374 Obtaining Iridium and Osmium from the Platinum reiidue. 



Expecting a portion of osmium, to separate which a particular 

 treatment is required, the deutoxide of iridium still contains oxide of 

 iron. It is laid in a glass tube and hydrogen passed over it Thus 

 treated it generally becomes ignited of itself and may be reduced 

 without the application of heat. It is however better to lay a few 

 coals under the tube and pass the hydrogen over as long as water is 

 generated. 



Thus obtained, iridium is a black powder, containing much caustic 

 soda which was chemically combined with the oxide and may now be 

 extracted with water. Iron is separated by digestion with muriatic acid. 

 After being washed, the powder is laid between many folds of blot- 

 ting paper and powerfully pressed for several hours, in a screw press. 

 After the cake thus obtained has been fully dried it is laid in a cru- 

 cible and subjected to the heat of a forge. This iridium is gray, 



somewhat solid and capable of receiving a polish. 



In the same state it may be immediately obtained from the impure 

 oxide, but then it requires long continued digestion in aqua regia to 

 free it from iron, a portion of iridium is likewise dissolved and if it 

 contained silver this is also found in the solution. 



A still shorter process is to evaporate the tritochloride of iridium 

 and sodium to dryness and to expose it to a strong red heat till it fuses 

 and chloride of sodium begins to vaporize. The metal is thus per- 

 fectly reduced and remains, by dissolving the salt in water, as a heavy 

 gray or black powder. It is however impure and on account of its 

 compact state can scarcely be freed from iron. 



Palladium is not contained in the chloride solution nor as it appears, 

 rhodium. Muriate of ammonia and chloride of potassium added to the 

 same to saturation, throw down but a small part of the iridium even 

 when, in order to convert the whole into a chloride, the solution is pre- 

 viously saturated with chlorine. If the reddish black chloride of iri- 

 dium and potassium washed with chloride of potassium, be exposed to 

 a powerful white heat until all the chloride of potassium is vaporized, 

 pure iridium remains in the form of shining, silvery, crystalline 



scales. 



By treating the platinum remainder with chlorine and chloride of so- 



dium, it loses on an average 25 — 30 pr. ct. of its weight, but is by no 

 means exhausted; for exposed a second time to the same operation it 

 loses 5 — 7 pr. ct., and still the same particles of iridium and osmi- 

 um are to be seen in the remaining black mass. After the first 

 treatment, there may be distinctly seen powdery metallic osmium gen- 

 erated by the action of water upon chloride of osmium. 



