106 



THE ATOMIC WEIGHTS. 



± .0022 

 =b .0069 

 ifc .0077 



Result, zfc .0020, probable error of the general mean. 



We may now combine the results obtained from both 



magnesites 



Snarum mineral Per cent. MgO, 47.624, zb .0037 



Frankenstein mineral _. " 47.628, dr .0020 



General mean. 



47.627, zb .0018 



The last investigation upon the atomic weight of magne- 

 sium which we have to consider is that of Dumas.* Pure 

 magnesium chloride was placed in a boat of platinum, and 

 ignited in a stream of dry hydrochloric acid gas. The 

 excess of the latter having been expelled by a current of dry 

 carbon dioxide, the platinum boat, still warm, was placed 

 in a closed vessel and weighed therein. After weighing, the 

 chloride was dissolved and titrated in the usual manner 

 with a solution containing a known quantity of pure silver. 

 The weighings whicli Dumas reports give, as proportional to 

 100 parts of silver, the quantities of MgCl, stated in the 

 third column : 



Mean, 44.261, zfc .020 



There are now before us the following ratios, from which 

 to deduce the sought-for atomic weight : 



* Ann. Chem. Pharm., 113, ;i2- i860. 



