256 KOLLOCK AND SMITH— EFFECT OF [Novembers, 



about 0.25 gram of metal. The current was maintained at two 

 amperes, while the pressure varied from 4 to 4.5 volts. The sul- 

 phuric acid was concentrated. Curves were plotted from the results 



obtained. 



Zinc. 



When one cubic centimeter of sulphuric acid was present in a 

 solution of zinc sulphate, the zinc was completely deposited in ten 

 minutes. The solution contained 0.25 gram of metal, the volume 

 of the solution being eleven cubic centimeters. The following ob- 

 servations were made : 



In 2.5 minutes, 0.1040 gram of zinc was deposited. 



(Figure i, Curve i.) 



When two cubic centimeters of sulphuric acid were present, the 

 solution, which was siphoned from the cup, showed the presence of a 

 trace of zinc after it had been electrolyzed for ten minutes. Eleven 

 minutes were necessary for the complete removal of the ^inc. The 

 volume of the solution in this case was twelve cubic centimeters. 

 The following rate of deposition was observed : 



In 2.5 minutes, 0.0953 gram of zinc was deposited. 



In the presence of three cubic centimeters of acid, twelve minutes 

 were required for the deposition of the zinc. The volume of the 

 solution in these experiments was thirteen cubic centimeters. Under 

 these conditions — 



In 2.5 minutes, 0.0815 gram of zinc was deposited. 



" 5 " 0.1633 " 



" 7.5 " 0.2200 " 



"10 " 0.2428 " 



"12 " 0.2493 " 



(Figure i. Curve 3.) 



