MUTUAL DECOMPOSITION. 
author does not point under what circumstances this decompo- 
sition can take place ; but as, in order to verify it, water must 
necessarily be used, the fluate of soda, and the muriate of ba- 
rytes being both nearly equally soluble, they would immedi* 
diately reproduce the two primitive salts, without leaving any 
traces of their decomposition. In another place*, the author 
concludes, that because the phosphoric acid decomposes all the 
sulphites, it must, by consequence, follow, that all the phos- 
phates can decompose them. 
I shall confine myself to the mention of these two passages, These tables 
because it will be sufficient to look through these tables, in or- composed K y 
der to be soon convinced, that a large part of the facts they mere indne- 
. , , , .. . , tion as to the 
contain, have not been ascertained by direct observations ; and insolublesaits, 
it must also be remarked, that the theory according to which 
they have been predicted, is calculated to lead to' errors, in this 
instance, more than in any other. 
The action of the soluble carbonates on the insoluble salts, chemists have 
which appears at first to belong to this class of phenomena, is a , Uen ^. ed to 
rr , the effect of 
the only one that has fixed the attention of chemists. It has soluble carho- 
certainly been long since known, that the carbonates of potash ^Its^ 0 " 
and of soda will decompose a great number of insoluble salts • 
and this property has frequently been employed to great advan- 
vantage in analysis. But the theory of these decompositions, 
which, in the opinion of Bergmann, appears so satisfactory, 
can no longer be supported, since ti^e fundamental principles 
of its doctrine have been discovered to be incorrect, and the 
mutual decomposition of salts, in particular, has been proved 
to belong to a law that is independent of the different degrees 
of affinity of their principal constituents. 
Having had an opportunity, in some particular researches, ft esearches of 
(o observe a considerably extensive number of facts relating the author, be- 
to the mutual decomposition of the soluble and insoluble salts, tbiTiaft ob-^ 
I endeavoured to determine the general cause of these pheno-j ect * 
jnena, and the method of foreseeing their results without being 
pbliged to retain, by an effort of memory, of which few per-* 
* Tern. IV, p, 134, 
30ns 
