Ill 



A Simple Method of Measuring Electrolytic Resistance. 



By R. R. Ramsey. 



In measuring the resistance of electrolytes the back e. m. f. or 

 polarization of the cell is always a troublesome source of error. The 

 potential of the terminals of an electrolytic cell is never the same unless 

 the temperature, concentration, and purity are absolutely the same at 

 both electrodes. To avoid this error various methods have been used, 

 such as the alternating current and telephone method. 



While working- with electrolytic cells it occurred to me that the 

 ever-present and troublesome e. m. f. might be utilized in a very simple 

 manner for resistance measurement. This method consists of placing the 



Figure 1. 



cell in series with a resistance box and mirror galvanometer and taiiing 

 readings of the galvanometer deflection with several resistances in the 

 box. From these readings the cell resistance can be determined by 

 solving for Re in the two cciuations, 



Kdi 



and 



Kd2 = 



E_ 



R~fRi" 



E 



Re 



R2 + Rg + Re 



Rg, the galvanometer resistance being known. A preferable method 

 is to plot box resistance as a basis and the reciprocals of galvanometer 

 deflection as ordinates. The intercept on the X axis being Re -h Rg, 

 from which Re can be found. 



The specific resistance can be found from the resistance and the 

 dimensions of the cell which can be determined by filling with mercury 

 or water. 



