84 BOTANICAL GAZETTE [ AUGUST 
It has often been asked in what way Na ions and Cl ions differ 
from ordinary sodium in the metallic state and ordinary chlorine 
gas respectively. The difference lies in the energy possessed 
by the substances in the ordinary state and in the ionic state. 
Ten grams of chlorine ions, for example, contain less energy 
than do ten grams of chlorine. Supply the energy to the ions, 
as is done in the case of electrolysis, and the ions are changed 
to ordinary chlorine gas. The lack of understanding of this 
point at first caused much reluctance to accept the theory of 
electrolytic dissociation (or the theory of free ions as it is also 
called), notably on the part of English chemists. 
Since Arrhenius published his theory of electrolytic dissocia- 
tion, all investigations made on salt solutions have confirmed it. 
In addition to the lowering of the freezing point and the elec- 
trical conductivity, the elevation of the boiling point, the specific 
volume, and the optical and thermal properties of solutions of 
electrolytes, all strongly support the, views of Arrhenius. This 
theory in the hands of Nernst® has yielded a clearer understand- 
ing of the processes that take place in voltaic combinations and 
has made it possible to calculate with accuracy in advance what 
the electro-motive force of a galvanic chain will be. It has ena 
bled Ostwald? to place analytical chemistry upon a firmer scien 
tific basis. In short, all the physical and chemical properties of 
aqueous solutions of electrolytes are well explained by o 
assumption that in these solutions the dissolved substances a 
split up into part-molecules or ions, and that the various proper 
ties that the solutions possess are due to the properties of the 
ions, 
The more dilute the solution of an electrolyte is, the greater 
is the percentage of the dissolved substance that is dissociated, 
and only at infinite dilution is this dissociation complete. In the 
case of many substances, however, namely strong acids 
bases as well as salts of these, dissociation goes on very rapidly 
Pea Nernst, Theoretische Chemie 563-569, where other references will also be 
ound, iat 
* Die wissenschaftlichen Grundlagen der analytischen Chemie, Leipzig, 1894- 
