248 ESSAYS anp OBSERVATIONS 
THE volatile alkali and magnefia are 
placed in the fame line of this column; 
becaufe their force ‘of. attraction feems 
pretty equal. When we commit a mix- 
ture of magnefia and falt ammoniac to 
diftillation, the alkali arifes and leaves the 
acid with the magnefia ; becaufe this 
earth, by attracting the acid, reprefles its 
volatility, and it feems alfo to diminifli 
the cohefion of the acid and alkali, and 
to render them feparable by a gentle heat. 
If the magnefia be faturated with air, this 
likewife, on account of its volatile nature 
and attraction for the alkali, is driven up 
along with it, and makes it appear under 
a mild form, and in the fame manner do 
the alkali and air arife from a mixture of 
falt ammoniac and of a crude calcarious 
earth. 
ART. 
