ATOMIC WEIGHTS 345 



The subjoined columns give the quantity of each salt proportional to 100 

 of ASoOg : 



KJCr^O,. KCIO,. 



98.95 41.15G 



98.94 41.116 



99.17 41.200 



98.98 41.255 



99.08 41.201 



99.15 41.086 



41.199 



Mean, 99.045, ± .028 41.224 



41.161 



41.193 



41.149 



41.126 



Mean, 41.172, ± .009 



Hence Cr = 53.31. 



Eeducing the later series to the standard of the earlier, the two com- 

 bine as follows : 



(1). 2KC103:K,Cr„Or: : 100: 120.191, ± .028 

 (2). 2KC103:K,CrA: : 100:120.282, ± .043 



General mean 120.216. it .0235 



Siewert's determinations, which do not seem to have attracted general 

 attention, were published in 1861.^ He, reviewing Berlin's work, found 

 that upon reducing silver chromate with hydrochloric acid and alcohol, 

 the chromic chloride solution always retained traces of silver chloride 

 dissolved in it. These could be precipitated by dilution with water; 

 but, in Berlin's process, they naturally came down with the chromium 

 hydroxide, making the weight of the latter too high; lience too large a 

 value for the atomic weight of chromium. In order to find a more cor- 

 rect value Siewert resorted to the analysis of sublimed, violet, chromic 

 chloride. This salt he fused with sodium carbonate and a little nitre, 

 treated the fused mass with water, and precipitated from the resulting 

 solution the chlorine by silver nitrate in presence of nitric acid. The 

 weight of the silver chloride thus obtained, estimated after the usual 

 manner, gave means for calculating the atomic weight of chromium. 

 His figures, reduced to a common standard, give, as proportional to 100 



^ Zeit. gesammt. Wissensehaften, 17, 530. 



