240 NOTICES OF THE MEETINGS [Jan. 28, 
acid by a base such as potash, it was conceived that this oxide 
replaced the water. The existence of anhydrous sulphuric acid 
in an isolated state, and the fact that it so readily combines 
with water, was urged as an argument in favour of this theory ; 
and the same holds good with phosphoric, carbonic, sulphurous, 
lactic, nitrous, and even (according to the recent discovery of 
Dessaignes) nitric acid. 
However simple this view might appear and however satis- 
factory it might be in explaining those cases of combination for 
which it was specially intended, chemists soon became acquainted 
with bodies perfectly analogous in their general properties to the 
oxygen-acids, and producing by their action upon bases similar 
effects, but which, from the fact of their containing no oxygen, 
could not possibly be conceived as made up of water and an 
anhydrous-acid. For instance, hydrochloric acid was proved, 
both analytically and synthetically, to be composed of nothing 
but chlorine and hydrogen; and when it combines with potash, 
the hydrogen is found to leave the chlorine, whilst potassium 
takes its place. 
Being desirous of simplifying as far as possible their views 
of these phenomena, and of extending the same explanation to 
all like cases, certain chemists were led to imagine a new mode 
of representing the constitution and reactions of oxygen-acids, 
which had the advantage of connecting the two classes of ana- 
logous reactions by the same theory. This consisted in con- 
ceiving, that in the formation of a hydrated acid, a compound 
radical is produced in combination with hydrogen ; so that hydrated 
sulphuric acid is the hydrogen-compound of S O,, in the same 
way as hydrochloric acid is the hydrogen-compound of chlorine. 
There were many arguments in favour of this view, amongst 
which the inost prominent was derived from the fact, that when 
a salt of the one class, as chloride of potassium, decomposes a salt 
of the other, as sulphate of silver, the result is exactly in con- 
formity with what must occur on the supposition of the compound 
radical; and in like manner, the electrolytic decomposition of a 
sulphate moves the group SO, to the positive pole, where it 
either combines with a metal or undergoes decomposition. 
One of the strongest arguments against the view that the 
oxygen-acids contain water, is afforded by the results of recent 
researches (especially of MM. Laurent and Gerhardt) on the atomic 
weight of acids. Those chemists have rendered more definite and 
exact than they had been before, our ideas on the distinctions 
between monobasic, bibasic, and tribasic acids, and have clearly 
established that the correct expression of the atom of nitric acid 
must be such as contains half as much hydrogen as is contained in 
one atom of water (inasmuch as water is bibasic, and nitric acid 
monobasic). Of course this proportion may beas well established 
