Voltaic Electricity on Alcohol, &c. 339 
oxyacid in solution, if such a decomposition is likely to occur. 
Two of the tubes (Fig. 5), formerly described, * were filled with 
a solution of one part of iodic acid, in about ten parts of water, 
and inverted in an evaporating basin. ‘Two others were filled 
with sulphuric acid, diluted with twelve parts of water, and also 
inverted. After connecting them together, as formerly described, 
the current from fifty pairs of two inch plates was passed through 
them. Iodine separated from the negative pole of the iodic so- 
lution, without any evolution of elastic fluid from that pole. Gas 
was liberated from all the other poles. In a quarter of an hour, 
the following quantities of gas were obtained :— 
Cub. In. 
In the positive tube of iodic solution, : s ‘ 14 
cite? pl by iB AS a ta sulphuric solution, - : : 2 
In the negative tube of do. do. : 3 : OG 
Now, here there can hardly be a doubt that, in the iodic solu- 
tion, the water only was directly decomposed, and the iodine was 
a secondary product, arising from the reducing action of hydrogen. 
Had the iodic acid been directly decomposed, the quantity of 
oxygen liberated ought to have been five times greater than that 
got from the dilute sulphuric acid, in which we already know 
that water is the subject of direct decomposition. 
The next point of inquiry is, whether, in the case of the hy- 
dracids, water or the acid is the subject of direct electric agency ? 
and this question becomes one of considerable importance ; be- 
cause, if the acid is directly decomposed, the experimental results 
obtained afford an example of the application of the principle of 
definite voltaic action to another substance than water, whilst, if 
the water is decomposed, it is only another instance applicable to 
that liquid. It is with considerable hesitation that I have brought 
myself to differ on this point from so high an authority as the first 
propounder of the doctrine of definite voltaic action ; and I have 
* Page 327. 
VOL. XIII. PART II. >. E>. 4 
