i08 



Dr. Taylor and Mr. Inglis ; 



reproduce the peculiarities of the aluminium electrode with a 

 platinum electrode and a film of aluminium hydroxide. There 

 are various ways in which this might be done, but for 

 practical. reasons the following was adopted. The cell con- 

 sisted of two large pieces of platinum foil as electrodes, an 

 inner porous cell containing ammonia solution (1 molar) and 

 an outer glass beaker containing aluminium sulphate solution 

 (jr molar) . In this way a film of aluminium hydroxide was 

 deposited in the wall of the porous cell. 



If the aluminium sulphate solution contained the anode, 

 no current should pass, since Al"* ions cannot migrate 

 through the film to the cathode, nor OH' ions to the anode. 

 Addition of SO/ 7 ions to the ammonia should have no effect 

 on the current, but addition of CI' ions should cause a current 

 to pass. Reversal of the poles, also,, should cause a current 

 to pass, for NH.± ions can readily pass through the film. 

 With such a cell, and with the 12-volt storage-battery and 

 the same arrangement of apparatus as already described, the 

 following results were obtained : — 



Aluminium 



sulphate solution 



contained : 



Time from 



closing circuit 



(minutes). 



Voltmeter. 



Ammeter. 



Anode. 







60 



1140 



11-6 



120 



120 



0-20 

 007 

 0-03 



Cathode. 



immediately. 

 45 



11-2 

 10-4 



0-20 

 0-41 



Anode. 



10 



180 



11-7 



11-95 



010 

 003 



Cathode. 



1-5 



10-8 



0-43 



Anode. 

 Anode. 



6 

 immediately. 



4 

 20 



11-7 



(50 volt current 

 used.) 



0-13 

 022 



0-07 

 0-04 



Cathode. 



immediately. 



(50 volts.) 



0-83 

 (42 ohms in circuit. ) 



The small current which passes is due to the low con- 

 ductivity of ammonia solution ; so a similar experiment was 

 made with a solution of sodium carbonate in the porous cell, 

 as sodium hydroxide might act on the film. The only 

 difference found was that the maximum current was much 

 greater. 



