ATOMIC WEIGHTS 467 



Hence, 



From ratio 1 Pd = 105.072, ± .0224 



" 5 106.472, ± .0077 



" 2 106.613, ± .1112 



" 3 106.627, ± .0016 



" 4 100.682, ± .0015 



" 8 106.948, ± .0087 



" 6 107.009, ± .0115 



" 7 107.014, ± .0109 



" 9 107.299, ± .0491 



General mean, Pd = 106.662, ± .0011 



The final mean is a little lower than the values found in Gutbiers 

 laboratory. The latter, however, could not be uncjualifiedly accepted 

 without rejecting other determinations which seem to be good. Tlie 

 international value, Pd = 106.7, is not far from the truth. 



OSMIUM. 



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

 bv 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 only from the ratio between the 

 Os and the KCl, the data give Os = 198.94. 



Fremy's determination " is based upon the composition of osmium 

 tetroxide. ISI"o details as to weighings or methods are given ; barely tlie 

 final result is stated, namely, Os = 199.65. 



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 was therefore undertaken by Seubert,^ 

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

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

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

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



1 Poggend. Annalen, 13, 530. 1828. 



^Compt. Rend., 19, 468. Journ. prakt. Chem., 31, 410. 1844. 



3Ber. Deutsch. chem. Ges., 21, 1839. 1888. 



