236 ESSAYS anp OBSERVATIONS 
athes are for any time expofed to the air, 
or if we feparate the alkali from them by 
the addition of a large quantity of water 
and fubfequent evaporation, the falt im- 
bibes fixed air from the atmoiphere, and 
becomes nearly faturated with it: Though, 
even in this condition, it is generally more 
acrid than falt of tartar, when this is pre- 
pared with a gentle heat. 
Boxax has fometimes been referred 
to the clafs of alkalis, on account of fome 
refemblance it bears to thofe falts: But 
it has been demonftrated by accurate ex= 
periments, that we fhould rather confider 
it as a neutral falt; that it is compofed of 
an alkali and of a particular faline fub- 
{tance called the fedative falt, which ad- 
heres to the alkali in the {ime manner as 
an acid, bat can be feparated by the ad- 
dition of any acid whatever, the added a- 
cid joining itfelf to the alkali in the place 
of the fedative falt- As this conjunction 
of an acid with the alkali of borax hap- 
pens without the leaft etlervefcence, our 
principles lay us under a neceflity of al- 
lowing that alkali to be perfectly free of 
air,, 
