Irreciprocal Conduction. 



141 



Vibrating the anode, when the film is on the point of being 

 formed, certainly helps its formation, but after the film has 

 formed violent agitation does not affect it, though by this 

 means the outer layers, at least, of the sheath of bubbles 

 round the anode may be removed. We have tried the effect 

 of mounting the voltameter on a whirling table, the electrodes 

 being kept fixed, and find that we can form the film when 



The 



value of A with the 

 any, different from that 

 Touching the anode with 



the voltameter is rapidly rotating. 



rotating voltameter was little, if 



obtained when it was stationary. 



an iron wire immediately destroys the film; this is also the 



case if a platinum wire is used to touch the anode, but when 



the platinum wire is not too large the film reforms. 



According to our measurements the E.M.F. of polarization 

 is about 2'b volts; if after the film has been formed we re- 

 duce the battery E.M.F. to a value rather less than this without 

 breaking circuit, we find that the film disappears more slowly 

 than if the circuit is broken. 



e. Influence of Degree of Concentration of Acid. — A small 

 percentage of water appears to exercise but little influence 

 on A, but when the liquid contains as much as 70 per cent, 

 water by volume we have been unable to produce the film. 

 The general effect of dilution is exhibited in the following 

 tables; the variations of A for percentages of acid between 

 98 and 87 being probably due to accidental causes. The 

 dilution seems also to diminish the rate at which the film is 

 formed. 



Table III. — Showing Effect of Concentration. 



A. Impure H S0 4 . 

 Temperature 9° -2 C. 



B. Pure H 2 S0 4 . 



Percentage of 



Kelative values 



Percentage of 



Temperature. 



Relative values 



acid by vol. 



of A. 



acid by vol. 



of A. 



98 



248 



70 



+n c 0. 



25 



97 



273 



60 



+ 13 D -5C. 



62 



96 



272 



50 



+ 14°-3 0. 



150 



95 



272 



40* 



+15°-8C. 



500 



93 



242 



30 



-10° C. 



No film. 



90 



250 









87 



250 









82 



340 









78 



360 









* The production of the film in acid of this degree of dilution effectually 

 disposes of any idea that hydroxyl can have any influence in forming the 

 him. See footnote of our former paper (Phil. Mag. April 1888, p. 279). 



