METHODS OF ELECTRICAL STIMULATION 29 



320,QOO tons' weight is required. To diffuse 

 1 gm. urea through pure water at the rate of 

 1 cm. per second, 40,000 tons' weight is required. 

 In dilute aqueous solutions at 18 C. a difference 

 of potential of 1 volt between electrodes 1 cm. 

 apart will drive the cation H 10.8 cm. per hour, 

 the cation Na 1.26 cm,, the anion OH 5.6 cm., 

 and the anion Cl 2.12 cm. per hour. 



As the ions move so slowly and as the products 

 of electrolysis appear at each electrode the 

 moment the current is made, it is evident that 

 the ions which immediately appear at the anode 

 cannot be derived from the same molecules as the 

 ions which simultaneously appear at the cathode. 



" Clausius explains this in the following way : 

 According to the theory of molecular motion, of 

 which he has himself been the chief founder, 

 every molecule of the fluid is moving in an ex- 

 ceedingly irregular manner, being driven first one 

 way and then another by the impacts of other 

 molecules which are also in a state of agitation. 



" This molecular agitation goes on at all times 

 independently of the action of electromotive force. 

 The diffusion of one fluid through another is 

 brought about by this molecular agitation, which 

 increases in velocity as the temperature rises. The 

 agitation being exceedingly irregular, the encoun- 

 ters of the molecules take place with various 



