RICHARDS AND BAXTER. — ATOMIC WEIGHT OF COBALT. 127 



Third Series. 2 Ag : CoBr2. 



added, and after long agitation the precipitate was collected as usual 

 upon the Goocli crucible. The shreds of displaced asbestos were col- 

 lected and weighed ; and from the total was subtracted the small amount 

 (if any) of argentic bromide resulting from hydrobromic acid added in 

 titration. One experiment (No. 5), in which the cobaltous bromide con- 

 tained a few visible chips of porcelain from the tube used in subliming, 

 was rejected ; and in one (No. 10) the weight of the silver was not de- 

 termined. 



As usual in cases of this sort, we may obtain a useful check upon the 

 accuracy of these results by comparing the amount of silver required 

 with the amount of argentic bromide formed. Thus, in all these experi- 

 ments taken together 18.16302 grams of silver yielded 31.61642 grnms 

 of argentic bromide, — a ratio of 57.448 to 100.000. If we take only the 

 last five experiments (8, 9, 11, 12, and 13) which were the most care- 

 fully made, the ratio becomes 57.446 : 100.000, while Stas's result is 

 57.445. The value of this comparison has been pointed out in the pre- 

 vious paper on nickel. 



A still more important consideration is the identity of the results ob- 

 tained from the various samples. The average of all the results of each 

 of the four preparations is given below, — the first average comprehend- 



