274 A Comparison of the Old and New Theories [Aprit, 
sition, as may be inferred from analogy with several other acids ; 
and if the radicle of muriatic acid has a greater affinity for oxygen 
than charcoal has, which is neither improbable, nor without example, 
then the preceding expectation could not be fulfilled, and yet it 
would not be necessary to infer that oxymuriatic acid is a simple 
body. This fact, therefore, though on the one side it seems favour- 
able to the new opinion, yet on the other side it does not militate 
against the accuracy of the old opinion. 
The impossibility of altering oxymuriatic acid by means of char- 
coal gave occasion to Davy’s idea that this substance is simple. The 
fact, that when it unites with bases it disengages a quantity of oxygen 
exactly equal to what was contained in the base, he considered as a 
clear proof of the accuracy of that idea. We shall now, therefore, 
examine this proof. 
Scientific propositions, which require to be proved, must be exa- 
mined on all sides; because that which, seen only on one side, appears 
to be true, shows itself, when examined on another side, either quite 
inaccurate, or at least very doubtful. When Davy made these pro- 
bable discoveries, his writings show that he was entirely ignorant of 
the experiments showing the constant proportions in which bodies 
unite. Since that time this branch of science has been much cul- 
tivated, and is, I conceive, fully established. It is necessary, there- 
fore, to examine these opinions on the side of chemical proportions. 
According to the old opinion, oxymuriatic acid is a super-oxide, 
and the separation of oxygen from it in the preceding experiments 
is the consequence of the greater affinity which the acid has to the 
base ; just as by the action of sulphuric acid on the super-oxide of 
manganese, the excess of oxygen is separated, and sulphate of man- 
ganese formed. But, that the base of a super-oxide, capable of be- 
coming an acid, should by the action of a base be reduced to an 
acid with the disengagement of oxygen, is in fact no more impro- 
bable than that the super-oxide of a substance capable of becoming 
a salifiable basis, should by the action of an acid be reduced to this 
basis with the same disengagement of oxygen. The quantity of 
oxygen disengaged in such cases must bear a determinate propor- 
tion as well to that in the acid as to that in the base ; and this pro- 
portion may be easily determined by the analysis of some compounds 
of the acid and the base. Now when we determine the compounds 
of muriatic acid, and the proportions of their constituents, we ob- 
tain as a result that if oxymuriatic acid, according to ihe old 
opinion, be a compound of muriatic acid with an excess of oxygen, 
which it gives out when it combines with salifiable bases, this oxygen 
must be just the same which euchlorine gives out when it is con- 
verted into oxymuriatic acid; that is to say, 1th of the quantity 
which hyper-oxymuriate of potash gives out when heated to redness, 
2 as much as must be contained in pure muriatic acid, and just as 
much as each of those bases contains with which the muriatic acid 
in the oxymuriatic acid is saturated. Consequently when oxymu- 
riatic acid gas is absorbed by a hot salifiable basis, it must give out 
