i 9 o 5 ] 



KOLLOCK-SMITH — ELECTRO-ANALYSIS. 



143 



To 10 c.c. of the zinc sulphate solution 0.4 c.c. of concentrated 

 sulphuric acid was added, after which it was electrolyzed by a cur- 

 rent of 5 amperes and 7 volts ; the speed of the anode being 640 

 revolutions per minute. Under these conditions 0.405 gram of zinc 

 was precipitated in five minutes. 



Copper. 



Having found that .405 gram of zinc e 

 could be deposited in from five to eight 

 minutes it was decided to try other 

 conditions upon copper than those rec- 

 orded in the previous paper, in order 

 to reduce the time factor. By using 

 higher currents and greater concentra- 

 tion of the electrolyte this was accom- 

 plished. 



A solution of copper sulphate con- 

 taining 0.3945 gram of metallic copper 

 in five cubic centimeters was used for 

 these experiments. This quantity of 

 metal was precipitated finally in five 

 minutes. The solution became color- 

 less in three minutes. Twice this quan- 

 tity (.789 gram) was deposited in ten 

 minutes, although the solution had be- 

 come colorless at the expiration of Curve 5. 

 seven minutes. The volume in this P eres > 6 volts - 

 case being ten cubic centimeters it appeared the last traces of cop- 

 per required more time for precipitation. A current of 5 amperes 

 and 6 volts was used, sulphuric acid being introduced to increase 

 the conductivity. 



The current strength recorded in the following table was main- 

 tained during the greater part of the electrolysis. When it showed 

 a tendency to rise, on the liberation of the acid, additional resis- 

 tance was thrown into the circuit. The following rates of depo- 

 sition of copper were determined under the preceding conditions. 

 The anode made 640 revolutions per minute. 



In I minute 0. 1800 gram of copper was deposited. 

 "2 " 0.3400 " " " " " 



" 3 " 0.3664 " " " 

 " 4 " 0.3945 " " 



" 5 " 0.3945 " " « 



