102 THE ATOMIC WEIGHTS. 



and combined with the latter, the mean will be 193.700, ±: 

 .0331. Fr6m this the atomic weight of magnesium becomes 

 24.244, ±: .033. This again, corrected according to Scheerer 

 for the magnesium salts carried down b}^ the barium sul- 

 phate, becomes 0.39 higher, or INIg = 24.283. Of course 

 this correction, determined by Scheerer for a single experi- 

 ment, can only be a rough approximation in a mean like 

 the foregoing. It is better than no correction at all, the 

 character of the error involved being known. 



Bahr's* work resembles in part that of Jacquelain. This 

 chemist converted pure magnesium oxide into sulphate, and 

 from the increase in weight determined the composition of 

 the latter salt. From his weighings 100 parts of MgO ecj^ual 

 the amounts of MgSO^ given in the third column : 



1.6938 grm. MgO gave 5.0157 grm. MgSO^. 296.122 

 2.0459 " 6.0648 " 296.437 



1.0784 " 3-1925 " 296.040 



Mean, 296.200, rfc .0815 



About four years previous to the investigations of Bahr 

 the paper of Svanberg and Nordenfeldtf appeared. These 

 chemists started with the oxalate of magnesium, which was 

 dried at a temperature of from 100° to 105° until it no 

 longer lost weight. The salt then contained two molecules 

 of water, and upon strong ignition it left a residue of MgO. 

 The percentage of ]\IgO in the oxalate comes out as follows : 



7.2634 grm. oxalate gave I.9S72 grm. oxide. 27.359 per cent. 



6.3795 " 1-7464 " 27.375 



6.3653 " I. 7418 " 27.364 " 



6.2216 " 1.7027 " 27.36S " 



Mean, 27.3665, d= .0023 



In three of these experiments the MgO was treated with 

 H2SO4, and converted, as by Jacquelain and by Bahr in 

 their later researches, into MgSO^. One hundred parts of 

 MgO gave of MgSO^ as follows : 



* Journ. fiir Prakt. Chem., 56, 310. 1852. 

 f Journ. fur Prakt. Chem., 45, 473. 1848. 



