378 Conduction in Solutions and Gases, 



constant condition (V being constant) when it is extended. 

 Integrating the previous equation, we have 



Lippmann found that when the external electromotive force 

 was applied, the surface-tension increased at first, until, when 

 the external electromotive force amounted to about one volt, 

 the surface-tension attained a maximum value, after which it 

 diminished. He found that d-y/d F 2 was sensibly independent 

 of F, so that the curve which represents the relation between 

 7 and F is a parabola.* 



The theory so far is more or less independent of assumptions 

 as to what actually takes place at the electrode : on this latter 

 question many conflicting views have been put forward. In 

 1878 Josiah Willard Gibbs,t of Yale (b. 1839, d. 1903), discussed 

 the problem on the supposition that the polarizing current is 

 simply an ordinary electrolytic conduction-current, which 

 causes a liberation of hydrogen from the ionic form at the 

 cathode. If this be so, the amount of electricity which passes 

 through the cell in any displacement must be proportional to 

 the quantity of hydrogen which is yielded up to the electrode 

 in the displacement; so that dy/dV must be proportional to 

 the amount of hydrogen deposited per unit area of the 

 electrode.:}: 



A different view of the physical conditions at the polarized 

 electrode was taken by Helmholtz, who assumed that the ions 

 of hydrogen which are brought to the cathode by the polarizing 

 current do not give up their charges there, but remain in the 

 vicinity of the electrode, and form one face of a quasi-condenser 



* Lippman, Coniptes Eendus, xcv (1882), p. 686. 



t Trans. Conn. Acad. iii (1876-1878), pp. 108, 343; Gibbs' Scientific Papers, 

 i, p. 55. 



J This is embodied in equation (690) of Gibbs' memoir. 



Berlin Monatsber., 1881, p. 945 ; Wiss. Abh. i, p. 925 ; Ann. d. Phys. xvi. 

 (1882), p. 31. Cf. also Planck, Ann. d. Phys. xliv (1891), p. 385. 



