46 



BELL SYSTEM TECHNICAL JOURNAL 



serving as a condenser only while the aluminum is at a higher positive 

 potential than the electrolyte. 



A cell with a non-film-forming cathode makes a suitable con- 

 denser to operate on direct-current or pulsating-current circuits, in 



\ \ \ \ r 



SIMILAR CONDENSERS OPERATED AT HALF OF THE FORMATION 

 VOLTAGE. BOTH CONDENSERS IN AMMONIUM BORATE ELECTRO- 

 LYTES OF THE SAME CONDUCTIVITY 



100 150 



TIME IN DAYS 



Fig. 3 — Effect of electrolyte temperature on the rate of capacity change in con- 

 densers operating at voltages below the formation voltage 



<2400 



SIMILAR CONDENSERS FORMED TO 60 VOLTS AND OPERATED ON A 

 30 VOLT CIRCUIT AT ROOM TEMPERATURE. IN DIFFERENT AM- 

 MONIUM BORATE ELECTROLYTES 



100 150 



TIME IN DAYS 



Fig. 4- — Effect of electrolyte conductivity on the capacity change due to 

 reduced operating voltage 



which the aluminum always remains positively charged. On alter- 

 nating-current circuits, however, such a cell will operate as a rectifier 

 rather than as a condenser, unless two similar units are connected in 

 a series-opposed relationship. 

 A suitable condenser for operation on alternating current can also 



