A REVISION OF THE ATOMIC WEIGHT OF MANGANESE. 



41 



All weights were reduced to the vacuum standard by applying the following 

 corrections for each apparent gram of substance. 



The balance was a new Troemner, No. 10, and was easily sensitive to 0.02 

 mg. with a load of less than 50 gm. The weights, which were of brass, gold- 

 plated, were occasionally carefully standardized to hundredths of a miUigram. 

 The corrections did not vary with time, however. All weighings were made by 

 substitution, with tare vessels as nearly like those being weighed as possible. 

 (See tables on pp. 42 and 43.) 



The close agreement of the averages of the two series is conclusive evidence 

 that no serious error, such as occlusion by the silver bromide, affected the 

 method of analysis. This is strikingly shown by the ratio between the silver 

 used and the silver bromide obtained in the same analysis. 



Analyses 



Ag : AgBr 



1 and 18 57.4438 



2 " 19 57-4459 



3 " 20 57-4426 



4 " 21 57-4425 



5 " 23 57-4439 



8 " 24 57-4439 



9 " 25 57-4457 



10 " 26 57-4432 



11 " 27 57-4423 



12 " 28 57.4421 



13 " 29 57-4454 



14 " 30 57-4387 



15 "31 57-4456 



Average, 57-4435 



• - 57-4439 



Average, rejecting analyses 14 and 30 



The most probable value for this ratio has recently been shown to be 57.4453.^ 

 Although the foregoing figures furnish strong evidence that the atomic 

 weight of manganese lies very close to 54.93, it seemed advisable to attempt to 

 confirm this result by the analysis of other manganese compounds. The suc- 

 cess which accompanied this investigation of the bromide led to the selection of 

 manganous chloride for the next series of experiments. A comparison of the 

 different specimens of material and a discussion of all the results is to be found 

 at the end of this paper. 



^ Baxter: Proc. Amer. Acad., 42, 210 (1906); Jour. Amer. Chem. Soc, 28, 1332; Zeit. 

 anorg. Chem. 50, 398. (See page 59.) 



