PLATINUM METALS AND ORE. 115 



so that the sides may be covered with it, then eight 

 grains of finely-divided silver are placed in it, and 

 upon this two grains of platinum ore, which is covered 

 with about ten grains of fused borax. The mixture is 

 kept in a state of fusion for some time at a temperature 

 sufficient to melt the silver. After cooling the regulus 

 is freed from slag and weighed. All the sand is taken 

 up by the slag and the metal by the silver. 



For analysis, ten grammes of the grains of real plati- 

 num are picked out and dissolved at a boiling heat, in 

 a mixture of five parts of fuming hydrochloric acid and 

 one part of fuming nitric acid, in a retort connected 

 with a receiver which is to be kept perfectly cold. 



Fig. 14. 



The acid is distilled off' until the contents of the retort 

 have acquired the consistence of a syrup. The mass 

 becomes solid on cooling; it is then dissolved in a 

 small quantity of water and the clear solution carefully 

 poured off'from'the residue. The acid which was dis- 

 tilled over contains osmic acid, and is colored yellow 

 by a portion of the solution which was mechanically 

 carried over ; it is poured back on the residue and 

 again distilled, in order to complete the solution. 



The distillate containing osmic acid may be saturated 

 with ammonia and the osmium separated as in No. 71. 

 Or it is nearly saturated with hydrate of lime, mixed 

 with an alkaline formate and boiled, when the osmium 

 is reduced as a bluish-black powder, which is ignited 



