Ml: 



318 THE ATOMIC WEIGHTS. 



Keller and Smith,* reviewing Reiser's work, find that palladiam- 

 monium chloride, prepared as Keiser prepared it, may retain traces of 

 foreign metals, and especially of copper. Accordingly, they prepared a 

 quantity of the salt, after a thorough and elaborate process of purifica- 

 tion, dried it with extreme care, and then determined the palladium by 

 electrolysis in silver-coated .platinum dishes. The precipitated palladium 

 was dried under varying conditions, concerning which the original me- 

 moir must be consulted, and was proved to be free from occluded hydro- 

 gen. By this method two sets of experiments were made to determine 

 the atomic weight of palladium ; but for present purposes the two may 

 fairly be treated as one. The data obtained are as follows, but the 

 weights do not appear to have been reduced to a vacuum : 



Pd(NH^Cl\. Pd. Percent. Pd. 



C i. 29960 .65630 50-504 



A. J 1.05430 .53 2 53 50.51 



(i.92945 -97455 50509 



f i. 94722 .98343 50.504 



1.08649 .54870 50.502 



28423 .64858 50.503 



68275 . .85010 S-5 1 9 



1.69113 -85431 5o.5 J 7 



1.80805 .91310 50.502 



Mean, 50.508, =b .0014 



Hence Pd 106.368, a result notably higher than Reiser's. 



Reller and Smith account for the difference between their determina- 

 tions and Reiser's partly by the assumption that the materials used by 

 the latter were not pure, and partly by considerations based on the pro- 

 cess. In order to clarify the latter part of the question they made three 

 sets of experiments by Reiser's method, slightly varying the conditions. 

 First, the chloride was not pulverized before ignition, and slight decrepi- 

 tation took place, while dark stains of palladium appeared in the reduc- 

 tion tube, indicating loss by volatilization. Secondly, the chloride was 

 prepared from crude palladium exactly as described by Reiser, but was 

 pulverized before reduction. No decrepitation ensued, but traces of pal- 

 ladium were volatilized. The third series, also on finely pulverized 

 material, was like the second ; but the palladiammonium chloride was 

 purified by Reller and Smith's process. The three series, here treated 

 as one, are as follows : 



Pd(NH z Cl) v Pd. Per cent. Pd. 



.62955 -3 r 743 50-422 



First series.... J -77*70 .38942 5 O-397 



.83252 .41918 50.350 



9955 .49895 50.371 



*Amer. Cheni. Journ., 14, 423. 1892. 



