208 



PROCEEDINGS OF THE AMERICAN ACADEMY 



cibles was melted away. The arrangement of data in the table is 

 similar to that already described. 



Magnesic Oxide. 



The experiments with the oxide of magnesium led to very unex- 

 pected results, the amount of gas evolved upon the solution of this 

 compound being five to twenty times as much as was obtained from 

 zincic oxide, and over twenty-five times as much as from the oxide of 

 nickel. More difficulty was found in decomposing the nitrate than 

 before, and the remaining oxide was in a much harder and more com- 

 pact' state, and consequently more difficult to pulverize. The process 

 used was similar to that employed in the case of the other oxides. 



Magnesic nitrate made from pure nitric acid and magnesic carbon- 

 ate of commerce was evaporated to dryness in porcelain. The residue 

 was pulverized in an agate mortar, heated by means of the blast lamp 

 in a covered porcelain crucible, and cooled over calcic chloride. For 

 a parallel experiment, a portion of the original carbonate was con- 

 verted into the oxide by simple ignition, the magnesia formed in this 

 way evolving only an extremely small amount of gas upon solution 

 (Experiment 2 below). 



A third portion of magnesic nitrate was made from pure magnesium 

 ribbon and pure nitric acid, and the oxide was obtained from this salt 

 by evaporation and ignition in porcelain as usual (Experiment 7). 



Sulphuric acid was used for the solution of the magnesic oxide, as in 

 the case of zincic and cupric oxides. The following table explains 

 itself. 



