at the Electrodes in a Solution. 



67 



very heavy tripod stand of 1J inch iron tubing, which was 

 adjustable by three levelling-screws. As I was anxious to 

 avoid vibrations, which are exceedingly great at Mason 

 College, I followed a suggestion of Prof. Pointing's,- and 

 mounted the stand on three 50 kg. weights, each resting on 

 three pieces of rubber. Before each experiment the tubes 

 were allowed to rest for at least twelve hours. 



The solutions for electrolysis were- prepared by diluting the 

 requisite amount of carefully standardized copper sulphate 

 and sulphuric-acid solution to 1 litre. The former solution,, 

 which was prepared from purest commercial copper sulphate, 

 recrystallized twice, was analysed by electrolytic copper 

 determination, the latter by precipitation with BaCl 2 . 



The electrical arrangements, which were in principle the 

 same throughout all the experiments described, will be readily 

 understood from the accompanying diagram (fig. 4). The 



Fig. 4. 





k. 



current from a suitable number of accumulators was passed 

 through a known resistance, an adjustable resistance, the 

 electrolytic cell, and the measuring instrument, which, as 

 already mentioned, consisted in all experiments either of an 

 Ayrton-Mather D'Arsonval or a Weston miilivoltmeter, in 

 either case suitably shunted. The measuring instrument was 

 carefully calibrated, and also standardized before each expe- 

 riment by taking its reading when a current of approxi- 

 mately the same magnitude as that employed in the experiment 



F2 



