56 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Scheerer, 1846. Poggeud. Ann., 1846, LXIX. 535 24.5 



Scheerer, 1847, Later Correction. Poggeud. Ann., 



1847, LXX. 407 24.5? 



Jacquelain, 1851. Annal. Chim. Phys., 1851, (3.), 



XXXII. 195 24.2 



Conversion of oxalate into oxide. 



Svanberg and Nordeufeldt, 1848. Erdmann's Journ. 



Prak. Chera., 1848, XLV. 473 24.7 



Determination of chlorine in maguesic chloride. 



Dumas, 1859. Ann. Chim. Phys., 1859, (3), LV. 



129, 187 ' 24.6 



Conversion of carbonate into the oxide. 



Marchand and Scheerer, 1850. Erdmann's Journ. Prak. 



Chem., 1850, L. 385 24.0 



Scheerer, 1859, Later Correction. Liebig's Ann., 1859, 



ex. 236 24.0 



Conversion of metal into oxide. 



Burton and Vorce, 1890. Am. Chem. Journ,, 1890, 



XIL 219 24.29 



It will be seen that, with the exception of the results obtained by the 

 precipitation of the sulphuric acid with barium chloride and the precipita- 

 tion of the chlorine with argentic nitrate, all the methods employed 

 involve the use of magnesic oxide. The fact that all such results are 

 untrustworthy was shown by T. W. Richards and E. F. Rogers* in their 

 work upon the occlusion of gases by the oxides of certain metals when 

 obtained by the ignition of various salts. The error from this source is so 

 large that it seems hopeless to apply a correction to previous work upon 

 the atomic weight of magnesium, as the amount of gas occluded depends 

 in a large degree upon the method and thoroughness of ignition. 



Concerning the results obtained by the precipitation of the sulphuric 

 acid in magnesic sulphate, it is only necessary to point out the error due 

 to the occlusion of various soluble substances present in the solution 

 from which the precipitation was made. This error was recognized by 

 Scheerer, after publishing his results, and an approximate correction was 

 made; but such a correction does not merit much confidence, as will be 

 seen. 



In the work of Dumas it is evident that some magnesic oxychloride 



* Tliese Proceedings, Vol. XXVIII. p. 200. 



