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fediment : for fuch is the native appearance of the 
martial earth, as well as of all the other earths con- 
tained in thefe waters, as will be fhewn hereafter. 
In thefe decompofitions of acidulous waters, by 
means of alcalies, no effervefcence, or dilcharge of 
air-bubbles, takes place ; for here the air is all ab- 
forbed by the alcali added thereto, and not expelled 
from the water, as it is in the decompofition of the 
fame waters, by means of ftronger acids. 
When the acidulce are mixed with common foap, 
a two- fold decompofition takes place. The fixed 
alcali , quitting the unftuous fubftances, to which 
it was joined in the foap, unites itfelf to the aereal 
fpirit, or mephitic air, of thofe waters, while this 
air, at the fame time, deferts the earthy fubftances 
with which it was before combined. The fame 
new combinations feem to take place, when foap 
is mixed with any of thofe waters which are ufuaily 
called hard ; many of which waters have been found 
to contain an earthy fubftance, diffolved by means 
of this fubtile aereal principle. 
The above obfervations and experiments fliew an 
exad agreement, in the feveral ways, by which the 
various neutral falts, and thofe laline concretes 
formed of mephitic air united to an earthy bafe, 
are decompounded. It ought, however, here to be 
remarked, that the faline concretes, which exift in 
the pouhon water, in a diffolved date, though evi- 
dently of the neutral kind, have not hitherto been 
obtained in a folid form ; owing, perhaps, in fome 
meafure, to the great volatility of their fpirituous 
principle ; but chiefly to their being fubjedt to de- 
compofition, from the precipitation of their earthy 
