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| PHYSICAL anv LITERARY. 245 
thofe which difpofe them ‘to unite with 
the acid. The repulfions however hinted 
in thesfecond are perhaps more doubtful, 
thoughthey are fuggefied in many other 
initances of decompofition ; butthe bounds 
of my prefent purpofe will not allow me 
to enter upon this fubject, which is one of 
the moft extenfive in chemiftry. 
We meet alfo with a difficulty with re- 
fpect to the volatile alkali fimilar to the 
above. Thus a calcarious earth that is 
pure or free of air has a much ftronger at- 
traction for acids than a pure volatile al- 
kali, as is evident when we mix quick- 
lime with falt ammoniac; for the alkali 
4s then immediately detached from the a- 
cid : And agreeably to this I found, upon 
the trial, that a pure or cauftic volatile 
alkali does not feparate a calcarious earth 
from an acid... Yet, if we mix a mild vo- 
latile alkali, which is acompound of alka- 
li and air, with acompound of acid and 
calcarious earth, thefe two laft, which at- 
tract oneanother molt {trongly, do not re- 
main united; butthe acid is joined to 
the alkali andthe earth to the air, as hap- 
pens 
