ATOMIC WEIGHTS 



219 



Marignac's second series was obtained by the calcination of the sul- 

 phate, with results as follows: 



Mean, 298.30, ± .0150 



Hence Mg= 40.377. 



These data may now be combined with the work of previous investi- 

 gators, giving Macdonnell's one result and Jacquelain's two, each equal 

 weight with a single experiment in Bahr's series : 



Macdonnell 300.193, ± .1413 



Jacquelain 297.968, ± .0999 



Bahr 296.200, ± .0815 



Svanberg and Nordenfeldt 296.671, ± .0720 



Marignac, synthetic 298.27, ± .0149 



Marignac, calcination 298.30, ± .0150 



General mean 298.210, ± .0103 



Burton and Vorce,^ who published their work on magnesium in 1890, 

 began with the metal itself, which had been purified by distillation in 

 a Sprengel vacuum. This metal was dissolved in pure nitric acid, and 

 the resulting nitrate was converted into oxide by calcination at a white 

 heat. The oxide was carefully tested for oxides of nitrogen, which were 

 proved to be absent, but occluded gases, the impurity pointed out by 

 Eichards and Rogers, were not suspected. This impurity must have been 

 present, and it would tend to lower the apparent atomic weight of mag- 

 nesium as calculated from the data obtained. The results were as follows, 

 together with the percentage of Mg in MgO : 



1 Amer. Chem. Journ., 12, 219. 1890. 



