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ON ELECTROLYSIS AND ELECTRO-CHEMISTRY. 203 
the alteration due to the increase of volumes in the cathode vessel be 
separately allowed for, the decomposed molecules for different strengths of 
solution would come out very nearly the same, and hence a great simplifi- 
cation would result. This view, to some extent on the ground of the 
probable identity of ions in solutions of different strengths, is in fact 
adopted, and the change of volumes regarded as a separate phenomenon 
due to the diaphragm and called electric endosmose. Separating this we 
get for the decomposed molecule 
Cu,(CuSO,)/(SO4)2; 
in other words, the complex molecule decomposed consists of an aggre- 
gate of CuSO, molecules of which the electrolysis separates a portion only 
of the constituent atoms. 
But further, the nature of the decomposed molecule would still be 
somewhat different for different degrees of dilution, for the dilution of the 
liquid round the cathode only becomes constant when the degree of dilu- 
tion passes a certain limit. However, this also can be explained on the 
assumption of the simplest possible molecular decomposition, that of 
CuSO, into Cu and SOQ,, by attributing the alteration with the concentra- 
tion of solution to the migration of molecules of salt through the solution 
produced by the motion of the ions with unequal velocities. A separate 
section is devoted to this theory, so that it will suffice here to point out 
that its introduction reduces the electrolysis to the simplest possible form, 
namely, the resolution of a single molecule (CuSO,) into atoms or their 
equivalents, viz., Cuand SO,. As this is the hypothesis upon which the 
dissociation theory is based, but little objection arises on that score, but it 
should be borne in mind that although this resolution into atoms or 
atomic equivalents is the simplest possible, and has not met any facts that 
it is definitely incompetent to explain, yet it is only one of many more com- 
plex arrangements that might be suggested, and it is not yet clear by any 
crucial experiment whether simplicity or complexity is the rule observed 
by nature in the process of electrolysis. The following paragraph suggests 
one reason in favour of complexity. 
The phenomena that are exhibited in a battery cell, consisting of 
electrodes of different nature in a liquid or in two liquids, are paralleled 
by corresponding phenomena exhibited with two similar electrodes in 
solutions of different strengths. The electromotive force of polarisation 
in the first case is represented in the second by an electromotive force 
resisting or promoting the alteration of strength of solution; and the 
heat of chemical action at the electrodes, part of which goes to produce 
the electromotive force, is represented by the heating effect of dilution of 
the solution.! There seems, on the ground here mentioned, reason for 
thinking that, in solutions which are not infinitely dilute at any rate, the 
migration of the ions may be a part of the primary electrolytic process, 
and indicate a corresponding complexity of the ions. 
It may further be remarked that Bouty classifies salts into normal and 
abnormal ones. Those of the former class tend to closer equality of 
molecular conductivity in extreme dilution, and they are characterised by 
having a migration constant equal to ‘5 for each ion, that is to say, they 
produce no alteration of concentration in the two vessels, or the decom- 
posed molecule as directly determined by chemical analysis is a simple 
1 See papers by Moser, Wied. Ann. 3, p. 216, 1878. 
