RICHARDS AND CUSHMAN. ATOMIC WEIGHT OP NICKEL. Ill 



A very interesting evidence of the accuracy of these results is the 

 relationship between the amount of silver taken and the amount of 

 argentic bromide obtained. From the second and third series, we find 

 that 15.51556 grams of nickelous bromide yielded 26.67078 grams of 

 argentic bromide, requiring 15.32086 grams of silver. This leads to the 

 inference that argentic bromide contains 57.444 per cent of silver, a 

 quantity which agrees essentially with the value 57.445 per cent found 

 by Stas. Since the bromine used had been already found to be free 

 from other halogens, and the silver was known to be perfectly pure, we 

 have in these results conclusive proof that no nickel salt was occluded 

 by the argentic bromide, as well as a satisfactory "check" upon the 

 accuracy of the work. 



When we examine the results with respect to the various samjDles of 

 the salt analyzed, we find a very interesting and satisfying uniformity. 

 The four samples of nickelous bromide gave the following results for the 

 atomic weight of nickel : — 



Sample I. 58.677 



Sample II. 58.683 



Sample III. 58.688 



Sample IV. 58.689 



The slight rise in the value with increasing purity is not large enough 

 to have any weight, for there are analyses in the lowest series giving 

 higher individual results than any in the highest series. Hence we are 

 forced to the conclusion, that the least carefully purified specimens of 

 nickelous bromide must have been essentially identical with the most 

 carefully purified. The chances are evidently exceedingly small that the 

 impurities would so combine as exactly to counterbalance one another. 



The further discussion of this important question will be reserved 

 until more experimental work has been done. For the present, it is our 

 opinion, at this first halting place in a long investigation, that the atomic 

 weight of nickel cannot be far from 58.69 if O — 16.00, or 58.25 if 

 O rl 15.88. 



