213 SMITHSONIAX MISCELLANEOUS COLLECTIONS VOL. 54 



MAGXE8IUM. 



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 chem- 

 ical analysis, and ought consequently to be accurately ascertained. 



The early determinations made by Berzelius, Longchamp and Gay- 

 Lussac need not be considered here, as they have only antiquarian value. 

 The investigations which demand attention are those of Scheerer, Svan- 

 berg and ISTordenfeldt, Jacquelain, Macdonnell, Bahr, Marchand and 

 Scheerer, Dumas, Marignac, Burton and Vorce, and Eichards and Parker. 



Scheerer's method of investigation, was exceedingly simple.' He 

 merely estimated the sulphuric acid in anhydrous magnesium sulphate, 

 employing the usual process of precipitation as barium sulphate. He 

 gives no weighings, but reports the percentages of SO.^ thus found. In 

 his calculations, = 100, SO, = 500.75, and Ba6 = 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 MgS04 yield 

 the following quantities of BaSO^ : 



Per cent. SOs. 

 193.575 66.573 



193.677 66.608 



193.767 66.639 



193.631 66.592 



Mean. 193.6625, ± .0274 



Hence Mg = 24.467. 



In a later note *" Scheerer shows that the barium sulphate of these ex- 

 periments carries down with it magnesium salts in such quantity as to 

 make the atomic weight of magnesium 0.039 too low. 



The work of Bahr, Jacquelain, Macdonnell, and Marignac, and in part 

 that of Svanberg and Nordenfeldt, also relates to the composition of mag- 

 nesium sulphate. 



Jacquelain's experiments were as follows : ^ Dry magnesium sulphate 

 was prepared by mixing the ordinary hydrous salt to a paste with sul- 



^Pogrgend. Annal., 69, 535. 1846. 



^ Poggend. Annal., 70, 407. 



" Ann. Chim. Phvs. (.3), 32, 202. 



