101 



Mean, 193.6625, ± .0274 



Hence, using the atomic weights deduced in previous 

 chapters for Ba, S, and 0, Mg = 24.544, ± .0311. In a sub- 

 sequent note* Scheerer shows that the barium sulphate of 

 the foregoing experiments carried down with it magnesium 

 salts in such quantity as to make the atomic weight of mag- 

 nesium 0.39 too low. Corrected, Mg becomes = 24.545. 



The work of Bahr, of Jacquelain, and in part that of 

 S van berg and Nordenfeldt, also relates to the composition 

 of magnesium sulphate. Jacquelain's experiments were as 

 follows. t Dry magnesium sulphate was prepared by mix- 

 ing the ordinary hydrous salt to a paste with sulphuric acid, 

 and calcining the mass in a platinum crucible over a spirit 

 lamp to constant weight and complete neutrality of reaction. 

 This dry sulphate was weighed and intensely ignited three 

 successive times. The weight of the residual MgO having 

 been determined, it was moistened with sulphuric acid and 

 recalcined over a spirit lamp, thus reproducing the original 

 weight of MgSO^. Jacquelain's weighings for these two 

 experiments show that 100 parts of MgO correspond to the 

 quantities of MgSO^ given in the last column : 



1.466 grm. MgS04 g^-^e .492 grm. MgO. 297. 96S 



.492 " MgO " 1.466 " MgSO^. 297.968 



Jacquelain also made one estimation of sulphuric acid in 

 the foregoing sulphate as BaS04. His result, (1.464 grm. 

 MgSO^ = 2.838 grm. BaSO,,) reduced to the standard 

 adopted in dealing with Scheerer's experiments, give for 100 

 parts of MgSO^, 193.852 BaSO^. If this figure be given 

 equal weight with a single experiment in Scheerer's series, 



* Poggend. Annal., 70, 407. 



f Ann. d. Chim. et Pliys., 3 serie, 32, 202. 



