REVISIONS OF THE THEORY OF ELECTROLYSIS. 155 



not entirely unchangeable, attract each other at this same instant. As soon 

 as this condition occurs it will soon join itself to this negative part-molecule 

 and the positive part-molecule formerly bound to the same thereby becomes 

 free. This one now in turn moves about free and after a time decomposes 

 another whole molecule in the same manner, and so on. All these movements 

 and decompositions occur in the same irregular manner as the heat motions by 

 which they are set going. 



When now in a liquid, whose molecules already find themselves in such 

 motion that they exchange their part-molecules in an irregular way, an electric 

 force acts which tries to drive all the positive part-molecules in one direction 

 and the negative ones in the opposite, then it is easy to understand what dif- 

 ferences in the mode of the molecular movements must ensue. 



A free part-molecule will then no longer follow the irregularly changing direc- 

 tions which it is forced to pursue by the heat motions, but it will change the 

 direction of its motion to correspond with the acting force; so that although 

 the motions of the positive part-molecules are very irregular still a certain 

 direction will prevail among them ; and likewise the negative part-molecules 

 will move under compulsion in the opposite direction. 



* :!: :i: * * * * 



If one considers within a liquid on which an electric force acts a small sur- 

 face at right angles to the direction of the force, then through this area more 

 positive part-molecules pass in unit time in the positive dii'ection than in the 

 negative, and more negative part-molecules in the negative than in the posi- 

 tive direction, * * * gQ j-jjat a certain excess number of positive part-mole- 

 cules go in the positive direction and a certain excess number of negative part- 

 molecules in the negative direction through the small area. The magnitude 

 of these two numbers does not need to be the same, since it depends also, out- 

 side of the force urging them, which is the same for both, on the degree of their 

 mobility, and this may for many reasons be different for different part-mole- 

 cules. 



These opposite movements of the two kinds of part-molecules compose the 

 voltaic ciu-rent within a liquid. 



:;: ^: :|: * * * * 



By this conception of the state of liquids the difficulty mentioned above 

 vanishes. It is readily seen that the influence which the electric force exerts 

 on the irregular molecular decompositions and motions already existing does 

 not begin when the force has reached a certain value, but that even the smallest 

 force must act on them, and that the amount of this action must increase with 

 the magnitude of the force. The entire process then agrees well with Ohm's 

 law. 



******* 



If we compare the older Grotthus theory with the one here developed, the 

 difference lies chiefly in this : In the former it was assumed that the motion 

 is first brought about by the electric force and takes place in two definite direc- 

 tions only, while the decompositions go on regularly from molecule to molecule, 

 but in the latter the motions already present are only modified, not to the extent 

 of making them entirely regular, but only so that among the great multitude of 

 motions those in the two definite directions prevail. 



These ideas of Clausius are so fundamental in the modern theory 

 of electrolysis that I have thought it best to translate them freely 



