, rhodium, palladium, and probably titanium. Vauquelin could find no gold 

 among the grains. 



Platinum is largely produced in the Eussian territories, in the auriferous sands of 

 Kuschwa, 250 worsts from Ekaterinbourg, and consequently in a geological position 

 which seems to be analogous to that of South America. It also occurs at Nischne- 

 Tagilsk and Goroblagodat, in the Ural, in alluvial and drift material. 



These auriferous sands are, indeed, almost all superficial ; they cover an argillaceous 

 soil, and include, along with gold and platinum, debris of dolerite (a kind of basalt) 

 magnetic iron-ore, grains of corundum, &c. The platinum grains are not so flat 

 as those from Choco, but they are thicker ; they have less brilliancy, and more of a 

 leaden hue. This platinum, by M. Laugier's analysis, is similar in purity to that cf 

 Choco ; but the leaden-grey grains, which were taken for a mixture of osmium and 

 iridium, are merely an alloy of platinum, containing 25 per cent, of these metals. In 

 Russia platinum has been formed into coins of eleven and twenty-two roubles each ; and 

 this country affords annually about 800 cwts. of platinum, which is nearly ten times 

 the amount from other parts of the world. 



Platinum has also been found in Borneo, in California, in North Carolina, in 

 Canada, in Australia, in the sands of the Rhine, and in Co. Wicklow, Ireland. 



M. Vauquelin found nearly 10 per cent, of platinum in an ore of argentiferous 

 copper, which was transmitted to him as coming from Guadalcanal, in Spain. This 

 would be the only example of platinum existing in a rock and in a vein. The same 

 thing has not again been met with, even in other specimens from Guadalcanal. 



Platinum has been known in Europe only since 1748, though it was noticed by 

 Ulloa in 1741. It was compared at first to gold; and was, in fact, brought into the 

 market under the name of white gold. The term ' platinum,' however, is derived from 

 the Spanish word plata, silver, on account of its resemblance in colour to that metal. 



The whole of the platinum ore from the Urals is sent to St. Petersburg, where it is, 

 or formerly was, treated by the following simple process : 



One part of the ore is put into open platina vessels, capable of containing from 6 to 

 8 Ibs., along with 3 parts of muriatic acid at 25 B. and 1 part of nitric acid at 40. 

 Thirty of these vessels are placed upon a sand-bath covered with a glazed dome with 

 moveable panes, which is surmounted by a ventilating chimney to carry the vapours 

 out of the laboratory. Heat is applied for 8 or 10 hours, till no more red vapours 

 appear : a proof that the whole nitric acid is decomposed, though some of the 

 muriatic remains. After settling the supernatant liquid is decanted off into large 

 cylindrical glass vessels, the residuum is washed, and the washing is also decanted 

 off. A fresh quantity of nitro-muriatic acid is now poured upon the residuum. Thitf 



