256 THE ATOMIC WEIGHTS. 



From these data several values for the atomic weight of 

 iridium may be calculated : 



From per cent. Ir in (NH^)2lrCl6 Ir = 192. 951, d= .064 



" KjIrClg " = 192.536, ± .060 



" KCl in " " = 192.474, rb -III 



CI4 in " "=192.757,^.148 



General mean " ==192.702,^.039 



If O -= IC, this becomes Ir = 193.145. 



In the potassium salt, instead of calculating from the per- 

 centages directly, we may reckon upon the ratios between 

 Ir and CI4, and between Ir and 2KC1 : 



From Ir : Ci^ ratio Ir ~ 192.626, ±: .081 



" Ir : 2KCI ratio " = 192.514,.^ .044 



General mean " = 192.539, rt .039 



Or, if =- 10, Ir = 192.982. 



Again, we may combine this mean with the value derived 

 from the ammonium iridichloride, and so estimate the re- 

 lative importance of the latter : 



From KJrClg Ir = I92.539> ± -039 



" (NH^lJrClg " = 192.951. ± .064 



General mean " = 192. 651, dr .033 



If O = K). this becomes Ir = 193.094. 



We may assume, then, from all the facts before us, that if 

 O = 16, the atomic weight of iridium varies from the even 

 number 193 only within the limits of experimental error. 



PALLADIUM. 



The atomic weight of palladium has been studied by Bcr- 

 zelius and by Quintus Icilius. In an early paper Berzelius* 

 found that 100 parts of the metal united with 28.15 of sul- 

 phur. Hence Pd ^= 113.63, a vesult which is unquestionably 

 far too hiffli. 



* Poggend. Annal., 8, 177. 1826. 



