382 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



stant long charging time (1 minute), complete discharge, and a variable 

 time of insulation. The curves for short charging times are similar 

 in form, but lie a little above or below the curves given. These 

 curves show very clearly the point already mentioned, that such a 

 condenser can under certain conditions act more perfectly at vol- 

 tages below the voltage of formation. 



It is also of interest to know the shape of the leak-curves at the 

 forming voltage itself. Data on this factor is given in Figure 13 for 



26 



20 



15 





O. 



OI>° 



10 



.05 



1 2 3 .4 5 6 



TIME ■ SECONDS 



Figure 11. 



Capacity vs. insulation time. Plate formed at 36 volts. Curves for 36, 30, 

 22, and 14 volts. Long charge. Long discharge. 



plates formed at 36, 80, 140, and 300 volts. They offer one means of 

 examining the change which takes place in the active film during 

 insulation, but they are complicated by all the other factors involved, 

 and it seems probable that the study of such curves can only lead to a 

 definite solution of the problem when they are examined in connection 

 with the other variables. They do not appear to follow any simple 

 exponential formula. 



It should be noted that in these last cases we have not measured a 

 true capacity, but values of Q/ V after various times of insulation. 

 The " condenser " is so leaky that even during a very short time of 



