PLATINUM. 309 



rocks, and is the origin of the detritus. One to three pounds 

 are procured from 3700 pounds of sand. 



Though commonly in small grains, masses of considerable 

 size have occasionally been found. A mass weighing 1088 

 grains was brought by Humboldt from South America and 

 deposited in the Berlin Museum. Its specific gravity was 

 18*94. In the year 1822, a mass from Condoto was de- 

 posited in the Madrid museum, measuring 2 inches and 4 

 lines in diameter, and weighing 11,641 grains. A more 

 remarkable specimen was found in the year 1827 in the 

 Urals, not far from the Demidoff mines, which weighed 11^ 

 (more accurately, 11-57) pounds troy; and similar masses 

 are now not uncommon. The largest yet discovered weighed 

 21 pounds troy; it is in the Demidoff cabinet. 



Russia affords annually about 80 cwt. of platinum, which 

 is nearly ten times the amount from Brazil, Columbia, St. 

 Domingo, and Borneo. Borneo affords six or eight hundred 

 pounds per year. 



The North Carolina platinum was found with gold in 

 Rutherford county. It was a single reniform granule, weigh 

 ing 2*54 grains. Other instances are reported from the 

 southern gold region, and from Point Orford and elsewhere 

 in California. 



Uses. The infusibility of platinum and its resistance to 

 the action of the air, and moisture and most chemical agents, 

 renders it of great value for the construction of chemical and 

 philosophical apparatus. The large vessels employed in the 

 concentration of sulphuric acid are now made of platinum, as 

 it is unaffected by this corrosive acid. It is also used for 

 crucibles and capsules in chemical analysis ; for galvanic bat- 

 teries ; as foil or worked into cups or forceps for supporting 

 objects before the blowpipe. It alloys readily when heated 

 with iron, lead, and several of the metals, and is also at- 

 tacked by caustic potash, and phosphoric acid, in contact with 

 carbon ; and consequently there should be caution when heat- 

 ing it not to expose it to these agents. 



It is employed for coating copper and • brass ; also for 

 painting porcelain and giving it a steel luster, formerly highly 

 prized. It admits of being drawn into wire of extreme ten- 

 lity : Dr. Wollaston obtained a wire not exceeding a two- 

 housandth of an inch in diameter. 



Platinum is coined in Russia, but is not a legal tender. 



What are the uses of platinum 1 



