374 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



from an aluminium film may be considered to consist of two portions, 

 one of which takes place so slowly that part of it passes through the 

 circuit even after the slowest of our galvanometers begins its swing. 

 The results of careful preliminary tests made it probable that this error 

 would be negligible in our measurements, and the experimental results 

 all confirm this assumption. The galvanometers were calibrated against 

 standard mica condensers charged from a storage battery, and the 



to 



o 





q- e 



1.0 



16 



VOLTAGE 



Figure 3. 



Capacity (A), Quantity (B), and Energy (C) curves for low formation 

 voltages. From tables of Scott (64) and our own measurements. 



Long charge. 



Long discharge. 



Insulation time, 0.002 seconds. 



calibration was repeated several times during the progress of the 

 measurements. 



1. Apparent Capacity and Forming Voltage. — In Figure 2 the ap- 

 parent capacity in microfarads per square centimeter of anode surface is 

 plotted in curve A against the forming voltage applied to the cell, the 

 charging voltage being in this case the same as the forming voltage. 

 The following factors are constant throughout this curve: charging 

 time, 1 minute ; insulation time, 0.002 sec. ; discharge time, complete. 

 The cell was left short-circuited through the galvanometer. It is evi- 

 dent that the curve approaches an hyperbola in its general course, and 

 it has been assumed by Gordon (27), Corbino and Maresca (17), Schultze 



