IRIDIUM. 255 



analysis was not far from Ir = 196.7. This is now known 

 to be too high. I have ]iot, therefore, thought it worth 

 while to recalculate Berzelius' figures, but give his estima- 

 tion as it is stated in Roscoe and Schorlemmer's " Treatise 

 on Chemistiy." 



In 1878 the matter was taken up by Seubert,* who had at 

 his disposal 150 grammes of pure iridium. From this he 

 prepared the iridichlorides of ammonium and potassium, 

 (NH4)2lrCle and KoIrClg, which salts were made the basis 

 of his determinations. The potassium salt was dried by 

 gentle heating in a stream of dry chlorine. 



Upon ignition of the ammonium salt in hydrogen, metal- 

 lic iridium was left behind in white coherent laminae. The 

 percentages of metal found in seven estimations were as fol- 

 lows: 



742 

 725 

 745 

 739 

 726 



739 



705 



Mean, 43-732, ± .0035 



The potassium salt was also analyzed by decomposition 

 in hydrogen with special precautions. In the residue the 

 iridium and the potassium chloride were separated after the 

 usual method, and both w^ere estimated. Eight analyses 

 gave the following results, expressed in percentages : 



/r. 



39.881 

 39.890 

 39.868 

 39.876 

 39-877 

 39-879 

 39-882 



39-883 



Mean, 39.880, ± .0015 



* Ber. d. Deutsch. Chem. Gesell., 11, 1767. 



