AND ON SOME SUBJECTS OF CHEMICAL THEORY. 327 
oxygen and hydrogen ; and these last, like the analogous order 
among the acids possess the highest power. Many of the me- 
tallic oxides, however, in the state in which they combine with 
the greatest facility with the acids, are hydrates,—that is, sup- 
posed compounds of the oxide with water, but probably ter- 
nary compounds of the metal with oxygen and hydrogen; and 
their facility of combination, may depend on this constitution. 
The same principle explains the necessity, not otherwise easi- 
ly accounted for, of the presence of water, to enable some of 
the earths, as barytes, to combine with acids. 
There are two views under which the neutral’ salts may be 
considered in the preceding theory. It has been shown, that 
when water is obtained in the action of a salifiable base, whe- 
ther alkali, earth, or metallic oxide, there is reason to infer that 
this water is formed by the hydrogen and part of the oxygen 
of the acid entering into binary combinations ; and when water 
is obtained from an alkali by the action of an acid, there is the 
same reason to believe, that it is formed by the combination of 
the hydrogen of the alkali with a portion of its oxygen. In 
these cases it may be supposed, that the radical of the acid 
combines with its remaining oxygen, forming a binary com- 
pound, which may still be considered as an acid; and that the 
radical of the alkali combines with its remaining oxygen, form- 
ing a binary compound, which may be regarded as an alkali; 
and these two compounds may unite with each other, forming 
the neutral salt. This is conformable nearly to the common 
doctrine. But there is another point of view under which the 
subject may also be considered. A ternary combination, into 
which oxygen and hydrogen enter, gives rise apparently to a 
higher state of acidity, and to a greater degree of alkaline ener- 
gy than is acquired from a mere binary combination into which 
‘oxygen enters. It is doubtful, therefore, if such binary com- 
pounds 
