and the Electro- Chemical Equivalent of Copper. 85 



solutions used in obtaining the numbers given in the 1st Series 

 were alike in that they were neutral with respect to the copper 

 and contained NH,C1. 





First Series. 





Second Series. 



No. 



Equivalent x 10 7 



No. 



Equivalent x 10 7 



1 



3291 



33 



3294 



2 



3291 



34 



3296 



3 



3293 



35 



3290 



4 



3293 



36 



3293 



5 



[3305] 



37 



3295 



12 



3296 



38 



3294 



13 



3297 



39 



3296 



14 



[3305] 



40 



3298 



15 



3293 



41 



3293 



10 



3294 



42 



3291 



17 



3296 



43 



3292 



18 



3294 



44 



3302 



19 



3292 



45 



3296 



20 



3300 



46 



3293 



21 



3299 



47 



3294 



22 



3299 



48 



3291 



23 



3291 



49 



3292 



24 



3295 



50 



3293 



25 



3294 



51 



3292 



26 



3292 



52 



3293 



27 



3300 



53 



3292 



28 



3292 



54 



3291 



29 



3296 



55 



3298 



30 



3301 







31 



3291 







32 



3295 







The mean of the First Series, including Nos. 5 and 14, is 

 3295*6 ± 54. If these experiments be excluded we get 

 3294/8 ± 0-43. 



Neutralization of the solution in the experiments described 

 had been effected by repeated use. A readier method which 

 suggested itself was to boil the nitrate in order to expel the air, 

 allowing a piece of clean copper to stand in the hot solution 

 until its solvent action had been exhausted. Such solutions 

 were prepared and after the addition of a small amount of 

 XH 4 C1 yielded values tabulated in the Second Series, the mean 

 of which is 3293-9 ± 04. 



In some cases the solutions employed were used many times 

 so that the tests to which the nitrate has been subjected are in 

 this respect particularly severe. There is good reason for sup- 

 posing that the numbers would have been more consistent if a 

 fresh solution had been used each time. 



