of Electrodes in Electrolytic Cells. 253 



in the solution of potassic bromide at 8° 0. ; no current was 

 produced. I measured their amounts of " surface-resistance" 

 in the same manner, by means of a middle plate of platinum 

 and a total current of *00058 ampere. As anodes, the " resist- 

 ance " of the large one was 140 ohms less ; and, as cathodes, 

 23 ohms less than that of the small one. 



And in another similar experiment with plates of copper, 

 one being 1*0 x 1*0 centim. and the other 2*0x5*0 centim., 

 8*0 centim. apart, and varnished on their backs, with a middle 

 plate of copper, in a solution composed of 1*0 gramme of 

 glacial phosphoric acid and 10*0 cubic centim. of water at 

 8° C. As anodes the " resistance " at the surface of the large 

 one was 50 ohms less, and as cathodes 249 ohms less, than that 

 at the small one. 



In the first three of these combinations difference of " sur- 

 face-resistance " was obtained by employing plates of different 

 kinds of metal, and in the last two by using plates of the 

 same of different sizes. I have already stated (Proc. Boy. 

 Soc. 1885, No. 236, p. 209), "that this resistance varies 

 largely in amount with different metals in the same solution;" 

 also, that " the usual effect of diminishing the density of 

 current alone, by enlarging one electrode only, was to 

 diminish the resistance at that electrode." 



The results of each of these ten experiments show that the 

 influence which opposes the current at the surfaces of metallic 

 electrodes in electrolytes, exists independently of counter 

 electromotive force, polarization, and all other forms of electric 

 potential, and is therefore a distinct phenomenon, and cannot 

 be due to those causes. 



The magnitudes of " surface-resistance " at each plate of 

 different metal in the first three liquids were also separatelv 

 measured by means of an ordinary method with a condenser. 

 The two end plates were immersed, 4*0 centim. apart, in the 

 liquid in a glass beaker ; the battery, regulator, D'Arsonval 

 galvanometer, a coil of 200 ohms resistance, and a closed 

 connecting-key being in the circuit. A condenser of *33 

 microfarad capacity was then connected, through a Thomson's 

 reflecting galvanometer of 3040 ohms resistance and a key, 

 with the electrolyte close to one of the plates by means of a 

 wire of the same metal as one of the electrodes, and with the 

 wire circuit near that electrode, and the deflection noted. 

 After discharging the condenser, a second deflection was ob- 

 tained in a similar manner by means of the potentials on each 

 side of the other plate ; and a third by means of those at the 

 two ends of the coil ; and the "resistances " calculated from 

 the results. 



