142 THE ATOMIC WEIGHTS. 



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, zh .0103 



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

 started out 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 b}^ calcination at a 

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

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

 by Richards and Rogers, were not suspected. This impurity must have 

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

 magnesium as calculated from the data obtained. The results were as 

 follows, together with the percentage of Mg in MgO: 



Mean, 60.2845, ± .0027 



The latest determinations of all are those of Richards and Parker,t 

 who studied magnesium chloride with all the precautions suggested by 

 the most recent researches. The salt itself was not only free from oxy- 

 chloride, but also spectroscopically pure as regards alkaline contamina- 

 tions, and all weighings were reduced to a vacuum standard. The first 

 series of experiments gives the ratio between silver chloride and mag- 

 nesium chloride, and I have reduced the data to the form 2AgCl : MgClj : : 

 100 : %. The weighings and values for x are subjoined : 



* Am. Chem. Journ., 12, 219. 1890. 

 f Zeitsch. Anorg. Chem., 13, 81. 1896. 



