338 Mr Conne tu on the Action of 
influence on that body. I have compared dilute sulphuric acid 
of a given strength, with the same acid of different strengths, 
with alkaline solutions, and with solutions of alkaline sulphates, 
by transmitting the same electric stream through them, and have 
found that the quantity of hydrogen evolved from the negative 
pole was always, with trifling deviations, a fixed quantity for the 
same current. The quantity of oxygen separating at the positive 
pole was subject to those variations from the absorption of the 
fluid, which Mr Farapay has pointed out; but the quantity in 
one experiment with ariother was evidently such as corresponded 
with the hydrogen evolved, after allowing for the absorption. 
It is evident how important an aid this principle affords us, in 
explaining what passes during the electric decomposition of 
aqueous solutions; for if, in comparing with one another, solu- 
tions of substances of different atomic constitutions, we obtain 
hydrogen or oxygen, or both, in the proportions contained in 
water, we have strong grounds for concluding that the solvent, 
and not the matter dissolved, has been the subject of decomposi- 
tion. 
Accordingly, it is in this way that we are enabled to determine, 
with every appearance of probability, that in a great many, per- 
haps in all cases of solutions of the oxyacids, water only is the 
subject of direct voltaic decomposition. Thus the same voltaic 
current was passed through dilute sulphuric acid, and a solution 
of boracic acid, and it was found that very nearly the same rela- 
tive quantities of hydrogen and oxygen were evolved from both 
solutions in the same time, notwithstanding the difference in the 
atomic constitution of the two acids. There was, therefore, little 
doubt that, in both solutions, the water, and not the acid, had 
suffered decomposition. lodic acid appeared to me to be ex- 
tremely well calculated for such an experiment, as the feeble 
affinity by which its elements are held together, afforded the 
most favourable circumstances for a direct decomposition of an 
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