426 Mr. J. Larmor on the Molecular 



in the surface-tension practically takes place at the fine 

 electrode, as the corresponding charge at the other electrode 

 is spread over so much greater area. The change in the 

 capillary constant is measured by the column of mercury 

 whose pressure is required to restore the meniscus to its 

 former position. 



Lippmann has given a series of observations with this 

 instrument in his paper in the Annates de Chimie, vol. v. 

 p. 507, the electrolyte being water containing one sixth part 

 by volume of sulphuric acid. He finds that the maximum 

 surface-tension is attained when the applied electromotive 

 force is *905 of a DanielPs cell. This value, therefore, cor- 

 responds to absence of polarization at the electrode meniscus. 

 The following Table, calculated from his results, gives 8e the 

 excess (positive or negative) of the electromotive force above 

 this value, Bp the excess of the pressure required to neutra- 

 lize its effect over its value when £ = # 905 D, and (8e) 2 /8p, 

 which is proportional to the capacity of the electrode, and 

 therefore inversely to the distance between the two electrified 

 layers, — on the supposition that the condensing arrangement 

 remains analogous to an ordinary condenser, viz. consists of 

 two infinitely thin layers separated by a dielectric sheet. 



W 2 oc 

 tie. dp. ty 



- -89 B 3434 2307 



- -88 337 23-0 



- -86 3184 23-07 



- -805 2694 234 



- -76 2474 233 



- -71 2104 240 



- -63 170 233 



- -54 1234 236 



- -405 70 2326 



- -32 444 23-01 



- -07 2 2405 

 + '35 57| 21*3 

 + "43 79£ 23*3 

 + '54 119j 244 

 + '81 2304 28-5 

 4- -93 248J 34-8 

 4- *98 254| 34-2 

 4-MO 2644 45-8 



The pressure supported by the tension of the meniscus 

 when £ = *905 D was 1108^ millim. of mercury, which is 

 therefore proportional to the maximum surface-tension of the 

 film. The surface-tension, as ordinarily measured, corresponds 

 to 6=0, and is therefore proportional to the pressure, which 

 was then 750 millim. 



The last column of this table is in good agreement with 

 Helmholtz's result, that for electromotive forces from zero up 



