Two Fluids, and of Two Metals not in Contact, 547 
since, nevertheless, a specific distinction remains between the 
effects of the two acids, the one, added to the water, developing 
a slighter, and the other a greater electromotive force than the 
iodide of potassium, we should be forced to admit that the qua- 
lity of the chemical action produces a specific difference in the 
excited electricity, and should thus again be brought back to 
the position maintained by De la Rive, but hitherto not proved, 
of the variety of electricities. I know not whether this is the 
opinion of the English philosopher ; but the above-mentioned 
position, and another in which he expresses as a conjecture, ^^The 
same quantity of electricity may pass in the same time, in at 
the same surface, into the same decomposing body in the same 
state, and yet, differing in intensity, will decompose in one case, 
and in the other noV^* — would admit of such a construction. 
But be this as it may, so much is certain, that there is no 
need of the hypothesis of an increase of the intensity of the 
chemical action, in order to explain the experiment in question. 
I have in fact convinced myself in the most positive manner 
that the result of the addition of the nitric acid does decidedly 
not arise from the chemical attack of this acid on the zinc, but 
solely from an action of it on the platina. 
Instead of placing the zinc and platina in common in the 
stronger mixture of acids mentioned at p. 545, I separated the 
two acids by anim.al membrane (bladder), inserted the zinc 
(amalgamated) in the sulphuric acid (1 vol. concentrated acid, 
and 4 vol. water), and the platina in the nitric acid (1 vol. con- 
cent. acid, and 6 vol. water), while the two other plates, zinc 
and platina, stood in the solution of iodide of potassium. Now 
although in this case the zinc underwent no other attack 
in quantity and quality than in the experiment mentioned at 
p. 543, in which the iodide of potassium had the ascendency 
over the sulphuric acid, yet the direction of the current was the 
reverse ; the iodide of potassium succumbed to the acid. The 
current also possessed a very considerable intensity, and, if not 
quite so powerful as in the case in which the zinc stood in the 
acid mixture, this, evidently, merely arose from collateral cir- 
cumstances, partly from the separated acids having perhaps a 
weaker power of conduction than the mixed, partly, and with- 
out doubt chiefly, from the metals in the present arrangement 
being in a somewhat disadvantageous position, the communica- 
tion between the two being made only by the membranous 
moderate degrees of concentration ; for it is at least in part decomposed, which 
is indicated by the altered development of gas at the zinc, and more decidedly 
evident from the ammonia, the existence of which in the solution of zinc may 
be distinctly demonstrated by the addition of an excess of caustic potassa. 
* Faraday, Experim. Res. § 988. 
