120 IRIDOSMINE AND PLATINUM RESIDUES. 



filtrate is acidified with hydrochloric acid, and the 

 ruthenium precipitated by pure zinc. 



The following method may be used for the analysis 

 of iridosmine. Two .grains of the substance, in a fine 

 powder, are intimately mixed with six grains of per- 

 oxide of barium and two of nitrate of baryta* in a close 

 covered silver crucible, and heated to redness for about 

 two hours. The unfused mass is taken from the cru- 

 cible, treated with water, and hydrochloric acid added 

 until it dissolves. It is then mixed with nitric acid, 

 and gently boiled until the smell of osmic acid is no 

 longer perceptible/)* It is then carefully evaporated 

 to dryness, dissolved in hot water, the liquid decanted 

 from the iridosmine, which has been somewhat acted 

 upon. 



The baryta in the solution is precipitated by sulphu- 

 ric acid, and after it has completely settled, and the 

 liquid become clear, it is filtered. 



About eight grammes of pure chloride of ammonium 

 are mixed with the yellowish-red solution, evaporated 

 to dryness, and a small quantity of chloride of ammo- 

 nium mixed with alcohol added to the mass, the salt 

 of iridium filtered off, washed as at first, with a solu- 

 tion of chloride of ammonium, then with weak and 

 afterwards strong alcohol. The dried salt, together 

 with the filter, is placed in a covered platinum cru- 

 cible and very gradually and carefully heated to red- 

 ness, the filter then thoroughly burned, and the metal 

 reduced by conducting hydrogen gas into the crucible 

 or holding a piece of carbonate of ammonia in it 

 while heated. 



* These two products should be very accurately weighed, in 

 order to determine beforehand the exact quantity of sulphurous 

 acid necessary to precipitate the baryta. The nitrate of baryta 

 must be decrepitated. 



f The osmic acid may be driven off in a retort and absorbed by 

 a solution of ammonia. 



