276 
MUTUAL DECOMPOSITION. 
Mutual de- 
compositions 
of the insolu- 
ble neutral 
sails, &c. 
could no longer act upon this salt ; nevertheless it contained a 
tolerably large portion of the carbonate of potash not decompos- 
ed. Upon fresh quantities of alkali being successively added, 
and at each addition the above mentioned operation repeated* 
each time the carbonate of barytes was produced, but by 
degrees in smaller quantities. After four operations of the same 
description, there still remained a small portion of carbonic acid 
in the liquid. 
The sub-carbonate of soda, and pure soda presented the 
ssme phenomena. 
As the sub-carbonates of potash and of soda comported them- 
selves in the manner with regard to all the insoluble salts, I con- 
sidered it to no purpose to subject the others to this proof. 
The result of the preceding facts is, that the sub-carbonates 
of potash and soda can never be entirely decomposed by any 
insoluble salt. Some comparative experiments made with 
several of these salts and the sub-carbonate of potash, have 
proved to me that the relation between the quantity of carbonic 
acid which is precipitated, and that of the same acid which 
remains in the liquid when the equilibrium is established, is not 
the same with regard to the salts formed of the same acid and 
of different bases, but that it varies from each kind of insoluble 
salt. It remained to be determined, whether, with respect to 
the same insoluble salt, This relation would be the same with 
the sub-carbonate of potash, as with the sub-carbonate of soda, 
and to ascertain this the following expeiiment was made ; 
Experiment C. I took 10 grammes of the sub-carbonate of 
potash dry, and 'J’QQO grammes of the sub-carbonate of soda, 
also dry 5 quantities which ought each to contain 3 07 grammes 
of carbonic acid* : these were separately dissolved in 250 
grammes 
* The proportions of carbonic acid admitted by M. Berard in the 
sub-carbonate of potash and of soda, appears to be too weak, especi- 
ally in the latter, 4 grammes of the sub-carbonate of dry soda precipi- 
tated by the nitrate of barytes, produced 7*425 grammes of carbonate 
of barytes. Now admitting with M. Berzelius, that 100 parts of the 
latter salt contain 21*6 of acid, (and this proportion must be too weak) 
it is found tliat in 100 parts of the sub-carbonate of soda, there are 
40*09 
