504 



Transactions. 



Results. 

 Each experiment of the series was repeated a number of times, and the 

 agreement between the sets of values was found very satisfactory, and 

 sufficient to confirm the general nature of the results. Typical series of 

 values and curves are given below : — ■ 



1. Variation of P.D. between terminals 



2. Variation of P.D., cathode solution (fig. 2, a) 



3. Rate of deposition of nickel (fig. 4, b) 



Series 2. 



In this series of experiments varying amounts of ammonium nitrate 

 were added to the solution, and the observations repeated as in the preceding 

 series. The conditions were precisely similar, but in this case the current 

 was kept at a constant value. 



Results. 



1. P.D. across terminals : The variations were not so general and defi- 

 nite as in the former series. During the larger part of an experiment the 

 P.D. remained practically constant, and towards the end a fall, and not 

 a rise, was observed. Whatever the explanation may be, the presence of 

 the nitrate appears to have the effect of removing the polarization by 

 destroying the film deposited on the cathode, which, as Marshall suggests, 

 is the cause of the increased resistance observed in the previous case. 



2. P.D. cathode solution : Here an interesting periodicity was found 

 to be quite general. The curves indicating the variation of the P.D. with 

 time are appended, and it will be seen that they consist of three distinct 

 portions : (a.) At first a gradual diminution is observed, the extent of the 

 diminution and the period during which it persists depending upon the 

 actual amount of nitrate present in the solution, (b.) This is in every case 

 followed by a sudden rise — very pronounced, (c.) After the maximum 

 value of (b) is attained, the P.D. gradually diminishes as time proceeds. 



Values — 



(a.) One equivalent of ammonium nitrate < 

 (fig. 2, b) 



