116 PLATINUM METALS AND ORE. 



in a current of hydrogen when the osmium is obtained 

 in the metallic state, and weighed. 



The platinum-solution is filtered off from the insolu- 

 ble residue, which is collected on a weighed filter and 

 washed. It consists of irid-osmine, and is farther 

 treated as in No. 71. 



The solution is evaporated to dryness, the mass 

 heated to 150 in order to convert the chloride of 

 iridium into sesquichloride. It is then dissolved in a 

 little water containing a few drops of hydrochloric 

 acid, mixed with a concentrated solution of chloride 

 of ammonium, the precipitate filtered oft^ washed with 

 a solution of chloride of ammonium, and then with 

 alcohol. The double salt, when dried, is ignited with 

 the filter, a few crystals of oxalic acid being placed in 

 the crucible to facilitate the reduction. 



The platinum and iridium thus obtained are weighed, 

 again dissolved in dilute aqua-regia, and the iridium 

 which remains filtered off, washed, and ignited in a 

 stream of hydrogen. 



The filtrate from which the double chloride of plati- 

 num and ammonium was precipitated, is concentrated 

 by evaporation, boiled with concentrated nitric acid 

 to decompose the chloride of ammonium, saturated 

 with chlorine gas until the solution of chloride of 

 iridium has a brownish-red color. It is then com- 

 pletely evaporated to dryness on a water-bath, the mass 

 pulverized and treated with alcohol" of 80 per cent., 

 filtered and washed with alcohol until it flows through 

 colorless. This solution contains all the iron and cop- 

 per which are determined by themselves. 



The insoluble salt, which contains besides the os- 

 mium and ruthenium, all the platinum metals, is washed 

 with a weak solution of chloride of ammonium until 

 the reddish solution becomes colorless. This solution 

 contains all the rhodium and palladium. It is evapo- 

 rated to dryness, ignited in a covered platinum crucible, 



