322 THE ATOMIC WEIGHTS. 



Hence, for the atomic weight of palladium, we have — 



From (i) Pel = 104.874, ± .0243 



From (2) " = 105.858, ± .0200 



From (3) " =105.808,^.2117 



From (4) " = 106.550, zb .0491 



General mean I'd = 105.556, ± .0147 



AVith = 16, Pd = 106.364. 

 '' Taking the values separately, the second is probably the best; but in 

 view of the work done by Bailey and Lamb on one side, and by Keller 

 and Smith on the other, it cannot be accej^ted unreservedly. Until the 

 cause of variation in the results is clearly determined, it is better to take 

 the general mean of all the data, as given above. 



OSMIUM. 



The atomic weight of this metal has been determined by Berzelius, by 

 Fremy, and by Seubert. 



Berzelius* analyzed potassium osmichloride, igniting it in hydrogen 

 like the corresponding platinum salt. 1.3165 grammes lost .3805 of 

 chlorine, and the residue consisted of .401 grm. of potassium chloride, 

 with .535 grm. of osmium. Calculating onl}^ from the ratio between the 

 Os and the KCl, the data give Os = 197.523. 



Fremy's determination f is based upon the- composition of osmium 

 tetroxide. No details as to weighings or methods are given; barely the 

 final result is stated. This, if 6= 16, is Os = 199.648. 



When the periodic law came into general acceptance, it became clearly 

 evident that both of the foregoing values for osmium must be several 

 units too high. A redetermination w^as therefore undertaken b}" Seubert, + 

 who adopted methods based upon that of Berzelius. First, ammonium 

 osmichloride was reduced by heating in a stream of h3airogen. The 

 residual osmium was weighed, and the ammonium chloride and hydro- 

 chloric acid given off were collected in a suitable apparatus, so that the 

 total chlorine could be estimated as silver chloride. The weights were 

 as follows : 



6^0- a. 



3-5S97 

 4.0460 



4.1950 

 4.1614 



*Poggend. Annalen, 13, 530. 1828. 



tCorapt. Rend., ig, 468. Journ. fur Prakt. Chem., 31, 410. 1844. 



I Bericnte Deutsch. Chem. Gesell., 21, 1839. 1888. 



