262 



PROCEEDINGS OF THE AMERICAN ACADEMY 



the coaclasion seems to be warranted that little if any sulphuric acid 

 is lost during electrolysis. 



In order to prove like relations with regard to copper a similar 

 method was adopted. Weighed amounts of electrolytic copper were 

 dissolved in pure nitric acid in a flask provided with bulb tubes for 

 the condensation of spray. The cupric nitrate was then evaporated 

 with an excess of sulphuric acid upon the water bath, and the cupric 

 sulphate was electrolyzed as usual. 



Electrolysis op Copper. 



Here again, the manipulation was so much more elaborate than in 

 a simple electrolysis that it is difficult to decide where the slight loss 

 took place. In another experiment (No. 17) both copper and sul- 

 phuric acid were weighed before and afterward, but the experimental 

 operations were so doubly involved that the determination was of very 

 doubtful value. The result was not materially different from the 

 others, however. The significant portions of the data are given in 

 anotlier place.* 



In the course of these experiments it was found that a compact and 

 brilliant copper film may be safely washed by decantation if sulphuric 

 acid alone is present. Indeed, during most of the preceding deter- 

 minations this method was adopted to insure complete collection of 

 the acid, and in only one case (P^xperiment 7) was as much as one 

 twentieth of a milligram of copper found in the filtrate. In this case 

 that amount was added to the larger quantity, and the sum is given in 

 the table. Potassic ferrocyanide was the reagent used in the colori- 

 metric tests. 



Assuming the deficiency of copper and acid as found above to 

 represent a real loss during electrolysis, the composition of cupric 

 sulphate would be : — 



* Page 268. 



