100 THE ATOMIC WEIGHTS. 



MAGNESIUM. 



There is perhaps no common metal of which the atomic 

 weight has been subjected to closer scrutiny than that of 

 magnesium. The value is low, and its determination should, 

 therefore, be relatively free from many of the ordinary 

 sources of error; it is extensively applied in chemical anal- 

 ysis, and ought consequently to be accurately ascertained. 

 Strange discrepancies, however, exist between the results 

 obtained by different investigators; so that the generally 

 accepted figure cannot be regarded as absolutely free from 

 doubt. 



The determinations of Berzelius* and other early chemists 

 need not be here considered. Nor does the estimation made 

 by Macdonnellf deserve more than a passing mention. He 

 puts the atomic weight of magnesium at 23.9, but gives no 

 details concerning his method of determination-. The re- 

 searches which we have to consider are those of Scheerer, 

 Svanberg and Nordenfeldt, Jacquelain, Bahr, Marchand and 

 Scheerer, and Dumas. 



Scheerer's method of investigation was exceedingly sim- 

 ple.J He merely estimated the sulphuric acid in anhydrous 

 magnesium sulphate, employing the usual process of pre- 

 cipitation as barium sulphate. He gives no weighings, but 

 reports the percentages of SO 3 thus found. In his calcula- 

 tions, == 100, SO 3 = 500.75, and BaO = 955.29. It is 

 easy, therefore, to recalculate the figures which he gives, so 

 as to establish what his method really represents, viz., the 

 ratio between the sulphates of barium and magnesium. 



Thus revised, his four analyses show that 100 parts of 

 MgSO^ yield the following quantities of BaS04 : 



* Lehrbuch, 5 Aufl., Bd. 3, s. 1227. 



f British Association Report, 1852, part 2, p. 



J Poggend. Annal.,69, 535. 1846. 



