MUTUAL DECOMPOSITIOy; 
13 
of insoluble carbonates by insoluble salts, an equally strong 
argument may be deduced against this theory. 
Since the reaction of these bodies ceases at a certain period 
of the operation, we may conclude, that the powers which de- 
cide it, undergo some modification dependent upon the progress 
even of the decomposition. 
Now, during the course of this decomposition, only one 
remarkable change takes place, that of the -state of saturation 
of the liquid. 
When a soluble sub-carbonate acts on an Insoluble salt, in 
proportion as the carbonic acid is precipitated on the base of 
the insoluble salt, it is replaced in the solution by a quantity of 
another acid, capable of exactly neutralizing the alkali with 
which it constitutes a sub-carbonate. Thus, during the whole 
course of the decomposition, fresh quantities of neutral salt replace 
the corresponding quantities of an alkaline salt, and if we con- 
sider the alkali, which exceeds the neutralization of the car- 
bonic acid, in the sub-carbonate which is not decomposed, as 
acting upon the two acids, it is evident, that in proportion as 
the decomposition advances, the liquid approaches more and 
more to the neutral or saturated state. In the inverse experi- 
ment, a contrary alteration is seen j each portion of the acid of 
the soluble salt, which is precipitated ©n the base of the inso- 
luble carbonate, is replaced by a quantity of carbonic acid, 
which forms, with the corresponding base, a perfect sub-car- 
bonate ; and the more the acid is precipitated upon the inso- 
luble carbonate, the more sub-carbonate the liquid contains, 
and the more its state of saturation is distant from neutraliza- 
tion. 
This consideration seems to lead directly to the following ex- 
planation. 
It is known, that all the salts, even those which possess the 
greatest cohesion, yield to potash or caustic soda, a more or 
less considera’ le portion of their acid, according to circum- 
stances. Now, the soluble sub-carbonates may be considered 
as w'eak alkalies, which may take from all the insoluble salts a 
small quantity of their acids; this effect would ^oon be limited, 
if 
Mutual <Jf 
oompoiitioii 
of tlie insolu- 
ble neutral 
salts, dec. 
