MUTUAL DECOM POSITION . 
215 
The carbonate of soda comported itself precisely in the same Carbonate ot 
soda lia,d the 
i manner. same effect. 
Similar experiments were made with the phosphates of The carbo- 
barytes, strontian, the oxalate of lime, &c. a more or less con- 
siderable part of the insoluble salt was constantly transformed otherinsoluble 
into a carbonate of the same base ; but on reaching a certain i.‘ ame conse _ 
limit, the decomposition stopped, although there remained quenees. 
sometimes a very inconsiderable quantity of the soluble carbonate 
1 not decomposed. 
Since the neutral carbonates when at the temperature of 
ebullition, retain a much greater quantity of carbonic acid than 
agrees with the mutual exchange of their principles with the 
insoluble salts,* it may be supposed that, in the preceding 
experiments the action of the carbonates was limited from this 
cause : and in order to determine its influence, these same 
experiments were repeated ; but instead of the saturated 
carbonates, the fused sub* carbonates were substituted. 
The same phenomena occured, that is to sav, a portion of the 
insoluble salt was always decomposed, but the decomposition 
; stopped at a certain period, though the sub-carbonate of potash 
or of soda, were still in the liquid. 
I am convinced by comparative experiments, which it would 
be useless to relate, that the different degrees of concentration 
of the solution, produce but very slight variations in the results 
of this decomposition. 
Experiment B. After remaining a long time in a state of 
ebullition, with a considerable excess of sulphate of barytes., a 
solution of the sub-carbonate of potash, which consequently 
would no longer have any action upon this salt, to the filtered 
hquor was added a small quantity of caustic potash, merely 
containing the traces of carbonic acid, and it was then again 
boiled with a new portion of sulphate of barytes. After an 
hour of ebullition, the residue contained a considerable quantitj 
of carbonate of barytes : as care had been taken to add a great 
excess of sulphate of barytes, it is evident that the solution 
* Mem.d’Arcueil, tom. II. p. 474. 
could 
