A Theory of the 



Aluminium Anode. 30! 



Aluminium Time from 



sulphate solution closing circuit 



contained : (minutes). 



Voltmeter. 



1 



! 



i Ammeter. 



0-22 

 007 

 0-04 



Ancde. 

 13 

 65 



11-3 

 11-8 

 11-95 



Catbode. immediately. 

 3 

 4 



10-3 

 96 

 91 



0-5 

 0-8 

 1-0 



Anode. 9 

 19 



11-8 

 11*9 



0-09 

 0'06 



In the next experiment also sodium carbonate solution was 

 used, and after the current had fallen to O07 ampere, part 

 of the sodium carbonate solution was replaced by a saturated 

 solution of potassium chloride. The current increased steadily, 

 after 60 minutes it was 0*35 ampere. On reversal, the 

 current rose immediately to over 2 amperes. 



In a similar experiment, after the current had fallen to 

 0'08 ampere, half of the sodium carbonate solution was 

 removed, and a saturated solution of potassium sulphate 

 added ; even after 60 minutes there was no change in the 

 current. Ammonia was also used in the inner cell, and half 

 of it replaced by saturated solution of potassium sulphate 

 after the current had decreased to 0*04 ampere. After 60 

 minutes the current was 0*05 ampere, and after 20 hours it 

 was constant at 0*10 ampere. On reversal it immediately 

 rose to over 2 amperes. 



An experiment was also made with solutions of sodium 

 carbonate and aluminium chloride. In this case, after the 

 current had fallen to 0*05 ampere, the poles were reversed 

 and the current increased rapidly (to 0'6 ampere in 1*5 

 minute) ; but on again reversing, it quickly diminished to 

 its former value. 



There is still another way in which the explanation might 

 be tested — by direct measurement of the resistance which 

 the film offers to the passage of different ions. Suppose that 

 solutions of the four salts AI 2 (S0 4 ) 3 , A1C1 3 , K 2 SO,, KC1, be 

 prepared so that they have the same conductivity at say 

 25° C, and that now the two electrodes be separated by ;i 

 film of Al(OH) 3 ; then the resistances depend, upon the rapidity 

 with which the ions can pass through the film, and the four 

 solutions will, in this case, have different conductivities. 

 The differences should, moreover, be of quite a high order. 



Phil. Mag. S. 6. Vol. 5. No. 27. March 1903. Y 



