118 Notice of some Recent [Feb. 



or by proper hammering. It is then polished by a lathe, 

 and completed. 



Method of obtaining Iridium and Osmium, after the separa- 

 tion of Platinum, by F. Wohler. (Pogg. Ann. xxxi.) — The 

 black pulverulent residue which remains after the solution 

 of native platinum in aqua regia, contains, besides the com- 

 bination of osmium and iridium, a considerable quantity of 

 free iridium, and some iron titanium. Wohler recommends 

 the following process for separating them : Mix equal por- 

 tions of the residue and decrepitated common salt, and 

 place them in a green glass tube, which is to be passed 

 through a tube furnace similar to that in the apparatus of 

 Liebig. To one end is fixed an apparatus for the production 

 of chlorine, and the other communicates with a vessel filled 

 with ammonia, preceded by a bulb for the absorption of the 

 oxide of osmium . Under the tube, hot coals are to be placed, in 

 order that the mixture contained in it, which should occupy 

 three fourths of its diameter, may be exposed to a strong 

 heat. The chlorine is then allowed to pass through the 

 tube. By this operation sodium-chloride of iridium, and 

 sodium-chloride of osmium are formed, both of which salts 

 are soluble in water, while the iserine remains insoluble. 

 A little chloride of osmium will be formed in the first 

 portion of the tube. The greater portion of the oxide of 

 osmium will have crystallized in the bulb situated at the 

 extremity of the tube. The bulb is to be exposed to a heat 

 so as to melt the oxide, and in this state it may be poured 

 into a flask or glass tube. The tube may be placed on one 

 side, so as to allow the oxides to sublime in the form of 

 long crystals on the opposite side. 



To the ammonia, which contains more or less oxide of 

 osmium, and is coloured yellow by it, let some sal-ammoniac 

 and carbonate of soda be added, and let the whole be then 

 evaporated to dryness, and heated to redness in a glass re- 

 tort. By this method the oxide will be reduced to the 

 metallic state, which, by treating with water, will remain 

 in the form of a black powder. It is then washed and dried. 

 The oxide in the bulb may be reduced in the same manner 

 after it has been dissolved in ammonia. 



When the tube with its contents is placed in a cylindrical 

 vessel full of water, all the soluble portion dissolves. A 



