540 M. PoggendorfF on Galvanic Circuits composed of 
the solution of chlorine acts more powerfully than hydrochloric 
acid, in which^ nevertheless^ the chlorine is electrolytically com- 
bined with hydrogen, and without doubt is more strongly re- 
tained by the hydrogen than in the solution of chlorine by the 
water. 
It might perhaps be replied, that the solution of chlorine is 
not a mere solution of the chlorine, but a mixture of hydrochlo- 
ric acid and the oxide of chlorine ; but setting aside that this 
supposition is not proved, is not even very probable, and is 
accompanied by a second supposition not more probable, that 
this mixture or the oxide of chlorine is of more difficult decom- 
position than hydrochloric acid, we need only call to mind the 
other cases where non-electrolytes exert a sensible influence on 
the development of the electromotive force, — the actions of sul- 
phuric acid, of nitric acid, ammonia, water impregnated with oxy- 
gen, of the peroxide of hydrogen^, of the §'wi??./o-sulphuret of 
potassium {K S^)—-to perceive that such a supposition is neither 
required nor can be generalized. 
The position, that those bodies which, brought between the 
metallic plates of a voltaic pile, render it active, are all electro- 
lytes {Exp, Res, § 858, 921), must therefore be thus altered, 
that the fluids between the metallic plates must, it is true, be 
electrolytes, i. e, decomposable bodies, since, at least with 
aqueous fluids and with a certain intensity of current, no con- 
duction can take place without decomposition ; but that the 
electromotive force which is developed on the contact of these 
fluids with the metals is not in any necessary connexion with 
the conductivity or decomposability, and can be increased or 
diminished by bodies which are not electrolytes, i. e. not directly 
decomposablef. I shall hereafter communicate another proof 
on this point. 
Not less difficult for the disputed theory would be the cases 
in which hydrochloric acid and sal-ammoniac, hydrochloric acid 
and salt, or salt and sal-ammoniac are opposed to each other. In 
each of them, according to it, only the chlorine could act on 
both sides, and consequently no current arise. But I will pass 
over the discussion of these cases and turn to the iodide of 
potassium, from which Faraday has derived the new argument 
in favour of the chemieal theory. 
In the preceding tables I have enumerated the action of the 
iodide of potassium in 1? metallic combinations, both towards 
* Becquerel, Ann. de Chim. et de Phys., vol. xxviii. p. 19. 
f De la Rive and other supporters of the oxidation-theory, admit also, as is 
well known, that it is the oxidation of the zinc alone, no matter whether it be 
caused by the oxygen of the atmosphere absorbed by the water or any other 
action, which determines the current. 
