A REVISION OF THE ATOMIC WEIGHT OF MANGANESE. 

 THE ANALYSES OF MANGANOUS BROMIDE AND CHLORIDE. 



INTRODUCTION. 



The following table, adapted from Clarke's "A Recalculation of the Atomic 

 Weights" ^ gives a brief resume of previous work upon the atomic weight of 

 manganese which has other than historical interest. 



The close agreement of the greater part of these determinations is striking, 

 the experiments of Schnieder and Rawack being the only ones which indicate a 

 value for manganese very different from 55.0. The variations of their results 

 from the others is not surprising, however, since manganoso-manganic oxide 

 and manganous oxalate, with which they worked, are undoubtedly difficult to 

 obtain in a pure condition. The remaining determinations all fall within limits 

 two tenths of a unit apart, and all but two agree within thirteen hundredths of 

 a unit. 



For this investigation the substances chosen for examination were manganous 

 bromide and chloride, since the analysis of halogen compounds may be ef- 

 fected with great accuracy. Furthermore, these compounds have not been in- 

 vestigated by any of the more recent experimenters except Dewar and Scott,^ 

 who performed one analysis each of the chloride and bromide and obtained the 

 values 54.89 and 54.95 respectively. 



* Smiih. Misc. Coll., The Constants of Nature, Part V., 1910. The results have been 

 calculated with the use of the following atomic weights: O = 16.00; C = 12.00; S = 32.07; 

 CI. = 35-46; K = 39.10: Ag = 107.88. 



' Loc. cit. 



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