ATOMIC WEIGHTS 333 



Although Cooke's work was practically conclusive^ as between the rival 

 values for antimony, his results were severely criticised by Kessler/ who 

 evidently had read Cooke's paper in a very careless way. On the other 

 hand, Schneider published in Poggendorff's Annalen a friendly review 

 of the new determinations, which so well vindicated his own accuracy. 

 In reply to Kessler, Cooke undertook still. another series of experiments 

 with antimony bromide,^ and obtained absolute confirmation of his 

 previous results. To a solution of antimony bromide was added a solu- 

 tion containing a known weight of silver not quite sufficient to precipi- 

 tate all the bromine. The excess of the latter was estimated by titration 

 with a normal silver solution. Five analyses gave values for antimony 

 ranging from 119.98 to 120.02. when Ag = 108 and Br = 80. Reduced 

 to a common standard, the weights obtained gave the amounts of SbBr, 

 stated in the third column as proportional to 100 parts of silver : 



2.5032 grm. SbBr3 = 2.2528 grm. Ag. 111.115 



111.119 

 111.115 

 111.106 

 111.113 



Mean, 111.114, ± .0014 



Hence Sb = 119.85. 



Schneider,^ also, in order to more fully answer Kessler's objections, 

 repeated his work upon the Arnsberg stibnite. This he reduced in hydro- 

 gen as before, correcting scrupulously for impurities. The following 

 percentages of sulphur were found : 



28.546 

 28.534 



28.542 



Mean, 28.541, ± .0024 



Hence Sb = 120.43. 



These figures confirm his old results, and may be fairly combined with 

 them and with the percentages found by Cooke, as follows : 



Schneider, early series 28.520, ±.008 



Schneider, late series 28.541, ±.0024 



Cooke 28.5182, ± .0120 



General mean 28.5385, ± .0023 



1 Berichte Deutsch. .ohem. GeseU., 12, 1044. 1S79. 

 ^Amer. Journ. Sci., May, 1880. Berichte. 13, 951. 

 sjourn. prakt Cheni. (2), 22, 131. 



