322 Mr. W. Marshall's Account of the Russian Method 



and conducting it into the fire-place underneath, the chlorine 

 and nitrous gas are conveyed off', yet sufficient fumes find their 

 way into the room to render the atmosphere very disagree- 

 able. The solution, now finished, is, by means of a syphon, 

 drawn off" from the black sediment, and contains muriate of 

 platinum, which upon the evaporation of the liquid remains in 

 the form of a mass, showing some tendency to crystallization. 



This mass is now dissolved in rain-water, and precipitated 

 with sal-ammoniac. The precipitate pi'esents the appearance 

 of a yellow powder, being a muriate of platinum and ammo- 

 nia, containing a small portion of ii'idium. This yellow pre- 

 cipitate is again clean washed and dried, and then, in a cast- 

 iron pan, brought to a red heat, by which means the ammonia 

 and muriatic acid are volatilized, leaving the platinum of a 

 gray colour and in a metallic state, but combined with a small 

 portion of iridium. Three pounds of this gray platinum are 

 now ground in an iron mortar, it being found, (conti"ary to the 

 experience of Dr. Wollaston, who used a xwoden mortar and 

 pestle,) that even the small lumps which are formed by the 

 action of the pestle, thus receiving a certain polish, will not- 

 withstanding cohere or weld perfectly well together. The 

 fine ground gray powder of platinum is now wrapped in paper, 

 in order to keep it together, inclosed by a thick iron ring, 

 placed upon an anvil, and by the force of two men slowly and 

 gently pressed with a powerful screw-press into a compact 

 mass. This cake is now again subjected to a red heat in a 

 charcoal fire, and, being a second time placed under the 

 action of the press, is very quickly, forcibly and repeatedly 

 pressed, in order to bring it into as compact and dense a mass 

 as possible; — and thus is the platinum brought to a perfectly 

 malleable state. 



During the digestion the osmium, or at least the greatest 

 part of it, finds its way into the recipient; the palladium and 

 rhodium, with a small portion of iridium, remain in the black 

 sediment. The portion of iridium which remains in the rain- 

 water after the precipitation of the platinum with sal-ammo- 

 niac, may be afterwards obtained, by evaporation, in the shape 

 of small red crystals of muriate of iridium and ammonia; if 

 these crystals be subjected to a retl heat, the ammonia and 

 muriatic acid will be volatilized, and the pure iridium will re- 

 main as a gray powder. The osmium is not used in the arts ; 

 the rhodium and iridium form very good alloys with steel ; 

 and the palladium may for many purposes be used in the 

 place of platinum. The iridium which remains in the pla- 

 tinum is not detrimental : it is even affirmed that a small pro- 

 portion is beneficial, for which reason probably the old pla- 

 tinum vessels made by Gianetti of Paris were so lasting. 



The 



