134 Reality of "Transfer-resistance" in Electrolytic Cells. 



acid was *17 ohm, or £ the former amount. The amount 

 of "resistance," therefore, at the surface of the bottle in the 

 two liquids varied directly as the heat evolved and expansion 

 produced. As the liquids were not stirred, the " resistances " 

 measured included that due to polarization and its counter 

 electromotive force. As I had already in many cases found 

 large differences of "resistance" at the surfaces of the same 

 metal in different electrolytes, whilst the latter was being 

 rapidly stirred in order to prevent polarization, I did not 

 repeat these experiments under the additional condition of 

 stirring. 



Separate experiments were carefully made to measure any 

 alterations of temperature occurring in the mass of the liquids 

 during the passage of the current of '454 ampere through 

 them, under exactly the above conditions ; the thermometer 

 employed being capable of indicating one fiftieth of a Centi- 

 grade degree. With the dilute sulphuric acid (1 to 10), and 

 with the strong nitric acid, no perceptible alteration of tem- 

 perature took place, even by continuing the current during 

 three minutes. This fact agrees with the circumstance ob- 

 served, that in each of these liquids, on stopping the current, 

 the bottle cooled quickly ; but had its heat been derived from 

 the mass of the liquid this would not have happened. The 

 absence of change of temperature in the dilute sulphuric acid 

 is consistent with the inference that the heat produced by the 

 resistance of the liquid, and that produced by surface "re- 

 sistance " at the anode and cathode, and imparted to the 

 liquid, was exactly neutralized by that absorbed by the chemical 

 changes at the electrodes. In strong nitric acid the cir- 

 cumstances were somewhat different, although the final result 

 was similar. In that case both the amount of heat of con- 

 duction-resistance of the liquid, and that of " resistance " at 

 the electrodes were comparatively small, and the portion of 

 heat absorbed by chemical action was also small, and these 

 two quantities neutralized each other. 



The surface " resistances " were measured by means of a 

 Wheatstone's slide-wire bridge, one terminal of a low-resistance 

 galvanometer being connected with the slider, and the other 

 connected first to the cathode and then to a platinum wire 

 (idle electrode) close to the cathode, but not touching it, in 

 the liquid ; a balance being obtained in each case by moving 

 the slider. 



