680 PLATINUM. 



ORDER IX. 



METALS IN NATIVE PLATINUM. 



SECTION I. 



PLATINUM. 

 Eq. 1233.5 or 98.84. Pt. 



This metal was discovered in the auriferous sand of certain 

 rivers in America. Its name is a diminutive of plata silver, and 

 was applied to it on account of its whiteness. It occurs in the 

 form of rounded or flattened grains of a metallic lustre. It has 

 been found in Brazil, Colombia, Mexico, St. Domingo, and on 

 the eastern declivity of the Ural chain -, it is everywhere asso- 

 ciated with the debris of a rock easily recognized as belonging 

 to one of the earliest volcanic formations. 



The grains of native platinum contain from 75 to 87 per cent 

 of that metal, so much iron that they are generally magnetic, 

 from J to 1 per cent of palladium, but sometimes much less, 

 with small quantities of copper, rhodium, osmium and iridium. 

 To separate the platinum from these bodies, the ore is digested 

 in a retort with hydrochloric acid, to which additions of nitric 

 acid are made from time to time. When the hydrochloric acid 

 is nearly saturated, the liquid is evaporated in the retort to a 

 syrup, then diluted with water and drawn off from the in- 

 soluble residue. If the mineral is not completely decomposed, 

 more aqua regia is added and the distillation continued. A 

 portion always remains undissolved, consisting of grains of a 

 compound of osmium and iridium, and little brilliant plates of 

 the same alloy, besides foreign mineral substances which may 

 be mixed with the ore. The solution is generally deep red, and 

 emits chlorine from the presence of perchloride of palladium ; 

 to decompose which, the liquid is boiled, chlorine escapes, and 

 the palladium is reduced to protochloride. Chloride of potas- 

 sium is then added, which precipitates the platinum as a spa- 

 ringly soluble double chloride of platinum and potassium, of 

 which the colour is yellow, but red if it is accompanied by the 



