IOWA ACADEMY OF SCIENCES. 
17 
of the Electrolytic Dissociation Theory by its author, together 
with Nernst and Ostwald. 
The main features of the theory may be stated as follows: 
It assumes that when a salt, such as sodium chloride, is dis- 
solved in water, a certain number of the salt molecules separate 
into, primarily, two simple parts or ions, in this case sodium and 
chlorine, charged respectively with positive and negative elec- 
tricity. These ions are to be thought of as playing the part of 
new atoms or radicals for the time being, capable of independ- 
ent motion throughout the solution. This separation or dis- 
sociation of molecules into ions is going on continuously and is 
accompanied by a continuous re-association of ions into mole- 
cules. These opposite actions must, when the conditions are 
constant, ultimately balance one another, the number of mole- 
cules dissociated in the unit of time, becoming exactly equal to 
the number reproduced in the same period from the ions; as in 
a region of constant population the number of deaths must 
equal the number of births. 
In the solution, this state of equilibrium is reached very rap- 
idly, in fact, as we measure time, instantaneously. 
If, in such a solution we plunge a pair of positive and nega- 
tive electrodes, the previously existing equilibrium will be dis- 
turbed, for the negative ions will be attracted to the positive 
electrode, while the positive ions travel to the negative elec- 
trode. As each ion carries its electric charge and deposits it' 
upon the electrode, we have the phenomenon of an electric cur- 
rent passing through the solution. As the ions are thus 
removed from the solution their place is supplied by fresh dis- 
sociation of molecules. It is important to bear in mind that 
Arrhenius’ Theory affords a simple and rational explanation of 
the fact that those solutions of compounds, which, by methods 
based on Raoult’s law, give results for the melecular weight of 
the substance dissolved that are below normal, are all capable 
of electrolysis. 
It may be of interest to follow out some of the consequences 
of the theory and compare them with observed facts. Since 
both the conductivity of the solution and its departure from 
Raoult’s law are due to the presence of ions, that is to the dis- 
sociation of molecules, we might infer that on comparing two 
salts, one of which gives an aqueous solution of high con- 
ductivity and the other low, the latter would nearly conform to 
Raoult’s law, the former not. This is in fact the case. For 
