Thin Metal Partition in a Voltameter. 299 



a reading is, however, not more than 5 per cent., I think. 

 Only " XX " gold-leaf has been used in a solution of sodium 

 acetate. The method was to set up the voltameter with gold- 

 leaf partition, close the circuit, and run the current up till 

 the " critical current-density " was reached. Current and 

 temperature were recorded, the current slightly reduced and 

 allowed to pass till the temperature had risen, say 5 degrees, 

 when the current was again increased to the " critical " 

 value for this new temperature. The limit was reached at 

 about 45 degrees C, when the sealing-wax softened. Since 

 both " critical current-density" and conductivity of the electro- 

 lyte increase with temperature, effort was made to learn 

 whether both these quantities have the same temperature co- 

 efficient by raising the current just to the critical value, and 

 without altering the outside resistance to observe if the 

 increasing current, due to increasing conductivity of the 

 electrolyte, just sufficed to maintain an incipient escape of 

 gas at the partition. In every case the gas soon ceased to 

 escape on being left alone after adjusting the current to a 

 given temperature, requiring always some reduction of the 

 outside resistance to regain the critical current for the higher 

 temperature. A quantitative correction for the temperature 

 coefficient of the outside metallic resistance in the circuit 

 would probably account for the discrepancy. 



Table VII. 

 Temperature Coefficient of Critical Current. 



Sodium Acetate ; sp. gr. = l*06. Gold-leaf partition, 



Temperature 22° 24° 26° 29° 30° 33° 35° 



Current '65 "70 -76 '80 '85 -92 -96 



Temperature 24° 27° 



Current '53 "64 



New partition. 



Temperature 24° 26° 



Current -54 "60 



New partition. 



Temperature 22° 23° 24° 



Current '53 -57 "59 



New partition. 



Temperature 24° 33° 41° 45° 



Current -77 M8 133 148 



New partition. 



Temperature 15° 17° 19° 20° 23° 26° 30° 33° 37° 40" 



Current -30 -37 '45 -50 '65 -74 -83 -96 192 115 



