1889.] Experiments on the Resistance of Electrolytic Cells. 541 

 The results may be thus summarised : 



II. " Experiments on the Resistance of Electrolytic Cells." By 

 Capt. H. R. SANKEY, R.E. Communicated by W. H. PREECE, 

 F.R.S. Received March 21, 1889. 



(Abstract.) 



It was observed during the course of some experiments on the 

 electrolytic deposition of copper that the resistance of the electrolytic 

 cells employed was greater the lower the current density, and the 

 experiments described in this paper were undertaken to inquire more 

 definitely into the matter. 



Many physicists have already observed the same effect, and have 

 ascribed it to a resistance at the junctions of the electrodes with the 

 electrolyte, and called it " transfer " resistance. 



In these experiments a prismatic electrolytic cell of triangular 

 cross-section was employed, and the area of the electrodes was equal 

 to that of the cross-section of the liquid. The electrodes experimented 

 with were electrotype copper, lead, zinc, and platinum, and the 

 electrolytes, solutions of CuS0 4 of various sp. gr., neutral and 

 acidulated, of ZnS0 4 , MgS0 4 , NaCl, Na 2 C0 3 , dilute H 2 S0 4 , Ac. The 

 electrodes were placed at different distances apart, but in general had 

 an area of 50 square cm. 



All the measurements were made by noting the swing of a 

 Thomson's reflecting galvanometer, used as a potentiometer, and 

 standardised before each trial by means of a Clark's cell. 



The current was measured by observing the potential difference 

 across a known resistance. 



The P.D. of the cell was proportional to the swing of the spot of 

 light. 



The counter E.M.F. was obtained by taking the swing on breaking 

 the circuit, the galvanometer being connected across the terminals of 

 the cell ; but this swing is not proportional to the C.E.M.F. existing 

 in the cell whilst the circuit is completed. Readings were, there- 



