258 



KOLLOCK AND SMITH— EFFECT OF 



[November 3, 



In the presence of one cubic centimeter of sulphuric acid, all the 

 copper was deposited in ten minutes. The current registered two 

 amperes and showed a pressure of from 3 to 3.5 volts. The solution 

 became colorless in seven minutes. Three minutes additional were 



Fig. 2. Copper. 



necessary to deposit the remaining 0.007 gram of copper. The fol- 

 lowing rate of precipitation was observed : 



In 2.5 minutes, 0.0985 gram of copper was deposited. 



•' 5 " 0.1887 " 



" 7-5 " 0.2418 " 



" 10 " 0.2437 " 



(Figure 2, Curve i.) 



When two cubic centimeters of acid were present and the cur- 

 rent was maintained at two amperes, the pressure varying from 4 to 

 4.5 volts, it was found that the copper was completely deposited in 

 ten minutes. It will be observed that the pressure in this case was 

 half a volt to a volt greater than in the previous experiment. The 

 two curves almost coincide. 



