344 Mr ConneE.u on the Action of 
its elements, but the acid is not decomposed. If it were, iodine 
would have immediately made itself manifest. If after ten mi- 
nutes in the first mentioned experiment a trace appeared in the 
positive water, this was due to a small quantity of the acid itself 
which had passed over, and was reduced by nascent oxygen, as 
is evident from the acid action on test-paper which soon follow- 
ed, and from the circumstance that no iodine appeared in a longer 
time, when precautions were taken to diminish the quantity of 
acid passing over. On the other hand, the instant the acid was 
made positive, iodine appeared, and oxygen disappeared, the lat- 
ter giving rise to the former by combining with the hydrogen of 
the acid. 
From these experiments, therefore, I consider myself entitled 
to conclude, that, when solutions of muriatic and hydriodic acids, 
and doubtless of other hydracids, in water are submitted to vol- 
taic agency, the chlorine, iodine, or other electro-negative consti- 
tuent of the acid, is a secondary product, and the hydrogen arises 
from water directly decomposed by the voltaic agency. ‘This ac- 
tion, consequently, does not furnish an instance of definite vol- 
taic action on the hydracids, but is merely another example of 
the application of that principle to water. 
Questions of a similar nature arise relative to the decomposi- 
tion of the haloid salts, and are also of importance; because, if 
chlorides, iodides, &c. are dissolved as such, and are directly de- 
composed by the electric current, we have, as before, an instance 
of definite action in regard to another class of substances than 
water. Mr Farapay inclines to the affirmative of this opinion, 
although not with the same confidence as in regard to the hy- 
dracids. 'The fact is equally certain in this instance, that the 
hydrogen is evolved in a fixed proportion, as I have verified for 
alkaline chlorides and iodides ; but, by a set of experiments of 
the same description as those detailed in regard to the hydracids, 
I have been led to the conclusion, that the chlorine and iodine 
