192 ESSAYS ann OBSERVATIONS 
THE water, from its properties, feems 
to contain a fniall portion of volatile alka- 
hi, which was probably formed from the 
earth, air, and water, or from fome of 
thefe combined together ; and perhaps al- 
fo from a fmall quantity of inflammable 
matter which adhered accidentally to the 
magnefia, Whenever chemifts meet with 
this falt, they are inclined to afcribe its 
origin to fome animal or putrid vegetable 
fubftance; and this they have always done, 
when they obtained it from the calcarious 
earths, all of which afford a fmall quan- 
tity of it. There is, however, no doubt 
that it can fometimes be produced inde- 
pendently of any fuch mixture, fince ma= 
ny frefh vegetables and tartar afford a con- 
fiderable quantity of it. And how can it, 
in the prefent inftance, be fuppofed, that 
any animal or vegetable matter adhered 
to the magnefia, while it was diffolved by 
an acid, feparated from this by an alkali, 
and wafhed with fo much water? 
Two drams of magnefia were calcined 
in a crucible, in the manner defcribed a: 
bove, and thus reduced to two feruples 
an 
