34 ESSAYS aNd OBSERVATIONS ~ 
merely by adding any ordinary volatild 
alkali to a proper quantity ofa cauftic ley; 
for, inthis cafe, the air pafles from the vo- 
latile to the fixed alkali, by a fuperior at- 
traction for the laft, and, by a gentle heat, 
the compound yields a fpirit fimilar to 
that prepared from falt ammoniac and 
quick-lime. 
' Ir is therefore probable, that, had we 
alfo a method of feparating the fixed alka- 
li from an acid, without, at the fame time, 
faturating it with air, we fhould then ob- 
tain it in a cauftic form; but I am not 
acquainted with an inflance of this fepa- 
ration in chymiftry. ‘| here are two in- 
deed which, at firtt fight, appear to be of 
this kind; thefe are the feparation of the 
fixed alkali from the nitrous acid by 
means of inflamed charcoal, in the pr o- 
cefs for making nitrum fixatum, and of 
the fame alkali, from vegetable acids 
merely by heat ; but, upon examining 
the product of each procefs, we find the 
alkali either fully or nearly faturated with 
air. In the farft, either the charcoal or 
the acid, or both together, are almoft 
_wholly 
