MUTUAL DECOMPOSITION. 
Mntnal de- 
composition 
of tile iiisolu- 
l>lo neiitial 
salts, &c. 
if the alkali was pure, by the resistance progressively arising 
from the base. But the latter meeting in the liquid an acid 
with which it can form an insoluble sub-salt, unites with it, 
and tlius le-establishes the primitive conditions of the expe- 
riment ; the same effect is produced successively on the new 
portions of substances until the degree of saturation of the 'I 
liquid is in equilibrium with the power of cohesion of the 
insoluble salt, so that the less this resistance is, the more pro- 
gress the decomposition will make. 
It may not, perhaps, be evident why the base of the insoluble 
salt having abandoned its abid to the dissolved alkali, should, at 
the same time, take from it another acid. But I shall observe, 
that the insoluble carbonate which is the result of this action, i 
being naturally with an excess of base, and at the same degree | 
of saturation as the soluble carbonate, the latter cannot oppose j 
any resistance to the formation of the first. It would not be g 
the same if the liquid contained an acid which would not form | 
a neutral salt with the base of the insoluble salt. Experience I 
has demonstrated to me, that the soluble salts, which cannot j 
decompose when they are neutral, a given insoluble salt, in 
the same manner, cannot when they are with an excess of . 
alkali. The following experiment seems to confirm this i 
reasoning still further. 
Experiment F . — A solution of caustic potash, which re- 
tained sufficient carbonic acid to produce a remarkable effer- 
vescence with the acids, was boiled for the space of an hour | 
upon the sulphate of barites carefully pulverized. The fluid i 
separated from the precipitate contained sulphuric acid ; I 
but concentrated nitric acid being poured upon the insoluble li 
matter, it did not disengage the smallest bubble of gas, though 
this acid had dissolved the barytes. It is evident, that in this i 
case the alkali being too distant from the degree of saturation > 
which belongs to the sub.carbonates, opposes even the forma- 1 
tion of this alkaline salt, and all the action of this kind of sub- 
carbonate is reduced to taking up a certain quantity of sul- I 
phuric acid from the sulphate of barytes. 
The inverse experiment is explained with the same facility. i 
The : 
