PLATINUM METALS AND ORE. Ill 



nickel are separated by cyanide of potassium as in 

 No. 65. 



70. THE PLATINUM METALS AND ORE. 



1. PLATINUM. Only fusible in the oxyhydrogen 

 flame. Density when fused is 21.15. Free from iri- 

 dium it is very soft and malleable. Soluble in aqua 

 regia. The reddish-yellow solution gives with the 

 salts of ammonium and potassium a crystalline lemon 

 yellow precipitate, NH 4 Cl + PtCl 2 and K Cl-f PtCl 2 . 

 The former ignited forms a gray platinum sponge, and 

 the latter, fused with common salt, crystallized platinum. 



2. PALLADIUM. In color, lustre, and malleability, 

 similar to platinum. Difficultly fusible, but more 

 easily than platinum. Density 11.8. Heated in the 

 air it is colored steel-gray, and in the flame of a gas 

 burner becomes rusty, and uniting with carbon becomes 

 brittle. Soluble in cold nitric acid without disengage- 

 ment of gas. Its oxides are Pd 2 O, PdO, and PdO 2 ; 

 they are black and reduced without a flux. 



In aqua regia it gives a dark-brown solution of per- 

 chloride. By evaporation it becomes a dark-brown 

 deliquescent protochloride Pd Cl. Iodide of potassium 

 added to this solution forms a black iodide of palladium, 

 Pdl, and cyanide of mercury a yellowish-white cyanide 

 of palladium Pd Cy. 



Ammonia throws down a flesh-red crystalline precipi- 

 tate PdCl-hNH,, forming a colorless solution if an 

 excess of ammonia is added. Hydrochloric acid gives 

 in this solution a lemon-yellow crystalline precipitate 

 = N. PdH 3 -fCL, which leaves, after ignition, the gray 

 metal. If one ami a half times the weight of the metal 

 of chloride of potassium be added to the solution of 

 palladium in aqua regia, and evaporated to dryness, a 

 dark red crystalline Pd C1 2 + KC1 is formed, insoluble 



